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/* Helper routines for parsing XML using Expat.

   Copyright (C) 2006, 2007, 2008, 2009, 2010 Free Software Foundation, Inc.

   This file is part of GDB.

   This program is free software; you can redistribute it and/or modify

   it under the terms of the GNU General Public License as published by

   the Free Software Foundation; either version 3 of the License, or

   (at your option) any later version.

   This program is distributed in the hope that it will be useful,

   but WITHOUT ANY WARRANTY; without even the implied warranty of

   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License

   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */

#include "defs.h"

#include "gdbcmd.h"

#include "exceptions.h"

#include "xml-support.h"

#include "gdb_string.h"

#include "safe-ctype.h"

/* Debugging flag.  */

static int debug_xml;

/* The contents of this file are only useful if XML support is

   available.  */

#ifdef HAVE_LIBEXPAT

#include "gdb_expat.h"

/* The maximum depth of <xi:include> nesting.  No need to be miserly,

   we just want to avoid running out of stack on loops.  */

#define MAX_XINCLUDE_DEPTH 30

/* Simplified XML parser infrastructure.  */

/* A parsing level -- used to keep track of the current element

   nesting.  */

struct scope_level

{

  /* Elements we allow at this level.  */

  const struct gdb_xml_element *elements;

  /* The element which we are within.  */

  const struct gdb_xml_element *element;

  /* Mask of which elements we've seen at this level (used for

     optional and repeatable checking).  */

  unsigned int seen;

  /* Body text accumulation.  */

  struct obstack *body;

};

typedef struct scope_level scope_level_s;

DEF_VEC_O(scope_level_s);

/* The parser itself, and our additional state.  */

struct gdb_xml_parser

{

  XML_Parser expat_parser;      /* The underlying expat parser.  */

  const char *name;             /* Name of this parser.  */

  void *user_data;              /* The user's callback data, for handlers.  */

  VEC(scope_level_s) *scopes;   /* Scoping stack.  */

  struct gdb_exception error;   /* A thrown error, if any.  */

  int last_line;                /* The line of the thrown error, or 0.  */

  const char *dtd_name;         /* The name of the expected / default DTD,

                                   if specified.  */

  int is_xinclude;              /* Are we the special <xi:include> parser?  */

};

/* Process some body text.  We accumulate the text for later use; it's

   wrong to do anything with it immediately, because a single block of

   text might be broken up into multiple calls to this function.  */

static void

gdb_xml_body_text (void *data, const XML_Char *text, int length)

{

  struct gdb_xml_parser *parser = data;

  struct scope_level *scope = VEC_last (scope_level_s, parser->scopes);

  if (parser->error.reason < 0)

    return;

  if (scope->body == NULL)

    {

      scope->body = XZALLOC (struct obstack);

      obstack_init (scope->body);

    }

  obstack_grow (scope->body, text, length);

}

/* Issue a debugging message from one of PARSER's handlers.  */

void

gdb_xml_debug (struct gdb_xml_parser *parser, const char *format, ...)

{

  int line = XML_GetCurrentLineNumber (parser->expat_parser);

  va_list ap;

  char *message;

  if (!debug_xml)

    return;

  va_start (ap, format);

  message = xstrvprintf (format, ap);

  if (line)

    fprintf_unfiltered (gdb_stderr, "%s (line %d): %s\n",

                        parser->name, line, message);

  else

    fprintf_unfiltered (gdb_stderr, "%s: %s\n",

                        parser->name, message);

  xfree (message);

}

/* Issue an error message from one of PARSER's handlers, and stop

   parsing.  */

void

gdb_xml_error (struct gdb_xml_parser *parser, const char *format, ...)

