/src/postgres/src/common/jsonapi.c

Source
/*-------------------------------------------------------------------------
 *
 * jsonapi.c
 *    JSON parser and lexer interfaces
 *
 * Portions Copyright (c) 1996-2026, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * IDENTIFICATION
 *    src/common/jsonapi.c
 *
 *-------------------------------------------------------------------------
 */
#ifndef FRONTEND
#include "postgres.h"
#else
#include "postgres_fe.h"
#endif

#include "common/jsonapi.h"
#include "mb/pg_wchar.h"
#include "port/pg_lfind.h"

#ifdef JSONAPI_USE_PQEXPBUFFER
#include "pqexpbuffer.h"
#else
#include "lib/stringinfo.h"
#include "miscadmin.h"
#endif

/*
 * By default, we will use palloc/pfree along with StringInfo.  In libpq,
 * use malloc and PQExpBuffer, and return JSON_OUT_OF_MEMORY on out-of-memory.
 */
#ifdef JSONAPI_USE_PQEXPBUFFER

#define STRDUP(s) strdup(s)
#define ALLOC(size) malloc(size)
#define ALLOC0(size) calloc(1, size)
#define REALLOC realloc
#define FREE(s) free(s)

#define jsonapi_appendStringInfo      appendPQExpBuffer
#define jsonapi_appendBinaryStringInfo    appendBinaryPQExpBuffer
#define jsonapi_appendStringInfoChar    appendPQExpBufferChar
/* XXX should we add a macro version to PQExpBuffer? */
#define jsonapi_appendStringInfoCharMacro appendPQExpBufferChar
#define jsonapi_makeStringInfo        createPQExpBuffer
#define jsonapi_initStringInfo        initPQExpBuffer
#define jsonapi_resetStringInfo       resetPQExpBuffer
#define jsonapi_termStringInfo        termPQExpBuffer
#define jsonapi_destroyStringInfo     destroyPQExpBuffer

#else             /* !JSONAPI_USE_PQEXPBUFFER */

#define STRDUP(s) pstrdup(s)
#define ALLOC(size) palloc(size)
#define ALLOC0(size) palloc0(size)
#define REALLOC repalloc

#ifdef FRONTEND
#define FREE pfree
#else
/*
 * Backend pfree() doesn't handle NULL pointers like the frontend's does; smooth
 * that over to reduce mental gymnastics. Avoid multiple evaluation of the macro
 * argument to avoid future hair-pulling.
 */
#define FREE(s) do { \
  void *__v = (s);  \
  if (__v)     \
    pfree(__v);   \
} while (0)
#endif

#define jsonapi_appendStringInfo      appendStringInfo
#define jsonapi_appendBinaryStringInfo    appendBinaryStringInfo
#define jsonapi_appendStringInfoChar    appendStringInfoChar
#define jsonapi_appendStringInfoCharMacro appendStringInfoCharMacro
#define jsonapi_makeStringInfo        makeStringInfo
#define jsonapi_initStringInfo        initStringInfo
#define jsonapi_resetStringInfo       resetStringInfo
#define jsonapi_termStringInfo(s)     pfree((s)->data)
#define jsonapi_destroyStringInfo     destroyStringInfo

#endif              /* JSONAPI_USE_PQEXPBUFFER */

/*
 * The context of the parser is maintained by the recursive descent
 * mechanism, but is passed explicitly to the error reporting routine
 * for better diagnostics.
 */
typedef enum          /* contexts of JSON parser */
{
  JSON_PARSE_VALUE,     /* expecting a value */
  JSON_PARSE_STRING,      /* expecting a string (for a field name) */
  JSON_PARSE_ARRAY_START,   /* saw '[', expecting value or ']' */
  JSON_PARSE_ARRAY_NEXT,    /* saw array element, expecting ',' or ']' */
  JSON_PARSE_OBJECT_START,  /* saw '{', expecting label or '}' */
  JSON_PARSE_OBJECT_LABEL,  /* saw object label, expecting ':' */
  JSON_PARSE_OBJECT_NEXT,   /* saw object value, expecting ',' or '}' */
  JSON_PARSE_OBJECT_COMMA,  /* saw object ',', expecting next label */
  JSON_PARSE_END,       /* saw the end of a document, expect nothing */
} JsonParseContext;

/*
 * Setup for table-driven parser.
 * These enums need to be separate from the JsonTokenType and from each other
 * so we can have all of them on the prediction stack, which consists of
 * tokens, non-terminals, and semantic action markers.
 */

enum JsonNonTerminal
{
  JSON_NT_JSON = 32,
  JSON_NT_ARRAY_ELEMENTS,
  JSON_NT_MORE_ARRAY_ELEMENTS,
  JSON_NT_KEY_PAIRS,
  JSON_NT_MORE_KEY_PAIRS,
};

enum JsonParserSem
{
  JSON_SEM_OSTART = 64,
  JSON_SEM_OEND,
  JSON_SEM_ASTART,
  JSON_SEM_AEND,
  JSON_SEM_OFIELD_INIT,
  JSON_SEM_OFIELD_START,
  JSON_SEM_OFIELD_END,
  JSON_SEM_AELEM_START,
  JSON_SEM_AELEM_END,
  JSON_SEM_SCALAR_INIT,
  JSON_SEM_SCALAR_CALL,
};

/*
 * struct containing the 3 stacks used in non-recursive parsing,
 * and the token and value for scalars that need to be preserved
 * across calls.
 *
 * typedef appears in jsonapi.h
 */
struct JsonParserStack
{
  int     stack_size;
  char     *prediction;
  size_t    pred_index;
  /* these two are indexed by lex_level */
  char    **fnames;
  bool     *fnull;
  JsonTokenType scalar_tok;
  char     *scalar_val;
};

/*
 * struct containing state used when there is a possible partial token at the
 * end of a json chunk when we are doing incremental parsing.
 *
 * typedef appears in jsonapi.h
 */
struct JsonIncrementalState
{
  bool    started;
  bool    is_last_chunk;
  bool    partial_completed;
  jsonapi_StrValType partial_token;
};

/*
 * constants and macros used in the nonrecursive parser
 */
#define JSON_NUM_TERMINALS 13
#define JSON_NUM_NONTERMINALS 5
#define JSON_NT_OFFSET JSON_NT_JSON
/* for indexing the table */
#define OFS(NT) (NT) - JSON_NT_OFFSET
/* classify items we get off the stack */
#define IS_SEM(x) ((x) & 0x40)
#define IS_NT(x)  ((x) & 0x20)

/*
 * These productions are stored in reverse order right to left so that when
 * they are pushed on the stack what we expect next is at the top of the stack.
 */
static char JSON_PROD_EPSILON[] = {0};  /* epsilon - an empty production */

/* JSON -> string */
static char JSON_PROD_SCALAR_STRING[] = {JSON_SEM_SCALAR_CALL, JSON_TOKEN_STRING, JSON_SEM_SCALAR_INIT, 0};

/* JSON -> number */
static char JSON_PROD_SCALAR_NUMBER[] = {JSON_SEM_SCALAR_CALL, JSON_TOKEN_NUMBER, JSON_SEM_SCALAR_INIT, 0};

/* JSON -> 'true' */
static char JSON_PROD_SCALAR_TRUE[] = {JSON_SEM_SCALAR_CALL, JSON_TOKEN_TRUE, JSON_SEM_SCALAR_INIT, 0};

/* JSON -> 'false' */
static char JSON_PROD_SCALAR_FALSE[] = {JSON_SEM_SCALAR_CALL, JSON_TOKEN_FALSE, JSON_SEM_SCALAR_INIT, 0};

/* JSON -> 'null' */
static char JSON_PROD_SCALAR_NULL[] = {JSON_SEM_SCALAR_CALL, JSON_TOKEN_NULL, JSON_SEM_SCALAR_INIT, 0};

/* JSON -> '{' KEY_PAIRS '}' */
static char JSON_PROD_OBJECT[] = {JSON_SEM_OEND, JSON_TOKEN_OBJECT_END, JSON_NT_KEY_PAIRS, JSON_TOKEN_OBJECT_START, JSON_SEM_OSTART, 0};

/* JSON -> '[' ARRAY_ELEMENTS ']' */
static char JSON_PROD_ARRAY[] = {JSON_SEM_AEND, JSON_TOKEN_ARRAY_END, JSON_NT_ARRAY_ELEMENTS, JSON_TOKEN_ARRAY_START, JSON_SEM_ASTART, 0};

/* ARRAY_ELEMENTS -> JSON MORE_ARRAY_ELEMENTS */
static char JSON_PROD_ARRAY_ELEMENTS[] = {JSON_NT_MORE_ARRAY_ELEMENTS, JSON_SEM_AELEM_END, JSON_NT_JSON, JSON_SEM_AELEM_START, 0};

/* MORE_ARRAY_ELEMENTS -> ',' JSON MORE_ARRAY_ELEMENTS */
static char JSON_PROD_MORE_ARRAY_ELEMENTS[] = {JSON_NT_MORE_ARRAY_ELEMENTS, JSON_SEM_AELEM_END, JSON_NT_JSON, JSON_SEM_AELEM_START, JSON_TOKEN_COMMA, 0};

/* KEY_PAIRS -> string ':' JSON MORE_KEY_PAIRS */
static char JSON_PROD_KEY_PAIRS[] = {JSON_NT_MORE_KEY_PAIRS, JSON_SEM_OFIELD_END, JSON_NT_JSON, JSON_SEM_OFIELD_START, JSON_TOKEN_COLON, JSON_TOKEN_STRING, JSON_SEM_OFIELD_INIT, 0};

/* MORE_KEY_PAIRS -> ',' string ':'  JSON MORE_KEY_PAIRS */
static char JSON_PROD_MORE_KEY_PAIRS[] = {JSON_NT_MORE_KEY_PAIRS, JSON_SEM_OFIELD_END, JSON_NT_JSON, JSON_SEM_OFIELD_START, JSON_TOKEN_COLON, JSON_TOKEN_STRING, JSON_SEM_OFIELD_INIT, JSON_TOKEN_COMMA, 0};

/*
 * Note: there are also epsilon productions for ARRAY_ELEMENTS,
 * MORE_ARRAY_ELEMENTS, KEY_PAIRS and MORE_KEY_PAIRS
 * They are all the same as none require any semantic actions.
 */

