/src/open62541_15/src/server/ua_subscription_event.c

Source
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
 *
 *    Copyright 2018 (c) Ari Breitkreuz, fortiss GmbH
 *    Copyright 2020 (c) Christian von Arnim, ISW University of Stuttgart (for VDW and umati)
 *    Copyright 2021 (c) Fraunhofer IOSB (Author: Andreas Ebner)
 *    Copyright 2022, 2025 (c) Fraunhofer IOSB (Author: Julius Pfrommer)
 */

#include <open62541/types.h>
#include "ua_server_internal.h"
#include "ua_subscription.h"

#ifdef UA_ENABLE_SUBSCRIPTIONS_EVENTS

static UA_StatusCode
readSAOfromEventInstance(UA_FilterEvalContext *ctx,
                         const UA_SimpleAttributeOperand *sao,
                         UA_Variant *value) {
    /* EventInstance in the information model defined? */
    const UA_NodeId *ei = ctx->ed.eventInstance;
    if(!ei)
        return UA_STATUSCODE_BADINVALIDARGUMENT;

    /* Prepare the ReadValueId */
    UA_ReadValueId rvi;
    UA_ReadValueId_init(&rvi);
    rvi.indexRange = sao->indexRange;
    rvi.attributeId = sao->attributeId;

    /* Read the value */
    UA_DataValue v;
    if(sao->browsePathSize == 0) {
        /* If this list (browsePath) is empty, the Node is the instance of the
         * TypeDefinition. (Part 4, 7.4.4.5) */
        rvi.nodeId = *ei;

        /* A Condition is an indirection. Look up the target node. */
        /* TODO: check for Branches! One Condition could have multiple Branches */
        UA_NodeId conditionTypeId = UA_NODEID_NUMERIC(0, UA_NS0ID_CONDITIONTYPE);
        if(UA_NodeId_equal(&sao->typeDefinitionId, &conditionTypeId)) {
#ifdef UA_ENABLE_SUBSCRIPTIONS_ALARMS_CONDITIONS
            UA_StatusCode res = UA_getConditionId(ctx->server, ctx->ed.eventInstance, &rvi.nodeId);
            UA_CHECK_STATUS(res, return res);
#else
            return UA_STATUSCODE_BADNOTSUPPORTED;
#endif
        }

        v = readWithSession(ctx->server, ctx->session, &rvi, UA_TIMESTAMPSTORETURN_NEITHER);
    } else {
        /* Resolve the browse path, starting from the event-source (and not the
         * typeDefinitionId). */
        UA_BrowsePathResult bpr =
            browseSimplifiedBrowsePath(ctx->server, *ei, sao->browsePathSize, sao->browsePath);
        if(bpr.targetsSize == 0 && bpr.statusCode == UA_STATUSCODE_GOOD)
            bpr.statusCode = UA_STATUSCODE_BADNOTFOUND;
        if(bpr.statusCode != UA_STATUSCODE_GOOD) {
            UA_StatusCode res = bpr.statusCode;
            UA_BrowsePathResult_clear(&bpr);
            return res;
        }

        /* Use the first match */
        rvi.nodeId = bpr.targets[0].targetId.nodeId;
        v = readWithSession(ctx->server, ctx->session, &rvi, UA_TIMESTAMPSTORETURN_NEITHER);
        UA_BrowsePathResult_clear(&bpr);
    }

    /* Validate the result */
    if(v.status != UA_STATUSCODE_GOOD) {
        UA_Variant_clear(&v.value);
        return v.status;
    }
    if(!v.hasValue)
        return UA_STATUSCODE_BADNODATAAVAILABLE;

    /* Move the result to the output */
    *value = v.value;
    return UA_STATUSCODE_GOOD;
}

/***************/
/* Filter Eval */
/***************/

/* Names of the mandatory event properties (in the BaseEventType) */
#define MANDATORY_EVENT_PROPERTIES_COUNT 8
static UA_String mandatoryEventProperties[MANDATORY_EVENT_PROPERTIES_COUNT] = {
    UA_STRING_STATIC("/EventId"),
    UA_STRING_STATIC("/EventType"),
    UA_STRING_STATIC("/SourceNode"),
    UA_STRING_STATIC("/SourceName"),
    UA_STRING_STATIC("/Time"),
    UA_STRING_STATIC("/ReceiveTime"),
    UA_STRING_STATIC("/Message"),
    UA_STRING_STATIC("/Severity")
};

void
UA_FilterEvalContext_init(UA_FilterEvalContext *ctx) {
    memset(ctx, 0, sizeof(UA_FilterEvalContext));
}

void
UA_FilterEvalContext_reset(UA_FilterEvalContext *ctx) {
    UA_KeyValueMap_clear(&ctx->fieldCache);

    /* The data of the EventId is either in the eventIdBuf or in the fieldCache
     * or in the ed. So no memory to free here. Keep the EventId if it points to
     * the random-id bytes for the next evaluation. */
    if(ctx->eventId.data != ctx->eventIdBuf)
        UA_ByteString_init(&ctx->eventId);
}

UA_StatusCode
cacheEventId(UA_FilterEvalContext *ctx) {
    /* Already cached */
    if(ctx->eventId.length > 0)
        return UA_STATUSCODE_GOOD;

    /* Resolve from the Key-Value Map - This does not make a deep copy */
    const UA_EventDescription *ed = &ctx->ed;
    if(ed && ed->eventFields) {
        const UA_Variant *found =
            UA_KeyValueMap_get(ed->eventFields, UA_QUALIFIEDNAME(0, "/EventId"));
        if(found) {
            if(!UA_Variant_hasScalarType(found, &UA_TYPES[UA_TYPES_BYTESTRING]))
                return UA_STATUSCODE_BADTYPEMISMATCH;
            ctx->eventId = *(UA_ByteString*)found->data; /* shallow copy */
            return UA_STATUSCODE_GOOD;
        }
    }

    /* Resolve from the EventInstance. But only if a useful identifier
     * (ByteString, length > 0) has been set in the information model. */
    static UA_QualifiedName eventIdName = {0, UA_STRING_STATIC("EventId")};
    UA_SimpleAttributeOperand sao;
    UA_SimpleAttributeOperand_init(&sao);
    sao.attributeId = UA_ATTRIBUTEID_VALUE;
    sao.browsePath = &eventIdName;
    sao.browsePathSize = 1;

    UA_Variant val;
    UA_Variant_init(&val);
    UA_StatusCode res = readSAOfromEventInstance(ctx, &sao, &val);
    if(res == UA_STATUSCODE_GOOD) {
        UA_Boolean isIdString = UA_Variant_hasScalarType(&val, &UA_TYPES[UA_TYPES_BYTESTRING]);
        UA_assert(!isIdString || val.data != NULL); /* pacify a clang-analyzer warning */
        if(isIdString && ((UA_ByteString*)val.data)->length > 0) {
            res = UA_KeyValueMap_set(&ctx->fieldCache,
                                     UA_QUALIFIEDNAME(0, "/EventId"), &val);
            UA_Variant_clear(&val);
            if(res != UA_STATUSCODE_GOOD)
                return res;
            const UA_Variant *cached =
                UA_KeyValueMap_get(&ctx->fieldCache,
                                   UA_QUALIFIEDNAME(0, "/EventId"));
            ctx->eventId = *(UA_ByteString*)cached->data; /* shallow copy */
            return UA_STATUSCODE_GOOD;
        }

        /* Continue to create a random ByteString */
        UA_Variant_clear(&val);
    }

    /* If nothing is explicitly defined, create a random 16-byte ByteString */
    UA_UInt32 *ids = (UA_UInt32*)ctx->eventIdBuf;
    ids[0] = UA_UInt32_random();
    ids[1] = UA_UInt32_random();
    ids[2] = UA_UInt32_random();
    ids[3] = UA_UInt32_random();
    ctx->eventId = (UA_ByteString){16, ctx->eventIdBuf};
    return UA_STATUSCODE_GOOD;
}

/* The SAO string is not always in the "normal form" that is the output of
 * UA_SimpleAttributeOperand_print. For example, we can have an implicit #Value
 * postfix or the path-browsenames prefixed with 0: for ns0. Also, for the
 * map-keys as QualifiedNames, we use the key-nsindex as the default nsindex for
 * the path.
 *
 * In order to compare with a non-normal-form SAO string, we decode and compare
 * the SAO directly. This is slower, so we try the normal form string-compare
 * first. */
static UA_Variant *
getEventFieldNonNormalForm(UA_Server *server, const UA_KeyValueMap *eventFields,
                           const UA_SimpleAttributeOperand *sao) {
    if(!eventFields)
        return NULL;

    UA_SimpleAttributeOperand keySao;
    for(size_t i = 0; i < eventFields->mapSize; i++) {
        UA_KeyValuePair *kvp = &eventFields->map[i];
        UA_StatusCode res =
            sao_parseWithDefaultNsIdx(&keySao, kvp->key.name,
                                      kvp->key.namespaceIndex);
        if(res != UA_STATUSCODE_GOOD)
            continue;
        UA_Boolean found = UA_SimpleAttributeOperand_equal(sao, &keySao);
        UA_SimpleAttributeOperand_clear(&keySao);
        if(found)
            return &kvp->value;
    }
    return NULL;
}

/* Can return an in-situ value. Check for UA_VARIANT_DATA_NODELETE. */
UA_StatusCode
resolveSAO(UA_FilterEvalContext *ctx, const UA_SimpleAttributeOperand *sao,
           UA_Variant *out) {
    UA_StatusCode res = UA_STATUSCODE_GOOD;
    const UA_EventDescription *ed = &ctx->ed;
    const UA_Variant *found;
    UA_Byte pathBuf[512];
    UA_QualifiedName pathString = {0, {512, pathBuf}};
    static UA_NodeId baseEventTypeId = {0, UA_NODEIDTYPE_NUMERIC, {UA_NS0ID_BASEEVENTTYPE}};

    /* Copy into a mutable SAO */
    UA_SimpleAttributeOperand tmp_sao = *sao;

    /* Do the lookup without the index-range.
     * The index-range from the original sao is used later. */
    tmp_sao.indexRange = UA_STRING_NULL;

    /* Initially use the BaseEventTypeId if not defined explicitly.
     * If this does not resolve, we try again with i=0 (goto search again). */
    if(UA_NodeId_isNull(&tmp_sao.typeDefinitionId))
        tmp_sao.typeDefinitionId = baseEventTypeId;

 search_again:
    res = UA_SimpleAttributeOperand_print(&tmp_sao, &pathString.name);
    if(res != UA_STATUSCODE_GOOD)
        return res;

    /* Special Case: EventId (generated only once per Event, ignores the IndexRange) */
    if(UA_String_equal(&pathString.name, &mandatoryEventProperties[0])) {
        res = cacheEventId(ctx);
        if(res != UA_STATUSCODE_GOOD)
            return res;
        UA_Variant_setScalar(out, &ctx->eventId, &UA_TYPES[UA_TYPES_BYTESTRING]);
        out->storageType = UA_VARIANT_DATA_NODELETE;
        return UA_STATUSCODE_GOOD;
    }

