1
2#include "yaml_private.h"
3
4/*
5 * Declarations.
6 */
7
8static int
9yaml_parser_set_reader_error(yaml_parser_t *parser, const char *problem,
10        size_t offset, int value);
11
12static int
13yaml_parser_update_raw_buffer(yaml_parser_t *parser);
14
15static int
16yaml_parser_determine_encoding(yaml_parser_t *parser);
17
18YAML_DECLARE(int)
19yaml_parser_update_buffer(yaml_parser_t *parser, size_t length);
20
21/*
22 * Set the reader error and return 0.
23 */
24
25static int
26yaml_parser_set_reader_error(yaml_parser_t *parser, const char *problem,
27        size_t offset, int value)
28{
29    parser->error = YAML_READER_ERROR;
30    parser->problem = problem;
31    parser->problem_offset = offset;
32    parser->problem_value = value;
33
34    return 0;
35}
36
37/*
38 * Byte order marks.
39 */
40
41#define BOM_UTF8    "\xef\xbb\xbf"
42#define BOM_UTF16LE "\xff\xfe"
43#define BOM_UTF16BE "\xfe\xff"
44
45/*
46 * Determine the input stream encoding by checking the BOM symbol. If no BOM is
47 * found, the UTF-8 encoding is assumed. Return 1 on success, 0 on failure.
48 */
49
50static int
51yaml_parser_determine_encoding(yaml_parser_t *parser)
52{
53    /* Ensure that we had enough bytes in the raw buffer. */
54
55    while (!parser->eof
56            && parser->raw_buffer.last - parser->raw_buffer.pointer < 3) {
57        if (!yaml_parser_update_raw_buffer(parser)) {
58            return 0;
59        }
60    }
61
62    /* Determine the encoding. */
63
64    if (parser->raw_buffer.last - parser->raw_buffer.pointer >= 2
65            && !memcmp(parser->raw_buffer.pointer, BOM_UTF16LE, 2)) {
66        parser->encoding = YAML_UTF16LE_ENCODING;
67        parser->raw_buffer.pointer += 2;
68        parser->offset += 2;
69    }
70    else if (parser->raw_buffer.last - parser->raw_buffer.pointer >= 2
71            && !memcmp(parser->raw_buffer.pointer, BOM_UTF16BE, 2)) {
72        parser->encoding = YAML_UTF16BE_ENCODING;
73        parser->raw_buffer.pointer += 2;
74        parser->offset += 2;
75    }
76    else if (parser->raw_buffer.last - parser->raw_buffer.pointer >= 3
77            && !memcmp(parser->raw_buffer.pointer, BOM_UTF8, 3)) {
78        parser->encoding = YAML_UTF8_ENCODING;
79        parser->raw_buffer.pointer += 3;
80        parser->offset += 3;
81    }
82    else {
83        parser->encoding = YAML_UTF8_ENCODING;
84    }
85
86    return 1;
87}
88
89/*
90 * Update the raw buffer.
91 */
92
93static int
94yaml_parser_update_raw_buffer(yaml_parser_t *parser)
95{
96    size_t size_read = 0;
97
98    /* Return if the raw buffer is full. */
99
100    if (parser->raw_buffer.start == parser->raw_buffer.pointer
101            && parser->raw_buffer.last == parser->raw_buffer.end)
102        return 1;
103
104    /* Return on EOF. */
105
106    if (parser->eof) return 1;
107
108    /* Move the remaining bytes in the raw buffer to the beginning. */
109
110    if (parser->raw_buffer.start < parser->raw_buffer.pointer
111            && parser->raw_buffer.pointer < parser->raw_buffer.last) {
112        memmove(parser->raw_buffer.start, parser->raw_buffer.pointer,
113                parser->raw_buffer.last - parser->raw_buffer.pointer);
114    }
115    parser->raw_buffer.last -=
116        parser->raw_buffer.pointer - parser->raw_buffer.start;
117    parser->raw_buffer.pointer = parser->raw_buffer.start;
118
119    /* Call the read handler to fill the buffer. */
120
121    if (!parser->read_handler(parser->read_handler_data, parser->raw_buffer.last,
122                parser->raw_buffer.end - parser->raw_buffer.last, &size_read)) {
123        return yaml_parser_set_reader_error(parser, "input error",
124                parser->offset, -1);
125    }
126    parser->raw_buffer.last += size_read;
127    if (!size_read) {
128        parser->eof = 1;
129    }
130
131    return 1;
132}
133
134/*
135 * Ensure that the buffer contains at least `length` characters.
