Date: 2026-03-31T05:46:33+00:00

Actual source code: reader.c

      2: #include "yaml_private.h"

      4: /*
      5:  * Declarations.
      6:  */

      8: static int
      9: yaml_parser_set_reader_error(yaml_parser_t *parser, const char *problem,
     10:         size_t offset, int value);

     12: static int
     13: yaml_parser_update_raw_buffer(yaml_parser_t *parser);

     15: static int
     16: yaml_parser_determine_encoding(yaml_parser_t *parser);

     18: YAML_DECLARE(int)
     19: yaml_parser_update_buffer(yaml_parser_t *parser, size_t length);

     21: /*
     22:  * Set the reader error and return 0.
     23:  */

     25: static int
     26: yaml_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;

     34:     return 0;
     35: }

     37: /*
     38:  * Byte order marks.
     39:  */

     41: #define BOM_UTF8    "\xef\xbb\xbf"
     42: #define BOM_UTF16LE "\xff\xfe"
     43: #define BOM_UTF16BE "\xfe\xff"

     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:  */

     50: static int
     51: yaml_parser_determine_encoding(yaml_parser_t *parser)
     52: {
     53:     /* Ensure that we had enough bytes in the raw buffer. */

     55:     while (!parser->eof
     56:             && parser->raw_buffer.last - parser->raw_buffer.pointer < 3) {
     57:         if (!yaml_parser_update_raw_buffer(parser)) return 0;
     58:     }

     60:     /* Determine the encoding. */

     62:     if (parser->raw_buffer.last - parser->raw_buffer.pointer >= 2
     63:             && !memcmp(parser->raw_buffer.pointer, BOM_UTF16LE, 2)) {
     64:         parser->encoding = YAML_UTF16LE_ENCODING;
     65:         parser->raw_buffer.pointer += 2;
     66:         parser->offset += 2;
     67:     }
     68:     else if (parser->raw_buffer.last - parser->raw_buffer.pointer >= 2
     69:             && !memcmp(parser->raw_buffer.pointer, BOM_UTF16BE, 2)) {
     70:         parser->encoding = YAML_UTF16BE_ENCODING;
     71:         parser->raw_buffer.pointer += 2;
     72:         parser->offset += 2;
     73:     }
     74:     else if (parser->raw_buffer.last - parser->raw_buffer.pointer >= 3
     75:             && !memcmp(parser->raw_buffer.pointer, BOM_UTF8, 3)) {
     76:         parser->encoding = YAML_UTF8_ENCODING;
     77:         parser->raw_buffer.pointer += 3;
     78:         parser->offset += 3;
     79:     }
     80:     else {
     81:         parser->encoding = YAML_UTF8_ENCODING;
     82:     }

     84:     return 1;
     85: }

     87: /*
     88:  * Update the raw buffer.
     89:  */

     91: static int
     92: yaml_parser_update_raw_buffer(yaml_parser_t *parser)
     93: {
     94:     size_t size_read = 0;

     96:     /* Return if the raw buffer is full. */

     98:     if (parser->raw_buffer.start == parser->raw_buffer.pointer
     99:             && parser->raw_buffer.last == parser->raw_buffer.end)
    100:         return 1;

    102:     /* Return on EOF. */

    104:     if (parser->eof) return 1;

    106:     /* Move the remaining bytes in the raw buffer to the beginning. */

    108:     if (parser->raw_buffer.start < parser->raw_buffer.pointer
    109:             && parser->raw_buffer.pointer < parser->raw_buffer.last) {
    110:         memmove(parser->raw_buffer.start, parser->raw_buffer.pointer,
    111:                 parser->raw_buffer.last - parser->raw_buffer.pointer);
    112:     }
    113:     parser->raw_buffer.last -=
    114:         parser->raw_buffer.pointer - parser->raw_buffer.start;
    115:     parser->raw_buffer.pointer = parser->raw_buffer.start;

    117:     /* Call the read handler to fill the buffer. */

    119:     if (!parser->read_handler(parser->read_handler_data, parser->raw_buffer.last,
    120:                 parser->raw_buffer.end - parser->raw_buffer.last, &size_read)) {
    121:         return yaml_parser_set_reader_error(parser, "input error",
    122:                 parser->offset, -1);
    123:     }
    124:     parser->raw_buffer.last += size_read;
    125:     if (!size_read) parser->eof = 1;