    /* Source 1: Use the SAO-string to look up from the user-defined key-value
     * map (and from the cache) */
    found = UA_KeyValueMap_get(ed->eventFields, pathString);
    if(!found)
        found = UA_KeyValueMap_get(&ctx->fieldCache, pathString);
    if(!found)
        found = getEventFieldNonNormalForm(ctx->server, ed->eventFields, &tmp_sao);
    if(found) {
        if(sao->indexRange.length == 0) {
            *out = *found;
            out->storageType = UA_VARIANT_DATA_NODELETE;
        } else {
            UA_NumericRange range;
            res = UA_NumericRange_parse(&range, sao->indexRange);
            if(res != UA_STATUSCODE_GOOD)
               return res;
            res = UA_Variant_copyRange(found, out, range);
            UA_free(range.dimensions);
        }
        return res;
    }

    /* Not found. Print the SAO again with BaseEventTypeId as the
     * TypeDefinitionId and try again. This removes any TypeDefinitionId prefix
     * from the printed SAO-string. */
    if(!UA_NodeId_equal(&tmp_sao.typeDefinitionId, &baseEventTypeId)) {
        tmp_sao.typeDefinitionId = baseEventTypeId;
        goto search_again;
    }

    /* Source 2: Read from the information model */
    res = readSAOfromEventInstance(ctx, sao, out);
    if(res == UA_STATUSCODE_GOOD)
        return UA_STATUSCODE_GOOD;

    /* Source 3: Use a default for the mandatory fields of the BaseEventType.
     * Here we ignore the IndexRange. */
    UA_String_init(&tmp_sao.indexRange); /* No index range allowed */
    if(UA_String_equal(&pathString.name, &mandatoryEventProperties[1])) {
        /* EventType */
        return UA_Variant_setScalarCopy(out, &ed->eventType, &UA_TYPES[UA_TYPES_NODEID]);
    } else if(UA_String_equal(&pathString.name, &mandatoryEventProperties[2])) {
        /* SourceNode */
        return UA_Variant_setScalarCopy(out, &ed->sourceNode, &UA_TYPES[UA_TYPES_NODEID]);
    } else if(UA_String_equal(&pathString.name, &mandatoryEventProperties[3])) {
        /* SourceName. Read the DisplayName from the information model. This
         * uses the locale of the session. */
        UA_ReadValueId rvi;
        UA_ReadValueId_init(&rvi);
        rvi.nodeId = ed->sourceNode;
        rvi.attributeId = UA_ATTRIBUTEID_DISPLAYNAME;
        UA_DataValue dv = readWithSession(ctx->server, ctx->session, &rvi,
                                          UA_TIMESTAMPSTORETURN_NEITHER);
        if(dv.status != UA_STATUSCODE_GOOD) {
            res = dv.status;
            UA_DataValue_clear(&dv);
            return res;
        }
        if(dv.value.type != &UA_TYPES[UA_TYPES_LOCALIZEDTEXT]) {
            UA_DataValue_clear(&dv);
            return UA_STATUSCODE_BADINTERNALERROR;
        }
        UA_LocalizedText *displayName = (UA_LocalizedText*)dv.value.data;
        res = UA_Variant_setScalarCopy(out, &displayName->text, &UA_TYPES[UA_TYPES_STRING]);
        UA_DataValue_clear(&dv);
        return res;
    } else if(UA_String_equal(&pathString.name, &mandatoryEventProperties[4]) ||
              UA_String_equal(&pathString.name, &mandatoryEventProperties[5])) {
        /* Time / ReceiveTime */
        UA_EventLoop *el = ctx->server->config.eventLoop;
        UA_DateTime rcvTime = el->dateTime_now(el);
        return UA_Variant_setScalarCopy(out, &rcvTime, &UA_TYPES[UA_TYPES_DATETIME]);
    } else if(UA_String_equal(&pathString.name, &mandatoryEventProperties[6])) {
        /* Message */
        return UA_Variant_setScalarCopy(out, &ed->message, &UA_TYPES[UA_TYPES_LOCALIZEDTEXT]);
    } else if(UA_String_equal(&pathString.name, &mandatoryEventProperties[7])) {
        /* Severity */
        return UA_Variant_setScalarCopy(out, &ed->severity, &UA_TYPES[UA_TYPES_UINT16]);
    }

    /* Not found, return an empty Variant */
    return UA_STATUSCODE_GOOD;
}

/***************************/
/* Where-Clause Evaluation */
/***************************/

/* Ternary Logic
 * -------------
 * Similar to SQL, OPC UA Queries use the K3 - Strong Kleene Logic that
 * considers ternary values true/false/null (unknown). Every operator result
 * (Variant) can be cast to a ternary truth value. See the v2t method below.
 * We cast all operands to a ternary truth value before a logical operator is
 * applied. */

typedef enum {
    UA_TERNARY_FALSE = -1,
    UA_TERNARY_NULL = 0,
    UA_TERNARY_TRUE = 1
} UA_Ternary;

static UA_Ternary
UA_Ternary_and(UA_Ternary first, UA_Ternary second) {
    if(first == UA_TERNARY_FALSE || second == UA_TERNARY_FALSE)
        return UA_TERNARY_FALSE;
    if(first == UA_TERNARY_NULL || second == UA_TERNARY_NULL)
        return UA_TERNARY_NULL;
    return UA_TERNARY_TRUE;
}

static UA_Ternary
UA_Ternary_or(UA_Ternary first, UA_Ternary second) {
    if(first == UA_TERNARY_TRUE || second == UA_TERNARY_TRUE)
        return UA_TERNARY_TRUE;
    if(first == UA_TERNARY_NULL || second == UA_TERNARY_NULL)
        return UA_TERNARY_NULL;
    return UA_TERNARY_FALSE;
}

/* Part 4: The NOT operator always evaluates to NULL if applied to a NULL
 * operand. We simply swap true/false. */
static UA_Ternary
UA_Ternary_not(UA_Ternary v) {
    return (UA_Ternary)((int)v * -1);
}

static const UA_Boolean bFalse = false;
static const UA_Boolean bTrue  = true;

static UA_Variant t2v(UA_Ternary t) {
    UA_Variant v;
    UA_Variant_init(&v);
    switch(t) {
    case UA_TERNARY_FALSE:
        UA_Variant_setScalar(&v, (void*)(uintptr_t)&bFalse, &UA_TYPES[UA_TYPES_BOOLEAN]);
        break;
    case UA_TERNARY_TRUE:
        UA_Variant_setScalar(&v, (void*)(uintptr_t)&bTrue, &UA_TYPES[UA_TYPES_BOOLEAN]);
        break;
    default:
        return v;
    }
    v.storageType = UA_VARIANT_DATA_NODELETE;
    return v;
}

/* Forward declarations */
static void
castNumerical(const UA_Variant *in, const UA_DataType *type, UA_Variant *out);
static UA_StatusCode
castImplicitFromString(const UA_Variant *in, const UA_DataType *outType, UA_Variant *out);

/* For translating to a ternary truth-value we apply the rules for the "explicit
 * casting" to a Boolean. Because implicit casting from numerical to Boolean is
 * not possible as per Table 125 in the standard. */
static UA_Ternary v2t(const UA_Variant *v) {
    /* Empty -> NULL, Arrays are undefined in the standard */
    if(UA_Variant_isEmpty(v) || !UA_Variant_isScalar(v))
        return UA_TERNARY_NULL;

    /* Try to cast to Boolean. The variant remains empty if this fails.
     * Otherwise the bTrue/bFalse singletons are set. */
    UA_Variant vBool;
    UA_Variant_init(&vBool);
    if(v->type != &UA_TYPES[UA_TYPES_STRING])
        castNumerical(v, &UA_TYPES[UA_TYPES_BOOLEAN], &vBool);
    else
        castImplicitFromString(v, &UA_TYPES[UA_TYPES_BOOLEAN], &vBool);

    if(!vBool.type)
        return UA_TERNARY_NULL;
    return (vBool.data == &bTrue) ? UA_TERNARY_TRUE : UA_TERNARY_FALSE;
}

/* Type Casting Rules
 * ------------------
 * For comparison operations values from different datatypes can be implicitly
 * or explicitly cast. The standard defines rules to selected the target type
 * for casting and when implicit casts are possible. */

/* Defined in Part 4 Table 123 "Data Precedence Rules". Implicit casting is
 * always to the type of lower precedence value. */
static UA_Byte typePrecedence[UA_DATATYPEKINDS] = {
    12, 10, 11, 8, 9, 5, 6, 3, 4, 2, 1, 14, 255, 13, 255, 255, 16,
    15, 7, 18, 17, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255
};

/* Type conversion table from the standard.
 * 0 -> Same Type, 1 -> Implicit Cast, 2 -> Only explicit Cast, -1 -> cast invalid */
static UA_SByte convertLookup[21][21] = {
    { 0, 1,-1,-1, 1,-1, 1,-1, 1, 1, 1,-1, 1,-1, 2,-1,-1, 1, 1, 1,-1},
    { 2, 0,-1,-1, 1,-1, 1,-1, 1, 1, 1,-1, 1,-1, 2,-1,-1, 1, 1, 1,-1},
    {-1,-1, 0,-1,-1,-1,-1, 2,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1},
    {-1,-1,-1, 0,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1, 2,-1,-1,-1,-1,-1,-1},
    { 2, 2,-1,-1, 0,-1, 2,-1, 2, 2, 2,-1, 2,-1, 2,-1,-1, 2, 2, 2,-1},
    {-1,-1,-1,-1,-1, 0,-1,-1,-1,-1,-1, 2,-1,-1, 1,-1,-1,-1,-1,-1,-1},
    { 2, 2,-1,-1, 1,-1, 0,-1, 2, 2, 2,-1, 2,-1, 2,-1,-1, 2, 2, 2,-1},
    {-1,-1, 2,-1,-1,-1,-1, 0,-1,-1,-1,-1,-1,-1, 2,-1,-1,-1,-1,-1,-1},
    { 2, 2,-1,-1, 1,-1, 1,-1, 0, 1, 1,-1, 2,-1, 2,-1,-1, 2, 1, 1,-1},
    { 2, 2,-1,-1, 1,-1, 1,-1, 2, 0, 1,-1, 2, 2, 2,-1,-1, 2, 2, 1,-1},
    { 2, 2,-1,-1, 1,-1, 1,-1, 2, 2, 0,-1, 2, 2, 2,-1,-1, 2, 2, 2,-1},
    {-1,-1,-1,-1,-1, 1,-1,-1,-1,-1,-1, 0,-1,-1, 1,-1,-1,-1,-1,-1,-1},
    { 2, 2,-1,-1, 1,-1, 1,-1, 1, 1, 1,-1, 0,-1, 2,-1,-1, 1, 1, 1,-1},
    {-1,-1,-1,-1,-1,-1,-1,-1,-1, 1, 1,-1,-1, 0,-1,-1,-1, 2, 1, 1,-1},
    { 1, 1,-1, 2, 1, 2, 1, 1, 1, 1, 1, 2, 1,-1, 0, 2, 2, 1, 1, 1,-1},
    {-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1, 1, 0,-1,-1,-1,-1,-1},
    {-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1, 1, 1, 0,-1,-1,-1,-1},
    { 2, 2,-1,-1, 1,-1, 1,-1, 1, 1, 1,-1, 2, 1, 2,-1,-1, 0, 1, 1,-1},
    { 2, 2,-1,-1, 1,-1, 1,-1, 2, 1, 1,-1, 2, 2, 2,-1,-1, 2, 0, 1,-1},
    { 2, 2,-1,-1, 1,-1, 1,-1, 2, 2, 1,-1, 2, 2, 2,-1,-1, 2, 2, 0,-1},
    {-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1, 0}
};