{

  int line = XML_GetCurrentLineNumber (parser->expat_parser);

  va_list ap;

  parser->last_line = line;

  va_start (ap, format);

  throw_verror (XML_PARSE_ERROR, format, ap);

}

/* Clean up a vector of parsed attribute values.  */

static void

gdb_xml_values_cleanup (void *data)

{

  VEC(gdb_xml_value_s) **values = data;

  struct gdb_xml_value *value;

  int ix;

  for (ix = 0; VEC_iterate (gdb_xml_value_s, *values, ix, value); ix++)

    xfree (value->value);

  VEC_free (gdb_xml_value_s, *values);

}

/* Handle the start of an element.  DATA is our local XML parser, NAME

   is the element, and ATTRS are the names and values of this

   element's attributes.  */

static void

gdb_xml_start_element (void *data, const XML_Char *name,

                       const XML_Char **attrs)

{

  struct gdb_xml_parser *parser = data;

  struct scope_level *scope;

  struct scope_level new_scope;

  const struct gdb_xml_element *element;

  const struct gdb_xml_attribute *attribute;

  VEC(gdb_xml_value_s) *attributes = NULL;

  unsigned int seen;

  struct cleanup *back_to;

  /* Push an error scope.  If we return or throw an exception before

     filling this in, it will tell us to ignore children of this

     element.  */

  VEC_reserve (scope_level_s, parser->scopes, 1);

  scope = VEC_last (scope_level_s, parser->scopes);

  memset (&new_scope, 0, sizeof (new_scope));

  VEC_quick_push (scope_level_s, parser->scopes, &new_scope);

  gdb_xml_debug (parser, _("Entering element <%s>"), name);

  /* Find this element in the list of the current scope's allowed

     children.  Record that we've seen it.  */

  seen = 1;

  for (element = scope->elements; element && element->name;

       element++, seen <<= 1)

    if (strcmp (element->name, name) == 0)

      break;

  if (element == NULL || element->name == NULL)

    {

      /* If we're working on XInclude, <xi:include> can be the child

         of absolutely anything.  Copy the previous scope's element

         list into the new scope even if there was no match.  */

      if (parser->is_xinclude)

        {

          struct scope_level *unknown_scope;

          XML_DefaultCurrent (parser->expat_parser);

          unknown_scope = VEC_last (scope_level_s, parser->scopes);

          unknown_scope->elements = scope->elements;

          return;

        }

      gdb_xml_debug (parser, _("Element <%s> unknown"), name);

      return;

    }

  if (!(element->flags & GDB_XML_EF_REPEATABLE) && (seen & scope->seen))

    gdb_xml_error (parser, _("Element <%s> only expected once"), name);

  scope->seen |= seen;

  back_to = make_cleanup (gdb_xml_values_cleanup, &attributes);

  for (attribute = element->attributes;

       attribute != NULL && attribute->name != NULL;

       attribute++)

    {

      const char *val = NULL;

      const XML_Char **p;

      void *parsed_value;

      struct gdb_xml_value new_value;

      for (p = attrs; *p != NULL; p += 2)

        if (!strcmp (attribute->name, p[0]))

          {

            val = p[1];

            break;

          }

      if (*p != NULL && val == NULL)

        {

          gdb_xml_debug (parser, _("Attribute \"%s\" missing a value"),

                         attribute->name);

          continue;

        }

      if (*p == NULL && !(attribute->flags & GDB_XML_AF_OPTIONAL))

        {

          gdb_xml_error (parser, _("Required attribute \"%s\" of "

                                   "<%s> not specified"),

                         attribute->name, element->name);

          continue;

        }

      if (*p == NULL)

        continue;

      gdb_xml_debug (parser, _("Parsing attribute %s=\"%s\""),

                     attribute->name, val);

      if (attribute->handler)

        parsed_value = attribute->handler (parser, attribute, val);

      else

        parsed_value = xstrdup (val);

      new_value.name = attribute->name;

      new_value.value = parsed_value;

      VEC_safe_push (gdb_xml_value_s, attributes, &new_value);

    }

  /* Check for unrecognized attributes.  */

  if (debug_xml)

    {

      const XML_Char **p;

      for (p = attrs; *p != NULL; p += 2)

        {

          for (attribute = element->attributes;

               attribute != NULL && attribute->name != NULL;

               attribute++)

            if (strcmp (attribute->name, *p) == 0)

              break;

          if (attribute == NULL || attribute->name == NULL)

            gdb_xml_debug (parser, _("Ignoring unknown attribute %s"), *p);