/*
 * Table connecting the productions with their director sets of
 * terminal symbols.
 * Any combination not specified here represents an error.
 */

typedef struct
{
  size_t    len;
  char     *prod;
} td_entry;

#define TD_ENTRY(PROD) { sizeof(PROD) - 1, (PROD) }

static td_entry td_parser_table[JSON_NUM_NONTERMINALS][JSON_NUM_TERMINALS] =
{
  /* JSON */
  [OFS(JSON_NT_JSON)][JSON_TOKEN_STRING] = TD_ENTRY(JSON_PROD_SCALAR_STRING),
  [OFS(JSON_NT_JSON)][JSON_TOKEN_NUMBER] = TD_ENTRY(JSON_PROD_SCALAR_NUMBER),
  [OFS(JSON_NT_JSON)][JSON_TOKEN_TRUE] = TD_ENTRY(JSON_PROD_SCALAR_TRUE),
  [OFS(JSON_NT_JSON)][JSON_TOKEN_FALSE] = TD_ENTRY(JSON_PROD_SCALAR_FALSE),
  [OFS(JSON_NT_JSON)][JSON_TOKEN_NULL] = TD_ENTRY(JSON_PROD_SCALAR_NULL),
  [OFS(JSON_NT_JSON)][JSON_TOKEN_ARRAY_START] = TD_ENTRY(JSON_PROD_ARRAY),
  [OFS(JSON_NT_JSON)][JSON_TOKEN_OBJECT_START] = TD_ENTRY(JSON_PROD_OBJECT),
  /* ARRAY_ELEMENTS */
  [OFS(JSON_NT_ARRAY_ELEMENTS)][JSON_TOKEN_ARRAY_START] = TD_ENTRY(JSON_PROD_ARRAY_ELEMENTS),
  [OFS(JSON_NT_ARRAY_ELEMENTS)][JSON_TOKEN_OBJECT_START] = TD_ENTRY(JSON_PROD_ARRAY_ELEMENTS),
  [OFS(JSON_NT_ARRAY_ELEMENTS)][JSON_TOKEN_STRING] = TD_ENTRY(JSON_PROD_ARRAY_ELEMENTS),
  [OFS(JSON_NT_ARRAY_ELEMENTS)][JSON_TOKEN_NUMBER] = TD_ENTRY(JSON_PROD_ARRAY_ELEMENTS),
  [OFS(JSON_NT_ARRAY_ELEMENTS)][JSON_TOKEN_TRUE] = TD_ENTRY(JSON_PROD_ARRAY_ELEMENTS),
  [OFS(JSON_NT_ARRAY_ELEMENTS)][JSON_TOKEN_FALSE] = TD_ENTRY(JSON_PROD_ARRAY_ELEMENTS),
  [OFS(JSON_NT_ARRAY_ELEMENTS)][JSON_TOKEN_NULL] = TD_ENTRY(JSON_PROD_ARRAY_ELEMENTS),
  [OFS(JSON_NT_ARRAY_ELEMENTS)][JSON_TOKEN_ARRAY_END] = TD_ENTRY(JSON_PROD_EPSILON),
  /* MORE_ARRAY_ELEMENTS */
  [OFS(JSON_NT_MORE_ARRAY_ELEMENTS)][JSON_TOKEN_COMMA] = TD_ENTRY(JSON_PROD_MORE_ARRAY_ELEMENTS),
  [OFS(JSON_NT_MORE_ARRAY_ELEMENTS)][JSON_TOKEN_ARRAY_END] = TD_ENTRY(JSON_PROD_EPSILON),
  /* KEY_PAIRS */
  [OFS(JSON_NT_KEY_PAIRS)][JSON_TOKEN_STRING] = TD_ENTRY(JSON_PROD_KEY_PAIRS),
  [OFS(JSON_NT_KEY_PAIRS)][JSON_TOKEN_OBJECT_END] = TD_ENTRY(JSON_PROD_EPSILON),
  /* MORE_KEY_PAIRS */
  [OFS(JSON_NT_MORE_KEY_PAIRS)][JSON_TOKEN_COMMA] = TD_ENTRY(JSON_PROD_MORE_KEY_PAIRS),
  [OFS(JSON_NT_MORE_KEY_PAIRS)][JSON_TOKEN_OBJECT_END] = TD_ENTRY(JSON_PROD_EPSILON),
};

/* the GOAL production. Not stored in the table, but will be the initial contents of the prediction stack */
static char JSON_PROD_GOAL[] = {JSON_TOKEN_END, JSON_NT_JSON, 0};

static inline JsonParseErrorType json_lex_string(JsonLexContext *lex);
static inline JsonParseErrorType json_lex_number(JsonLexContext *lex, const char *s,
                         bool *num_err, size_t *total_len);
static inline JsonParseErrorType parse_scalar(JsonLexContext *lex, const JsonSemAction *sem);
static JsonParseErrorType parse_object_field(JsonLexContext *lex, const JsonSemAction *sem);
static JsonParseErrorType parse_object(JsonLexContext *lex, const JsonSemAction *sem);
static JsonParseErrorType parse_array_element(JsonLexContext *lex, const JsonSemAction *sem);
static JsonParseErrorType parse_array(JsonLexContext *lex, const JsonSemAction *sem);
static JsonParseErrorType report_parse_error(JsonParseContext ctx, JsonLexContext *lex);
static bool allocate_incremental_state(JsonLexContext *lex);
static inline void set_fname(JsonLexContext *lex, char *fname);

/* the null action object used for pure validation */
const JsonSemAction nullSemAction =
{
  NULL, NULL, NULL, NULL, NULL,
  NULL, NULL, NULL, NULL, NULL
};

/* sentinels used for out-of-memory conditions */
static JsonLexContext failed_oom;
static JsonIncrementalState failed_inc_oom;

/* Parser support routines */

/*
 * lex_peek
 *
 * what is the current look_ahead token?
 */
static inline JsonTokenType
lex_peek(JsonLexContext *lex)
{
  return lex->token_type;
}

/*
 * lex_expect
 *
 * move the lexer to the next token if the current look_ahead token matches
 * the parameter token. Otherwise, report an error.
 */
static inline JsonParseErrorType
lex_expect(JsonParseContext ctx, JsonLexContext *lex, JsonTokenType token)
{
  if (lex_peek(lex) == token)
    return json_lex(lex);
  else
    return report_parse_error(ctx, lex);
}

/* chars to consider as part of an alphanumeric token */
#define JSON_ALPHANUMERIC_CHAR(c)  \
  (((c) >= 'a' && (c) <= 'z') || \
   ((c) >= 'A' && (c) <= 'Z') || \
   ((c) >= '0' && (c) <= '9') || \
   (c) == '_' || \
   IS_HIGHBIT_SET(c))

/*
 * Utility function to check if a string is a valid JSON number.
 *
 * str is of length len, and need not be null-terminated.
 */
bool
IsValidJsonNumber(const char *str, size_t len)
{
  bool    numeric_error;
  size_t    total_len;
  JsonLexContext dummy_lex = {0};

  if (len <= 0)
    return false;

  /*
   * json_lex_number expects a leading  '-' to have been eaten already.
   *
   * having to cast away the constness of str is ugly, but there's not much
   * easy alternative.
   */
  if (*str == '-')
  {
    dummy_lex.input = str + 1;
    dummy_lex.input_length = len - 1;
  }
  else
  {
    dummy_lex.input = str;
    dummy_lex.input_length = len;
  }

  dummy_lex.token_start = dummy_lex.input;

  json_lex_number(&dummy_lex, dummy_lex.input, &numeric_error, &total_len);

  return (!numeric_error) && (total_len == dummy_lex.input_length);
}

/*
 * makeJsonLexContextCstringLen
 *    Initialize the given JsonLexContext object, or create one
 *
 * If a valid 'lex' pointer is given, it is initialized.  This can
 * be used for stack-allocated structs, saving overhead.  If NULL is
 * given, a new struct is allocated.
 *
 * If need_escapes is true, ->strval stores the unescaped lexemes.
 * Unescaping is expensive, so only request it when necessary.
 *
 * If need_escapes is true or lex was given as NULL, then caller is
 * responsible for freeing the returned struct, either by calling
 * freeJsonLexContext() or (in backend environment) via memory context
 * cleanup.
 *
 * In shlib code, any out-of-memory failures will be deferred to time
 * of use; this function is guaranteed to return a valid JsonLexContext.
 */
JsonLexContext *
makeJsonLexContextCstringLen(JsonLexContext *lex, const char *json,
               size_t len, int encoding, bool need_escapes)
{
  if (lex == NULL)
  {
    lex = ALLOC0(sizeof(JsonLexContext));
    if (!lex)
      return &failed_oom;
    lex->flags |= JSONLEX_FREE_STRUCT;
  }
  else
    memset(lex, 0, sizeof(JsonLexContext));

  lex->errormsg = NULL;
  lex->input = lex->token_terminator = lex->line_start = json;
  lex->line_number = 1;
  lex->input_length = len;
  lex->input_encoding = encoding;
  lex->need_escapes = need_escapes;
  if (need_escapes)
  {
    /*
     * This call can fail in shlib code. We defer error handling to time
     * of use (json_lex_string()) since we might not need to parse any
     * strings anyway.
     */
    lex->strval = jsonapi_makeStringInfo();
    lex->flags |= JSONLEX_FREE_STRVAL;
  }

  return lex;
}

/*
 * Allocates the internal bookkeeping structures for incremental parsing. This
 * can only fail in-band with shlib code.
 */
#define JS_STACK_CHUNK_SIZE 64
#define JS_MAX_PROD_LEN 10    /* more than we need */
#define JSON_TD_MAX_STACK 6400  /* hard coded for now - this is a REALLY high
                 * number */
static bool
allocate_incremental_state(JsonLexContext *lex)
{
  void     *pstack,
         *prediction,
         *fnames,
         *fnull;

  lex->inc_state = ALLOC0(sizeof(JsonIncrementalState));
  pstack = ALLOC0(sizeof(JsonParserStack));
  prediction = ALLOC(JS_STACK_CHUNK_SIZE * JS_MAX_PROD_LEN);
  fnames = ALLOC(JS_STACK_CHUNK_SIZE * sizeof(char *));
  fnull = ALLOC(JS_STACK_CHUNK_SIZE * sizeof(bool));