/* This array maps the index of the DataType-Kind to the index of the type
 * conversion matrix (255 -> not contained in the matrix) */
static UA_Byte convertLookupIndex[UA_DATATYPEKINDS] = {
    0,  12,  1,  8, 17,  9, 18, 10, 19,  6, 4,  14,  3,  7,  2,
    20, 11,  5, 13, 16, 15,255,255,255,255,255,255,255,255,255,255
};

/* Returns the target type for implicit cassting or NULL if no implicit casting
 * is possible */
static const UA_DataType *
implicitCastTargetType(const UA_DataType *t1, const UA_DataType *t2) {
    if(!t1 || !t2)
        return NULL;
    if(t1 == t2)
        return t1;

    /* Get the type precedence. Return if no implicit casting is possible. */
    UA_Byte p1 = typePrecedence[t1->typeKind];
    UA_Byte p2 = typePrecedence[t2->typeKind];
    if(p1 == UA_BYTE_MAX || p2 == UA_BYTE_MAX)
        return NULL;

    /* Which is the target type based on the precedence rules? */
    const UA_DataType *targetType = (p1 < p2) ? t1 : t2;
    const UA_DataType *sourceType = (p1 < p2) ? t2 : t1;

    /* Lookup the casting rule */
    UA_Byte sourceIndex = convertLookupIndex[sourceType->typeKind];
    UA_Byte targetIndex = convertLookupIndex[targetType->typeKind];
    if(sourceIndex == UA_BYTE_MAX || targetIndex == UA_BYTE_MAX)
        return NULL;
    UA_SByte castingRule = convertLookup[sourceIndex][targetIndex];

    /* Is implicit casting allowed? */
    if(castingRule != 0 && castingRule != 1)
        return NULL;
    return targetType;
}

/* Cast Numerical
 * --------------
 * To reduce the number of cases we first "normalize" to either of
 * Int64/UInt64/Double. Then cast from there to the target type. This works for
 * all numericals (not only the implicit conversion).
 *
 * Numerical conversion rules from the standard:
 *
 * - If the conversion fails the result is a null value.
 * - Floating point values are rounded by adding 0.5 and truncating when they
 *   are converted to integer values.
 * - Converting a value that is outside the range of the target type causes a
 *   conversion error. */

#define UA_CAST_SIGNED(t, T)                                           \
    if(i < (UA_Int64)T##_MIN || i > (UA_Int64)T##_MAX) {               \
        UA_free(data);                                                 \
        return;                                                        \
    }                                                                  \
    *(t*)data = (t)i;                                                  \
    do { } while(0)

#define UA_CAST_UNSIGNED(t, T)                                         \
    if(u > T##_MAX) {                                                  \
        UA_free(data);                                                 \
        return;                                                        \
    }                                                                  \
    *(t*)data = (t)u;                                                  \
    do { } while(0)

#define UA_CAST_FLOAT(t, T)                                            \
    if(f + 0.5 < (UA_Double)T##_MIN || f + 0.5 > (UA_Double)T##_MAX) { \
        UA_free(data);                                                 \
        return;                                                        \
    }                                                                  \
    *(t*)data = (t)(f + 0.5);                                          \
    do { } while(0)

/* We can cast between any numerical type. So this can be reused for explicit casting. */
static void
castNumerical(const UA_Variant *in, const UA_DataType *type, UA_Variant *out) {
    UA_assert(UA_Variant_isScalar(in));
    UA_assert(UA_Variant_isEmpty(out));

    UA_Int64  i = 0;
    UA_UInt64 u = 0;
    UA_Double f = 0.0;

    const UA_DataTypeKind ink = (UA_DataTypeKind)in->type->typeKind;
    switch(ink) {
    case UA_DATATYPEKIND_SBYTE:  i = *(UA_SByte*)in->data; break;
    case UA_DATATYPEKIND_INT16:  i = *(UA_Int16*)in->data; break;
    case UA_DATATYPEKIND_INT32:  i = *(UA_Int32*)in->data; break;
    case UA_DATATYPEKIND_INT64:  i = *(UA_Int64*)in->data; break;
    case UA_DATATYPEKIND_BYTE: /* or */
    case UA_DATATYPEKIND_BOOLEAN: u = *(UA_Byte*)in->data; break;
    case UA_DATATYPEKIND_UINT16:  u = *(UA_UInt16*)in->data; break;
    case UA_DATATYPEKIND_UINT32: /* or */
    case UA_DATATYPEKIND_STATUSCODE: u = *(UA_UInt32*)in->data; break;
    case UA_DATATYPEKIND_UINT64: u = *(UA_UInt64*)in->data; break;
    case UA_DATATYPEKIND_FLOAT:  f = *(UA_Float*)in->data; break;
    case UA_DATATYPEKIND_DOUBLE: f = *(UA_Double*)in->data; break;
    default: return;
    }

    /* Boolean is true if the numerical input is nonzero */
    if(type == &UA_TYPES[UA_TYPES_BOOLEAN]) {
        const UA_Boolean *b = &bFalse;
        if(i != 0 || u != 0 || f != 0.0)
            b = &bTrue;
        UA_Variant_setScalar(out, (void*)(uintptr_t)b, type);
        out->storageType = UA_VARIANT_DATA_NODELETE;
        return;
    }

    /* Allocate the output data. Return NULL value if malloc fails. */
    void *data = UA_new(type);
    if(!data)
        return;

    if(ink == UA_DATATYPEKIND_SBYTE || ink == UA_DATATYPEKIND_INT16 ||
       ink == UA_DATATYPEKIND_INT32 || ink == UA_DATATYPEKIND_INT64) {
        /* Cast from signed */
        switch(type->typeKind) {
        case UA_DATATYPEKIND_SBYTE:  UA_CAST_SIGNED(UA_SByte, UA_SBYTE); break;
        case UA_DATATYPEKIND_INT16:  UA_CAST_SIGNED(UA_Int16, UA_INT16); break;
        case UA_DATATYPEKIND_INT32:  UA_CAST_SIGNED(UA_Int32, UA_INT32); break;
        case UA_DATATYPEKIND_INT64:  *(UA_Int64*)data = i; break;
        case UA_DATATYPEKIND_BYTE:   UA_CAST_SIGNED(UA_Byte, UA_BYTE); break;
        case UA_DATATYPEKIND_UINT16: UA_CAST_SIGNED(UA_UInt16, UA_UINT16); break;
        case UA_DATATYPEKIND_UINT32: UA_CAST_SIGNED(UA_UInt32, UA_UINT32); break;
        case UA_DATATYPEKIND_UINT64: UA_CAST_SIGNED(UA_UInt64, UA_UINT64); break;
        case UA_DATATYPEKIND_FLOAT:  *(UA_Float*)data = (UA_Float)i; break;
        case UA_DATATYPEKIND_DOUBLE: *(UA_Double*)data = (UA_Double)i; break;
        default:
            UA_free(data);
            return;
        }
    } else if(ink == UA_DATATYPEKIND_BOOLEAN || ink == UA_DATATYPEKIND_STATUSCODE ||
              ink == UA_DATATYPEKIND_BYTE || ink == UA_DATATYPEKIND_UINT16 ||
              ink == UA_DATATYPEKIND_UINT32 || ink == UA_DATATYPEKIND_UINT64) {
        /* Cast from unsigned */
        switch(type->typeKind) {
        case UA_DATATYPEKIND_SBYTE:  UA_CAST_UNSIGNED(UA_SByte, UA_SBYTE); break;
        case UA_DATATYPEKIND_INT16:  UA_CAST_UNSIGNED(UA_Int16, UA_INT16); break;
        case UA_DATATYPEKIND_INT32:  UA_CAST_UNSIGNED(UA_Int32, UA_INT32); break;
        case UA_DATATYPEKIND_INT64:  UA_CAST_UNSIGNED(UA_Int64, UA_INT64); break;
        case UA_DATATYPEKIND_BYTE:   UA_CAST_UNSIGNED(UA_Byte, UA_BYTE); break;
        case UA_DATATYPEKIND_UINT16: UA_CAST_UNSIGNED(UA_UInt16, UA_UINT16); break;
        case UA_DATATYPEKIND_UINT32: UA_CAST_UNSIGNED(UA_UInt32, UA_UINT32); break;
        case UA_DATATYPEKIND_UINT64: *(UA_UInt64*)data = u; break;
        case UA_DATATYPEKIND_FLOAT:  *(UA_Float*)data = (UA_Float)u; break;
        case UA_DATATYPEKIND_DOUBLE: *(UA_Double*)data = (UA_Double)u; break;
        default:
            UA_free(data);
            return;
        }
    } else {
        /* Cast from float */
        if(f != f) {
            /* NaN cannot be cast */
            UA_free(data);
            return;
        }
        switch(type->typeKind) {
        case UA_DATATYPEKIND_SBYTE:  UA_CAST_FLOAT(UA_SByte, UA_SBYTE); break;
        case UA_DATATYPEKIND_INT16:  UA_CAST_FLOAT(UA_Int16, UA_INT16); break;
        case UA_DATATYPEKIND_INT32:  UA_CAST_FLOAT(UA_Int32, UA_INT32); break;
        case UA_DATATYPEKIND_INT64:  UA_CAST_FLOAT(UA_Int64, UA_INT64); break;
        case UA_DATATYPEKIND_BYTE:   UA_CAST_FLOAT(UA_Byte, UA_BYTE); break;
        case UA_DATATYPEKIND_UINT16: UA_CAST_FLOAT(UA_UInt16, UA_UINT16); break;
        case UA_DATATYPEKIND_UINT32: UA_CAST_FLOAT(UA_UInt32, UA_UINT32); break;
        case UA_DATATYPEKIND_UINT64: UA_CAST_FLOAT(UA_UInt64, UA_UINT64); break;
        case UA_DATATYPEKIND_FLOAT:  *(UA_Float*)data = (UA_Float)f; break;
        case UA_DATATYPEKIND_DOUBLE: *(UA_Double*)data = (UA_Double)f; break;
        default:
            UA_free(data);
            return;
        }
    }