136 * Return 1 on success, 0 on failure.
137 *
138 * The length is supposed to be significantly less that the buffer size.
139 */
140
141YAML_DECLARE(int)
142yaml_parser_update_buffer(yaml_parser_t *parser, size_t length)
143{
144    int first = 1;
145
146    assert(parser->read_handler);   /* Read handler must be set. */
147
148    /* If the EOF flag is set and the raw buffer is empty, do nothing. */
149
150    if (parser->eof && parser->raw_buffer.pointer == parser->raw_buffer.last)
151        return 1;
152
153    /* Return if the buffer contains enough characters. */
154
155    if (parser->unread >= length)
156        return 1;
157
158    /* Determine the input encoding if it is not known yet. */
159
160    if (!parser->encoding) {
161        if (!yaml_parser_determine_encoding(parser))
162            return 0;
163    }
164
165    /* Move the unread characters to the beginning of the buffer. */
166
167    if (parser->buffer.start < parser->buffer.pointer
168            && parser->buffer.pointer < parser->buffer.last) {
169        size_t size = parser->buffer.last - parser->buffer.pointer;
170        memmove(parser->buffer.start, parser->buffer.pointer, size);
171        parser->buffer.pointer = parser->buffer.start;
172        parser->buffer.last = parser->buffer.start + size;
173    }
174    else if (parser->buffer.pointer == parser->buffer.last) {
175        parser->buffer.pointer = parser->buffer.start;
176        parser->buffer.last = parser->buffer.start;
177    }
178
179    /* Fill the buffer until it has enough characters. */
180
181    while (parser->unread < length)
182    {
183        /* Fill the raw buffer if necessary. */
184
185        if (!first || parser->raw_buffer.pointer == parser->raw_buffer.last) {
186            if (!yaml_parser_update_raw_buffer(parser)) return 0;
187        }
188        first = 0;
189
190        /* Decode the raw buffer. */
191
192        while (parser->raw_buffer.pointer != parser->raw_buffer.last)
193        {
194            unsigned int value = 0, value2 = 0;
195            int incomplete = 0;
196            unsigned char octet;
197            unsigned int width = 0;
198            int low, high;
199            size_t k;
200            size_t raw_unread = parser->raw_buffer.last - parser->raw_buffer.pointer;
201
202            /* Decode the next character. */
203
204            switch (parser->encoding)
205            {
206                case YAML_UTF8_ENCODING:
207
208                    /*
209                     * Decode a UTF-8 character.  Check RFC 3629
210                     * (http://www.ietf.org/rfc/rfc3629.txt) for more details.
211                     *
212                     * The following table (taken from the RFC) is used for
213                     * decoding.
214                     *
215                     *    Char. number range |        UTF-8 octet sequence
216                     *      (hexadecimal)    |              (binary)
217                     *   --------------------+------------------------------------
218                     *   0000 0000-0000 007F | 0xxxxxxx
219                     *   0000 0080-0000 07FF | 110xxxxx 10xxxxxx
220                     *   0000 0800-0000 FFFF | 1110xxxx 10xxxxxx 10xxxxxx
221                     *   0001 0000-0010 FFFF | 11110xxx 10xxxxxx 10xxxxxx 10xxxxxx
222                     *
223                     * Additionally, the characters in the range 0xD800-0xDFFF
224                     * are prohibited as they are reserved for use with UTF-16
225                     * surrogate pairs.
