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  1. /*
  2.  * FLAC parser
  3.  * Copyright (c) 2010 Michael Chinen
  4.  *
  5.  * This file is part of FFmpeg.
  6.  *
  7.  * FFmpeg is free software; you can redistribute it and/or
  8.  * modify it under the terms of the GNU Lesser General Public
  9.  * License as published by the Free Software Foundation; either
  10.  * version 2.1 of the License, or (at your option) any later version.
  11.  *
  12.  * FFmpeg is distributed in the hope that it will be useful,
  13.  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14.  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15.  * Lesser General Public License for more details.
  16.  *
  17.  * You should have received a copy of the GNU Lesser General Public
  18.  * License along with FFmpeg; if not, write to the Free Software
  19.  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  20.  */
  21.  
  22. /**
  23.  * @file
  24.  * FLAC parser
  25.  *
  26.  * The FLAC parser buffers input until FLAC_MIN_HEADERS has been found.
  27.  * Each time it finds and verifies a CRC-8 header it sees which of the
  28.  * FLAC_MAX_SEQUENTIAL_HEADERS that came before it have a valid CRC-16 footer
  29.  * that ends at the newly found header.
  30.  * Headers are scored by FLAC_HEADER_BASE_SCORE plus the max of its crc-verified
  31.  * children, penalized by changes in sample rate, frame number, etc.
  32.  * The parser returns the frame with the highest score.
  33.  **/
  34.  
  35. #include "libavutil/attributes.h"
  36. #include "libavutil/crc.h"
  37. #include "libavutil/fifo.h"
  38. #include "bytestream.h"
  39. #include "parser.h"
  40. #include "flac.h"
  41.  
  42. /** maximum number of adjacent headers that compare CRCs against each other   */
  43. #define FLAC_MAX_SEQUENTIAL_HEADERS 3
  44. /** minimum number of headers buffered and checked before returning frames    */
  45. #define FLAC_MIN_HEADERS 10
  46. /** estimate for average size of a FLAC frame                                 */
  47. #define FLAC_AVG_FRAME_SIZE 8192
  48.  
  49. /** scoring settings for score_header */
  50. #define FLAC_HEADER_BASE_SCORE        10
  51. #define FLAC_HEADER_CHANGED_PENALTY   7
  52. #define FLAC_HEADER_CRC_FAIL_PENALTY  50
  53. #define FLAC_HEADER_NOT_PENALIZED_YET 100000
  54. #define FLAC_HEADER_NOT_SCORED_YET    -100000
  55.  
  56. /** largest possible size of flac header */
  57. #define MAX_FRAME_HEADER_SIZE 16
  58.  
  59. typedef struct FLACHeaderMarker {
  60.     int offset;       /**< byte offset from start of FLACParseContext->buffer */
  61.     int *link_penalty;  /**< pointer to array of local scores between this header
  62.                            and the one at a distance equal array position     */
  63.     int max_score;    /**< maximum score found after checking each child that
  64.                            has a valid CRC                                    */
  65.     FLACFrameInfo fi; /**< decoded frame header info                          */
  66.     struct FLACHeaderMarker *next;       /**< next CRC-8 verified header that
  67.                                               immediately follows this one in
  68.                                               the bytestream                  */
  69.     struct FLACHeaderMarker *best_child; /**< following frame header with
  70.                                               which this frame has the best
  71.                                               score with                      */
  72. } FLACHeaderMarker;
  73.  
  74. typedef struct FLACParseContext {
  75.     AVCodecParserContext *pc;      /**< parent context                        */
  76.     AVCodecContext *avctx;         /**< codec context pointer for logging     */
  77.     FLACHeaderMarker *headers;     /**< linked-list that starts at the first
  78.                                         CRC-8 verified header within buffer   */
  79.     FLACHeaderMarker *best_header; /**< highest scoring header within buffer  */
  80.     int nb_headers_found;          /**< number of headers found in the last
  81.                                         flac_parse() call                     */
  82.     int nb_headers_buffered;       /**< number of headers that are buffered   */
  83.     int best_header_valid;         /**< flag set when the parser returns junk;
  84.                                         if set return best_header next time   */
  85.     AVFifoBuffer *fifo_buf;        /**< buffer to store all data until headers
  86.                                         can be verified                       */
  87.     int end_padded;                /**< specifies if fifo_buf's end is padded */
  88.     uint8_t *wrap_buf;             /**< general fifo read buffer when wrapped */
  89.     int wrap_buf_allocated_size;   /**< actual allocated size of the buffer   */
  90.     FLACFrameInfo last_fi;         /**< last decoded frame header info        */
  91.     int last_fi_valid;             /**< set if last_fi is valid               */
  92. } FLACParseContext;
  93.  
  94. static int frame_header_is_valid(AVCodecContext *avctx, const uint8_t *buf,
  95.                                  FLACFrameInfo *fi)
  96. {
  97.     GetBitContext gb;
  98.     init_get_bits(&gb, buf, MAX_FRAME_HEADER_SIZE * 8);
  99.     return !ff_flac_decode_frame_header(avctx, &gb, fi, 127);
  100. }
  101.  