    127:     return 1;
    128: }

    130: /*
    131:  * Ensure that the buffer contains at least `length` characters.
    132:  * Return 1 on success, 0 on failure.
    133:  *
    134:  * The length is supposed to be significantly less that the buffer size.
    135:  */

    137: YAML_DECLARE(int)
    138: yaml_parser_update_buffer(yaml_parser_t *parser, size_t length)
    139: {
    140:     int first = 1;

    142:     assert(parser->read_handler);   /* Read handler must be set. */

    144:     /* If the EOF flag is set and the raw buffer is empty, do nothing. */

    146:     if (parser->eof && parser->raw_buffer.pointer == parser->raw_buffer.last)
    147:         return 1;

    149:     /* Return if the buffer contains enough characters. */

    151:     if (parser->unread >= length)
    152:         return 1;

    154:     /* Determine the input encoding if it is not known yet. */

    156:     if (!parser->encoding) {
    157:         if (!yaml_parser_determine_encoding(parser))
    158:             return 0;
    159:     }

    161:     /* Move the unread characters to the beginning of the buffer. */

    163:     if (parser->buffer.start < parser->buffer.pointer
    164:             && parser->buffer.pointer < parser->buffer.last) {
    165:         size_t size = parser->buffer.last - parser->buffer.pointer;
    166:         memmove(parser->buffer.start, parser->buffer.pointer, size);
    167:         parser->buffer.pointer = parser->buffer.start;
    168:         parser->buffer.last = parser->buffer.start + size;
    169:     }
    170:     else if (parser->buffer.pointer == parser->buffer.last) {
    171:         parser->buffer.pointer = parser->buffer.start;
    172:         parser->buffer.last = parser->buffer.start;
    173:     }

    175:     /* Fill the buffer until it has enough characters. */

    177:     while (parser->unread < length)
    178:     {
    179:         /* Fill the raw buffer if necessary. */

    181:         if (!first || parser->raw_buffer.pointer == parser->raw_buffer.last) {
    182:             if (!yaml_parser_update_raw_buffer(parser)) return 0;
    183:         }
    184:         first = 0;

    186:         /* Decode the raw buffer. */

    188:         while (parser->raw_buffer.pointer != parser->raw_buffer.last)
    189:         {
    190:             unsigned int value = 0, value2 = 0;
    191:             int incomplete = 0;
    192:             unsigned char octet;
    193:             unsigned int width = 0;
    194:             int low, high;
    195:             size_t k;
    196:             size_t raw_unread = parser->raw_buffer.last - parser->raw_buffer.pointer;

    198:             /* Decode the next character. */

    200:             switch (parser->encoding)
    201:             {
    202:                 case YAML_UTF8_ENCODING:

    204:                     /*
    205:                      * Decode a UTF-8 character.  Check RFC 3629
    206:                      * (http://www.ietf.org/rfc/rfc3629.txt) for more details.
    207:                      *
    208:                      * The following table (taken from the RFC) is used for
    209:                      * decoding.
    210:                      *
    211:                      *    Char. number range |        UTF-8 octet sequence
    212:                      *      (hexadecimal)    |              (binary)
    213:                      *   --------------------+------------------------------------
    214:                      *   0000 0000-0000 007F | 0xxxxxxx
    215:                      *   0000 0080-0000 07FF | 110xxxxx 10xxxxxx
    216:                      *   0000 0800-0000 FFFF | 1110xxxx 10xxxxxx 10xxxxxx
    217:                      *   0001 0000-0010 FFFF | 11110xxx 10xxxxxx 10xxxxxx 10xxxxxx
    218:                      *
    219:                      * Additionally, the characters in the range 0xD800-0xDFFF
    220:                      * are prohibited as they are reserved for use with UTF-16
    221:                      * surrogate pairs.
    222:                      */

    224:                     /* Determine the length of the UTF-8 sequence. */

    226:                     octet = parser->raw_buffer.pointer[0];
    227:                     width = (octet & 0x80) == 0x00 ? 1 :
    228:                             (octet & 0xE0) == 0xC0 ? 2 :
    229:                             (octet & 0xF0) == 0xE0 ? 3 :
    230:                             (octet & 0xF8) == 0xF0 ? 4 : 0;

    232:                     /* Check if the leading octet is valid. */

    234:                     if (!width)
    235:                         return yaml_parser_set_reader_error(parser,
    236:                                 "invalid leading UTF-8 octet",
    237:                                 parser->offset, octet);

    239:                     /* Check if the raw buffer contains an incomplete character. */