#ifdef JSONAPI_USE_PQEXPBUFFER
  if (!lex->inc_state
    || !pstack
    || !prediction
    || !fnames
    || !fnull)
  {
    FREE(lex->inc_state);
    FREE(pstack);
    FREE(prediction);
    FREE(fnames);
    FREE(fnull);

    lex->inc_state = &failed_inc_oom;
    return false;
  }
#endif

  jsonapi_initStringInfo(&(lex->inc_state->partial_token));
  lex->pstack = pstack;
  lex->pstack->stack_size = JS_STACK_CHUNK_SIZE;
  lex->pstack->prediction = prediction;
  lex->pstack->fnames = fnames;
  lex->pstack->fnull = fnull;

  /*
   * fnames between 0 and lex_level must always be defined so that
   * freeJsonLexContext() can handle them safely. inc/dec_lex_level() handle
   * the rest.
   */
  Assert(lex->lex_level == 0);
  lex->pstack->fnames[0] = NULL;

  lex->incremental = true;
  return true;
}


/*
 * makeJsonLexContextIncremental
 *
 * Similar to above but set up for use in incremental parsing. That means we
 * need explicit stacks for predictions, field names and null indicators, but
 * we don't need the input, that will be handed in bit by bit to the
 * parse routine. We also need an accumulator for partial tokens in case
 * the boundary between chunks happens to fall in the middle of a token.
 *
 * In shlib code, any out-of-memory failures will be deferred to time of use;
 * this function is guaranteed to return a valid JsonLexContext.
 */
JsonLexContext *
makeJsonLexContextIncremental(JsonLexContext *lex, int encoding,
                bool need_escapes)
{
  if (lex == NULL)
  {
    lex = ALLOC0(sizeof(JsonLexContext));
    if (!lex)
      return &failed_oom;

    lex->flags |= JSONLEX_FREE_STRUCT;
  }
  else
    memset(lex, 0, sizeof(JsonLexContext));

  lex->line_number = 1;
  lex->input_encoding = encoding;

  if (!allocate_incremental_state(lex))
  {
    if (lex->flags & JSONLEX_FREE_STRUCT)
    {
      FREE(lex);
      return &failed_oom;
    }

    /* lex->inc_state tracks the OOM failure; we can return here. */
    return lex;
  }

  lex->need_escapes = need_escapes;
  if (need_escapes)
  {
    /*
     * This call can fail in shlib code. We defer error handling to time
     * of use (json_lex_string()) since we might not need to parse any
     * strings anyway.
     */
    lex->strval = jsonapi_makeStringInfo();
    lex->flags |= JSONLEX_FREE_STRVAL;
  }

  return lex;
}

void
setJsonLexContextOwnsTokens(JsonLexContext *lex, bool owned_by_context)
{
  if (lex->incremental && lex->inc_state->started)
  {
    /*
     * Switching this flag after parsing has already started is a
     * programming error.
     */
    Assert(false);
    return;
  }

  if (owned_by_context)
    lex->flags |= JSONLEX_CTX_OWNS_TOKENS;
  else
    lex->flags &= ~JSONLEX_CTX_OWNS_TOKENS;
}

static inline bool
inc_lex_level(JsonLexContext *lex)
{
  if (lex->incremental && (lex->lex_level + 1) >= lex->pstack->stack_size)
  {
    size_t    new_stack_size;
    char     *new_prediction;
    char    **new_fnames;
    bool     *new_fnull;

    new_stack_size = lex->pstack->stack_size + JS_STACK_CHUNK_SIZE;

    new_prediction = REALLOC(lex->pstack->prediction,
                 new_stack_size * JS_MAX_PROD_LEN);
#ifdef JSONAPI_USE_PQEXPBUFFER
    if (!new_prediction)
      return false;
#endif
    lex->pstack->prediction = new_prediction;

    new_fnames = REALLOC(lex->pstack->fnames,
               new_stack_size * sizeof(char *));
#ifdef JSONAPI_USE_PQEXPBUFFER
    if (!new_fnames)
      return false;
#endif
    lex->pstack->fnames = new_fnames;

    new_fnull = REALLOC(lex->pstack->fnull, new_stack_size * sizeof(bool));
#ifdef JSONAPI_USE_PQEXPBUFFER
    if (!new_fnull)
      return false;
#endif
    lex->pstack->fnull = new_fnull;

    lex->pstack->stack_size = new_stack_size;
  }

  lex->lex_level += 1;

  if (lex->incremental)
  {
    /*
     * Ensure freeJsonLexContext() remains safe even if no fname is
     * assigned at this level.
     */
    lex->pstack->fnames[lex->lex_level] = NULL;
  }

  return true;
}

static inline void
dec_lex_level(JsonLexContext *lex)
{
  set_fname(lex, NULL);    /* free the current level's fname, if needed */
  lex->lex_level -= 1;
}

static inline void
push_prediction(JsonParserStack *pstack, td_entry entry)
{
  memcpy(pstack->prediction + pstack->pred_index, entry.prod, entry.len);
  pstack->pred_index += entry.len;
}

static inline char
pop_prediction(JsonParserStack *pstack)
{
  Assert(pstack->pred_index > 0);
  return pstack->prediction[--pstack->pred_index];
}

static inline char
next_prediction(JsonParserStack *pstack)
{
  Assert(pstack->pred_index > 0);
  return pstack->prediction[pstack->pred_index - 1];
}

static inline bool
have_prediction(JsonParserStack *pstack)
{
  return pstack->pred_index > 0;
}

static inline void
set_fname(JsonLexContext *lex, char *fname)
{
  if (lex->flags & JSONLEX_CTX_OWNS_TOKENS)
  {
    /*
     * Don't leak prior fnames. If one hasn't been assigned yet,
     * inc_lex_level ensured that it's NULL (and therefore safe to free).
     */
    FREE(lex->pstack->fnames[lex->lex_level]);
  }

  lex->pstack->fnames[lex->lex_level] = fname;
}

static inline char *
get_fname(JsonLexContext *lex)
{
  return lex->pstack->fnames[lex->lex_level];
}

static inline void
set_fnull(JsonLexContext *lex, bool fnull)
{
  lex->pstack->fnull[lex->lex_level] = fnull;
}

static inline bool
get_fnull(JsonLexContext *lex)
{
  return lex->pstack->fnull[lex->lex_level];
}

/*
 * Free memory in a JsonLexContext.
 *
 * There's no need for this if a *lex pointer was given when the object was
 * made, need_escapes was false, and json_errdetail() was not called; or if (in
 * backend environment) a memory context delete/reset is imminent.
 */
void
freeJsonLexContext(JsonLexContext *lex)
{
  static const JsonLexContext empty = {0};

  if (!lex || lex == &failed_oom)
    return;

  if (lex->flags & JSONLEX_FREE_STRVAL)
    jsonapi_destroyStringInfo(lex->strval);

  if (lex->errormsg)
    jsonapi_destroyStringInfo(lex->errormsg);

  if (lex->incremental)
  {
    jsonapi_termStringInfo(&lex->inc_state->partial_token);
    FREE(lex->inc_state);
    FREE(lex->pstack->prediction);

    if (lex->flags & JSONLEX_CTX_OWNS_TOKENS)
    {
      int     i;

      /* Clean up any tokens that were left behind. */
      for (i = 0; i <= lex->lex_level; i++)
        FREE(lex->pstack->fnames[i]);
    }

    FREE(lex->pstack->fnames);
    FREE(lex->pstack->fnull);
    FREE(lex->pstack->scalar_val);
    FREE(lex->pstack);
  }

  if (lex->flags & JSONLEX_FREE_STRUCT)
    FREE(lex);
  else
    *lex = empty;
}

/*
 * pg_parse_json
 *
 * Publicly visible entry point for the JSON parser.
 *
 * lex is a lexing context, set up for the json to be processed by calling
 * makeJsonLexContext(). sem is a structure of function pointers to semantic
 * action routines to be called at appropriate spots during parsing, and a
 * pointer to a state object to be passed to those routines.
 *
 * If FORCE_JSON_PSTACK is defined then the routine will call the non-recursive
 * JSON parser. This is a useful way to validate that it's doing the right
 * thing at least for non-incremental cases. If this is on we expect to see
 * regression diffs relating to error messages about stack depth, but no
 * other differences.
 */
JsonParseErrorType
pg_parse_json(JsonLexContext *lex, const JsonSemAction *sem)
{
#ifdef FORCE_JSON_PSTACK
  /*
   * We don't need partial token processing, there is only one chunk. But we
   * still need to init the partial token string so that freeJsonLexContext
   * works, so perform the full incremental initialization.
   */
  if (!allocate_incremental_state(lex))
    return JSON_OUT_OF_MEMORY;

  return pg_parse_json_incremental(lex, sem, lex->input, lex->input_length, true);

#else

  JsonTokenType tok;
  JsonParseErrorType result;

  if (lex == &failed_oom)
    return JSON_OUT_OF_MEMORY;
  if (lex->incremental)
    return JSON_INVALID_LEXER_TYPE;

  /* get the initial token */
  result = json_lex(lex);
  if (result != JSON_SUCCESS)
    return result;

  tok = lex_peek(lex);

  /* parse by recursive descent */
  switch (tok)
  {
    case JSON_TOKEN_OBJECT_START:
      result = parse_object(lex, sem);
      break;
    case JSON_TOKEN_ARRAY_START:
      result = parse_array(lex, sem);
      break;
    default:
      result = parse_scalar(lex, sem); /* json can be a bare scalar */
  }

  if (result == JSON_SUCCESS)
    result = lex_expect(JSON_PARSE_END, lex, JSON_TOKEN_END);

  return result;
#endif
}

/*
 * json_count_array_elements
 *
 * Returns number of array elements in lex context at start of array token
 * until end of array token at same nesting level.
 *
 * Designed to be called from array_start routines.
 */
JsonParseErrorType
json_count_array_elements(JsonLexContext *lex, int *elements)
{
  JsonLexContext copylex;
  int     count;
  JsonParseErrorType result;

  if (lex == &failed_oom)
    return JSON_OUT_OF_MEMORY;