226                     */
227
228                    /* Determine the length of the UTF-8 sequence. */
229
230                    octet = parser->raw_buffer.pointer[0];
231                    width = (octet & 0x80) == 0x00 ? 1 :
232                            (octet & 0xE0) == 0xC0 ? 2 :
233                            (octet & 0xF0) == 0xE0 ? 3 :
234                            (octet & 0xF8) == 0xF0 ? 4 : 0;
235
236                    /* Check if the leading octet is valid. */
237
238                    if (!width)
239                        return yaml_parser_set_reader_error(parser,
240                                "invalid leading UTF-8 octet",
241                                parser->offset, octet);
242
243                    /* Check if the raw buffer contains an incomplete character. */
244
245                    if (width > raw_unread) {
246                        if (parser->eof) {
247                            return yaml_parser_set_reader_error(parser,
248                                    "incomplete UTF-8 octet sequence",
249                                    parser->offset, -1);
250                        }
251                        incomplete = 1;
252                        break;
253                    }
254
255                    /* Decode the leading octet. */
256
257                    value = (octet & 0x80) == 0x00 ? octet & 0x7F :
258                            (octet & 0xE0) == 0xC0 ? octet & 0x1F :
259                            (octet & 0xF0) == 0xE0 ? octet & 0x0F :
260                            (octet & 0xF8) == 0xF0 ? octet & 0x07 : 0;
261
262                    /* Check and decode the trailing octets. */
263
264                    for (k = 1; k < width; k ++)
265                    {
266                        octet = parser->raw_buffer.pointer[k];
267
268                        /* Check if the octet is valid. */
269
270                        if ((octet & 0xC0) != 0x80)
271                            return yaml_parser_set_reader_error(parser,
272                                    "invalid trailing UTF-8 octet",
273                                    parser->offset+k, octet);
274
275                        /* Decode the octet. */
276
277                        value = (value << 6) + (octet & 0x3F);
278                    }
279
280                    /* Check the length of the sequence against the value. */
281
282                    if (!((width == 1) ||
283                            (width == 2 && value >= 0x80) ||
284                            (width == 3 && value >= 0x800) ||
285                            (width == 4 && value >= 0x10000)))
286                        return yaml_parser_set_reader_error(parser,
287                                "invalid length of a UTF-8 sequence",
288                                parser->offset, -1);
289
290                    /* Check the range of the value. */
291
292                    if ((value >= 0xD800 && value <= 0xDFFF) || value > 0x10FFFF)
293                        return yaml_parser_set_reader_error(parser,
294                                "invalid Unicode character",
295                                parser->offset, value);
296
297                    break;
298
299                case YAML_UTF16LE_ENCODING:
300                case YAML_UTF16BE_ENCODING:
301
302                    low = (parser->encoding == YAML_UTF16LE_ENCODING ? 0 : 1);
303                    high = (parser->encoding == YAML_UTF16LE_ENCODING ? 1 : 0);
304
305                    /*
306                     * The UTF-16 encoding is not as simple as one might
307                     * naively think.  Check RFC 2781
308                     * (http://www.ietf.org/rfc/rfc2781.txt).
309                     *
310                     * Normally, two subsequent bytes describe a Unicode
311                     * character.  However a special technique (called a
312                     * surrogate pair) is used for specifying character
313                     * values larger than 0xFFFF.
314                     *
315                     * A surrogate pair consists of two pseudo-characters:
316                     *      high surrogate area (0xD800-0xDBFF)
317                     *      low surrogate area (0xDC00-0xDFFF)
318                     *
319                     * The following formulas are used for decoding
320                     * and encoding characters using surrogate pairs:
321                     *
322                     *  U  = U' + 0x10000   (0x01 00 00 <= U <= 0x10 FF FF)
323                     *  U' = yyyyyyyyyyxxxxxxxxxx   (0 <= U' <= 0x0F FF FF)
324                     *  W1 = 110110yyyyyyyyyy
325                     *  W2 = 110111xxxxxxxxxx
326                     *
327                     * where U is the character value, W1 is the high surrogate
328                     * area, W2 is the low surrogate area.
