/*

 * xpointer.c : Code to handle XML Pointer

 *

 * Base implementation was made accordingly to

 * W3C Candidate Recommendation 7 June 2000

 * http://www.w3.org/TR/2000/CR-xptr-20000607

 *

 * Added support for the element() scheme described in:

 * W3C Proposed Recommendation 13 November 2002

 * http://www.w3.org/TR/2002/PR-xptr-element-20021113/

 *

 * See Copyright for the status of this software.

 *

 * Author: Daniel Veillard

 */

/* To avoid EBCDIC trouble when parsing on zOS */

#if defined(__MVS__)

#pragma convert("ISO8859-1")

#endif

#define IN_LIBXML

#include "libxml.h"

/*

 * TODO: better handling of error cases, the full expression should

 *       be parsed beforehand instead of a progressive evaluation

 * TODO: Access into entities references are not supported now ...

 *       need a start to be able to pop out of entities refs since

 *       parent is the entity declaration, not the ref.

 */

#include <string.h>

#include <libxml/xpointer.h>

#include <libxml/xmlmemory.h>

#include <libxml/parserInternals.h>

#include <libxml/uri.h>

#include <libxml/xpath.h>

#include <libxml/xpathInternals.h>

#include <libxml/xmlerror.h>

#ifdef LIBXML_XPTR_ENABLED

/* Add support of the xmlns() xpointer scheme to initialize the namespaces */

#define XPTR_XMLNS_SCHEME

#include "private/error.h"

#include "private/xpath.h"

/************************************************************************

 *                  *

 *    Some factorized error routines        *

 *                  *

 ************************************************************************/

/**

 * Handle an XPointer error

 *

 * @param ctxt  an XPTR evaluation context

 * @param code  error code

 * @param msg  error message

 * @param extra  extra information

 */

static void LIBXML_ATTR_FORMAT(3,0)

xmlXPtrErr(xmlXPathParserContextPtr ctxt, int code,

           const char * msg, const xmlChar *extra)

{

    xmlStructuredErrorFunc serror = NULL;

    void *data = NULL;

    xmlNodePtr node = NULL;

    int res;

    if (ctxt == NULL)

        return;

    /* Only report the first error */

    if (ctxt->error != 0)

        return;

    ctxt->error = code;

    if (ctxt->context != NULL) {

        xmlErrorPtr err = &ctxt->context->lastError;

        /* cleanup current last error */

        xmlResetError(err);

        err->domain = XML_FROM_XPOINTER;

        err->code = code;

        err->level = XML_ERR_ERROR;

        err->str1 = (char *) xmlStrdup(ctxt->base);

        if (err->str1 == NULL) {

            xmlXPathPErrMemory(ctxt);

            return;

        }

        err->int1 = ctxt->cur - ctxt->base;

        err->node = ctxt->context->debugNode;

        serror = ctxt->context->error;

        data = ctxt->context->userData;

        node = ctxt->context->debugNode;

    }

    res = xmlRaiseError(serror, NULL, data, NULL, node,

                        XML_FROM_XPOINTER, code, XML_ERR_ERROR, NULL, 0,

                        (const char *) extra, (const char *) ctxt->base,

                        NULL, ctxt->cur - ctxt->base, 0,

                        msg, extra);

    if (res < 0)

        xmlXPathPErrMemory(ctxt);

}

/************************************************************************

 *                  *

 *    A few helper functions for child sequences    *

 *                  *

 ************************************************************************/

/**

 * @param cur  the node

 * @param no  the child number

 * @returns the `no`'th element child of `cur` or NULL

 */

static xmlNodePtr

xmlXPtrGetNthChild(xmlNodePtr cur, int no) {

    int i;

    if ((cur == NULL) || (cur->type == XML_NAMESPACE_DECL))

  return(cur);

    cur = cur->children;

    for (i = 0;i <= no;cur = cur->next) {

  if (cur == NULL)

      return(cur);

  if ((cur->type == XML_ELEMENT_NODE) ||

      (cur->type == XML_DOCUMENT_NODE) ||

      (cur->type == XML_HTML_DOCUMENT_NODE)) {

      i++;

      if (i == no)

    break;

  }

    }

    return(cur);

}

/************************************************************************

 *                  *

 *      The parser          *

 *                  *

 ************************************************************************/

static void xmlXPtrEvalChildSeq(xmlXPathParserContextPtr ctxt, xmlChar *name);

/*

 * Macros for accessing the content. Those should be used only by the parser,

 * and not exported.