  /*
   * It's safe to do this with a shallow copy because the lexical routines
   * don't scribble on the input. They do scribble on the other pointers
   * etc, so doing this with a copy makes that safe.
   */
  memcpy(&copylex, lex, sizeof(JsonLexContext));
  copylex.need_escapes = false;  /* not interested in values here */
  copylex.lex_level++;

  count = 0;
  result = lex_expect(JSON_PARSE_ARRAY_START, &copylex,
            JSON_TOKEN_ARRAY_START);
  if (result != JSON_SUCCESS)
    return result;
  if (lex_peek(&copylex) != JSON_TOKEN_ARRAY_END)
  {
    while (1)
    {
      count++;
      result = parse_array_element(&copylex, &nullSemAction);
      if (result != JSON_SUCCESS)
        return result;
      if (copylex.token_type != JSON_TOKEN_COMMA)
        break;
      result = json_lex(&copylex);
      if (result != JSON_SUCCESS)
        return result;
    }
  }
  result = lex_expect(JSON_PARSE_ARRAY_NEXT, &copylex,
            JSON_TOKEN_ARRAY_END);
  if (result != JSON_SUCCESS)
    return result;

  *elements = count;
  return JSON_SUCCESS;
}

/*
 * pg_parse_json_incremental
 *
 * Routine for incremental parsing of json. This uses the non-recursive top
 * down method of the Dragon Book Algorithm 4.3. It's somewhat slower than
 * the Recursive Descent pattern used above, so we only use it for incremental
 * parsing of JSON.
 *
 * The lexing context needs to be set up by a call to
 * makeJsonLexContextIncremental(). sem is a structure of function pointers
 * to semantic action routines, which should function exactly as those used
 * in the recursive descent parser.
 *
 * This routine can be called repeatedly with chunks of JSON. On the final
 * chunk is_last must be set to true. len is the length of the json chunk,
 * which does not need to be null terminated.
 */
JsonParseErrorType
pg_parse_json_incremental(JsonLexContext *lex,
              const JsonSemAction *sem,
              const char *json,
              size_t len,
              bool is_last)
{
  JsonTokenType tok;
  JsonParseErrorType result;
  JsonParseContext ctx = JSON_PARSE_VALUE;
  JsonParserStack *pstack = lex->pstack;

  if (lex == &failed_oom || lex->inc_state == &failed_inc_oom)
    return JSON_OUT_OF_MEMORY;
  if (!lex->incremental)
    return JSON_INVALID_LEXER_TYPE;

  lex->input = lex->token_terminator = lex->line_start = json;
  lex->input_length = len;
  lex->inc_state->is_last_chunk = is_last;
  lex->inc_state->started = true;

  /* get the initial token */
  result = json_lex(lex);
  if (result != JSON_SUCCESS)
    return result;

  tok = lex_peek(lex);

  /* use prediction stack for incremental parsing */

  if (!have_prediction(pstack))
  {
    td_entry  goal = TD_ENTRY(JSON_PROD_GOAL);

    push_prediction(pstack, goal);
  }

  while (have_prediction(pstack))
  {
    char    top = pop_prediction(pstack);
    td_entry  entry;

    /*
     * these first two branches are the guts of the Table Driven method
     */
    if (top == tok)
    {
      /*
       * tok can only be a terminal symbol, so top must be too. the
       * token matches the top of the stack, so get the next token.
       */
      if (tok < JSON_TOKEN_END)
      {
        result = json_lex(lex);
        if (result != JSON_SUCCESS)
          return result;
        tok = lex_peek(lex);
      }
    }
    else if (IS_NT(top) && (entry = td_parser_table[OFS(top)][tok]).prod != NULL)
    {
      /*
       * the token is in the director set for a production of the
       * non-terminal at the top of the stack, so push the reversed RHS
       * of the production onto the stack.
       */
      push_prediction(pstack, entry);
    }
    else if (IS_SEM(top))
    {
      /*
       * top is a semantic action marker, so take action accordingly.
       * It's important to have these markers in the prediction stack
       * before any token they might need so we don't advance the token
       * prematurely. Note in a couple of cases we need to do something
       * both before and after the token.
       */
      switch (top)
      {
        case JSON_SEM_OSTART:
          {
            json_struct_action ostart = sem->object_start;

            if (lex->lex_level >= JSON_TD_MAX_STACK)
              return JSON_NESTING_TOO_DEEP;

            if (ostart != NULL)
            {
              result = (*ostart) (sem->semstate);
              if (result != JSON_SUCCESS)
                return result;
            }

            if (!inc_lex_level(lex))
              return JSON_OUT_OF_MEMORY;
          }
          break;
        case JSON_SEM_OEND:
          {
            json_struct_action oend = sem->object_end;

            dec_lex_level(lex);
            if (oend != NULL)
            {
              result = (*oend) (sem->semstate);
              if (result != JSON_SUCCESS)
                return result;
            }
          }
          break;
        case JSON_SEM_ASTART:
          {
            json_struct_action astart = sem->array_start;

            if (lex->lex_level >= JSON_TD_MAX_STACK)
              return JSON_NESTING_TOO_DEEP;

            if (astart != NULL)
            {
              result = (*astart) (sem->semstate);
              if (result != JSON_SUCCESS)
                return result;
            }

            if (!inc_lex_level(lex))
              return JSON_OUT_OF_MEMORY;
          }
          break;
        case JSON_SEM_AEND:
          {
            json_struct_action aend = sem->array_end;

            dec_lex_level(lex);
            if (aend != NULL)
            {
              result = (*aend) (sem->semstate);
              if (result != JSON_SUCCESS)
                return result;
            }
          }
          break;
        case JSON_SEM_OFIELD_INIT:
          {
            /*
             * all we do here is save out the field name. We have
             * to wait to get past the ':' to see if the next
             * value is null so we can call the semantic routine
             */
            char     *fname = NULL;
            json_ofield_action ostart = sem->object_field_start;
            json_ofield_action oend = sem->object_field_end;

            if ((ostart != NULL || oend != NULL) && lex->need_escapes)
            {
              fname = STRDUP(lex->strval->data);
              if (fname == NULL)
                return JSON_OUT_OF_MEMORY;
            }
            set_fname(lex, fname);
          }
          break;
        case JSON_SEM_OFIELD_START:
          {
            /*
             * the current token should be the first token of the
             * value
             */
            bool    isnull = tok == JSON_TOKEN_NULL;
            json_ofield_action ostart = sem->object_field_start;

            set_fnull(lex, isnull);

            if (ostart != NULL)
            {
              char     *fname = get_fname(lex);

              result = (*ostart) (sem->semstate, fname, isnull);
              if (result != JSON_SUCCESS)
                return result;
            }
          }
          break;
        case JSON_SEM_OFIELD_END:
          {
            json_ofield_action oend = sem->object_field_end;

            if (oend != NULL)
            {
              char     *fname = get_fname(lex);
              bool    isnull = get_fnull(lex);

              result = (*oend) (sem->semstate, fname, isnull);
              if (result != JSON_SUCCESS)
                return result;
            }
          }
          break;
        case JSON_SEM_AELEM_START:
          {
            json_aelem_action astart = sem->array_element_start;
            bool    isnull = tok == JSON_TOKEN_NULL;

            set_fnull(lex, isnull);

            if (astart != NULL)
            {
              result = (*astart) (sem->semstate, isnull);
              if (result != JSON_SUCCESS)
                return result;
            }
          }
          break;
        case JSON_SEM_AELEM_END:
          {
            json_aelem_action aend = sem->array_element_end;

            if (aend != NULL)
            {
              bool    isnull = get_fnull(lex);

              result = (*aend) (sem->semstate, isnull);
              if (result != JSON_SUCCESS)
                return result;
            }
          }
          break;
        case JSON_SEM_SCALAR_INIT:
          {
            json_scalar_action sfunc = sem->scalar;

            pstack->scalar_val = NULL;

            if (sfunc != NULL)
            {
              /*
               * extract the de-escaped string value, or the raw
               * lexeme
               */
              /*
               * XXX copied from RD parser but looks like a
               * buglet
               */
              if (tok == JSON_TOKEN_STRING)
              {
                if (lex->need_escapes)
                {
                  pstack->scalar_val = STRDUP(lex->strval->data);
                  if (pstack->scalar_val == NULL)
                    return JSON_OUT_OF_MEMORY;
                }
              }
              else
              {
                ptrdiff_t tlen = (lex->token_terminator - lex->token_start);

                pstack->scalar_val = ALLOC(tlen + 1);
                if (pstack->scalar_val == NULL)
                  return JSON_OUT_OF_MEMORY;

                memcpy(pstack->scalar_val, lex->token_start, tlen);
                pstack->scalar_val[tlen] = '\0';
              }
              pstack->scalar_tok = tok;
            }
          }
          break;
        case JSON_SEM_SCALAR_CALL:
          {
            /*
             * We'd like to be able to get rid of this business of
             * two bits of scalar action, but we can't. It breaks
             * certain semantic actions which expect that when
             * called the lexer has consumed the item. See for
             * example get_scalar() in jsonfuncs.c.
             */
            json_scalar_action sfunc = sem->scalar;

            if (sfunc != NULL)
            {
              result = (*sfunc) (sem->semstate, pstack->scalar_val, pstack->scalar_tok);