        }

    }

  /* Call the element handler if there is one.  */

  if (element->start_handler)

    element->start_handler (parser, element, parser->user_data, attributes);

  /* Fill in a new scope level.  */

  scope = VEC_last (scope_level_s, parser->scopes);

  scope->element = element;

  scope->elements = element->children;

  do_cleanups (back_to);

}

/* Wrapper for gdb_xml_start_element, to prevent throwing exceptions

   through expat.  */

static void

gdb_xml_start_element_wrapper (void *data, const XML_Char *name,

                               const XML_Char **attrs)

{

  struct gdb_xml_parser *parser = data;

  volatile struct gdb_exception ex;

  if (parser->error.reason < 0)

    return;

  TRY_CATCH (ex, RETURN_MASK_ALL)

    {

      gdb_xml_start_element (data, name, attrs);

    }

  if (ex.reason < 0)

    {

      parser->error = ex;

#ifdef HAVE_XML_STOPPARSER

      XML_StopParser (parser->expat_parser, XML_FALSE);

#endif

    }

}

/* Handle the end of an element.  DATA is our local XML parser, and

   NAME is the current element.  */

static void

gdb_xml_end_element (void *data, const XML_Char *name)

{

  struct gdb_xml_parser *parser = data;

  struct scope_level *scope = VEC_last (scope_level_s, parser->scopes);

  const struct gdb_xml_element *element;

  unsigned int seen;

  gdb_xml_debug (parser, _("Leaving element <%s>"), name);

  for (element = scope->elements, seen = 1;

       element != NULL && element->name != NULL;

       element++, seen <<= 1)

    if ((scope->seen & seen) == 0

        && (element->flags & GDB_XML_EF_OPTIONAL) == 0)

      gdb_xml_error (parser, _("Required element <%s> is missing"),

                     element->name);

  /* Call the element processor. */

  if (scope->element != NULL && scope->element->end_handler)

    {

      char *body;

      if (scope->body == NULL)

        body = "";

      else

        {

          int length;

          length = obstack_object_size (scope->body);

          obstack_1grow (scope->body, '\0');

          body = obstack_finish (scope->body);

          /* Strip leading and trailing whitespace.  */

          while (length > 0 && ISSPACE (body[length-1]))

            body[--length] = '\0';

          while (*body && ISSPACE (*body))

            body++;

        }

      scope->element->end_handler (parser, scope->element, parser->user_data,

                                   body);

    }

  else if (scope->element == NULL)

    XML_DefaultCurrent (parser->expat_parser);

  /* Pop the scope level.  */

  if (scope->body)

    {

      obstack_free (scope->body, NULL);

      xfree (scope->body);

    }

  VEC_pop (scope_level_s, parser->scopes);

}

/* Wrapper for gdb_xml_end_element, to prevent throwing exceptions

   through expat.  */

static void

gdb_xml_end_element_wrapper (void *data, const XML_Char *name)

{

  struct gdb_xml_parser *parser = data;

  volatile struct gdb_exception ex;

  if (parser->error.reason < 0)

    return;

  TRY_CATCH (ex, RETURN_MASK_ALL)

    {

      gdb_xml_end_element (data, name);

    }

  if (ex.reason < 0)

    {

      parser->error = ex;

#ifdef HAVE_XML_STOPPARSER

      XML_StopParser (parser->expat_parser, XML_FALSE);

#endif

    }

}

/* Free a parser and all its associated state.  */

static void

gdb_xml_cleanup (void *arg)

{

  struct gdb_xml_parser *parser = arg;

  struct scope_level *scope;

  int ix;

  XML_ParserFree (parser->expat_parser);

  /* Clean up the scopes.  */

  for (ix = 0; VEC_iterate (scope_level_s, parser->scopes, ix, scope); ix++)

    if (scope->body)

      {

        obstack_free (scope->body, NULL);

        xfree (scope->body);

      }

  VEC_free (scope_level_s, parser->scopes);

  xfree (parser);

}

/* Initialize and return a parser.  Register a cleanup to destroy the

   parser.  */

struct gdb_xml_parser *

gdb_xml_create_parser_and_cleanup (const char *name,

                                   const struct gdb_xml_element *elements,

                                   void *user_data)

