xref: /freebsd/contrib/expat/examples/element_declarations.c (revision 2c41f7d8a034ee64a0aaa69a1aa5cb07748a1a32) 
1 /* Read an XML document from standard input and print
2    element declarations (if any) to standard output.
3    It must be used with Expat compiled for UTF-8 output.
4                             __  __            _
5                          ___\ \/ /_ __   __ _| |_
6                         / _ \\  /| '_ \ / _` | __|
7                        |  __//  \| |_) | (_| | |_
8                         \___/_/\_\ .__/ \__,_|\__|
9                                  |_| XML parser
10 
11    Copyright (c) 1997-2000 Thai Open Source Software Center Ltd
12    Copyright (c) 2001-2003 Fred L. Drake, Jr. <fdrake@users.sourceforge.net>
13    Copyright (c) 2004-2006 Karl Waclawek <karl@waclawek.net>
14    Copyright (c) 2005-2007 Steven Solie <steven@solie.ca>
15    Copyright (c) 2016-2024 Sebastian Pipping <sebastian@pipping.org>
16    Copyright (c) 2017      Rhodri James <rhodri@wildebeest.org.uk>
17    Copyright (c) 2019      Zhongyuan Zhou <zhouzhongyuan@huawei.com>
18    Copyright (c) 2024      Hanno Böck <hanno@gentoo.org>
19    Copyright (c) 2026      Matthew Fernandez <matthew.fernandez@gmail.com>
20    Licensed under the MIT license:
21 
22    Permission is  hereby granted,  free of charge,  to any  person obtaining
23    a  copy  of  this  software   and  associated  documentation  files  (the
24    "Software"),  to  deal in  the  Software  without restriction,  including
25    without  limitation the  rights  to use,  copy,  modify, merge,  publish,
26    distribute, sublicense, and/or sell copies of the Software, and to permit
27    persons  to whom  the Software  is  furnished to  do so,  subject to  the
28    following conditions:
29 
30    The above copyright  notice and this permission notice  shall be included
31    in all copies or substantial portions of the Software.
32 
33    THE  SOFTWARE  IS  PROVIDED  "AS  IS",  WITHOUT  WARRANTY  OF  ANY  KIND,
34    EXPRESS  OR IMPLIED,  INCLUDING  BUT  NOT LIMITED  TO  THE WARRANTIES  OF
35    MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
36    NO EVENT SHALL THE AUTHORS OR  COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
37    DAMAGES OR  OTHER LIABILITY, WHETHER  IN AN  ACTION OF CONTRACT,  TORT OR
38    OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
39    USE OR OTHER DEALINGS IN THE SOFTWARE.
40 
41    SPDX-License-Identifier: MIT
42 */
43 
44 #include <stdbool.h>
45 #include <stdio.h>
46 #include <stdlib.h>
47 #include <expat.h>
48 
49 #ifdef XML_LARGE_SIZE
50 #  define XML_FMT_INT_MOD "ll"
51 #else
52 #  define XML_FMT_INT_MOD "l"
53 #endif
54 
55 #ifdef XML_UNICODE_WCHAR_T
56 #  define XML_FMT_STR "ls"
57 #else
58 #  define XML_FMT_STR "s"
59 #endif
60 
61 // While traversing the XML_Content tree, we avoid recursion
62 // to not be vulnerable to a denial of service attack.