              /*
               * Either ownership of the token passed to the
               * callback, or we need to free it now. Either
               * way, clear our pointer to it so it doesn't get
               * freed in the future.
               */
              if (lex->flags & JSONLEX_CTX_OWNS_TOKENS)
                FREE(pstack->scalar_val);
              pstack->scalar_val = NULL;

              if (result != JSON_SUCCESS)
                return result;
            }
          }
          break;
        default:
          /* should not happen */
          break;
      }
    }
    else
    {
      /*
       * The token didn't match the stack top if it's a terminal nor a
       * production for the stack top if it's a non-terminal.
       *
       * Various cases here are Asserted to be not possible, as the
       * token would not appear at the top of the prediction stack
       * unless the lookahead matched.
       */
      switch (top)
      {
        case JSON_TOKEN_STRING:
          if (next_prediction(pstack) == JSON_TOKEN_COLON)
            ctx = JSON_PARSE_STRING;
          else
          {
            Assert(false);
            ctx = JSON_PARSE_VALUE;
          }
          break;
        case JSON_TOKEN_NUMBER:
        case JSON_TOKEN_TRUE:
        case JSON_TOKEN_FALSE:
        case JSON_TOKEN_NULL:
        case JSON_TOKEN_ARRAY_START:
        case JSON_TOKEN_OBJECT_START:
          Assert(false);
          ctx = JSON_PARSE_VALUE;
          break;
        case JSON_TOKEN_ARRAY_END:
          Assert(false);
          ctx = JSON_PARSE_ARRAY_NEXT;
          break;
        case JSON_TOKEN_OBJECT_END:
          Assert(false);
          ctx = JSON_PARSE_OBJECT_NEXT;
          break;
        case JSON_TOKEN_COMMA:
          Assert(false);
          if (next_prediction(pstack) == JSON_TOKEN_STRING)
            ctx = JSON_PARSE_OBJECT_NEXT;
          else
            ctx = JSON_PARSE_ARRAY_NEXT;
          break;
        case JSON_TOKEN_COLON:
          ctx = JSON_PARSE_OBJECT_LABEL;
          break;
        case JSON_TOKEN_END:
          ctx = JSON_PARSE_END;
          break;
        case JSON_NT_MORE_ARRAY_ELEMENTS:
          ctx = JSON_PARSE_ARRAY_NEXT;
          break;
        case JSON_NT_ARRAY_ELEMENTS:
          ctx = JSON_PARSE_ARRAY_START;
          break;
        case JSON_NT_MORE_KEY_PAIRS:
          ctx = JSON_PARSE_OBJECT_NEXT;
          break;
        case JSON_NT_KEY_PAIRS:
          ctx = JSON_PARSE_OBJECT_START;
          break;
        default:
          ctx = JSON_PARSE_VALUE;
      }
      return report_parse_error(ctx, lex);
    }
  }

  return JSON_SUCCESS;
}

/*
 *  Recursive Descent parse routines. There is one for each structural
 *  element in a json document:
 *    - scalar (string, number, true, false, null)
 *    - array  ( [ ] )
 *    - array element
 *    - object ( { } )
 *    - object field
 */
static inline JsonParseErrorType
parse_scalar(JsonLexContext *lex, const JsonSemAction *sem)
{
  char     *val = NULL;
  json_scalar_action sfunc = sem->scalar;
  JsonTokenType tok = lex_peek(lex);
  JsonParseErrorType result;

  /* a scalar must be a string, a number, true, false, or null */
  if (tok != JSON_TOKEN_STRING && tok != JSON_TOKEN_NUMBER &&
    tok != JSON_TOKEN_TRUE && tok != JSON_TOKEN_FALSE &&
    tok != JSON_TOKEN_NULL)
    return report_parse_error(JSON_PARSE_VALUE, lex);

  /* if no semantic function, just consume the token */
  if (sfunc == NULL)
    return json_lex(lex);

  /* extract the de-escaped string value, or the raw lexeme */
  if (lex_peek(lex) == JSON_TOKEN_STRING)
  {
    if (lex->need_escapes)
    {
      val = STRDUP(lex->strval->data);
      if (val == NULL)
        return JSON_OUT_OF_MEMORY;
    }
  }
  else
  {
    int     len = (lex->token_terminator - lex->token_start);

    val = ALLOC(len + 1);
    if (val == NULL)
      return JSON_OUT_OF_MEMORY;

    memcpy(val, lex->token_start, len);
    val[len] = '\0';
  }

  /* consume the token */
  result = json_lex(lex);
  if (result != JSON_SUCCESS)
  {
    FREE(val);
    return result;
  }

  /*
   * invoke the callback, which may take ownership of val. For string
   * values, val is NULL if need_escapes is false.
   */
  result = (*sfunc) (sem->semstate, val, tok);

  if (lex->flags & JSONLEX_CTX_OWNS_TOKENS)
    FREE(val);

  return result;
}

static JsonParseErrorType
parse_object_field(JsonLexContext *lex, const JsonSemAction *sem)
{
  /*
   * An object field is "fieldname" : value where value can be a scalar,
   * object or array.  Note: in user-facing docs and error messages, we
   * generally call a field name a "key".
   */

  char     *fname = NULL;
  json_ofield_action ostart = sem->object_field_start;
  json_ofield_action oend = sem->object_field_end;
  bool    isnull;
  JsonTokenType tok;
  JsonParseErrorType result;

  if (lex_peek(lex) != JSON_TOKEN_STRING)
    return report_parse_error(JSON_PARSE_STRING, lex);
  if ((ostart != NULL || oend != NULL) && lex->need_escapes)
  {
    /* fname is NULL if need_escapes is false */
    fname = STRDUP(lex->strval->data);
    if (fname == NULL)
      return JSON_OUT_OF_MEMORY;
  }
  result = json_lex(lex);
  if (result != JSON_SUCCESS)
  {
    FREE(fname);
    return result;
  }

  result = lex_expect(JSON_PARSE_OBJECT_LABEL, lex, JSON_TOKEN_COLON);
  if (result != JSON_SUCCESS)
  {
    FREE(fname);
    return result;
  }

  tok = lex_peek(lex);
  isnull = tok == JSON_TOKEN_NULL;

  if (ostart != NULL)
  {
    result = (*ostart) (sem->semstate, fname, isnull);
    if (result != JSON_SUCCESS)
      goto ofield_cleanup;
  }

  switch (tok)
  {
    case JSON_TOKEN_OBJECT_START:
      result = parse_object(lex, sem);
      break;
    case JSON_TOKEN_ARRAY_START:
      result = parse_array(lex, sem);
      break;
    default:
      result = parse_scalar(lex, sem);
  }
  if (result != JSON_SUCCESS)
    goto ofield_cleanup;

  if (oend != NULL)
  {
    result = (*oend) (sem->semstate, fname, isnull);
    if (result != JSON_SUCCESS)
      goto ofield_cleanup;
  }

ofield_cleanup:
  if (lex->flags & JSONLEX_CTX_OWNS_TOKENS)
    FREE(fname);
  return result;
}

static JsonParseErrorType
parse_object(JsonLexContext *lex, const JsonSemAction *sem)
{
  /*
   * an object is a possibly empty sequence of object fields, separated by
   * commas and surrounded by curly braces.
   */
  json_struct_action ostart = sem->object_start;
  json_struct_action oend = sem->object_end;
  JsonTokenType tok;
  JsonParseErrorType result;

#ifndef FRONTEND

  /*
   * TODO: clients need some way to put a bound on stack growth. Parse level
   * limits maybe?
   */
  check_stack_depth();
#endif

  if (ostart != NULL)
  {
    result = (*ostart) (sem->semstate);
    if (result != JSON_SUCCESS)
      return result;
  }

  /*
   * Data inside an object is at a higher nesting level than the object
   * itself. Note that we increment this after we call the semantic routine
   * for the object start and restore it before we call the routine for the
   * object end.
   */
  lex->lex_level++;

  Assert(lex_peek(lex) == JSON_TOKEN_OBJECT_START);
  result = json_lex(lex);
  if (result != JSON_SUCCESS)
    return result;

  tok = lex_peek(lex);
  switch (tok)
  {
    case JSON_TOKEN_STRING:
      result = parse_object_field(lex, sem);
      while (result == JSON_SUCCESS && lex_peek(lex) == JSON_TOKEN_COMMA)
      {
        result = json_lex(lex);
        if (result != JSON_SUCCESS)
          break;
        result = parse_object_field(lex, sem);
      }
      break;
    case JSON_TOKEN_OBJECT_END:
      break;
    default:
      /* case of an invalid initial token inside the object */
      result = report_parse_error(JSON_PARSE_OBJECT_START, lex);
  }
  if (result != JSON_SUCCESS)
    return result;

  result = lex_expect(JSON_PARSE_OBJECT_NEXT, lex, JSON_TOKEN_OBJECT_END);
  if (result != JSON_SUCCESS)
    return result;

  lex->lex_level--;

  if (oend != NULL)
  {
    result = (*oend) (sem->semstate);
    if (result != JSON_SUCCESS)
      return result;
  }

  return JSON_SUCCESS;
}

static JsonParseErrorType
parse_array_element(JsonLexContext *lex, const JsonSemAction *sem)
{
  json_aelem_action astart = sem->array_element_start;
  json_aelem_action aend = sem->array_element_end;
  JsonTokenType tok = lex_peek(lex);
  JsonParseErrorType result;
  bool    isnull;

  isnull = tok == JSON_TOKEN_NULL;

  if (astart != NULL)
  {
    result = (*astart) (sem->semstate, isnull);
    if (result != JSON_SUCCESS)
      return result;
  }

  /* an array element is any object, array or scalar */
  switch (tok)
  {
    case JSON_TOKEN_OBJECT_START:
      result = parse_object(lex, sem);
      break;
    case JSON_TOKEN_ARRAY_START:
      result = parse_array(lex, sem);
      break;
    default:
      result = parse_scalar(lex, sem);
  }

  if (result != JSON_SUCCESS)
    return result;

  if (aend != NULL)
  {
    result = (*aend) (sem->semstate, isnull);
    if (result != JSON_SUCCESS)
      return result;
  }

  return JSON_SUCCESS;
}

static JsonParseErrorType
parse_array(JsonLexContext *lex, const JsonSemAction *sem)
{
  /*
   * an array is a possibly empty sequence of array elements, separated by
   * commas and surrounded by square brackets.
   */
  json_struct_action astart = sem->array_start;
  json_struct_action aend = sem->array_end;
  JsonParseErrorType result;

#ifndef FRONTEND
  check_stack_depth();
#endif

  if (astart != NULL)
  {
    result = (*astart) (sem->semstate);
    if (result != JSON_SUCCESS)
      return result;
  }