    241:                     if (width > raw_unread) {
    242:                         if (parser->eof) {
    243:                             return yaml_parser_set_reader_error(parser,
    244:                                     "incomplete UTF-8 octet sequence",
    245:                                     parser->offset, -1);
    246:                         }
    247:                         incomplete = 1;
    248:                         break;
    249:                     }

    251:                     /* Decode the leading octet. */

    253:                     value = (octet & 0x80) == 0x00 ? octet & 0x7F :
    254:                             (octet & 0xE0) == 0xC0 ? octet & 0x1F :
    255:                             (octet & 0xF0) == 0xE0 ? octet & 0x0F :
    256:                             (octet & 0xF8) == 0xF0 ? octet & 0x07 : 0;

    258:                     /* Check and decode the trailing octets. */

    260:                     for (k = 1; k < width; k ++)
    261:                     {
    262:                         octet = parser->raw_buffer.pointer[k];

    264:                         /* Check if the octet is valid. */

    266:                         if ((octet & 0xC0) != 0x80)
    267:                             return yaml_parser_set_reader_error(parser,
    268:                                     "invalid trailing UTF-8 octet",
    269:                                     parser->offset+k, octet);

    271:                         /* Decode the octet. */

    273:                         value = (value << 6) + (octet & 0x3F);
    274:                     }

    276:                     /* Check the length of the sequence against the value. */

    278:                     if (!((width == 1) ||
    279:                             (width == 2 && value >= 0x80) ||
    280:                             (width == 3 && value >= 0x800) ||
    281:                             (width == 4 && value >= 0x10000)))
    282:                         return yaml_parser_set_reader_error(parser,
    283:                                 "invalid length of a UTF-8 sequence",
    284:                                 parser->offset, -1);

    286:                     /* Check the range of the value. */

    288:                     if ((value >= 0xD800 && value <= 0xDFFF) || value > 0x10FFFF)
    289:                         return yaml_parser_set_reader_error(parser,
    290:                                 "invalid Unicode character",
    291:                                 parser->offset, value);

    293:                     break;

    295:                 case YAML_UTF16LE_ENCODING:
    296:                 case YAML_UTF16BE_ENCODING:

    298:                     low = (parser->encoding == YAML_UTF16LE_ENCODING ? 0 : 1);
    299:                     high = (parser->encoding == YAML_UTF16LE_ENCODING ? 1 : 0);

    301:                     /*
    302:                      * The UTF-16 encoding is not as simple as one might
    303:                      * naively think.  Check RFC 2781
    304:                      * (http://www.ietf.org/rfc/rfc2781.txt).
    305:                      *
    306:                      * Normally, two subsequent bytes describe a Unicode
    307:                      * character.  However a special technique (called a
    308:                      * surrogate pair) is used for specifying character
    309:                      * values larger than 0xFFFF.
    310:                      *
    311:                      * A surrogate pair consists of two pseudo-characters:
    312:                      *      high surrogate area (0xD800-0xDBFF)
    313:                      *      low surrogate area (0xDC00-0xDFFF)
    314:                      *
    315:                      * The following formulas are used for decoding
    316:                      * and encoding characters using surrogate pairs:
    317:                      *
    318:                      *  U  = U' + 0x10000   (0x01 00 00 <= U <= 0x10 FF FF)
    319:                      *  U' = yyyyyyyyyyxxxxxxxxxx   (0 <= U' <= 0x0F FF FF)
    320:                      *  W1 = 110110yyyyyyyyyy
    321:                      *  W2 = 110111xxxxxxxxxx
    322:                      *
    323:                      * where U is the character value, W1 is the high surrogate
    324:                      * area, W2 is the low surrogate area.
    325:                      */

    327:                     /* Check for incomplete UTF-16 character. */

    329:                     if (raw_unread < 2) {
    330:                         if (parser->eof) {
    331:                             return yaml_parser_set_reader_error(parser,
    332:                                     "incomplete UTF-16 character",
    333:                                     parser->offset, -1);
    334:                         }
    335:                         incomplete = 1;
    336:                         break;
    337:                     }

    339:                     /* Get the character. */

    341:                     value = parser->raw_buffer.pointer[low]
    342:                         + (parser->raw_buffer.pointer[high] << 8);

    344:                     /* Check for unexpected low surrogate area. */

    346:                     if ((value & 0xFC00) == 0xDC00)
    347:                         return yaml_parser_set_reader_error(parser,
    348:                                 "unexpected low surrogate area",
    349:                                 parser->offset, value);