    UA_Variant_setScalar(out, data, type);
}

/* Implicit Casting
 * ---------------- */

static UA_INLINE UA_Byte uppercase(UA_Byte in) { return in & (UA_Byte)~32; }

static UA_StatusCode
castImplicitFromString(const UA_Variant *in, const UA_DataType *outType, UA_Variant *out) {
    UA_StatusCode res = UA_STATUSCODE_GOOD;

    if(outType == &UA_TYPES[UA_TYPES_BOOLEAN]) {
        /* String -> Boolean
         *
         * Part 4 says: String values containing "true", "false", "1" or "0"
         * can be converted to Boolean values. Other string values cause a
         * conversion error. In this case Strings are case-insensitive. */
        const UA_Boolean *b;
        const UA_String *inStr = (const UA_String*)in->data;
        if(inStr->length == 1 && inStr->data[0] == '0') {
            b = &bFalse;
        } else if(inStr->length == 1 && inStr->data[0] == '1') {
            b = &bTrue;
        } else if(inStr->length == 4 &&
                  uppercase(inStr->data[0])== 'T' && uppercase(inStr->data[1])== 'R' &&
                  uppercase(inStr->data[2])== 'U' && uppercase(inStr->data[3])== 'E') {
            b = &bTrue;
        } else if(inStr->length == 5              && uppercase(inStr->data[0])== 'F' &&
                  uppercase(inStr->data[1])== 'A' && uppercase(inStr->data[2])== 'L' &&
                  uppercase(inStr->data[3])== 'S' && uppercase(inStr->data[4])== 'E') {
            b = &bFalse;
        } else {
            return UA_STATUSCODE_BADTYPEMISMATCH;
        }
        UA_Variant_setScalar(out, (void*)(uintptr_t)b, outType);
        out->storageType = UA_VARIANT_DATA_NODELETE;
        return UA_STATUSCODE_GOOD;
    } else if(outType == &UA_TYPES[UA_TYPES_GUID]) {
        /* String -> Guid */
        UA_Guid guid;
        res = UA_Guid_parse(&guid, *(UA_String*)in->data);
        if(res != UA_STATUSCODE_GOOD)
            return res;
        return UA_Variant_setScalarCopy(out, &guid, outType);
    }

#ifdef UA_ENABLE_JSON_ENCODING
    /* String -> Numerical, uses the JSON decoding */
    else if(UA_DataType_isNumeric(outType)) {
        void *outData = UA_new(outType);
        if(!outData)
            return UA_STATUSCODE_BADOUTOFMEMORY;
        res = UA_decodeJson((const UA_ByteString*)in->data, outData, outType, NULL);
        if(res != UA_STATUSCODE_GOOD) {
            UA_free(outData);
            return res;
        }
        UA_Variant_setScalar(out, outData, outType);
        return UA_STATUSCODE_GOOD;
    }
#endif

    /* No implicit casting possible */
    return UA_STATUSCODE_BADTYPEMISMATCH;
}

static UA_StatusCode
castImplicit(const UA_Variant *in, const UA_DataType *outType, UA_Variant *out) {
    /* Of the input is empty, casting results in a NULL value */
    if(UA_Variant_isEmpty(in))
        return UA_STATUSCODE_GOOD;

    /* TODO: We only support scalar values for now */
    if(!UA_Variant_isScalar(in))
        return UA_STATUSCODE_BADFILTEROPERATORUNSUPPORTED;

    /* No casting necessary */
    if(in->type == outType) {
        *out = *in;
        out->storageType = UA_VARIANT_DATA_NODELETE;
        return UA_STATUSCODE_GOOD;
    }

    UA_StatusCode res = UA_STATUSCODE_GOOD;
    switch(in->type->typeKind) {
    case UA_DATATYPEKIND_EXPANDEDNODEID: {
        /* ExpandedNodeId -> String */
        if(outType != &UA_TYPES[UA_TYPES_STRING])
            break;
        UA_String *outStr = UA_String_new();
        if(!outStr)
            return UA_STATUSCODE_BADOUTOFMEMORY;
        res = UA_ExpandedNodeId_print((const UA_ExpandedNodeId*)in->data, outStr);
        if(res != UA_STATUSCODE_GOOD) {
            UA_free(outStr);
            break;
        }
        UA_Variant_setScalar(out, outStr, outType);
        break;
    }

    case UA_DATATYPEKIND_NODEID: {
        if(outType == &UA_TYPES[UA_TYPES_STRING]) {
            /* NodeId -> String */
            UA_String *outStr = UA_String_new();
            if(!outStr)
                return UA_STATUSCODE_BADOUTOFMEMORY;
            res = UA_NodeId_print((const UA_NodeId*)in->data, outStr);
            if(res != UA_STATUSCODE_GOOD) {
                UA_free(outStr);
                break;
            }
            UA_Variant_setScalar(out, outStr, outType);
        } else if(outType == &UA_TYPES[UA_TYPES_EXPANDEDNODEID]) {
            /* NodeId -> ExpandedNodeId */
            UA_ExpandedNodeId *eid = UA_ExpandedNodeId_new();
            if(!eid)
                return UA_STATUSCODE_BADOUTOFMEMORY;
            res = UA_NodeId_copy((const UA_NodeId*)in->data, &eid->nodeId);
            if(res != UA_STATUSCODE_GOOD) {
                UA_free(eid);
                break;
            }
            UA_Variant_setScalar(out, eid, outType);
        }
        break;
    }

    case UA_DATATYPEKIND_STRING:
        res = castImplicitFromString(in, outType, out);
        break;

    case UA_DATATYPEKIND_LOCALIZEDTEXT: {
        if(outType != &UA_TYPES[UA_TYPES_STRING])
            break;
        /* LocalizedText -> String */
        UA_LocalizedText *inLT = (UA_LocalizedText*)in->data;
        res = UA_Variant_setScalarCopy(out, &inLT->text, outType);
        break;
    }

    case UA_DATATYPEKIND_QUALIFIEDNAME: {
        UA_QualifiedName *inQN = (UA_QualifiedName*)in->data;
        if(outType == &UA_TYPES[UA_TYPES_STRING]) {
            /* QualifiedName -> String */
            res = UA_Variant_setScalarCopy(out, &inQN->name, outType);
        } else if(outType == &UA_TYPES[UA_TYPES_LOCALIZEDTEXT]) {
            /* QualifiedName -> LocalizedText */
            UA_LocalizedText lt;
            lt.text = inQN->name;
            lt.locale = UA_STRING_NULL;
            res = UA_Variant_setScalarCopy(out, &lt, outType);
        }
        break;
    }

    default:
        /* Implicit casting from a numerical value to Boolean is not possible.
         * Explicit casting is possible and evaluates to true if the value is
         * non-null. */
        if(outType == &UA_TYPES[UA_TYPES_BOOLEAN])
            return res;

        /* Try casting between numericals (also works for Boolean and StatusCode
         * input). The conversion can fail if the limits of the output type are
         * exceeded and then results in a NULL value. */
        castNumerical(in, outType, out);
    }

    return res;
}

/* Filter Evaluation
 * ----------------- */

/* Initialize every pushed operand so cleanup is safe even if resolution fails. */
static UA_Variant *
pushOperand(UA_FilterEvalContext *ctx) {
    UA_Variant *v = &ctx->operandStack[ctx->top++];
    UA_Variant_init(v);
    return v;
}

static UA_StatusCode
resolveOperand(UA_FilterEvalContext *ctx, UA_ExtensionObject *op, UA_Variant *out) {
    if(op->encoding != UA_EXTENSIONOBJECT_DECODED &&
       op->encoding != UA_EXTENSIONOBJECT_DECODED_NODELETE)
        return UA_STATUSCODE_BADFILTEROPERATORUNSUPPORTED;

    /* Result of an operator that was evaluated prior */
    if(op->content.decoded.type == &UA_TYPES[UA_TYPES_ELEMENTOPERAND]) {
        UA_ElementOperand *eo = (UA_ElementOperand*)op->content.decoded.data;
        *out = ctx->operatorResults[eo->index];
        out->storageType = UA_VARIANT_DATA_NODELETE;
        return UA_STATUSCODE_GOOD;
    }

    /* Literal value */
    if(op->content.decoded.type == &UA_TYPES[UA_TYPES_LITERALOPERAND]) {
        UA_LiteralOperand *lo = (UA_LiteralOperand*)op->content.decoded.data;
        *out = lo->value;
        out->storageType = UA_VARIANT_DATA_NODELETE;
        return UA_STATUSCODE_GOOD;
    }

    /* SimpleAttributeOperand with a BrowsePath */
    if(op->content.decoded.type == &UA_TYPES[UA_TYPES_SIMPLEATTRIBUTEOPERAND]) {
        UA_SimpleAttributeOperand *sao =
            (UA_SimpleAttributeOperand*)op->content.decoded.data;
        return resolveSAO(ctx, sao, out);
    }

    return UA_STATUSCODE_BADFILTEROPERATORUNSUPPORTED;
}

static UA_StatusCode
ofTypeOperator(UA_FilterEvalContext *ctx, size_t index) {
    const UA_ContentFilterElement *elm = &ctx->filter.whereClause.elements[index];
    UA_assert(elm->filterOperandsSize == 1);

    /* Get the operand. Must be a literal NodeId */
    UA_Variant *op0 = pushOperand(ctx);
    UA_StatusCode res = resolveOperand(ctx, &elm->filterOperands[0], op0);
    if(res != UA_STATUSCODE_GOOD || !UA_Variant_hasScalarType(op0, &UA_TYPES[UA_TYPES_NODEID]))
        return UA_STATUSCODE_BADFILTEROPERANDINVALID;
    const UA_NodeId *operandTypeId = (const UA_NodeId *)op0->data;

    /* Read the /EventType event field */
    static UA_QualifiedName eventTypeName = {0, UA_STRING_STATIC("EventType")};
    UA_SimpleAttributeOperand sao;
    UA_SimpleAttributeOperand_init(&sao);
    sao.attributeId = UA_ATTRIBUTEID_VALUE;
    sao.browsePath = &eventTypeName;
    sao.browsePathSize = 1;
    UA_Variant eventType;
    UA_Variant_init(&eventType);
    res = resolveSAO(ctx, &sao, &eventType);
    if(res != UA_STATUSCODE_GOOD)
        return res;
    if(!UA_Variant_hasScalarType(&eventType, &UA_TYPES[UA_TYPES_NODEID])) {
        UA_Variant_clear(&eventType);
        return UA_STATUSCODE_BADINTERNALERROR;
    }