 *

 * Dirty macros, i.e. one need to make assumption on the context to use them

 *

 *   CUR     returns the current xmlChar value, i.e. a 8 bit value

 *           in ISO-Latin or UTF-8.

 *           This should be used internally by the parser

 *           only to compare to ASCII values otherwise it would break when

 *           running with UTF-8 encoding.

 *   NXT(n)  returns the n'th next xmlChar. Same as CUR is should be used only

 *           to compare on ASCII based substring.

 *   SKIP(n) Skip n xmlChar, and must also be used only to skip ASCII defined

 *           strings within the parser.

 *   CURRENT Returns the current char value, with the full decoding of

 *           UTF-8 if we are using this mode. It returns an int.

 *   NEXT    Skip to the next character, this does the proper decoding

 *           in UTF-8 mode. It also pop-up unfinished entities on the fly.

 *           It returns the pointer to the current xmlChar.

 */

#define CUR (*ctxt->cur)

#define SKIP(val) ctxt->cur += (val)

#define NXT(val) ctxt->cur[(val)]

#define SKIP_BLANKS             \

    while (IS_BLANK_CH(*(ctxt->cur))) NEXT

#define CURRENT (*ctxt->cur)

#define NEXT ((*ctxt->cur) ?  ctxt->cur++: ctxt->cur)

/*

 * @param ctxt  the XPointer Parser context

 * @param index  the child number

 *

 * Move the current node of the nodeset on the stack to the

 * given child if found

 */

static void

xmlXPtrGetChildNo(xmlXPathParserContextPtr ctxt, int indx) {

    xmlNodePtr cur = NULL;

    xmlXPathObjectPtr obj;

    xmlNodeSetPtr oldset;

    CHECK_TYPE(XPATH_NODESET);

    obj = xmlXPathValuePop(ctxt);

    oldset = obj->nodesetval;

    if ((indx <= 0) || (oldset == NULL) || (oldset->nodeNr != 1)) {

  xmlXPathFreeObject(obj);

  xmlXPathValuePush(ctxt, xmlXPathNewNodeSet(NULL));

  return;

    }

    cur = xmlXPtrGetNthChild(oldset->nodeTab[0], indx);

    if (cur == NULL) {

  xmlXPathFreeObject(obj);

  xmlXPathValuePush(ctxt, xmlXPathNewNodeSet(NULL));

  return;

    }

    oldset->nodeTab[0] = cur;

    xmlXPathValuePush(ctxt, obj);

}

/**

 * XPtrPart ::= 'xpointer' '(' XPtrExpr ')'

 *            | Scheme '(' SchemeSpecificExpr ')'

 *

 * Scheme   ::=  NCName - 'xpointer' [VC: Non-XPointer schemes]

 *

 * SchemeSpecificExpr ::= StringWithBalancedParens

 *

 * StringWithBalancedParens ::=

 *              [^()]* ('(' StringWithBalancedParens ')' [^()]*)*

 *              [VC: Parenthesis escaping]

 *

 * XPtrExpr ::= Expr [VC: Parenthesis escaping]

 *

 * VC: Parenthesis escaping:

 *   The end of an XPointer part is signaled by the right parenthesis ")"

 *   character that is balanced with the left parenthesis "(" character

 *   that began the part. Any unbalanced parenthesis character inside the

 *   expression, even within literals, must be escaped with a circumflex (^)

 *   character preceding it. If the expression contains any literal

 *   occurrences of the circumflex, each must be escaped with an additional

 *   circumflex (that is, ^^). If the unescaped parentheses in the expression

 *   are not balanced, a syntax error results.

 *

 * Parse and evaluate an XPtrPart. Basically it generates the unescaped

 * string and if the scheme is 'xpointer' it will call the XPath interpreter.