    351:                     /* Check for a high surrogate area. */

    353:                     if ((value & 0xFC00) == 0xD800) {

    355:                         width = 4;

    357:                         /* Check for incomplete surrogate pair. */

    359:                         if (raw_unread < 4) {
    360:                             if (parser->eof) {
    361:                                 return yaml_parser_set_reader_error(parser,
    362:                                         "incomplete UTF-16 surrogate pair",
    363:                                         parser->offset, -1);
    364:                             }
    365:                             incomplete = 1;
    366:                             break;
    367:                         }

    369:                         /* Get the next character. */

    371:                         value2 = parser->raw_buffer.pointer[low+2]
    372:                             + (parser->raw_buffer.pointer[high+2] << 8);

    374:                         /* Check for a low surrogate area. */

    376:                         if ((value2 & 0xFC00) != 0xDC00)
    377:                             return yaml_parser_set_reader_error(parser,
    378:                                     "expected low surrogate area",
    379:                                     parser->offset+2, value2);

    381:                         /* Generate the value of the surrogate pair. */

    383:                         value = 0x10000 + ((value & 0x3FF) << 10) + (value2 & 0x3FF);
    384:                     }

    386:                     else {
    387:                         width = 2;
    388:                     }

    390:                     break;

    392:                 default:
    393:                     assert(1);      /* Impossible. */
    394:             }

    396:             /* Check if the raw buffer contains enough bytes to form a character. */

    398:             if (incomplete) break;

    400:             /*
    401:              * Check if the character is in the allowed range:
    402:              *      #x9 | #xA | #xD | [#x20-#x7E]               (8 bit)
    403:              *      | #x85 | [#xA0-#xD7FF] | [#xE000-#xFFFD]    (16 bit)
    404:              *      | [#x10000-#x10FFFF]                        (32 bit)
    405:              */

    407:             if (! (value == 0x09 || value == 0x0A || value == 0x0D
    408:                         || (value >= 0x20 && value <= 0x7E)
    409:                         || (value == 0x85) || (value >= 0xA0 && value <= 0xD7FF)
    410:                         || (value >= 0xE000 && value <= 0xFFFD)
    411:                         || (value >= 0x10000 && value <= 0x10FFFF)))
    412:                 return yaml_parser_set_reader_error(parser,
    413:                         "control characters are not allowed",
    414:                         parser->offset, value);

    416:             /* Move the raw pointers. */

    418:             parser->raw_buffer.pointer += width;
    419:             parser->offset += width;

    421:             /* Finally put the character into the buffer. */

    423:             /* 0000 0000-0000 007F -> 0xxxxxxx */
    424:             if (value <= 0x7F) *(parser->buffer.last++) = value;
    425:             /* 0000 0080-0000 07FF -> 110xxxxx 10xxxxxx */
    426:             else if (value <= 0x7FF) {
    427:                 *(parser->buffer.last++) = 0xC0 + (value >> 6);
    428:                 *(parser->buffer.last++) = 0x80 + (value & 0x3F);
    429:             }
    430:             /* 0000 0800-0000 FFFF -> 1110xxxx 10xxxxxx 10xxxxxx */
    431:             else if (value <= 0xFFFF) {
    432:                 *(parser->buffer.last++) = 0xE0 + (value >> 12);
    433:                 *(parser->buffer.last++) = 0x80 + ((value >> 6) & 0x3F);
    434:                 *(parser->buffer.last++) = 0x80 + (value & 0x3F);
    435:             }
    436:             /* 0001 0000-0010 FFFF -> 11110xxx 10xxxxxx 10xxxxxx 10xxxxxx */
    437:             else {
    438:                 *(parser->buffer.last++) = 0xF0 + (value >> 18);
    439:                 *(parser->buffer.last++) = 0x80 + ((value >> 12) & 0x3F);
    440:                 *(parser->buffer.last++) = 0x80 + ((value >> 6) & 0x3F);
    441:                 *(parser->buffer.last++) = 0x80 + (value & 0x3F);
    442:             }

    444:             parser->unread ++;
    445:         }

    447:         /* On EOF, put NUL into the buffer and return. */

    449:         if (parser->eof) {
    450:             *(parser->buffer.last++) = '\0';
    451:             parser->unread ++;
    452:             return 1;
    453:         }

    455:     }

    457:     if (parser->offset >= MAX_FILE_SIZE) {
    458:         return yaml_parser_set_reader_error(parser, "input is too long",
    459:             parser->offset, -1);
    460:     }

    462:     return 1;
    463: }