    /* Is the /EventType a subtype of the requested type? */
    UA_Boolean ofType =
        isNodeInTree_singleRef(ctx->server, (UA_NodeId*)eventType.data, operandTypeId,
                               UA_REFERENCETYPEINDEX_HASSUBTYPE);
    ctx->operatorResults[index] = t2v(ofType ? UA_TERNARY_TRUE : UA_TERNARY_FALSE);
    UA_Variant_clear(&eventType);
    return UA_STATUSCODE_GOOD;
}

static UA_StatusCode
andOperator(UA_FilterEvalContext *ctx, size_t index) {
    const UA_ContentFilterElement *elm = &ctx->filter.whereClause.elements[index];
    UA_assert(elm->filterOperandsSize == 2);
    UA_Variant *op0 = pushOperand(ctx);
    UA_StatusCode res = resolveOperand(ctx, &elm->filterOperands[0], op0);
    UA_CHECK_STATUS(res, return res);
    UA_Variant *op1 = pushOperand(ctx);
    res = resolveOperand(ctx, &elm->filterOperands[1], op1);
    UA_CHECK_STATUS(res, return res);
    ctx->operatorResults[index] = t2v(UA_Ternary_and(v2t(op0), v2t(op1)));
    return UA_STATUSCODE_GOOD;
}

static UA_StatusCode
orOperator(UA_FilterEvalContext *ctx, size_t index) {
    const UA_ContentFilterElement *elm = &ctx->filter.whereClause.elements[index];
    UA_assert(elm->filterOperandsSize == 2);
    UA_Variant *op0 = pushOperand(ctx);
    UA_StatusCode res = resolveOperand(ctx, &elm->filterOperands[0], op0);
    UA_CHECK_STATUS(res, return res);
    UA_Variant *op1 = pushOperand(ctx);
    res = resolveOperand(ctx, &elm->filterOperands[1], op1);
    UA_CHECK_STATUS(res, return res);
    ctx->operatorResults[index] = t2v(UA_Ternary_or(v2t(op0), v2t(op1)));
    return UA_STATUSCODE_GOOD;
}

static UA_StatusCode
notOperator(UA_FilterEvalContext *ctx, size_t index) {
    const UA_ContentFilterElement *elm = &ctx->filter.whereClause.elements[index];
    UA_assert(elm->filterOperandsSize == 1);
    UA_Variant *op0 = pushOperand(ctx);
    UA_StatusCode res = resolveOperand(ctx, &elm->filterOperands[0], op0);
    UA_CHECK_STATUS(res, return res);
    ctx->operatorResults[index] = t2v(UA_Ternary_not(v2t(op0)));
    return UA_STATUSCODE_GOOD;
}

/* Resolves the operands and casts them implicitly to the same type. The result
 * is set at &ctx->operandStack[ctx->top] (for the initial value of top). */
static UA_StatusCode
castResolveOperands(UA_FilterEvalContext *ctx, size_t index, UA_Boolean setError) {
    /* Enough space on the operand stack left? */
    const UA_ContentFilterElement *elm = &ctx->filter.whereClause.elements[index];
    if(ctx->top + elm->filterOperandsSize > UA_EVENTFILTER_MAXOPERANDS)
        return UA_STATUSCODE_BADOUTOFMEMORY;

    /* Resolve all operands */
    UA_assert(ctx->top == 0); /* Assume the operand stack is empty */
    UA_StatusCode res = UA_STATUSCODE_GOOD;
    for(size_t i = 0; i < elm->filterOperandsSize; i++) {
        res = resolveOperand(ctx, &elm->filterOperands[i], pushOperand(ctx));
        UA_CHECK_STATUS(res, return res);
    }
    UA_assert(ctx->top > 0); /* Assume the operand stack is no longer empty */

    /* Get the datatype for casting */
    const UA_DataType *targetType = ctx->operandStack[0].type;
    for(size_t pos = 1; pos < ctx->top; pos++) {
        if(targetType)
            targetType = implicitCastTargetType(targetType, ctx->operandStack[pos].type);
        if(!targetType)
            return UA_STATUSCODE_BADFILTEROPERANDINVALID;
    }

    /* Cast the operands. Put the result in the same location on the operand stack. */
    for(size_t pos = 0; pos < ctx->top; pos++) {
        UA_Variant orig = ctx->operandStack[pos];
        UA_Variant_init(&ctx->operandStack[pos]);
        res = castImplicit(&orig, targetType, &ctx->operandStack[pos]);
        if(ctx->operandStack[pos].data == orig.data) {
            /* Reuse the storage type of the original data if the variant is
             * identical or only the type has changed */
            ctx->operandStack[pos].storageType = orig.storageType;
        } else {
            UA_Variant_clear(&orig); /* Fresh allocation of the cast variant. Clean up. */
        }
        if(res != UA_STATUSCODE_GOOD)
            return res;
    }

    return UA_STATUSCODE_GOOD;
}

static UA_StatusCode
compareOperator(UA_FilterEvalContext *ctx, size_t index, UA_FilterOperator op) {
    UA_assert(ctx->filter.whereClause.elements[index].filterOperandsSize == 2);

    /* Resolve and cast the operands. A failed casting results in FALSE. Note
     * that operands could cast to NULL. */
    UA_assert(ctx->top == 0); /* Assume the operand stack is empty */
    UA_StatusCode res = castResolveOperands(ctx, index, false);
    if(res != UA_STATUSCODE_GOOD || !ctx->operandStack[0].type ||
       ctx->operandStack[0].type != ctx->operandStack[1].type) {
        ctx->operatorResults[index] = t2v(UA_TERNARY_FALSE);
        return UA_STATUSCODE_GOOD;
    }
    UA_assert(ctx->top == 2); /* Assume the operand stack is no longer empty */

    /* The equals operator is always possible. For the other comparisons it has
     * to be an ordered type: Numerical, Boolean, StatusCode or DateTime. */
    const UA_DataType *type = ctx->operandStack[0].type;
    if(op != UA_FILTEROPERATOR_EQUALS && !UA_DataType_isNumeric(type) &&
       type->typeKind != UA_DATATYPEKIND_BOOLEAN &&
       type->typeKind != UA_DATATYPEKIND_STATUSCODE &&
       type->typeKind != UA_DATATYPEKIND_DATETIME)
        return UA_STATUSCODE_BADFILTEROPERANDINVALID;

    /* Compute the order */
    UA_Order eq = UA_order(ctx->operandStack[0].data, ctx->operandStack[1].data, type);
    UA_Ternary operatorResult = UA_TERNARY_FALSE;
    switch(op) {
    case UA_FILTEROPERATOR_EQUALS:
    default:
        if(eq == UA_ORDER_EQ)
            operatorResult = UA_TERNARY_TRUE;
        break;
    case UA_FILTEROPERATOR_GREATERTHAN:
        if(eq == UA_ORDER_MORE)
            operatorResult = UA_TERNARY_TRUE;
        break;
    case UA_FILTEROPERATOR_LESSTHAN:
        if(eq == UA_ORDER_LESS)
            operatorResult = UA_TERNARY_TRUE;
        break;
    case UA_FILTEROPERATOR_GREATERTHANOREQUAL:
        if(eq == UA_ORDER_MORE || eq == UA_ORDER_EQ)
            operatorResult = UA_TERNARY_TRUE;
        break;
    case UA_FILTEROPERATOR_LESSTHANOREQUAL:
        if(eq == UA_ORDER_LESS || eq == UA_ORDER_EQ)
            operatorResult = UA_TERNARY_TRUE;
        break;
    }

    /* Set result as a literal value */
    ctx->operatorResults[index] = t2v(operatorResult);
    return UA_STATUSCODE_GOOD;
}

static UA_StatusCode
equalsOperator(UA_FilterEvalContext *ctx, size_t index) {
    return compareOperator(ctx, index, UA_FILTEROPERATOR_EQUALS);
}

static UA_StatusCode
gtOperator(UA_FilterEvalContext *ctx, size_t index) {
    return compareOperator(ctx, index, UA_FILTEROPERATOR_GREATERTHAN);
}

static UA_StatusCode
ltOperator(UA_FilterEvalContext *ctx, size_t index) {
    return compareOperator(ctx, index, UA_FILTEROPERATOR_LESSTHAN);
}

static UA_StatusCode
gteOperator(UA_FilterEvalContext *ctx, size_t index) {
    return compareOperator(ctx, index, UA_FILTEROPERATOR_GREATERTHANOREQUAL);
}

static UA_StatusCode
lteOperator(UA_FilterEvalContext *ctx, size_t index) {
    return compareOperator(ctx, index, UA_FILTEROPERATOR_LESSTHANOREQUAL);
}

static UA_StatusCode
bitwiseOperator(UA_FilterEvalContext *ctx, size_t index, UA_FilterOperator op) {
    UA_assert(ctx->filter.whereClause.elements[index].filterOperandsSize == 2);

    /* Resolve and cast the operands. Note that operands could cast to NULL. */
    UA_assert(ctx->top == 0); /* Assume the operand stack is empty */
    UA_StatusCode res = castResolveOperands(ctx, index, true);
    UA_CHECK_STATUS(res, return res);
    UA_assert(ctx->top == 2); /* Assume we have two elements */

    /* Operands can cast to NULL */
    const UA_DataType *type = ctx->operandStack[0].type;
    if(!type || !UA_DataType_isNumeric(type) ||
       ctx->operandStack[0].type != ctx->operandStack[1].type)
        return UA_STATUSCODE_BADTYPEMISMATCH;

    /* Copy the casted literal to the result */
    res = UA_Variant_copy(&ctx->operandStack[0], &ctx->operatorResults[index]);
    UA_CHECK_STATUS(res, return res);

    /* Do the bitwise operation on the result data */
    UA_Byte *bytesOut = (UA_Byte*)ctx->operatorResults[index].data;
    const UA_Byte *bytes2 = (const UA_Byte*)ctx->operandStack[1].data;
    for(size_t i = 0; i < type->memSize; i++) {
        if(op == UA_FILTEROPERATOR_BITWISEAND)
            bytesOut[i] = bytesOut[i] & bytes2[i];
        else
            bytesOut[i] = bytesOut[i] | bytes2[i];
    }
    return UA_STATUSCODE_GOOD;
}

static UA_StatusCode
bitwiseAndOperator(UA_FilterEvalContext *ctx, size_t index) {
    return bitwiseOperator(ctx, index, UA_FILTEROPERATOR_BITWISEAND);
}

static UA_StatusCode
bitwiseOrOperator(UA_FilterEvalContext *ctx, size_t index) {
    return bitwiseOperator(ctx, index, UA_FILTEROPERATOR_BITWISEOR);
}

static UA_StatusCode
betweenOperator(UA_FilterEvalContext *ctx, size_t index) {
    UA_assert(ctx->filter.whereClause.elements[index].filterOperandsSize == 3);

    /* If no implicit conversion is available and the operands are of different
     * types, the particular result is FALSE. */
    UA_assert(ctx->top == 0); /* Assume the operand stack is empty */
    UA_StatusCode res = castResolveOperands(ctx, index, false);
    if(res != UA_STATUSCODE_GOOD) {
        ctx->operatorResults[index] = t2v(UA_TERNARY_FALSE);
        return UA_STATUSCODE_GOOD;
    }
    UA_assert(ctx->top == 3); /* Assume we have three elements */

    /* The casting can result in NULL values or a non-numerical type */
    const UA_DataType *type = ctx->operandStack[0].type;
    if(!type || !UA_DataType_isNumeric(type) ||
       type != ctx->operandStack[1].type || type != ctx->operandStack[2].type)
        return UA_STATUSCODE_BADTYPEMISMATCH;