 *

 * TODO: there is no new scheme registration mechanism

 *

 * @param ctxt  the XPointer Parser context

 * @param name  the preparsed Scheme for the XPtrPart

 */

static void

xmlXPtrEvalXPtrPart(xmlXPathParserContextPtr ctxt, xmlChar *name) {

    xmlChar *buffer, *cur;

    int len;

    int level;

    if (name == NULL)

    name = xmlXPathParseName(ctxt);

    if (name == NULL)

  XP_ERROR(XPATH_EXPR_ERROR);

    if (CUR != '(') {

        xmlFree(name);

  XP_ERROR(XPATH_EXPR_ERROR);

    }

    NEXT;

    level = 1;

    len = xmlStrlen(ctxt->cur);

    /* Overflow in xmlStrlen */

    if (len == 0 && ctxt->cur != NULL && *ctxt->cur != 0) {

        xmlXPathPErrMemory(ctxt);

        xmlFree(name);

        return;

    }

    len++;

    buffer = xmlMalloc(len);

    if (buffer == NULL) {

        xmlXPathPErrMemory(ctxt);

        xmlFree(name);

  return;

    }

    cur = buffer;

    while (CUR != 0) {

  if (CUR == ')') {

      level--;

      if (level == 0) {

    NEXT;

    break;

      }

  } else if (CUR == '(') {

      level++;

  } else if (CUR == '^') {

            if ((NXT(1) == ')') || (NXT(1) == '(') || (NXT(1) == '^')) {

                NEXT;

            }

  }

        *cur++ = CUR;

  NEXT;

    }

    *cur = 0;

    if ((level != 0) && (CUR == 0)) {

        xmlFree(name);

  xmlFree(buffer);

  XP_ERROR(XPTR_SYNTAX_ERROR);

    }

    if (xmlStrEqual(name, (xmlChar *) "xpointer") ||

        xmlStrEqual(name, (xmlChar *) "xpath1")) {

  const xmlChar *oldBase = ctxt->base;

  const xmlChar *oldCur = ctxt->cur;

  ctxt->cur = ctxt->base = buffer;

  /*

   * To evaluate an xpointer scheme element (4.3) we need:

   *   context initialized to the root

   *   context position initialized to 1

   *   context size initialized to 1

   */

  ctxt->context->node = (xmlNodePtr)ctxt->context->doc;

  ctxt->context->proximityPosition = 1;

  ctxt->context->contextSize = 1;

  xmlXPathEvalExpr(ctxt);

  ctxt->base = oldBase;

        ctxt->cur = oldCur;

    } else if (xmlStrEqual(name, (xmlChar *) "element")) {

  const xmlChar *oldBase = ctxt->base;

  const xmlChar *oldCur = ctxt->cur;

  xmlChar *name2;

  ctxt->cur = ctxt->base = buffer;

  if (buffer[0] == '/') {

      xmlXPathRoot(ctxt);

      xmlXPtrEvalChildSeq(ctxt, NULL);

  } else {

      name2 = xmlXPathParseName(ctxt);

      if (name2 == NULL) {

                ctxt->base = oldBase;

                ctxt->cur = oldCur;

    xmlFree(buffer);

                xmlFree(name);

    XP_ERROR(XPATH_EXPR_ERROR);

      }

      xmlXPtrEvalChildSeq(ctxt, name2);

  }

  ctxt->base = oldBase;

        ctxt->cur = oldCur;

#ifdef XPTR_XMLNS_SCHEME

    } else if (xmlStrEqual(name, (xmlChar *) "xmlns")) {

  const xmlChar *oldBase = ctxt->base;

  const xmlChar *oldCur = ctxt->cur;

  xmlChar *prefix;

  ctxt->cur = ctxt->base = buffer;

        prefix = xmlXPathParseNCName(ctxt);

  if (prefix == NULL) {

            ctxt->base = oldBase;

            ctxt->cur = oldCur;

      xmlFree(buffer);

      xmlFree(name);

      XP_ERROR(XPTR_SYNTAX_ERROR);

  }

  SKIP_BLANKS;

  if (CUR != '=') {

            ctxt->base = oldBase;

            ctxt->cur = oldCur;

      xmlFree(prefix);

      xmlFree(buffer);

      xmlFree(name);

      XP_ERROR(XPTR_SYNTAX_ERROR);

  }

  NEXT;

  SKIP_BLANKS;

  if (xmlXPathRegisterNs(ctxt->context, prefix, ctxt->cur) < 0)

            xmlXPathPErrMemory(ctxt);

        ctxt->base = oldBase;

        ctxt->cur = oldCur;

  xmlFree(prefix);

#endif /* XPTR_XMLNS_SCHEME */

    } else {

        xmlXPtrErr(ctxt, XML_XPTR_UNKNOWN_SCHEME,

       "unsupported scheme '%s'\n", name);

