Merge pull request #673 from libexpat/examples-element-declarations

examples: Add new example on element declarations

expat/CMakeLists.txt

@@ -579,10 +579,8 @@ endif()
 # C code examples
 #
 if(EXPAT_BUILD_EXAMPLES)
-    add_executable(elements examples/elements.c)
-    add_executable(outline examples/outline.c)
-
-    foreach(_target elements outline)
+    foreach(_target element_declarations elements outline)
+        add_executable(${_target} examples/${_target}.c)
         set_property(TARGET ${_target} PROPERTY RUNTIME_OUTPUT_DIRECTORY examples)
         target_link_libraries(${_target} expat)
     endforeach()

expat/Changes

@@ -2,6 +2,10 @@ NOTE: We are looking for help with a few things:
       https://github.com/libexpat/libexpat/labels/help%20wanted
       If you can help, please get in touch.  Thanks!
 
+Release 2.5.1 xxx xxxxxxx xx xxxx
+        Other changes:
+            #673  examples: Add new example "element_declarations.c"
+
 Release 2.5.0 Tue October 25 2022
         Security fixes:
   #616 #649 #650  CVE-2022-43680 -- Fix heap use-after-free after overeager

expat/examples/Makefile.am

@@ -6,8 +6,8 @@
 #                      \___/_/\_\ .__/ \__,_|\__|
 #                               |_| XML parser
 #
-# Copyright (c) 2017 Sebastian Pipping <sebastian@pipping.org>
-# Copyright (c) 2020 Jeffrey Walton <noloader@gmail.com>
+# Copyright (c) 2017-2022 Sebastian Pipping <sebastian@pipping.org>
+# Copyright (c) 2020      Jeffrey Walton <noloader@gmail.com>
 # Licensed under the MIT license:
 #
 # Permission is  hereby granted,  free of charge,  to any  person obtaining
@@ -31,7 +31,10 @@
 
 AM_CPPFLAGS = @AM_CPPFLAGS@ -I$(srcdir)/../lib
 
-noinst_PROGRAMS = elements outline
+noinst_PROGRAMS = element_declarations elements outline
+
+element_declarations_SOURCES = element_declarations.c
+element_declarations_LDADD = ../lib/libexpat.la
 