  102. /**
  103.  * Non-destructive fast fifo pointer fetching
  104.  * Returns a pointer from the specified offset.
  105.  * If possible the pointer points within the fifo buffer.
  106.  * Otherwise (if it would cause a wrap around,) a pointer to a user-specified
  107.  * buffer is used.
  108.  * The pointer can be NULL.  In any case it will be reallocated to hold the size.
  109.  * If the returned pointer will be used after subsequent calls to flac_fifo_read_wrap
  110.  * then the subsequent calls should pass in a different wrap_buf so as to not
  111.  * overwrite the contents of the previous wrap_buf.
  112.  * This function is based on av_fifo_generic_read, which is why there is a comment
  113.  * about a memory barrier for SMP.
  114.  */
  115. static uint8_t* flac_fifo_read_wrap(FLACParseContext *fpc, int offset, int len,
  116.                                uint8_t** wrap_buf, int* allocated_size)
  117. {
  118.     AVFifoBuffer *f   = fpc->fifo_buf;
  119.     uint8_t *start    = f->rptr + offset;
  120.     uint8_t *tmp_buf;
  121.  
  122.     if (start >= f->end)
  123.         start -= f->end - f->buffer;
  124.     if (f->end - start >= len)
  125.         return start;
  126.  
  127.     tmp_buf = av_fast_realloc(*wrap_buf, allocated_size, len);
  128.  
  129.     if (!tmp_buf) {
  130.         av_log(fpc->avctx, AV_LOG_ERROR,
  131.                "couldn't reallocate wrap buffer of size %d", len);
  132.         return NULL;
  133.     }
  134.     *wrap_buf = tmp_buf;
  135.     do {
  136.         int seg_len = FFMIN(f->end - start, len);
  137.         memcpy(tmp_buf, start, seg_len);
  138.         tmp_buf = (uint8_t*)tmp_buf + seg_len;
  139. // memory barrier needed for SMP here in theory
  140.  
  141.         start += seg_len - (f->end - f->buffer);
  142.         len -= seg_len;
  143.     } while (len > 0);
  144.  
  145.     return *wrap_buf;
  146. }
  147.  
  148. /**
  149.  * Return a pointer in the fifo buffer where the offset starts at until
  150.  * the wrap point or end of request.
  151.  * len will contain the valid length of the returned buffer.
  152.  * A second call to flac_fifo_read (with new offset and len) should be called
  153.  * to get the post-wrap buf if the returned len is less than the requested.
  154.  **/
  155. static uint8_t* flac_fifo_read(FLACParseContext *fpc, int offset, int *len)
  156. {
  157.     AVFifoBuffer *f   = fpc->fifo_buf;
  158.     uint8_t *start    = f->rptr + offset;
  159.  
  160.     if (start >= f->end)
  161.         start -= f->end - f->buffer;
  162.     *len = FFMIN(*len, f->end - start);
  163.     return start;
  164. }
  165.  
  166. static int find_headers_search_validate(FLACParseContext *fpc, int offset)
  167. {
  168.     FLACFrameInfo fi;
  169.     uint8_t *header_buf;
  170.     int size = 0;
  171.     header_buf = flac_fifo_read_wrap(fpc, offset,
  172.                                      MAX_FRAME_HEADER_SIZE,
  173.                                      &fpc->wrap_buf,
  174.                                      &fpc->wrap_buf_allocated_size);
  175.     if (frame_header_is_valid(fpc->avctx, header_buf, &fi)) {
  176.         FLACHeaderMarker **end_handle = &fpc->headers;
  177.         int i;
  178.  
  179.         size = 0;
  180.         while (*end_handle) {
  181.             end_handle = &(*end_handle)->next;
  182.             size++;
  183.         }
  184.  
  185.         *end_handle = av_mallocz(sizeof(FLACHeaderMarker));
  186.         if (!*end_handle) {
  187.             av_log(fpc->avctx, AV_LOG_ERROR,
  188.                    "couldn't allocate FLACHeaderMarker\n");
  189.             return AVERROR(ENOMEM);
  190.         }
  191.         (*end_handle)->fi           = fi;
  192.         (*end_handle)->offset       = offset;
  193.         (*end_handle)->link_penalty = av_malloc(sizeof(int) *
  194.                                             FLAC_MAX_SEQUENTIAL_HEADERS);
  195.         for (i = 0; i < FLAC_MAX_SEQUENTIAL_HEADERS; i++)
  196.             (*end_handle)->link_penalty[i] = FLAC_HEADER_NOT_PENALIZED_YET;
  197.  
  198.         fpc->nb_headers_found++;
  199.         size++;
  200.     }
  201.     return size;
  202. }
  203.  
  204. static int find_headers_search(FLACParseContext *fpc, uint8_t *buf, int buf_size,
  205.                                int search_start)
  206.  
  207. {
  208.     int size = 0, mod_offset = (buf_size - 1) % 4, i, j;
  209.     uint32_t x;
  210.  
  211.     for (i = 0; i < mod_offset; i++) {
  212.         if ((AV_RB16(buf + i) & 0xFFFE) == 0xFFF8)
  213.             size = find_headers_search_validate(fpc, search_start + i);
  214.     }
  215.  