    }

    xmlFree(buffer);

    xmlFree(name);

}

/**

 * FullXPtr ::= XPtrPart (S? XPtrPart)*

 *

 * As the specs says:

 * -----------

 * When multiple XPtrParts are provided, they must be evaluated in

 * left-to-right order. If evaluation of one part fails, the nexti

 * is evaluated. The following conditions cause XPointer part failure:

 *

 * - An unknown scheme

 * - A scheme that does not locate any sub-resource present in the resource

 * - A scheme that is not applicable to the media type of the resource

 *

 * The XPointer application must consume a failed XPointer part and

 * attempt to evaluate the next one, if any. The result of the first

 * XPointer part whose evaluation succeeds is taken to be the fragment

 * located by the XPointer as a whole. If all the parts fail, the result

 * for the XPointer as a whole is a sub-resource error.

 * -----------

 *

 * Parse and evaluate a Full XPtr i.e. possibly a cascade of XPath based

 * expressions or other schemes.

 *

 * @param ctxt  the XPointer Parser context

 * @param name  the preparsed Scheme for the first XPtrPart

 */

static void

xmlXPtrEvalFullXPtr(xmlXPathParserContextPtr ctxt, xmlChar *name) {

    if (name == NULL)

    name = xmlXPathParseName(ctxt);

    if (name == NULL)

  XP_ERROR(XPATH_EXPR_ERROR);

    while (name != NULL) {

  ctxt->error = XPATH_EXPRESSION_OK;

  xmlXPtrEvalXPtrPart(ctxt, name);

  /* in case of syntax error, break here */

  if ((ctxt->error != XPATH_EXPRESSION_OK) &&

            (ctxt->error != XML_XPTR_UNKNOWN_SCHEME))

      return;

  /*

   * If the returned value is a non-empty nodeset

   * or location set, return here.

   */

  if (ctxt->value != NULL) {

      xmlXPathObjectPtr obj = ctxt->value;

      switch (obj->type) {

    case XPATH_NODESET: {

        xmlNodeSetPtr loc = ctxt->value->nodesetval;

        if ((loc != NULL) && (loc->nodeNr > 0))

      return;

        break;

    }

    default:

        break;

      }

      /*

       * Evaluating to improper values is equivalent to

       * a sub-resource error, clean-up the stack

       */

      do {

    obj = xmlXPathValuePop(ctxt);

    if (obj != NULL) {

        xmlXPathFreeObject(obj);

    }

      } while (obj != NULL);

  }

  /*

   * Is there another XPointer part.

   */

  SKIP_BLANKS;

  name = xmlXPathParseName(ctxt);

    }

}

/**

 *  ChildSeq ::= '/1' ('/' [0-9]*)*

 *             | Name ('/' [0-9]*)+

 *

 * Parse and evaluate a Child Sequence. This routine also handle the

 * case of a Bare Name used to get a document ID.

 *

 * @param ctxt  the XPointer Parser context

 * @param name  a possible ID name of the child sequence

 */

static void

xmlXPtrEvalChildSeq(xmlXPathParserContextPtr ctxt, xmlChar *name) {

    /*

     * XPointer don't allow by syntax to address in multirooted trees

     * this might prove useful in some cases, warn about it.

     */

    if ((name == NULL) && (CUR == '/') && (NXT(1) != '1')) {

        xmlXPtrErr(ctxt, XML_XPTR_CHILDSEQ_START,

       "warning: ChildSeq not starting by /1\n", NULL);

    }

    if (name != NULL) {

  xmlXPathValuePush(ctxt, xmlXPathNewString(name));

  xmlFree(name);

  xmlXPathIdFunction(ctxt, 1);

  CHECK_ERROR;

    }

    while (CUR == '/') {

  int child = 0, overflow = 0;

  NEXT;

  while ((CUR >= '0') && (CUR <= '9')) {

            int d = CUR - '0';

            if (child > INT_MAX / 10)

                overflow = 1;

            else

                child *= 10;

            if (child > INT_MAX - d)

                overflow = 1;

            else

                child += d;

      NEXT;

  }

        if (overflow)

            child = 0;

  xmlXPtrGetChildNo(ctxt, child);