  /*
   * Data inside an array is at a higher nesting level than the array
   * itself. Note that we increment this after we call the semantic routine
   * for the array start and restore it before we call the routine for the
   * array end.
   */
  lex->lex_level++;

  result = lex_expect(JSON_PARSE_ARRAY_START, lex, JSON_TOKEN_ARRAY_START);
  if (result == JSON_SUCCESS && lex_peek(lex) != JSON_TOKEN_ARRAY_END)
  {
    result = parse_array_element(lex, sem);

    while (result == JSON_SUCCESS && lex_peek(lex) == JSON_TOKEN_COMMA)
    {
      result = json_lex(lex);
      if (result != JSON_SUCCESS)
        break;
      result = parse_array_element(lex, sem);
    }
  }
  if (result != JSON_SUCCESS)
    return result;

  result = lex_expect(JSON_PARSE_ARRAY_NEXT, lex, JSON_TOKEN_ARRAY_END);
  if (result != JSON_SUCCESS)
    return result;

  lex->lex_level--;

  if (aend != NULL)
  {
    result = (*aend) (sem->semstate);
    if (result != JSON_SUCCESS)
      return result;
  }

  return JSON_SUCCESS;
}

/*
 * Lex one token from the input stream.
 *
 * When doing incremental parsing, we can reach the end of the input string
 * without having (or knowing we have) a complete token. If it's not the
 * final chunk of input, the partial token is then saved to the lex
 * structure's ptok StringInfo. On subsequent calls input is appended to this
 * buffer until we have something that we think is a complete token,
 * which is then lexed using a recursive call to json_lex. Processing then
 * continues as normal on subsequent calls.
 *
 * Note than when doing incremental processing, the lex.prev_token_terminator
 * should not be relied on. It could point into a previous input chunk or
 * worse.
 */
JsonParseErrorType
json_lex(JsonLexContext *lex)
{
  const char *s;
  const char *const end = lex->input + lex->input_length;
  JsonParseErrorType result;

  if (lex == &failed_oom || lex->inc_state == &failed_inc_oom)
    return JSON_OUT_OF_MEMORY;

  if (lex->incremental)
  {
    if (lex->inc_state->partial_completed)
    {
      /*
       * We just lexed a completed partial token on the last call, so
       * reset everything
       */
      jsonapi_resetStringInfo(&(lex->inc_state->partial_token));
      lex->token_terminator = lex->input;
      lex->inc_state->partial_completed = false;
    }

#ifdef JSONAPI_USE_PQEXPBUFFER
    /* Make sure our partial token buffer is valid before using it below. */
    if (PQExpBufferDataBroken(lex->inc_state->partial_token))
      return JSON_OUT_OF_MEMORY;
#endif
  }

  s = lex->token_terminator;

  if (lex->incremental && lex->inc_state->partial_token.len)
  {
    /*
     * We have a partial token. Extend it and if completed lex it by a
     * recursive call
     */
    jsonapi_StrValType *ptok = &(lex->inc_state->partial_token);
    size_t    added = 0;
    bool    tok_done = false;
    JsonLexContext dummy_lex = {0};
    JsonParseErrorType partial_result;

    if (ptok->data[0] == '"')
    {
      /*
       * It's a string. Accumulate characters until we reach an
       * unescaped '"'.
       */
      int     escapes = 0;

      for (int i = ptok->len - 1; i > 0; i--)
      {
        /* count the trailing backslashes on the partial token */
        if (ptok->data[i] == '\\')
          escapes++;
        else
          break;
      }

      for (size_t i = 0; i < lex->input_length; i++)
      {
        char    c = lex->input[i];

        jsonapi_appendStringInfoCharMacro(ptok, c);
        added++;
        if (c == '"' && escapes % 2 == 0)
        {
          tok_done = true;
          break;
        }
        if (c == '\\')
          escapes++;
        else
          escapes = 0;
      }
    }
    else
    {
      /* not a string */
      char    c = ptok->data[0];

      if (c == '-' || (c >= '0' && c <= '9'))
      {
        /*
         * Accumulate numeric continuations, respecting JSON number
         * grammar: -? int [frac] [exp]
         *
         * We must track what parts of the number we've already seen
         * so we don't over-consume.  '.' is valid only once and not
         * after 'e'/'E'; 'e'/'E' is valid only once; '+'/'-' are
         * valid only immediately after 'e'/'E'.
         */
        bool    numend = false;
        bool    seen_dot = false;
        bool    seen_exp = false;
        char    prev;

        /* Scan existing partial token for state */
        for (int j = 0; j < ptok->len; j++)
        {
          char    pc = ptok->data[j];

          if (pc == '.')
            seen_dot = true;
          else if (pc == 'e' || pc == 'E')
            seen_exp = true;
        }
        prev = ptok->data[ptok->len - 1];

        for (size_t i = 0; i < lex->input_length && !numend; i++)
        {
          char    cc = lex->input[i];

          switch (cc)
          {
            case '+':
            case '-':
              if (prev != 'e' && prev != 'E')
              {
                numend = true;
                break;
              }
              jsonapi_appendStringInfoCharMacro(ptok, cc);
              added++;
              break;
            case '.':
              if (seen_dot || seen_exp)
              {
                numend = true;
                break;
              }
              seen_dot = true;
              jsonapi_appendStringInfoCharMacro(ptok, cc);
              added++;
              break;
            case 'e':
            case 'E':
              if (seen_exp)
              {
                numend = true;
                break;
              }
              seen_exp = true;
              jsonapi_appendStringInfoCharMacro(ptok, cc);
              added++;
              break;
            case '0':
            case '1':
            case '2':
            case '3':
            case '4':
            case '5':
            case '6':
            case '7':
            case '8':
            case '9':
              jsonapi_appendStringInfoCharMacro(ptok, cc);
              added++;
              break;
            default:
              numend = true;
          }
          if (!numend)
            prev = cc;
        }
      }

      /*
       * Add any remaining alphanumeric chars. This takes care of the
       * {null, false, true} literals as well as any trailing
       * alphanumeric junk on non-string tokens.
       */
      for (size_t i = added; i < lex->input_length; i++)
      {
        char    cc = lex->input[i];

        if (JSON_ALPHANUMERIC_CHAR(cc))
        {
          jsonapi_appendStringInfoCharMacro(ptok, cc);
          added++;
        }
        else
        {
          tok_done = true;
          break;
        }
      }
      if (added == lex->input_length &&
        lex->inc_state->is_last_chunk)
      {
        tok_done = true;
      }
    }

    if (!tok_done)
    {
      /* We should have consumed the whole chunk in this case. */
      Assert(added == lex->input_length);

      if (!lex->inc_state->is_last_chunk)
        return JSON_INCOMPLETE;

      /* json_errdetail() needs access to the accumulated token. */
      lex->token_start = ptok->data;
      lex->token_terminator = ptok->data + ptok->len;
      return JSON_INVALID_TOKEN;
    }

    /*
     * Everything up to lex->input[added] has been added to the partial
     * token, so move the input past it.
     */
    lex->input += added;
    lex->input_length -= added;

    dummy_lex.input = dummy_lex.token_terminator =
      dummy_lex.line_start = ptok->data;
    dummy_lex.line_number = lex->line_number;
    dummy_lex.input_length = ptok->len;
    dummy_lex.input_encoding = lex->input_encoding;
    dummy_lex.incremental = false;
    dummy_lex.need_escapes = lex->need_escapes;
    dummy_lex.strval = lex->strval;

    partial_result = json_lex(&dummy_lex);

    /*
     * We either have a complete token or an error. In either case we need
     * to point to the partial token data for the semantic or error
     * routines. If it's not an error we'll readjust on the next call to
     * json_lex.
     */
    lex->token_type = dummy_lex.token_type;
    lex->line_number = dummy_lex.line_number;

    /*
     * We know the prev_token_terminator must be back in some previous
     * piece of input, so we just make it NULL.
     */
    lex->prev_token_terminator = NULL;

    /*
     * Normally token_start would be ptok->data, but it could be later,
     * see json_lex_string's handling of invalid escapes.
     */
    lex->token_start = dummy_lex.token_start;
    lex->token_terminator = dummy_lex.token_terminator;
    if (partial_result == JSON_SUCCESS)
    {
      /* make sure we've used all the input */
      if (lex->token_terminator - lex->token_start != ptok->len)
      {
        Assert(false);
        return JSON_INVALID_TOKEN;
      }

      lex->inc_state->partial_completed = true;
    }
    return partial_result;
    /* end of partial token processing */
  }

  /* Skip leading whitespace. */
  while (s < end && (*s == ' ' || *s == '\t' || *s == '\n' || *s == '\r'))
  {
    if (*s++ == '\n')
    {
      ++lex->line_number;
      lex->line_start = s;
    }
  }
  lex->token_start = s;

  /* Determine token type. */
  if (s >= end)
  {
    lex->token_start = NULL;
    lex->prev_token_terminator = lex->token_terminator;
    lex->token_terminator = s;
    lex->token_type = JSON_TOKEN_END;
  }
  else
  {
    switch (*s)
    {
        /* Single-character token, some kind of punctuation mark. */
      case '{':
        lex->prev_token_terminator = lex->token_terminator;
        lex->token_terminator = s + 1;
        lex->token_type = JSON_TOKEN_OBJECT_START;
        break;
      case '}':
        lex->prev_token_terminator = lex->token_terminator;
        lex->token_terminator = s + 1;
        lex->token_type = JSON_TOKEN_OBJECT_END;
        break;
      case '[':
        lex->prev_token_terminator = lex->token_terminator;
        lex->token_terminator = s + 1;
        lex->token_type = JSON_TOKEN_ARRAY_START;
        break;
      case ']':
        lex->prev_token_terminator = lex->token_terminator;
        lex->token_terminator = s + 1;
        lex->token_type = JSON_TOKEN_ARRAY_END;
        break;
      case ',':
        lex->prev_token_terminator = lex->token_terminator;
        lex->token_terminator = s + 1;
        lex->token_type = JSON_TOKEN_COMMA;
        break;
      case ':':
        lex->prev_token_terminator = lex->token_terminator;
        lex->token_terminator = s + 1;
        lex->token_type = JSON_TOKEN_COLON;
        break;
      case '"':
        /* string */
        result = json_lex_string(lex);
        if (result != JSON_SUCCESS)
          return result;
        lex->token_type = JSON_TOKEN_STRING;
        break;
      case '-':
        /* Negative number. */
        result = json_lex_number(lex, s + 1, NULL, NULL);
        if (result != JSON_SUCCESS)
          return result;
        lex->token_type = JSON_TOKEN_NUMBER;
        break;
      case '0':
      case '1':
      case '2':
      case '3':
      case '4':
      case '5':
      case '6':
      case '7':
      case '8':
      case '9':
        /* Positive number. */
        result = json_lex_number(lex, s, NULL, NULL);
        if (result != JSON_SUCCESS)
          return result;
        lex->token_type = JSON_TOKEN_NUMBER;
        break;
      default:
        {
          const char *p;

          /*
           * We're not dealing with a string, number, legal
           * punctuation mark, or end of string.  The only legal
           * tokens we might find here are true, false, and null,
           * but for error reporting purposes we scan until we see a
           * non-alphanumeric character.  That way, we can report
           * the whole word as an unexpected token, rather than just
           * some unintuitive prefix thereof.
           */
          for (p = s; p < end && JSON_ALPHANUMERIC_CHAR(*p); p++)
             /* skip */ ;