    UA_Order o1 = UA_order(ctx->operandStack[0].data, ctx->operandStack[1].data, type);
    UA_Order o2 = UA_order(ctx->operandStack[0].data, ctx->operandStack[2].data, type);
    UA_Ternary comp = ((o1 == UA_ORDER_MORE || o1 == UA_ORDER_EQ) &&
                       (o2 == UA_ORDER_LESS || o2 == UA_ORDER_EQ)) ?
        UA_TERNARY_TRUE : UA_TERNARY_FALSE;

    ctx->operatorResults[index] = t2v(comp);
    return UA_STATUSCODE_GOOD;
}

static UA_StatusCode
inListOperator(UA_FilterEvalContext *ctx, size_t index) {
    const UA_ContentFilterElement *elm = &ctx->filter.whereClause.elements[index];
    UA_assert(elm->filterOperandsSize >= 2);
    UA_Boolean found = false;
    UA_Variant *op0 = pushOperand(ctx);
    UA_Variant *op1 = pushOperand(ctx);
    UA_StatusCode res = resolveOperand(ctx, &elm->filterOperands[0], op0);
    UA_CHECK_STATUS(res, return res);
    for(size_t i = 1; i < elm->filterOperandsSize && !found; i++) {
        res = resolveOperand(ctx, &elm->filterOperands[i], op1);
        if(res != UA_STATUSCODE_GOOD)
            continue;
        if(UA_Variant_equal(op0, op1))
            found = true;
        UA_Variant_clear(op1);
    }
    ctx->operatorResults[index] = t2v((found) ? UA_TERNARY_TRUE: UA_TERNARY_FALSE);
    return UA_STATUSCODE_GOOD;
}

static UA_StatusCode
isNullOperator(UA_FilterEvalContext *ctx, size_t index) {
    const UA_ContentFilterElement *elm = &ctx->filter.whereClause.elements[index];
    UA_assert(elm->filterOperandsSize == 1);
    UA_Variant *op0 = pushOperand(ctx);
    UA_StatusCode res = resolveOperand(ctx, &elm->filterOperands[0], op0);
    UA_CHECK_STATUS(res, return res);
    ctx->operatorResults[index] =
        t2v(UA_Variant_isEmpty(op0) ? UA_TERNARY_TRUE : UA_TERNARY_FALSE);
    return UA_STATUSCODE_GOOD;
}

static UA_StatusCode
notImplementedOperator(UA_FilterEvalContext *ctx, size_t index) {
    return UA_STATUSCODE_BADFILTEROPERATORUNSUPPORTED;
}

typedef struct {
    UA_StatusCode (*operatorMethod)(UA_FilterEvalContext *ctx, size_t index);
    UA_Byte minOperatorCount;
    UA_Byte maxOperatorCount;
} UA_FilterOperatorJumptableElement;

static const UA_FilterOperatorJumptableElement operatorJumptable[18] = {
    {equalsOperator, 2, 2},
    {isNullOperator, 1, 1},
    {gtOperator, 2, 2},
    {ltOperator, 2, 2},
    {gteOperator, 2, 2},
    {lteOperator, 2, 2},
    {notImplementedOperator, 0, UA_EVENTFILTER_MAXOPERANDS}, /* like */
    {notOperator, 1, 1},
    {betweenOperator, 3, 3},
    {inListOperator, 2, UA_EVENTFILTER_MAXOPERANDS},
    {andOperator, 2, 2},
    {orOperator, 2, 2},
    {notImplementedOperator, 0, UA_EVENTFILTER_MAXOPERANDS}, /* cast */
    {notImplementedOperator, 0, UA_EVENTFILTER_MAXOPERANDS}, /* in view */
    {ofTypeOperator, 1, 1},
    {notImplementedOperator, 0, UA_EVENTFILTER_MAXOPERANDS}, /* related to */
    {bitwiseAndOperator, 2, 2},
    {bitwiseOrOperator, 2, 2}
};

/* Evaluate content filter, exported only for unit testing */
UA_StatusCode
evaluateWhereClause(UA_FilterEvalContext *ctx) {
    UA_LOCK_ASSERT(&ctx->server->serviceMutex);

    /* An empty filter always succeeds */
    if(ctx->filter.whereClause.elementsSize == 0)
        return UA_STATUSCODE_GOOD;

    /* Information-model filters may bypass creation-time validation. */
    for(size_t i = 0; i < ctx->filter.whereClause.elementsSize; i++) {
        if((UA_UInt32)ctx->filter.whereClause.elements[i].filterOperator >
           UA_FILTEROPERATOR_BITWISEOR)
            return UA_STATUSCODE_BADEVENTFILTERINVALID;
    }

    /* Pacify some compilers by initializing the first result */
    UA_assert(ctx->top == 0);
    UA_Variant_init(&ctx->operatorResults[0]);

    /* Evaluate the filter. Iterate backwards over the filter elements and
     * resolve each. This ensures that all element-index operands point to an
     * evaluated element. */
    UA_StatusCode res = UA_STATUSCODE_GOOD;
    const UA_ContentFilter *cf = &ctx->filter.whereClause;
    for(size_t i = cf->elementsSize - 1; i < cf->elementsSize; i--) {
        UA_ContentFilterElement *cfe = &cf->elements[i];
        res = operatorJumptable[cfe->filterOperator].operatorMethod(ctx, i);
        /* Clean up the operand stack */
        for(size_t j = 0; j < ctx->top; j++)
            UA_Variant_clear(&ctx->operandStack[j]);
        ctx->top = 0;
        if(res != UA_STATUSCODE_GOOD)
            break;
    }

    /* The filter matches if the operator at the first position evaluates to TRUE */
    if(res == UA_STATUSCODE_GOOD && v2t(&ctx->operatorResults[0]) != UA_TERNARY_TRUE)
        res = UA_STATUSCODE_BADNOMATCH;

    /* Clean up the results stack */
    for(size_t i = 0; i < cf->elementsSize; i++)
        UA_Variant_clear(&ctx->operatorResults[i]);
    return res;
}

/*****************************************/
/* Validation of Filters during Creation */
/*****************************************/

/* Initial select clause validation. The following checks are currently performed:
 * - Check if the TypeDefinitionId or BrowsePath of any clause is NULL
 * - Check if the EventType is a subtype of BaseEventType
 * - Check if the AttributeId is valid
 * - Check if the BrowsePath contains null
 * - Check if the IndexRange is defined and if it is parseable
 * - Check if the AttributeId is value when an IndexRange is defined */
UA_StatusCode
UA_SimpleAttributeOperandValidation(UA_Server *server,
                                    const UA_SimpleAttributeOperand *sao) {
    /* TypeDefinition is not NULL? */
    if(UA_NodeId_isNull(&sao->typeDefinitionId))
        return UA_STATUSCODE_BADTYPEDEFINITIONINVALID;

    /* EventType is a subtype of BaseEventType? */
    UA_NodeId baseEventTypeId = UA_NS0ID(BASEEVENTTYPE);
    if(!isNodeInTree_singleRef(server, &sao->typeDefinitionId, &baseEventTypeId,
                               UA_REFERENCETYPEINDEX_HASSUBTYPE))
        return UA_STATUSCODE_BADTYPEDEFINITIONINVALID;

    /* AttributeId is valid ? */
    if(sao->attributeId == 0 || sao->attributeId >= 28)
        return UA_STATUSCODE_BADATTRIBUTEIDINVALID;

    /* If the BrowsePath is empty, the Node is the instance of the
     * TypeDefinition. (Part 4, 7.4.4.5) */
    if(sao->browsePathSize > 0) {
        /* BrowsePath contains empty BrowseNames? */
        for(size_t j = 0; j < sao->browsePathSize; ++j) {
            if(UA_QualifiedName_isNull(&sao->browsePath[j]))
                return UA_STATUSCODE_BADBROWSENAMEINVALID;
        }

        /* Part 4: If the SimpleAttributeOperand is used in an EventFilter and
         * the typeDefinitionId is BaseEventType the Server shall evaluate the
         * browsePath without considering the typeDefinitionId. */
        if(!UA_NodeId_equal(&baseEventTypeId, &sao->typeDefinitionId)) {
            /* Part 4: The TypeDefinitionNode restricts the operand to instances
             * of the TypeDefinitionNode or one of its subtypes.
             * First get the list of subtypes from event type (including the
             * event type itself). */
            UA_ReferenceTypeSet reftypes_interface =
                UA_REFTYPESET(UA_REFERENCETYPEINDEX_HASSUBTYPE);
            UA_ExpandedNodeId *childTypeNodes = NULL;
            size_t childTypeNodesSize = 0;
            UA_StatusCode res =
                browseRecursive(server, 1, &sao->typeDefinitionId, UA_BROWSEDIRECTION_FORWARD,
                                &reftypes_interface, UA_NODECLASS_OBJECTTYPE, true,
                                &childTypeNodesSize, &childTypeNodes);
            if(res != UA_STATUSCODE_GOOD)
                return UA_STATUSCODE_BADATTRIBUTEIDINVALID;

            /* Is the browse path valid for one of the event types? */
            UA_Boolean subTypeContainField = false;
            for(size_t j = 0; j < childTypeNodesSize && !subTypeContainField; j++) {
                UA_BrowsePathResult bpr =
                    browseSimplifiedBrowsePath(server, childTypeNodes[j].nodeId,
                                               sao->browsePathSize, sao->browsePath);

                if(bpr.statusCode == UA_STATUSCODE_GOOD && bpr.targetsSize > 0)
                    subTypeContainField = true;
                UA_BrowsePathResult_clear(&bpr);
            }

            /* Clean up and return an error if not found */
            UA_Array_delete(childTypeNodes, childTypeNodesSize, &UA_TYPES[UA_TYPES_EXPANDEDNODEID]);
            if(!subTypeContainField)
                return UA_STATUSCODE_BADNODEIDUNKNOWN;
        }
    }

    /* IndexRange is defined ? */
    if(!UA_String_isEmpty(&sao->indexRange)) {
        UA_NumericRange numericRange = UA_NUMERICRANGE("");
        if(UA_NumericRange_parse(&numericRange, sao->indexRange) != UA_STATUSCODE_GOOD)
            return UA_STATUSCODE_BADINDEXRANGEINVALID;
        UA_free(numericRange.dimensions);

        /* AttributeId has to be a value if an IndexRange is defined */
        if(sao->attributeId != UA_ATTRIBUTEID_VALUE)
            return UA_STATUSCODE_BADTYPEMISMATCH;
    }

    return UA_STATUSCODE_GOOD;
}

/* Initial content filter (where clause) check. Current checks:
 * - Number of operands for each (supported) operator
 * - ElementOperands point forward only */
UA_ContentFilterElementResult
UA_ContentFilterElementValidation(UA_Server *server, size_t operatorIndex,
                                  size_t operatorsCount,
                                  const UA_ContentFilterElement *ef) {
    /* Initialize the result structure */
    UA_ContentFilterElementResult er;
    UA_ContentFilterElementResult_init(&er);
    er.operandStatusCodes = (UA_StatusCode *)
        UA_Array_new(ef->filterOperandsSize, &UA_TYPES[UA_TYPES_STATUSCODE]);
    if(!er.operandStatusCodes) {
        er.statusCode = UA_STATUSCODE_BADOUTOFMEMORY;
        return er;
    }
    er.operandStatusCodesSize = ef->filterOperandsSize;

    /* Is the operator in the defined range? Test this before the following
     * jumptable lookup. */
    if(ef->filterOperator < 0 || ef->filterOperator > UA_FILTEROPERATOR_BITWISEOR) {
        er.statusCode = UA_STATUSCODE_BADEVENTFILTERINVALID;
        return er;
    }