 elements_SOURCES = elements.c
 elements_LDADD = ../lib/libexpat.la

expat/examples/element_declarations.c

@@ -0,0 +1,229 @@
+/* Read an XML document from standard input and print
+   element declarations (if any) to standard output.
+   It must be used with Expat compiled for UTF-8 output.
+                            __  __            _
+                         ___\ \/ /_ __   __ _| |_
+                        / _ \\  /| '_ \ / _` | __|
+                       |  __//  \| |_) | (_| | |_
+                        \___/_/\_\ .__/ \__,_|\__|
+                                 |_| XML parser
+
+   Copyright (c) 1997-2000 Thai Open Source Software Center Ltd
+   Copyright (c) 2001-2003 Fred L. Drake, Jr. <fdrake@users.sourceforge.net>
+   Copyright (c) 2004-2006 Karl Waclawek <karl@waclawek.net>
+   Copyright (c) 2005-2007 Steven Solie <steven@solie.ca>
+   Copyright (c) 2016-2022 Sebastian Pipping <sebastian@pipping.org>
+   Copyright (c) 2017      Rhodri James <rhodri@wildebeest.org.uk>
+   Copyright (c) 2019      Zhongyuan Zhou <zhouzhongyuan@huawei.com>
+   Licensed under the MIT license:
+
+   Permission is  hereby granted,  free of charge,  to any  person obtaining
+   a  copy  of  this  software   and  associated  documentation  files  (the
+   "Software"),  to  deal in  the  Software  without restriction,  including
+   without  limitation the  rights  to use,  copy,  modify, merge,  publish,
+   distribute, sublicense, and/or sell copies of the Software, and to permit
+   persons  to whom  the Software  is  furnished to  do so,  subject to  the
+   following conditions:
+
+   The above copyright  notice and this permission notice  shall be included
+   in all copies or substantial portions of the Software.
+
+   THE  SOFTWARE  IS  PROVIDED  "AS  IS",  WITHOUT  WARRANTY  OF  ANY  KIND,
+   EXPRESS  OR IMPLIED,  INCLUDING  BUT  NOT LIMITED  TO  THE WARRANTIES  OF
+   MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
+   NO EVENT SHALL THE AUTHORS OR  COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
+   DAMAGES OR  OTHER LIABILITY, WHETHER  IN AN  ACTION OF CONTRACT,  TORT OR
+   OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
+   USE OR OTHER DEALINGS IN THE SOFTWARE.
+*/
+
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <expat.h>
+
+#ifdef XML_LARGE_SIZE
+#  define XML_FMT_INT_MOD "ll"
+#else
+#  define XML_FMT_INT_MOD "l"
+#endif
+
+#ifdef XML_UNICODE_WCHAR_T
+#  define XML_FMT_STR "ls"
+#else
+#  define XML_FMT_STR "s"
+#endif
+
+// While traversing the XML_Content tree, we avoid recursion
+// to not be vulnerable to a denial of service attack.
+typedef struct StackStruct {
+  const XML_Content *model;
+  unsigned level;
+  struct StackStruct *prev;
+} Stack;
+
+static Stack *
+stackPushMalloc(Stack *stackTop, const XML_Content *model, unsigned level) {
+  Stack *const newStackTop = malloc(sizeof(Stack));
+  if (! newStackTop) {
+    return NULL;
+  }
+  newStackTop->model = model;
+  newStackTop->level = level;
+  newStackTop->prev = stackTop;
+  return newStackTop;
+}
+
+static Stack *
+stackPopFree(Stack *stackTop) {
+  Stack *const newStackTop = stackTop->prev;
+  free(stackTop);
+  return newStackTop;
+}
+
+static char *
+contentTypeName(enum XML_Content_Type contentType) {
+  switch (contentType) {
+  case XML_CTYPE_EMPTY:
+    return "EMPTY";
+  case XML_CTYPE_ANY:
+    return "ANY";
+  case XML_CTYPE_MIXED:
+    return "MIXED";
+  case XML_CTYPE_NAME:
+    return "NAME";
+  case XML_CTYPE_CHOICE:
+    return "CHOICE";
+  case XML_CTYPE_SEQ:
+    return "SEQ";
+  default:
+    return "???";
+  }
+}
+
+static char *
+contentQuantName(enum XML_Content_Quant contentQuant) {
+  switch (contentQuant) {
+  case XML_CQUANT_NONE:
+    return "NONE";
+  case XML_CQUANT_OPT:
+    return "OPT";
+  case XML_CQUANT_REP:
+    return "REP";
+  case XML_CQUANT_PLUS:
+    return "PLUS";
+  default:
+    return "???";
+  }
+}
+
+static void
+dumpContentModelElement(const XML_Content *model, unsigned level,
+                        const XML_Content *root) {
+  // Indent
+  unsigned u = 0;
+  for (; u < level; u++) {
+    printf("  ");
+  }
+
+  // Node
+  printf("[%u] type=%s(%d), quant=%s(%d)", (unsigned)(model - root),
+         contentTypeName(model->type), model->type,
+         contentQuantName(model->quant), model->quant);
+  if (model->name) {
+    printf(", name=\"%" XML_FMT_STR "\"", model->name);
+  } else {
+    printf(", name=NULL");
+  }
+  printf(", numchildren=%d", model->numchildren);
+  printf("\n");
+}
+
+static bool
+dumpContentModel(const XML_Char *name, const XML_Content *root) {
+  printf("Element \"%" XML_FMT_STR "\":\n", name);
+  Stack *stackTop = NULL;
+  stackTop = stackPushMalloc(stackTop, root, 1);
+  if (! stackTop) {
+    return false;
+  }
+
+  while (stackTop) {
+    const XML_Content *const model = stackTop->model;
+    const unsigned level = stackTop->level;
+
+    dumpContentModelElement(model, level, root);
+
+    stackTop = stackPopFree(stackTop);
+
+    for (size_t u = model->numchildren; u >= 1; u--) {
+      stackTop
+          = stackPushMalloc(stackTop, model->children + (u - 1), level + 1);
+      if (! stackTop) {
+        return false;
+      }
+    }
+  }
+
+  printf("\n");
+  return true;
+}
+
+static void XMLCALL
+handleElementDeclaration(void *userData, const XML_Char *name,
+                         XML_Content *model) {
+  XML_Parser parser = (XML_Parser)userData;
+  const bool success = dumpContentModel(name, model);
+  XML_FreeContentModel(parser, model);
+  if (! success) {
+    XML_StopParser(parser, /* resumable= */ XML_FALSE);
+  }
+}
+
+int
+main(void) {
+  XML_Parser parser = XML_ParserCreate(NULL);
+  int done;
+
+  if (! parser) {
+    fprintf(stderr, "Couldn't allocate memory for parser\n");
+    return 1;
+  }
+
+  XML_SetUserData(parser, parser);
+  XML_SetElementDeclHandler(parser, handleElementDeclaration);
+
+  do {
+    void *const buf = XML_GetBuffer(parser, BUFSIZ);
+    if (! buf) {
+      fprintf(stderr, "Couldn't allocate memory for buffer\n");
+      XML_ParserFree(parser);
+      return 1;
+    }
+
+    const size_t len = fread(buf, 1, BUFSIZ, stdin);
+
+    if (ferror(stdin)) {
+      fprintf(stderr, "Read error\n");
+      XML_ParserFree(parser);
+      return 1;
+    }
+
+    done = feof(stdin);
+
+    if (XML_ParseBuffer(parser, (int)len, done) == XML_STATUS_ERROR) {
+      enum XML_Error errorCode = XML_GetErrorCode(parser);
+      if (errorCode == XML_ERROR_ABORTED) {
+        errorCode = XML_ERROR_NO_MEMORY;
+      }
+      fprintf(stderr,
+              "Parse error at line %" XML_FMT_INT_MOD "u:\n%" XML_FMT_STR "\n",
+              XML_GetCurrentLineNumber(parser), XML_ErrorString(errorCode));
+      XML_ParserFree(parser);
+      return 1;
+    }
+  } while (! done);
+
+  XML_ParserFree(parser);
+  return 0;
+}