    }

}

/**

 *  XPointer ::= Name

 *             | ChildSeq

 *             | FullXPtr

 *

 * Parse and evaluate an XPointer

 *

 * @param ctxt  the XPointer Parser context

 */

static void

xmlXPtrEvalXPointer(xmlXPathParserContextPtr ctxt) {

    if (ctxt->valueTab == NULL) {

  /* Allocate the value stack */

  ctxt->valueTab = (xmlXPathObjectPtr *)

       xmlMalloc(10 * sizeof(xmlXPathObjectPtr));

  if (ctxt->valueTab == NULL) {

      xmlXPathPErrMemory(ctxt);

      return;

  }

  ctxt->valueNr = 0;

  ctxt->valueMax = 10;

  ctxt->value = NULL;

    }

    SKIP_BLANKS;

    if (CUR == '/') {

  xmlXPathRoot(ctxt);

        xmlXPtrEvalChildSeq(ctxt, NULL);

    } else {

  xmlChar *name;

  name = xmlXPathParseName(ctxt);

  if (name == NULL)

      XP_ERROR(XPATH_EXPR_ERROR);

  if (CUR == '(') {

      xmlXPtrEvalFullXPtr(ctxt, name);

      /* Short evaluation */

      return;

  } else {

      /* this handle both Bare Names and Child Sequences */

      xmlXPtrEvalChildSeq(ctxt, name);

  }

    }

    SKIP_BLANKS;

    if (CUR != 0)

  XP_ERROR(XPATH_EXPR_ERROR);

}

/************************************************************************

 *                  *

 *      General routines        *

 *                  *

 ************************************************************************/

/**

 * Create a new XPointer context

 *

 * @deprecated Same as xmlXPathNewContext.

 *

 * @param doc  the XML document

 * @param here  unused

 * @param origin  unused

 * @returns the xmlXPathContext just allocated.

 */

xmlXPathContext *

xmlXPtrNewContext(xmlDoc *doc, xmlNode *here, xmlNode *origin) {

    xmlXPathContextPtr ret;

    (void) here;

    (void) origin;

    ret = xmlXPathNewContext(doc);

    if (ret == NULL)

  return(ret);

    return(ret);

}

/**

 * Evaluate an XPointer expression.

 *

 * This function can only return nodesets. The caller has to

 * free the object.

 *

 * @param str  an XPointer expression

 * @param ctx  an XPath context

 * @returns the xmlXPathObject resulting from the evaluation or NULL

 * in case of error.

 */

xmlXPathObject *

xmlXPtrEval(const xmlChar *str, xmlXPathContext *ctx) {

    xmlXPathParserContextPtr ctxt;

    xmlXPathObjectPtr res = NULL, tmp;

    xmlXPathObjectPtr init = NULL;

    int stack = 0;

    xmlInitParser();

    if ((ctx == NULL) || (str == NULL))

  return(NULL);

    xmlResetError(&ctx->lastError);

    ctxt = xmlXPathNewParserContext(str, ctx);

    if (ctxt == NULL) {

        xmlXPathErrMemory(ctx);

  return(NULL);

    }

    xmlXPtrEvalXPointer(ctxt);

    if (ctx->lastError.code != XML_ERR_OK)

        goto error;

    if ((ctxt->value != NULL) &&

  (ctxt->value->type != XPATH_NODESET)) {

        xmlXPtrErr(ctxt, XML_XPTR_EVAL_FAILED,

    "xmlXPtrEval: evaluation failed to return a node set\n",

       NULL);

    } else {

  res = xmlXPathValuePop(ctxt);

    }

    do {

        tmp = xmlXPathValuePop(ctxt);

  if (tmp != NULL) {

      if (tmp != init) {

    if (tmp->type == XPATH_NODESET) {

        /*

         * Evaluation may push a root nodeset which is unused

         */

        xmlNodeSetPtr set;

        set = tmp->nodesetval;

        if ((set == NULL) || (set->nodeNr != 1) ||

      (set->nodeTab[0] != (xmlNodePtr) ctx->doc))

      stack++;

    } else

        stack++;

      }

      xmlXPathFreeObject(tmp);

        }

    } while (tmp != NULL);

    if (stack != 0) {

        xmlXPtrErr(ctxt, XML_XPTR_EXTRA_OBJECTS,

       "xmlXPtrEval: object(s) left on the eval stack\n",

       NULL);

    }

    if (ctx->lastError.code != XML_ERR_OK) {

  xmlXPathFreeObject(res);

  res = NULL;

    }

error:

    xmlXPathFreeParserContext(ctxt);

    return(res);

}

#endif