    /* Number of operands supported for the operator? */
    if(ef->filterOperandsSize < operatorJumptable[ef->filterOperator].minOperatorCount ||
       ef->filterOperandsSize > operatorJumptable[ef->filterOperator].maxOperatorCount) {
        er.statusCode = UA_STATUSCODE_BADFILTEROPERANDCOUNTMISMATCH;
        return er;
    }

    /* Generic validation of the operands */
    for(size_t i = 0; i < ef->filterOperandsSize; i++) {
        /* Must be a decoded ExtensionObject */
        UA_ExtensionObject *op = &ef->filterOperands[i];
        if(op->encoding != UA_EXTENSIONOBJECT_DECODED &&
           op->encoding != UA_EXTENSIONOBJECT_DECODED_NODELETE) {
            er.operandStatusCodes[i] = UA_STATUSCODE_BADFILTEROPERANDINVALID;
            er.statusCode = UA_STATUSCODE_BADFILTEROPERANDINVALID;
            return er;
        }

        /* Supported type and conforming to the rules? */
        if(op->content.decoded.type == &UA_TYPES[UA_TYPES_ELEMENTOPERAND]) {
            /* Part 4, 7.4.4.2 defines conditions for Element Operands: An index
             * is considered valid if its value is greater than the element
             * index it is part of and it does not Reference a non-existent
             * element. Clients shall construct filters in this way to avoid
             * circular and invalid References. */
            UA_ElementOperand *eo = (UA_ElementOperand *)op->content.decoded.data;
            if(eo->index <= operatorIndex || eo->index >= operatorsCount) {
                er.operandStatusCodes[i] = UA_STATUSCODE_BADINDEXRANGEINVALID;
                er.statusCode = UA_STATUSCODE_BADINDEXRANGEINVALID;
                return er;
            }
        } else if(op->content.decoded.type == &UA_TYPES[UA_TYPES_ATTRIBUTEOPERAND]) {
            er.operandStatusCodes[i] = UA_STATUSCODE_BADNOTSUPPORTED;
            er.statusCode = UA_STATUSCODE_BADFILTERNOTALLOWED;
            return er;
        } else if(op->content.decoded.type != &UA_TYPES[UA_TYPES_SIMPLEATTRIBUTEOPERAND] &&
                  op->content.decoded.type != &UA_TYPES[UA_TYPES_LITERALOPERAND]) {
            er.operandStatusCodes[i] = UA_STATUSCODE_BADFILTEROPERANDINVALID;
            er.statusCode = UA_STATUSCODE_BADFILTEROPERANDINVALID;
            return er;
        }
    }

    /* Specific validations for different operators */
    switch(ef->filterOperator) {
        case UA_FILTEROPERATOR_INVIEW:
        case UA_FILTEROPERATOR_RELATEDTO:
            /* Not allowed for event WhereClause according to 7.17.3 in Part 4 */
            er.statusCode = UA_STATUSCODE_BADEVENTFILTERINVALID;
            break;

        case UA_FILTEROPERATOR_EQUALS:
        case UA_FILTEROPERATOR_GREATERTHAN:
        case UA_FILTEROPERATOR_LESSTHAN:
        case UA_FILTEROPERATOR_GREATERTHANOREQUAL:
        case UA_FILTEROPERATOR_LESSTHANOREQUAL:
        case UA_FILTEROPERATOR_BITWISEAND:
        case UA_FILTEROPERATOR_BITWISEOR:
        case UA_FILTEROPERATOR_BETWEEN:
        case UA_FILTEROPERATOR_INLIST:
        case UA_FILTEROPERATOR_AND:
        case UA_FILTEROPERATOR_OR:
        case UA_FILTEROPERATOR_ISNULL:
        case UA_FILTEROPERATOR_NOT:
            break;

        case UA_FILTEROPERATOR_OFTYPE: {
            /* Make sure the operand is a NodeId literal */
            UA_ExtensionObject *o = &ef->filterOperands[0];
            UA_LiteralOperand *lo = (UA_LiteralOperand *)o->content.decoded.data;
            if(o->content.decoded.type != &UA_TYPES[UA_TYPES_LITERALOPERAND] ||
               !UA_Variant_hasScalarType(&lo->value, &UA_TYPES[UA_TYPES_NODEID])) {
                er.operandStatusCodes[0] = UA_STATUSCODE_BADFILTEROPERANDINVALID;
                er.statusCode = UA_STATUSCODE_BADFILTEROPERANDINVALID;
                break;
            }

            /* Make sure the operand is a subtype of BaseEventType */
            UA_NodeId baseEventTypeId = UA_NODEID_NUMERIC(0, UA_NS0ID_BASEEVENTTYPE);
            if(!isNodeInTree_singleRef(server, (UA_NodeId *)lo->value.data, &baseEventTypeId,
                                       UA_REFERENCETYPEINDEX_HASSUBTYPE)) {
                er.operandStatusCodes[0] = UA_STATUSCODE_BADFILTEROPERANDINVALID;
                er.statusCode = UA_STATUSCODE_BADFILTEROPERANDINVALID;
                break;
            }
            break;
        }

        case UA_FILTEROPERATOR_LIKE:
        case UA_FILTEROPERATOR_CAST:
            er.statusCode = UA_STATUSCODE_BADFILTEROPERATORUNSUPPORTED;
            break;

        default:
            er.statusCode = UA_STATUSCODE_BADFILTEROPERATORINVALID;
            break;
    }
    return er;
}

/*************************/
/* Create Event Instance */
/*************************/

UA_StatusCode
evaluateSelectClause(UA_FilterEvalContext *ctx, UA_EventFieldList *efl) {
    /* Nothing to do */
    if(ctx->filter.selectClausesSize == 0)
        return UA_STATUSCODE_GOOD;

    /* Allocate the event fields list */
    efl->eventFields = (UA_Variant*)
        UA_calloc(ctx->filter.selectClausesSize, sizeof(UA_Variant));
    if(!efl->eventFields)
        return UA_STATUSCODE_BADOUTOFMEMORY;
    efl->eventFieldsSize = ctx->filter.selectClausesSize;

    /* Resolve the select clauses */
    UA_StatusCode res = UA_STATUSCODE_GOOD;
    for(size_t i = 0; i < ctx->filter.selectClausesSize; i++) {
        const UA_SimpleAttributeOperand *sao = &ctx->filter.selectClauses[i];
        UA_Variant *field = &efl->eventFields[i];
        res |= resolveSAO(ctx, sao, field);

        /* Ensure a deep copy */
        if(field->storageType == UA_VARIANT_DATA_NODELETE) {
            UA_Variant tmp_val;
            UA_StatusCode res_ign = UA_Variant_copy(field, &tmp_val);
            (void)res_ign; /* Ignore the result - returns an empty variant if copying fails */
            *field = tmp_val;
        }
    }

    return res;
}

/* Filters an event according to the filter specified by mon and then adds it to
 * mons notification queue */
static UA_StatusCode
UA_MonitoredItem_addEvent(UA_MonitoredItem *mon, UA_FilterEvalContext *ctx) {
    /* Evaluate the where clause */
    UA_StatusCode res = evaluateWhereClause(ctx);
    if(res != UA_STATUSCODE_GOOD) {
        if(res == UA_STATUSCODE_BADNOMATCH)
            res = UA_STATUSCODE_GOOD;
        return res;
    }

    /* Allocate memory for the notification */
    UA_Notification *n = UA_Notification_new();
    if(!n)
        return UA_STATUSCODE_BADOUTOFMEMORY;

    /* Evaluate the select clause to get the event fields */
    res = evaluateSelectClause(ctx, &n->data.event);
    if(res != UA_STATUSCODE_GOOD) {
        UA_EventFieldList_clear(&n->data.event);
        UA_free(n);
        return res;
    }

    /* Finalize and enqueue the notification */
    n->data.event.clientHandle = mon->parameters.clientHandle;
    n->mon = mon;
    UA_Notification_enqueueAndTrigger(ctx->server, n);
    return UA_STATUSCODE_GOOD;
}

#ifdef UA_ENABLE_HISTORIZING
static void
setHistoricalEvent(UA_Server *server, const UA_NodeId *emitNode,
                   const UA_EventDescription *ed) {
    UA_Variant historicalEventFilterValue;
    UA_Variant_init(&historicalEventFilterValue);

    /* A HistoricalEventNode that has event history available will provide this property */
    UA_StatusCode retval =
        readObjectProperty(server, *emitNode,
                           UA_QUALIFIEDNAME(0, "HistoricalEventFilter"),
                           &historicalEventFilterValue);
    if(retval != UA_STATUSCODE_GOOD) {
        if(retval != UA_STATUSCODE_BADNOMATCH)
            UA_LOG_WARNING(server->config.logging, UA_LOGCATEGORY_SERVER,
                           "Cannot read the HistoricalEventFilter property of a "
                           "listening node. StatusCode %s",
                           UA_StatusCode_name(retval));
        return;
    }

    /* If found then check if HistoricalEventFilter property has a valid value */
    if(!UA_Variant_hasScalarType(&historicalEventFilterValue,
                                 &UA_TYPES[UA_TYPES_EVENTFILTER])) {
        UA_LOG_WARNING(server->config.logging, UA_LOGCATEGORY_SERVER,
                       "HistoricalEventFilter property of a listening node "
                       "does not have a valid value");
        UA_Variant_clear(&historicalEventFilterValue);
        return;
    }
    UA_EventFilter *ef = (UA_EventFilter*)historicalEventFilterValue.data;

    UA_FilterEvalContext ctx;
    UA_FilterEvalContext_init(&ctx);
    ctx.server = server;
    ctx.session = &server->adminSession;
    ctx.filter = *ef;
    ctx.ed = *ed;

    /* Evaluate the where clause */
    UA_StatusCode res = evaluateWhereClause(&ctx);
    if(res != UA_STATUSCODE_GOOD) {
        UA_FilterEvalContext_reset(&ctx);
        UA_Variant_clear(&historicalEventFilterValue);
        return;
    }

    /* Get the event fields for the select clause */
    UA_EventFieldList efl;
    UA_EventFieldList_init(&efl);
    res = evaluateSelectClause(&ctx, &efl);

    /* Call the history database backend */
    if(UA_LIKELY(res == UA_STATUSCODE_GOOD)) {
        server->config.historyDatabase.
            setEvent(server, server->config.historyDatabase.context,
                     &ed->sourceNode, emitNode, ef, &efl);
    }

    UA_FilterEvalContext_reset(&ctx);
    UA_Variant_clear(&historicalEventFilterValue);
    UA_EventFieldList_clear(&efl);
}
#endif

#define EMIT_REFS_ROOT_COUNT 4
static const UA_NodeId emitReferencesRoots[EMIT_REFS_ROOT_COUNT] =
    {{0, UA_NODEIDTYPE_NUMERIC, {UA_NS0ID_ORGANIZES}},
     {0, UA_NODEIDTYPE_NUMERIC, {UA_NS0ID_HASCOMPONENT}},
     {0, UA_NODEIDTYPE_NUMERIC, {UA_NS0ID_HASEVENTSOURCE}},
     {0, UA_NODEIDTYPE_NUMERIC, {UA_NS0ID_HASNOTIFIER}}};