{

  struct gdb_xml_parser *parser;

  struct scope_level start_scope;

  /* Initialize the parser.  */

  parser = XZALLOC (struct gdb_xml_parser);

  parser->expat_parser = XML_ParserCreateNS (NULL, '!');

  if (parser->expat_parser == NULL)

    {

      xfree (parser);

      nomem (0);

    }

  parser->name = name;

  parser->user_data = user_data;

  XML_SetUserData (parser->expat_parser, parser);

  /* Set the callbacks.  */

  XML_SetElementHandler (parser->expat_parser, gdb_xml_start_element_wrapper,

                         gdb_xml_end_element_wrapper);

  XML_SetCharacterDataHandler (parser->expat_parser, gdb_xml_body_text);

  /* Initialize the outer scope.  */

  memset (&start_scope, 0, sizeof (start_scope));

  start_scope.elements = elements;

  VEC_safe_push (scope_level_s, parser->scopes, &start_scope);

  make_cleanup (gdb_xml_cleanup, parser);

  return parser;

}

/* External entity handler.  The only external entities we support

   are those compiled into GDB (we do not fetch entities from the

   target).  */

static int XMLCALL

gdb_xml_fetch_external_entity (XML_Parser expat_parser,

                               const XML_Char *context,

                               const XML_Char *base,

                               const XML_Char *systemId,

                               const XML_Char *publicId)

{

  struct gdb_xml_parser *parser = XML_GetUserData (expat_parser);

  XML_Parser entity_parser;

  const char *text;

  enum XML_Status status;

  if (systemId == NULL)

    {

      text = fetch_xml_builtin (parser->dtd_name);

      if (text == NULL)

        internal_error (__FILE__, __LINE__, "could not locate built-in DTD %s",

                        parser->dtd_name);

    }

  else

    {

      text = fetch_xml_builtin (systemId);

      if (text == NULL)

        return XML_STATUS_ERROR;

    }

  entity_parser = XML_ExternalEntityParserCreate (expat_parser, context, NULL);

  /* Don't use our handlers for the contents of the DTD.  Just let expat

     process it.  */

  XML_SetElementHandler (entity_parser, NULL, NULL);

  XML_SetDoctypeDeclHandler (entity_parser, NULL, NULL);

  XML_SetXmlDeclHandler (entity_parser, NULL);

  XML_SetDefaultHandler (entity_parser, NULL);

  XML_SetUserData (entity_parser, NULL);

  status = XML_Parse (entity_parser, text, strlen (text), 1);

  XML_ParserFree (entity_parser);

  return status;

}

/* Associate DTD_NAME, which must be the name of a compiled-in DTD,

   with PARSER.  */

void

gdb_xml_use_dtd (struct gdb_xml_parser *parser, const char *dtd_name)

{

  enum XML_Error err;

  parser->dtd_name = dtd_name;

  XML_SetParamEntityParsing (parser->expat_parser,

                             XML_PARAM_ENTITY_PARSING_UNLESS_STANDALONE);

  XML_SetExternalEntityRefHandler (parser->expat_parser,

                                   gdb_xml_fetch_external_entity);

  /* Even if no DTD is provided, use the built-in DTD anyway.  */

  err = XML_UseForeignDTD (parser->expat_parser, XML_TRUE);

  if (err != XML_ERROR_NONE)

    internal_error (__FILE__, __LINE__,

                    "XML_UseForeignDTD failed: %s", XML_ErrorString (err));

}

/* Invoke PARSER on BUFFER.  BUFFER is the data to parse, which

   should be NUL-terminated.