          /*
           * We got some sort of unexpected punctuation or an
           * otherwise unexpected character, so just complain about
           * that one character.
           */
          if (p == s)
          {
            lex->prev_token_terminator = lex->token_terminator;
            lex->token_terminator = s + 1;
            return JSON_INVALID_TOKEN;
          }

          if (lex->incremental && !lex->inc_state->is_last_chunk &&
            p == lex->input + lex->input_length)
          {
            jsonapi_appendBinaryStringInfo(&(lex->inc_state->partial_token), s, end - s);
            return JSON_INCOMPLETE;
          }

          /*
           * We've got a real alphanumeric token here.  If it
           * happens to be true, false, or null, all is well.  If
           * not, error out.
           */
          lex->prev_token_terminator = lex->token_terminator;
          lex->token_terminator = p;
          if (p - s == 4)
          {
            if (memcmp(s, "true", 4) == 0)
              lex->token_type = JSON_TOKEN_TRUE;
            else if (memcmp(s, "null", 4) == 0)
              lex->token_type = JSON_TOKEN_NULL;
            else
              return JSON_INVALID_TOKEN;
          }
          else if (p - s == 5 && memcmp(s, "false", 5) == 0)
            lex->token_type = JSON_TOKEN_FALSE;
          else
            return JSON_INVALID_TOKEN;
        }
    }           /* end of switch */
  }

  if (lex->incremental && lex->token_type == JSON_TOKEN_END && !lex->inc_state->is_last_chunk)
    return JSON_INCOMPLETE;
  else
    return JSON_SUCCESS;
}

/*
 * The next token in the input stream is known to be a string; lex it.
 *
 * If lex->strval isn't NULL, fill it with the decoded string.
 * Set lex->token_terminator to the end of the decoded input, and in
 * success cases, transfer its previous value to lex->prev_token_terminator.
 * Return JSON_SUCCESS or an error code.
 *
 * Note: be careful that all error exits advance lex->token_terminator
 * to the point after the character we detected the error on.
 */
static inline JsonParseErrorType
json_lex_string(JsonLexContext *lex)
{
  const char *s;
  const char *const end = lex->input + lex->input_length;
  int     hi_surrogate = -1;

  /* Convenience macros for error exits */
#define FAIL_OR_INCOMPLETE_AT_CHAR_START(code) \
  do { \
    if (lex->incremental && !lex->inc_state->is_last_chunk) \
    { \
      jsonapi_appendBinaryStringInfo(&lex->inc_state->partial_token, \
                       lex->token_start, \
                       end - lex->token_start); \
      return JSON_INCOMPLETE; \
    } \
    lex->token_terminator = s; \
    return code; \
  } while (0)
#define FAIL_AT_CHAR_END(code) \
  do { \
    ptrdiff_t remaining = end - s; \
    int     charlen; \
    charlen = pg_encoding_mblen_or_incomplete(lex->input_encoding, \
                          s, remaining); \
    lex->token_terminator = (charlen <= remaining) ? s + charlen : end; \
    return code; \
  } while (0)

  if (lex->need_escapes)
  {
#ifdef JSONAPI_USE_PQEXPBUFFER
    /* make sure initialization succeeded */
    if (lex->strval == NULL)
      return JSON_OUT_OF_MEMORY;
#endif
    jsonapi_resetStringInfo(lex->strval);
  }

  Assert(lex->input_length > 0);
  s = lex->token_start;
  for (;;)
  {
    s++;
    /* Premature end of the string. */
    if (s >= end)
      FAIL_OR_INCOMPLETE_AT_CHAR_START(JSON_INVALID_TOKEN);
    else if (*s == '"')
      break;
    else if (*s == '\\')
    {
      /* OK, we have an escape character. */
      s++;
      if (s >= end)
        FAIL_OR_INCOMPLETE_AT_CHAR_START(JSON_INVALID_TOKEN);
      else if (*s == 'u')
      {
        int     i;
        int     ch = 0;

        for (i = 1; i <= 4; i++)
        {
          s++;
          if (s >= end)
            FAIL_OR_INCOMPLETE_AT_CHAR_START(JSON_INVALID_TOKEN);
          else if (*s >= '0' && *s <= '9')
            ch = (ch * 16) + (*s - '0');
          else if (*s >= 'a' && *s <= 'f')
            ch = (ch * 16) + (*s - 'a') + 10;
          else if (*s >= 'A' && *s <= 'F')
            ch = (ch * 16) + (*s - 'A') + 10;
          else
            FAIL_AT_CHAR_END(JSON_UNICODE_ESCAPE_FORMAT);
        }
        if (lex->need_escapes)
        {
          /*
           * Combine surrogate pairs.
           */
          if (is_utf16_surrogate_first(ch))
          {
            if (hi_surrogate != -1)
              FAIL_AT_CHAR_END(JSON_UNICODE_HIGH_SURROGATE);
            hi_surrogate = ch;
            continue;
          }
          else if (is_utf16_surrogate_second(ch))
          {
            if (hi_surrogate == -1)
              FAIL_AT_CHAR_END(JSON_UNICODE_LOW_SURROGATE);
            ch = surrogate_pair_to_codepoint(hi_surrogate, ch);
            hi_surrogate = -1;
          }

          if (hi_surrogate != -1)
            FAIL_AT_CHAR_END(JSON_UNICODE_LOW_SURROGATE);

          /*
           * Reject invalid cases.  We can't have a value above
           * 0xFFFF here (since we only accepted 4 hex digits
           * above), so no need to test for out-of-range chars.
           */
          if (ch == 0)
          {
            /* We can't allow this, since our TEXT type doesn't */
            FAIL_AT_CHAR_END(JSON_UNICODE_CODE_POINT_ZERO);
          }

          /*
           * Add the represented character to lex->strval.  In the
           * backend, we can let pg_unicode_to_server_noerror()
           * handle any required character set conversion; in
           * frontend, we can only deal with trivial conversions.
           */
#ifndef FRONTEND
          {
            char    cbuf[MAX_UNICODE_EQUIVALENT_STRING + 1];

            if (!pg_unicode_to_server_noerror(ch, (unsigned char *) cbuf))
              FAIL_AT_CHAR_END(JSON_UNICODE_UNTRANSLATABLE);
            appendStringInfoString(lex->strval, cbuf);
          }
#else
          if (lex->input_encoding == PG_UTF8)
          {
            /* OK, we can map the code point to UTF8 easily */
            char    utf8str[5];
            int     utf8len;

            unicode_to_utf8(ch, (unsigned char *) utf8str);
            utf8len = pg_utf_mblen((unsigned char *) utf8str);
            jsonapi_appendBinaryStringInfo(lex->strval, utf8str, utf8len);
          }
          else if (ch <= 0x007f)
          {
            /* The ASCII range is the same in all encodings */
            jsonapi_appendStringInfoChar(lex->strval, (char) ch);
          }
          else
            FAIL_AT_CHAR_END(JSON_UNICODE_HIGH_ESCAPE);
#endif              /* FRONTEND */
        }
      }
      else if (lex->need_escapes)
      {
        if (hi_surrogate != -1)
          FAIL_AT_CHAR_END(JSON_UNICODE_LOW_SURROGATE);

        switch (*s)
        {
          case '"':
          case '\\':
          case '/':
            jsonapi_appendStringInfoChar(lex->strval, *s);
            break;
          case 'b':
            jsonapi_appendStringInfoChar(lex->strval, '\b');
            break;
          case 'f':
            jsonapi_appendStringInfoChar(lex->strval, '\f');
            break;
          case 'n':
            jsonapi_appendStringInfoChar(lex->strval, '\n');
            break;
          case 'r':
            jsonapi_appendStringInfoChar(lex->strval, '\r');
            break;
          case 't':
            jsonapi_appendStringInfoChar(lex->strval, '\t');
            break;
          default:

            /*
             * Not a valid string escape, so signal error.  We
             * adjust token_start so that just the escape sequence
             * is reported, not the whole string.
             */
            lex->token_start = s;
            FAIL_AT_CHAR_END(JSON_ESCAPING_INVALID);
        }
      }
      else if (strchr("\"\\/bfnrt", *s) == NULL)
      {
        /*
         * Simpler processing if we're not bothered about de-escaping
         *
         * It's very tempting to remove the strchr() call here and
         * replace it with a switch statement, but testing so far has
         * shown it's not a performance win.
         */
        lex->token_start = s;
        FAIL_AT_CHAR_END(JSON_ESCAPING_INVALID);
      }
    }
    else
    {
      const char *p = s;

      if (hi_surrogate != -1)
        FAIL_AT_CHAR_END(JSON_UNICODE_LOW_SURROGATE);

      /*
       * Skip to the first byte that requires special handling, so we
       * can batch calls to jsonapi_appendBinaryStringInfo.
       */
      while (p < end - sizeof(Vector8) &&
           !pg_lfind8('\\', (const uint8 *) p, sizeof(Vector8)) &&
           !pg_lfind8('"', (const uint8 *) p, sizeof(Vector8)) &&
           !pg_lfind8_le(31, (const uint8 *) p, sizeof(Vector8)))
        p += sizeof(Vector8);

      for (; p < end; p++)
      {
        if (*p == '\\' || *p == '"')
          break;
        else if ((unsigned char) *p <= 31)
        {
          /* Per RFC4627, these characters MUST be escaped. */
          /*
           * Since *p isn't printable, exclude it from the context
           * string
           */
          lex->token_terminator = p;
          return JSON_ESCAPING_REQUIRED;
        }
      }

      if (lex->need_escapes)
        jsonapi_appendBinaryStringInfo(lex->strval, s, p - s);

      /*
       * s will be incremented at the top of the loop, so set it to just
       * behind our lookahead position
       */
      s = p - 1;
    }
  }

  if (hi_surrogate != -1)
  {
    lex->token_terminator = s + 1;
    return JSON_UNICODE_LOW_SURROGATE;
  }

#ifdef JSONAPI_USE_PQEXPBUFFER
  if (lex->need_escapes && PQExpBufferBroken(lex->strval))
    return JSON_OUT_OF_MEMORY;
#endif

  /* Hooray, we found the end of the string! */
  lex->prev_token_terminator = lex->token_terminator;
  lex->token_terminator = s + 1;
  return JSON_SUCCESS;