UA_StatusCode
createEvent(UA_Server *server, const UA_EventDescription *ed,
            UA_ByteString *outEventId) {
    UA_StatusCode res = UA_STATUSCODE_GOOD;
    UA_LOCK_ASSERT(&server->serviceMutex);

    /* MonitoredItem can only be filtered if the Subscription is defined.
     * Subscription can only be filtered if a Session is defined. */
    if((ed->subscriptionId && !ed->sessionId) ||
       (ed->monitoredItemId && !ed->subscriptionId)) {
        UA_LOG_WARNING(server->config.logging, UA_LOGCATEGORY_SERVER,
                       "Event shall be created with a filter on Subscription (or MonitoredItem), "
                       "but no Session (or Subscription) is defined");
        return UA_STATUSCODE_BADINTERNALERROR;
    }

    UA_LOG_DEBUG(server->config.logging, UA_LOGCATEGORY_SERVER,
                 "Events: An event of severity %u is emitted by node %N",
                 ed->severity, ed->sourceNode);

#ifdef UA_ENABLE_SUBSCRIPTIONS_ALARMS_CONDITIONS
    UA_Boolean isCallerAC = false;
    if(isConditionOrBranch(server, &ed->eventType, &ed->sourceNode, &isCallerAC) &&
       !isCallerAC) {
        UA_LOG_WARNING(server->config.logging, UA_LOGCATEGORY_SERVER,
                       "Condition Events: Please use A&C API to trigger Condition Events 0x%08X",
                       UA_STATUSCODE_BADINVALIDARGUMENT);
        return UA_STATUSCODE_BADINVALIDARGUMENT;
    }
#endif /* UA_ENABLE_SUBSCRIPTIONS_ALARMS_CONDITIONS */

    /* The user must ensure that only nodes from the Objects folder (and Views)
     * emit events. The following commented code could enforce this, but is
     * computationally expensive. */

    /* static const UA_NodeId objectsFolderId = */
    /*     {0, UA_NODEIDTYPE_NUMERIC, {UA_NS0ID_OBJECTSFOLDER}}; */
    /* static const UA_NodeId isInFolderReferences[2] = */
    /*     {{0, UA_NODEIDTYPE_NUMERIC, {UA_NS0ID_ORGANIZES}}, */
    /*      {0, UA_NODEIDTYPE_NUMERIC, {UA_NS0ID_HASCOMPONENT}}}; */
    /* UA_ReferenceTypeSet refTypes; */
    /* UA_ReferenceTypeSet_init(&refTypes); */
    /* for(int i = 0; i < 2; ++i) { */
    /*     UA_ReferenceTypeSet tmpRefTypes; */
    /*     res = referenceTypeIndices(server, &isInFolderReferences[i], &tmpRefTypes, true); */
    /*     if(res != UA_STATUSCODE_GOOD) { */
    /*         UA_LOG_WARNING(server->config.logging, UA_LOGCATEGORY_SERVER, */
    /*                        "Events: Could not create the list of references and their subtypes " */
    /*                        "with StatusCode %s", UA_StatusCode_name(res)); */
    /*     } */
    /*     refTypes = UA_ReferenceTypeSet_union(refTypes, tmpRefTypes); */
    /* } */
    /* if(!isNodeInTree(server, &origin, &objectsFolderId, &refTypes)) { */
    /*     UA_LOG_ERROR(server->config.logging, UA_LOGCATEGORY_USERLAND, */
    /*                  "Node for event must be in ObjectsFolder!"); */
    /*     return UA_STATUSCODE_BADINVALIDARGUMENT; */
    /* } */

    /* Get all ReferenceTypes over which the events propagate */
    UA_ReferenceTypeSet emitRefTypes;
    UA_ReferenceTypeSet_init(&emitRefTypes);
    for(size_t i = 0; i < EMIT_REFS_ROOT_COUNT; i++) {
        UA_ReferenceTypeSet tmpRefTypes;
        res = referenceTypeIndices(server, &emitReferencesRoots[i], &tmpRefTypes, true);
        if(res != UA_STATUSCODE_GOOD) {
            UA_LOG_WARNING(server->config.logging, UA_LOGCATEGORY_SERVER,
                           "Events: Could not create the list of references for event "
                           "propagation with StatusCode %s", UA_StatusCode_name(res));
            return res;
        }
        emitRefTypes = UA_ReferenceTypeSet_union(emitRefTypes, tmpRefTypes);
    }

    /* Get the list of nodes in the hierarchy that emits the event. Add the
     * server node to the list of nodes from which the event is emitted. The
     * server node emits all events.
     *
     * Part 3, 7.17: In particular, the root notifier of a Server, the Server
     * Object defined in Part 5, is always capable of supplying all Events from
     * a Server and as such has implied HasEventSource References to every event
     * source in a Server. */
    UA_NodeId emitStartNodes[2];
    emitStartNodes[0] = ed->sourceNode;
    emitStartNodes[1] = UA_NODEID_NUMERIC(0, UA_NS0ID_SERVER);

    UA_ExpandedNodeId *emitNodes = NULL;
    size_t emitNodesSize = 0;
    res = browseRecursive(server, 2, emitStartNodes, UA_BROWSEDIRECTION_INVERSE,
                          &emitRefTypes, UA_NODECLASS_UNSPECIFIED, true,
                          &emitNodesSize, &emitNodes);
    if(res != UA_STATUSCODE_GOOD) {
        UA_LOG_WARNING(server->config.logging, UA_LOGCATEGORY_SERVER,
                       "Events: Could not create the list of nodes listening on the "
                       "event with StatusCode %s", UA_StatusCode_name(res));
        return res;
    }

    /* Set up the eval context. */
    UA_FilterEvalContext ctx;
    UA_FilterEvalContext_init(&ctx);
    ctx.server = server;
    ctx.ed = *ed;
    /* ctx.session is set below for each MonitoredItem */
    /* ctx.filter is set below for each MonitoredItem */

    /* Create / resolve the EventId and copy into outEventId */
    if(outEventId) {
        ctx.session = &server->adminSession;
        res = cacheEventId(&ctx);
        if(UA_LIKELY(res == UA_STATUSCODE_GOOD))
            res = UA_ByteString_copy(&ctx.eventId, outEventId);
        UA_FilterEvalContext_reset(&ctx);
        if(res != UA_STATUSCODE_GOOD)
            return res;
    }

    /* Loop over all nodes that emit this event instance */
    for(size_t i = 0; i < emitNodesSize; i++) {
        /* We can only emit on local nodes */
        if(!UA_ExpandedNodeId_isLocal(&emitNodes[i]))
            continue;

        /* Get the node */
        const UA_Node *node = UA_NODESTORE_GET(server, &emitNodes[i].nodeId);
        if(!node)
            continue;

        /* Only consider objects */
        if(node->head.nodeClass != UA_NODECLASS_OBJECT) {
            UA_NODESTORE_RELEASE(server, node);
            continue;
        }

        /* Iterate over all MonitoredItems registered in the node  */
        UA_MonitoredItem *mon;
        LIST_FOREACH(mon, (const UA_MonitoredItemList*)&node->head.monitoredItems,
                     sampling.nodeListEntry) {
            /* Is this an Event-MonitoredItem? */
            if(mon->itemToMonitor.attributeId != UA_ATTRIBUTEID_EVENTNOTIFIER)
                continue;

            /* Filter on the Session. If a subscription is not attached to a
             * session, then this filter never matches. */
            UA_Subscription *sub = mon->subscription;
            if(ed->sessionId && (!sub->session || !UA_NodeId_equal(ed->sessionId, &sub->session->sessionId)))
                continue;

            /* Filter on the SubscriptionId */
            if(ed->subscriptionId && *ed->subscriptionId != sub->subscriptionId)
                continue;

            /* Filter on the MonitoredItemId */
            if(ed->monitoredItemId && *ed->monitoredItemId != mon->monitoredItemId)
                continue;

            /* Get the EventFilter from the MonitoredItem */
            if(!UA_ExtensionObject_hasDecodedType(&mon->parameters.filter,
                                                  &UA_TYPES[UA_TYPES_EVENTFILTER])) {
                UA_LOG_ERROR_SUBSCRIPTION(server->config.logging, mon->subscription,
                                          "MonitoredItem %" PRIi32 " | "
                                          "The filter must be an EventFilter", mon->monitoredItemId);
                continue;
            }
            ctx.filter = *(UA_EventFilter*)mon->parameters.filter.content.decoded.data;

            /* Do not evaluate event fields for detached subscriptions.
             * Using adminSession would bypass per-session access control. */
            if(!sub->session)
                continue;
            ctx.session = sub->session;

            /* Evaluate the where-clause and create a notification */
            res = UA_MonitoredItem_addEvent(mon, &ctx);
            UA_FilterEvalContext_reset(&ctx);
            if(res != UA_STATUSCODE_GOOD) {
                UA_LOG_WARNING(server->config.logging, UA_LOGCATEGORY_SERVER,
                               "Events: Could not add the event to a listening "
                               "node with StatusCode %s", UA_StatusCode_name(res));
                res = UA_STATUSCODE_GOOD; /* Only log problems with individual emit nodes */
            }
        }

        UA_NODESTORE_RELEASE(server, node);

        /* Add event entry in the historical database */
#ifdef UA_ENABLE_HISTORIZING
        if(server->config.historyDatabase.setEvent)
            setHistoricalEvent(server, &emitNodes[i].nodeId, ed);
#endif
    }

    /* Clean up and return */
    if(outEventId && res != UA_STATUSCODE_GOOD)
        UA_ByteString_clear(outEventId);
    UA_Array_delete(emitNodes, emitNodesSize, &UA_TYPES[UA_TYPES_EXPANDEDNODEID]);
    return res;
}

UA_StatusCode
UA_Server_createEvent(UA_Server *server, const UA_NodeId sourceNode,
                      const UA_NodeId eventType, UA_UInt16 severity,
                      const UA_LocalizedText message,
                      const UA_KeyValueMap *eventFields,
                      const UA_NodeId *eventInstance,
                      UA_ByteString *outEventId) {
    UA_EventDescription ed = {0};
    ed.sourceNode = sourceNode;
    ed.eventType = eventType;
    ed.severity = severity;
    ed.message = message;
    ed.eventFields = eventFields;
    ed.eventInstance = eventInstance;

    lockServer(server);
    UA_StatusCode res = createEvent(server, &ed, outEventId);
    unlockServer(server);
    return res;
}

UA_StatusCode UA_EXPORT UA_THREADSAFE
UA_Server_createEventEx(UA_Server *server,
                        const UA_EventDescription *ed,
                        UA_ByteString *outEventId) {
    lockServer(server);
    UA_StatusCode res = createEvent(server, ed, outEventId);
    unlockServer(server);
    return res;
}

#endif /* UA_ENABLE_SUBSCRIPTIONS_EVENTS */

Coverage Report

Created: 2026-11-12 06:54