   The return value is 0 for success or -1 for error.  It may throw,

   but only if something unexpected goes wrong during parsing; parse

   errors will be caught, warned about, and reported as failure.  */

int

gdb_xml_parse (struct gdb_xml_parser *parser, const char *buffer)

{

  enum XML_Status status;

  const char *error_string;

  gdb_xml_debug (parser, _("Starting:\n%s"), buffer);

  status = XML_Parse (parser->expat_parser, buffer, strlen (buffer), 1);

  if (status == XML_STATUS_OK && parser->error.reason == 0)

    return 0;

  if (parser->error.reason == RETURN_ERROR

      && parser->error.error == XML_PARSE_ERROR)

    {

      gdb_assert (parser->error.message != NULL);

      error_string = parser->error.message;

    }

  else if (status == XML_STATUS_ERROR)

    {

      enum XML_Error err = XML_GetErrorCode (parser->expat_parser);

      error_string = XML_ErrorString (err);

    }

  else

    {

      gdb_assert (parser->error.reason < 0);

      throw_exception (parser->error);

    }

  if (parser->last_line != 0)

    warning (_("while parsing %s (at line %d): %s"), parser->name,

             parser->last_line, error_string);

  else

    warning (_("while parsing %s: %s"), parser->name, error_string);

  return -1;

}

/* Parse a field VALSTR that we expect to contain an integer value.

   The integer is returned in *VALP.  The string is parsed with an

   equivalent to strtoul.

   Returns 0 for success, -1 for error.  */

static int

xml_parse_unsigned_integer (const char *valstr, ULONGEST *valp)

{

  const char *endptr;

  ULONGEST result;

  if (*valstr == '\0')

    return -1;

  result = strtoulst (valstr, &endptr, 0);

  if (*endptr != '\0')

    return -1;

  *valp = result;

  return 0;

}

/* Parse an integer string into a ULONGEST and return it, or call

   gdb_xml_error if it could not be parsed.  */

ULONGEST

gdb_xml_parse_ulongest (struct gdb_xml_parser *parser, const char *value)

{

  ULONGEST result;

  if (xml_parse_unsigned_integer (value, &result) != 0)

    gdb_xml_error (parser, _("Can't convert \"%s\" to an integer"), value);

  return result;

}

/* Parse an integer attribute into a ULONGEST.  */

void *

gdb_xml_parse_attr_ulongest (struct gdb_xml_parser *parser,

                             const struct gdb_xml_attribute *attribute,

                             const char *value)

{

  ULONGEST result;

  void *ret;

  if (xml_parse_unsigned_integer (value, &result) != 0)

    gdb_xml_error (parser, _("Can't convert %s=\"%s\" to an integer"),

                   attribute->name, value);

  ret = xmalloc (sizeof (result));

  memcpy (ret, &result, sizeof (result));

  return ret;

}

/* A handler_data for yes/no boolean values.  */

const struct gdb_xml_enum gdb_xml_enums_boolean[] = {

  { "yes", 1 },

  { "no", 0 },

  { NULL, 0 }

};

/* Map NAME to VALUE.  A struct gdb_xml_enum * should be saved as the

   value of handler_data when using gdb_xml_parse_attr_enum to parse a

   fixed list of possible strings.  The list is terminated by an entry

   with NAME == NULL.  */

void *

gdb_xml_parse_attr_enum (struct gdb_xml_parser *parser,

                         const struct gdb_xml_attribute *attribute,

                         const char *value)

{

  const struct gdb_xml_enum *enums = attribute->handler_data;

  void *ret;

  for (enums = attribute->handler_data; enums->name != NULL; enums++)

    if (strcasecmp (enums->name, value) == 0)

      break;

  if (enums->name == NULL)

    gdb_xml_error (parser, _("Unknown attribute value %s=\"%s\""),

                 attribute->name, value);

  ret = xmalloc (sizeof (enums->value));

  memcpy (ret, &enums->value, sizeof (enums->value));

  return ret;

}

/* XInclude processing.  This is done as a separate step from actually

   parsing the document, so that we can produce a single combined XML

   document - e.g. to hand to a front end or to simplify comparing two

   documents.  We make extensive use of XML_DefaultCurrent, to pass

   input text directly into the output without reformatting or

   requoting it.

   We output the DOCTYPE declaration for the first document unchanged,

   if present, and discard DOCTYPEs from included documents.  Only the

   one we pass through here is used when we feed the result back to

   expat.  The XInclude standard explicitly does not discuss

   validation of the result; we choose to apply the same DTD applied

   to the outermost document.

   We can not simply include the external DTD subset in the document

   as an internal subset, because <!IGNORE> and <!INCLUDE> are valid