329                     */
330
331                    /* Check for incomplete UTF-16 character. */
332
333                    if (raw_unread < 2) {
334                        if (parser->eof) {
335                            return yaml_parser_set_reader_error(parser,
336                                    "incomplete UTF-16 character",
337                                    parser->offset, -1);
338                        }
339                        incomplete = 1;
340                        break;
341                    }
342
343                    /* Get the character. */
344
345                    value = parser->raw_buffer.pointer[low]
346                        + (parser->raw_buffer.pointer[high] << 8);
347
348                    /* Check for unexpected low surrogate area. */
349
350                    if ((value & 0xFC00) == 0xDC00)
351                        return yaml_parser_set_reader_error(parser,
352                                "unexpected low surrogate area",
353                                parser->offset, value);
354
355                    /* Check for a high surrogate area. */
356
357                    if ((value & 0xFC00) == 0xD800) {
358
359                        width = 4;
360
361                        /* Check for incomplete surrogate pair. */
362
363                        if (raw_unread < 4) {
364                            if (parser->eof) {
365                                return yaml_parser_set_reader_error(parser,
366                                        "incomplete UTF-16 surrogate pair",
367                                        parser->offset, -1);
368                            }
369                            incomplete = 1;
370                            break;
371                        }
372
373                        /* Get the next character. */
374
375                        value2 = parser->raw_buffer.pointer[low+2]
376                            + (parser->raw_buffer.pointer[high+2] << 8);
377
378                        /* Check for a low surrogate area. */
379
380                        if ((value2 & 0xFC00) != 0xDC00)
381                            return yaml_parser_set_reader_error(parser,
382                                    "expected low surrogate area",
383                                    parser->offset+2, value2);
384
385                        /* Generate the value of the surrogate pair. */
386
387                        value = 0x10000 + ((value & 0x3FF) << 10) + (value2 & 0x3FF);
388                    }
389
390                    else {
391                        width = 2;
392                    }
393
394                    break;
395
396                default:
397                    assert(1);      /* Impossible. */
398            }
399
400            /* Check if the raw buffer contains enough bytes to form a character. */
401
402            if (incomplete) break;
403
404            /*
405             * Check if the character is in the allowed range:
406             *      #x9 | #xA | #xD | [#x20-#x7E]               (8 bit)
407             *      | #x85 | [#xA0-#xD7FF] | [#xE000-#xFFFD]    (16 bit)
408             *      | [#x10000-#x10FFFF]                        (32 bit)
409             */
410
411            if (! (value == 0x09 || value == 0x0A || value == 0x0D
412                        || (value >= 0x20 && value <= 0x7E)
413                        || (value == 0x85) || (value >= 0xA0 && value <= 0xD7FF)
414                        || (value >= 0xE000 && value <= 0xFFFD)
415                        || (value >= 0x10000 && value <= 0x10FFFF)))
416                return yaml_parser_set_reader_error(parser,
417                        "control characters are not allowed",
418                        parser->offset, value);
419
420            /* Move the raw pointers. */
421
422            parser->raw_buffer.pointer += width;
423            parser->offset += width;
424
425            /* Finally put the character into the buffer. */
426
427            /* 0000 0000-0000 007F -> 0xxxxxxx */
428            if (value <= 0x7F) {
429                *(parser->buffer.last++) = value;
430            }
431            /* 0000 0080-0000 07FF -> 110xxxxx 10xxxxxx */
432            else if (value <= 0x7FF) {
433                *(parser->buffer.last++) = 0xC0 + (value >> 6);
434                *(parser->buffer.last++) = 0x80 + (value & 0x3F);
435            }
436            /* 0000 0800-0000 FFFF -> 1110xxxx 10xxxxxx 10xxxxxx */
437            else if (value <= 0xFFFF) {
438                *(parser->buffer.last++) = 0xE0 + (value >> 12);
439                *(parser->buffer.last++) = 0x80 + ((value >> 6) & 0x3F);
440                *(parser->buffer.last++) = 0x80 + (value & 0x3F);
441            }
442            /* 0001 0000-0010 FFFF -> 11110xxx 10xxxxxx 10xxxxxx 10xxxxxx */
443            else {
444                *(parser->buffer.last++) = 0xF0 + (value >> 18);
445                *(parser->buffer.last++) = 0x80 + ((value >> 12) & 0x3F);
446                *(parser->buffer.last++) = 0x80 + ((value >> 6) & 0x3F);
447                *(parser->buffer.last++) = 0x80 + (value & 0x3F);
448            }
449
450            parser->unread ++;
451        }
452
453        /* On EOF, put NUL into the buffer and return. */
454
455        if (parser->eof) {
456            *(parser->buffer.last++) = '\0';
457            parser->unread ++;
458            return 1;
459        }
460
461    }
462
463    if (parser->offset >= PTRDIFF_MAX)
464        return yaml_parser_set_reader_error(parser, "input is too long",
465                PTRDIFF_MAX, -1);
466
467    return 1;
468}
469
470