63 typedef struct StackStruct {
64   const XML_Content *model;
65   unsigned level;
66   struct StackStruct *prev;
67 } Stack;
68 
69 static Stack *
70 stackPushMalloc(Stack *stackTop, const XML_Content *model, unsigned level) {
71   Stack *const newStackTop = malloc(sizeof(Stack));
72   if (! newStackTop) {
73     return NULL;
74   }
75   newStackTop->model = model;
76   newStackTop->level = level;
77   newStackTop->prev = stackTop;
78   return newStackTop;
79 }
80 
81 static Stack *
82 stackPopFree(Stack *stackTop) {
83   Stack *const newStackTop = stackTop->prev;
84   free(stackTop);
85   return newStackTop;
86 }
87 
88 static const char *
89 contentTypeName(enum XML_Content_Type contentType) {
90   switch (contentType) {
91   case XML_CTYPE_EMPTY:
92     return "EMPTY";
93   case XML_CTYPE_ANY:
94     return "ANY";
95   case XML_CTYPE_MIXED:
96     return "MIXED";
97   case XML_CTYPE_NAME:
98     return "NAME";
99   case XML_CTYPE_CHOICE:
100     return "CHOICE";
101   case XML_CTYPE_SEQ:
102     return "SEQ";
103   default:
104     return "???";
105   }
106 }
107 
108 static const char *
109 contentQuantName(enum XML_Content_Quant contentQuant) {
110   switch (contentQuant) {
111   case XML_CQUANT_NONE:
112     return "NONE";
113   case XML_CQUANT_OPT:
114     return "OPT";
115   case XML_CQUANT_REP:
116     return "REP";
117   case XML_CQUANT_PLUS:
118     return "PLUS";
119   default:
120     return "???";
121   }
122 }
123 
124 static void
125 dumpContentModelElement(const XML_Content *model, unsigned level,
126                         const XML_Content *root) {
127   // Indent
128   unsigned u = 0;
129   for (; u < level; u++) {
130     printf("  ");
131   }
132 
133   // Node
134   printf("[%u] type=%s(%u), quant=%s(%u)", (unsigned)(model - root),
135          contentTypeName(model->type), (unsigned int)model->type,
136          contentQuantName(model->quant), (unsigned int)model->quant);
137   if (model->name) {
138     printf(", name=\"%" XML_FMT_STR "\"", model->name);
139   } else {
140     printf(", name=NULL");
141   }
142   printf(", numchildren=%u", model->numchildren);
143   printf("\n");
144 }
145 
146 static bool
147 dumpContentModel(const XML_Char *name, const XML_Content *root) {
148   printf("Element \"%" XML_FMT_STR "\":\n", name);
149   Stack *stackTop = stackPushMalloc(NULL, root, 1);
150   if (! stackTop) {
151     return false;
152   }
153 
154   while (stackTop) {
155     const XML_Content *const model = stackTop->model;
156     const unsigned level = stackTop->level;
157 
158     dumpContentModelElement(model, level, root);
159 
160     stackTop = stackPopFree(stackTop);
161 
162     for (size_t u = model->numchildren; u >= 1; u--) {
163       Stack *const newStackTop
164           = stackPushMalloc(stackTop, model->children + (u - 1), level + 1);
165       if (! newStackTop) {
166         // We ran out of memory, so let's free all memory allocated
167         // earlier in this function, to be leak-clean:
168         while (stackTop != NULL) {
169           stackTop = stackPopFree(stackTop);
170         }
171         return false;
172       }
173       stackTop = newStackTop;
174     }
175   }
176 
177   printf("\n");
178   return true;
179 }
180 
181 static void XMLCALL
182 handleElementDeclaration(void *userData, const XML_Char *name,
183                          XML_Content *model) {
184   XML_Parser parser = (XML_Parser)userData;
185   const bool success = dumpContentModel(name, model);
186   XML_FreeContentModel(parser, model);
187   if (! success) {
188     XML_StopParser(parser, /* resumable= */ XML_FALSE);
189   }
190 }
191 
192 int
193 main(void) {
194   XML_Parser parser = XML_ParserCreate(NULL);
195   int done;
196 
197   if (! parser) {
198     fprintf(stderr, "Couldn't allocate memory for parser\n");
199     return 1;
200   }
201 
202   XML_SetUserData(parser, parser);
203   XML_SetElementDeclHandler(parser, handleElementDeclaration);
204 
205   do {
206     void *const buf = XML_GetBuffer(parser, BUFSIZ);
207     if (! buf) {
208       fprintf(stderr, "Couldn't allocate memory for buffer\n");
209       XML_ParserFree(parser);
210       return 1;
211     }
212 
213     const size_t len = fread(buf, 1, BUFSIZ, stdin);
214 
215     if (ferror(stdin)) {
216       fprintf(stderr, "Read error\n");
217       XML_ParserFree(parser);
218       return 1;
219     }
220 
221     done = feof(stdin);
222 
223     if (XML_ParseBuffer(parser, (int)len, done) == XML_STATUS_ERROR) {
224       enum XML_Error errorCode = XML_GetErrorCode(parser);
225       if (errorCode == XML_ERROR_ABORTED) {
226         errorCode = XML_ERROR_NO_MEMORY;
227       }
228       fprintf(stderr,
229               "Parse error at line %" XML_FMT_INT_MOD "u:\n%" XML_FMT_STR "\n",
230               XML_GetCurrentLineNumber(parser), XML_ErrorString(errorCode));
231       XML_ParserFree(parser);
232       return 1;
233     }
234   } while (! done);
235 
236   XML_ParserFree(parser);
237   return 0;
238 }
239