#undef FAIL_OR_INCOMPLETE_AT_CHAR_START
#undef FAIL_AT_CHAR_END
}

/*
 * The next token in the input stream is known to be a number; lex it.
 *
 * In JSON, a number consists of four parts:
 *
 * (1) An optional minus sign ('-').
 *
 * (2) Either a single '0', or a string of one or more digits that does not
 *     begin with a '0'.
 *
 * (3) An optional decimal part, consisting of a period ('.') followed by
 *     one or more digits.  (Note: While this part can be omitted
 *     completely, it's not OK to have only the decimal point without
 *     any digits afterwards.)
 *
 * (4) An optional exponent part, consisting of 'e' or 'E', optionally
 *     followed by '+' or '-', followed by one or more digits.  (Note:
 *     As with the decimal part, if 'e' or 'E' is present, it must be
 *     followed by at least one digit.)
 *
 * The 's' argument to this function points to the ostensible beginning
 * of part 2 - i.e. the character after any optional minus sign, or the
 * first character of the string if there is none.
 *
 * If num_err is not NULL, we return an error flag to *num_err rather than
 * raising an error for a badly-formed number.  Also, if total_len is not NULL
 * the distance from lex->input to the token end+1 is returned to *total_len.
 */
static inline JsonParseErrorType
json_lex_number(JsonLexContext *lex, const char *s,
        bool *num_err, size_t *total_len)
{
  bool    error = false;
  int     len = s - lex->input;

  /* Part (1): leading sign indicator. */
  /* Caller already did this for us; so do nothing. */

  /* Part (2): parse main digit string. */
  if (len < lex->input_length && *s == '0')
  {
    s++;
    len++;
  }
  else if (len < lex->input_length && *s >= '1' && *s <= '9')
  {
    do
    {
      s++;
      len++;
    } while (len < lex->input_length && *s >= '0' && *s <= '9');
  }
  else
    error = true;

  /* Part (3): parse optional decimal portion. */
  if (len < lex->input_length && *s == '.')
  {
    s++;
    len++;
    if (len == lex->input_length || *s < '0' || *s > '9')
      error = true;
    else
    {
      do
      {
        s++;
        len++;
      } while (len < lex->input_length && *s >= '0' && *s <= '9');
    }
  }

  /* Part (4): parse optional exponent. */
  if (len < lex->input_length && (*s == 'e' || *s == 'E'))
  {
    s++;
    len++;
    if (len < lex->input_length && (*s == '+' || *s == '-'))
    {
      s++;
      len++;
    }
    if (len == lex->input_length || *s < '0' || *s > '9')
      error = true;
    else
    {
      do
      {
        s++;
        len++;
      } while (len < lex->input_length && *s >= '0' && *s <= '9');
    }
  }

  /*
   * Check for trailing garbage.  As in json_lex(), any alphanumeric stuff
   * here should be considered part of the token for error-reporting
   * purposes.
   */
  for (; len < lex->input_length && JSON_ALPHANUMERIC_CHAR(*s); s++, len++)
    error = true;

  if (total_len != NULL)
    *total_len = len;

  if (lex->incremental && !lex->inc_state->is_last_chunk &&
    len >= lex->input_length)
  {
    jsonapi_appendBinaryStringInfo(&lex->inc_state->partial_token,
                     lex->token_start, s - lex->token_start);
    if (num_err != NULL)
      *num_err = error;

    return JSON_INCOMPLETE;
  }
  else if (num_err != NULL)
  {
    /* let the caller handle any error */
    *num_err = error;
  }
  else
  {
    /* return token endpoint */
    lex->prev_token_terminator = lex->token_terminator;
    lex->token_terminator = s;
    /* handle error if any */
    if (error)
      return JSON_INVALID_TOKEN;
  }

  return JSON_SUCCESS;
}

/*
 * Report a parse error.
 *
 * lex->token_start and lex->token_terminator must identify the current token.
 */
static JsonParseErrorType
report_parse_error(JsonParseContext ctx, JsonLexContext *lex)
{
  /* Handle case where the input ended prematurely. */
  if (lex->token_start == NULL || lex->token_type == JSON_TOKEN_END)
    return JSON_EXPECTED_MORE;

  /* Otherwise choose the error type based on the parsing context. */
  switch (ctx)
  {
    case JSON_PARSE_END:
      return JSON_EXPECTED_END;
    case JSON_PARSE_VALUE:
      return JSON_EXPECTED_JSON;
    case JSON_PARSE_STRING:
      return JSON_EXPECTED_STRING;
    case JSON_PARSE_ARRAY_START:
      return JSON_EXPECTED_ARRAY_FIRST;
    case JSON_PARSE_ARRAY_NEXT:
      return JSON_EXPECTED_ARRAY_NEXT;
    case JSON_PARSE_OBJECT_START:
      return JSON_EXPECTED_OBJECT_FIRST;
    case JSON_PARSE_OBJECT_LABEL:
      return JSON_EXPECTED_COLON;
    case JSON_PARSE_OBJECT_NEXT:
      return JSON_EXPECTED_OBJECT_NEXT;
    case JSON_PARSE_OBJECT_COMMA:
      return JSON_EXPECTED_STRING;
  }

  /*
   * We don't use a default: case, so that the compiler will warn about
   * unhandled enum values.
   */
  Assert(false);
  return JSON_SUCCESS;   /* silence stupider compilers */
}

/*
 * Construct an (already translated) detail message for a JSON error.
 *
 * The returned pointer should not be freed, the allocation is either static
 * or owned by the JsonLexContext.
 */
char *
json_errdetail(JsonParseErrorType error, JsonLexContext *lex)
{
  if (error == JSON_OUT_OF_MEMORY || lex == &failed_oom)
  {
    /* Short circuit. Allocating anything for this case is unhelpful. */
    return _("out of memory");
  }

  if (lex->errormsg)
    jsonapi_resetStringInfo(lex->errormsg);
  else
    lex->errormsg = jsonapi_makeStringInfo();

  /*
   * A helper for error messages that should print the current token. The
   * format must contain exactly one %.*s specifier.
   */
#define json_token_error(lex, format) \
  jsonapi_appendStringInfo((lex)->errormsg, _(format), \
               (int) ((lex)->token_terminator - (lex)->token_start), \
               (lex)->token_start);

  switch (error)
  {
    case JSON_INCOMPLETE:
    case JSON_SUCCESS:
      /* fall through to the error code after switch */
      break;
    case JSON_INVALID_LEXER_TYPE:
      if (lex->incremental)
        return _("Recursive descent parser cannot use incremental lexer.");
      else
        return _("Incremental parser requires incremental lexer.");
    case JSON_NESTING_TOO_DEEP:
      return (_("JSON nested too deep, maximum permitted depth is 6400."));
    case JSON_ESCAPING_INVALID:
      json_token_error(lex, "Escape sequence \"\\%.*s\" is invalid.");
      break;
    case JSON_ESCAPING_REQUIRED:
      jsonapi_appendStringInfo(lex->errormsg,
                   _("Character with value 0x%02x must be escaped."),
                   (unsigned char) *(lex->token_terminator));
      break;
    case JSON_EXPECTED_END:
      json_token_error(lex, "Expected end of input, but found \"%.*s\".");
      break;
    case JSON_EXPECTED_ARRAY_FIRST:
      json_token_error(lex, "Expected array element or \"]\", but found \"%.*s\".");
      break;
    case JSON_EXPECTED_ARRAY_NEXT:
      json_token_error(lex, "Expected \",\" or \"]\", but found \"%.*s\".");
      break;
    case JSON_EXPECTED_COLON:
      json_token_error(lex, "Expected \":\", but found \"%.*s\".");
      break;
    case JSON_EXPECTED_JSON:
      json_token_error(lex, "Expected JSON value, but found \"%.*s\".");
      break;
    case JSON_EXPECTED_MORE:
      return _("The input string ended unexpectedly.");
    case JSON_EXPECTED_OBJECT_FIRST:
      json_token_error(lex, "Expected string or \"}\", but found \"%.*s\".");
      break;
    case JSON_EXPECTED_OBJECT_NEXT:
      json_token_error(lex, "Expected \",\" or \"}\", but found \"%.*s\".");
      break;
    case JSON_EXPECTED_STRING:
      json_token_error(lex, "Expected string, but found \"%.*s\".");
      break;
    case JSON_INVALID_TOKEN:
      json_token_error(lex, "Token \"%.*s\" is invalid.");
      break;
    case JSON_OUT_OF_MEMORY:
      /* should have been handled above; use the error path */
      break;
    case JSON_UNICODE_CODE_POINT_ZERO:
      return _("\\u0000 cannot be converted to text.");
    case JSON_UNICODE_ESCAPE_FORMAT:
      return _("\"\\u\" must be followed by four hexadecimal digits.");
    case JSON_UNICODE_HIGH_ESCAPE:
      /* note: this case is only reachable in frontend not backend */
      return _("Unicode escape values cannot be used for code point values above 007F when the encoding is not UTF8.");
    case JSON_UNICODE_UNTRANSLATABLE:

      /*
       * Note: this case is only reachable in backend and not frontend.
       * #ifdef it away so the frontend doesn't try to link against
       * backend functionality.
       */
#ifndef FRONTEND
      return psprintf(_("Unicode escape value could not be translated to the server's encoding %s."),
              GetDatabaseEncodingName());
#else
      Assert(false);
      break;
#endif
    case JSON_UNICODE_HIGH_SURROGATE:
      return _("Unicode high surrogate must not follow a high surrogate.");
    case JSON_UNICODE_LOW_SURROGATE:
      return _("Unicode low surrogate must follow a high surrogate.");
    case JSON_SEM_ACTION_FAILED:
      /* fall through to the error code after switch */
      break;
  }
#undef json_token_error

  /* Note that lex->errormsg can be NULL in shlib code. */
  if (lex->errormsg && lex->errormsg->len == 0)
  {
    /*
     * We don't use a default: case, so that the compiler will warn about
     * unhandled enum values.  But this needs to be here anyway to cover
     * the possibility of an incorrect input.
     */
    jsonapi_appendStringInfo(lex->errormsg,
                 "unexpected json parse error type: %d",
                 (int) error);
  }

#ifdef JSONAPI_USE_PQEXPBUFFER
  if (PQExpBufferBroken(lex->errormsg))
    return _("out of memory while constructing error description");
#endif

  return lex->errormsg->data;
}

Coverage Report

Created: 2026-11-12 07:20