  216.     for (; i < buf_size - 1; i += 4) {
  217.         x = AV_RB32(buf + i);
  218.         if (((x & ~(x + 0x01010101)) & 0x80808080)) {
  219.             for (j = 0; j < 4; j++) {
  220.                 if ((AV_RB16(buf + i + j) & 0xFFFE) == 0xFFF8)
  221.                     size = find_headers_search_validate(fpc, search_start + i + j);
  222.             }
  223.         }
  224.     }
  225.     return size;
  226. }
  227.  
  228. static int find_new_headers(FLACParseContext *fpc, int search_start)
  229. {
  230.     FLACHeaderMarker *end;
  231.     int search_end, size = 0, read_len, temp;
  232.     uint8_t *buf;
  233.     fpc->nb_headers_found = 0;
  234.  
  235.     /* Search for a new header of at most 16 bytes. */
  236.     search_end = av_fifo_size(fpc->fifo_buf) - (MAX_FRAME_HEADER_SIZE - 1);
  237.     read_len   = search_end - search_start + 1;
  238.     buf        = flac_fifo_read(fpc, search_start, &read_len);
  239.     size       = find_headers_search(fpc, buf, read_len, search_start);
  240.     search_start += read_len - 1;
  241.  
  242.     /* If fifo end was hit do the wrap around. */
  243.     if (search_start != search_end) {
  244.         uint8_t wrap[2];
  245.  
  246.         wrap[0]  = buf[read_len - 1];
  247.         read_len = search_end - search_start + 1;
  248.  
  249.         /* search_start + 1 is the post-wrap offset in the fifo. */
  250.         buf      = flac_fifo_read(fpc, search_start + 1, &read_len);
  251.         wrap[1]  = buf[0];
  252.  
  253.         if ((AV_RB16(wrap) & 0xFFFE) == 0xFFF8) {
  254.             temp = find_headers_search_validate(fpc, search_start);
  255.             size = FFMAX(size, temp);
  256.         }
  257.         search_start++;
  258.  
  259.         /* Continue to do the last half of the wrap. */
  260.         temp     = find_headers_search(fpc, buf, read_len, search_start);
  261.         size     = FFMAX(size, temp);
  262.         search_start += read_len - 1;
  263.     }
  264.  
  265.     /* Return the size even if no new headers were found. */
  266.     if (!size && fpc->headers)
  267.         for (end = fpc->headers; end; end = end->next)
  268.             size++;
  269.     return size;
  270. }
  271.  
  272. static int check_header_fi_mismatch(FLACParseContext  *fpc,
  273.                                     FLACFrameInfo     *header_fi,
  274.                                     FLACFrameInfo     *child_fi,
  275.                                     int                log_level_offset)
  276. {
  277.     int deduction = 0;
  278.     if (child_fi->samplerate != header_fi->samplerate) {
  279.         deduction += FLAC_HEADER_CHANGED_PENALTY;
  280.         av_log(fpc->avctx, AV_LOG_WARNING + log_level_offset,
  281.                "sample rate change detected in adjacent frames\n");
  282.     }
  283.     if (child_fi->bps != header_fi->bps) {
  284.         deduction += FLAC_HEADER_CHANGED_PENALTY;
  285.         av_log(fpc->avctx, AV_LOG_WARNING + log_level_offset,
  286.                "bits per sample change detected in adjacent frames\n");
  287.     }
  288.     if (child_fi->is_var_size != header_fi->is_var_size) {
  289.         /* Changing blocking strategy not allowed per the spec */
  290.         deduction += FLAC_HEADER_BASE_SCORE;
  291.         av_log(fpc->avctx, AV_LOG_WARNING + log_level_offset,
  292.                "blocking strategy change detected in adjacent frames\n");
  293.     }
  294.     if (child_fi->channels != header_fi->channels) {
  295.         deduction += FLAC_HEADER_CHANGED_PENALTY;
  296.         av_log(fpc->avctx, AV_LOG_WARNING + log_level_offset,
  297.                "number of channels change detected in adjacent frames\n");
  298.     }
  299.     return deduction;
  300. }
  301.  
  302. static int check_header_mismatch(FLACParseContext  *fpc,
  303.                                  FLACHeaderMarker  *header,
  304.                                  FLACHeaderMarker  *child,
  305.                                  int                log_level_offset)
  306. {
  307.     FLACFrameInfo  *header_fi = &header->fi, *child_fi = &child->fi;
  308.     int deduction, deduction_expected = 0, i;
  309.     deduction = check_header_fi_mismatch(fpc, header_fi, child_fi,
  310.                                          log_level_offset);
  311.     /* Check sample and frame numbers. */
  312.     if ((child_fi->frame_or_sample_num - header_fi->frame_or_sample_num
  313.          != header_fi->blocksize) &&
  314.         (child_fi->frame_or_sample_num
  315.          != header_fi->frame_or_sample_num + 1)) {
  316.         FLACHeaderMarker *curr;
  317.         int expected_frame_num, expected_sample_num;
  318.         /* If there are frames in the middle we expect this deduction,
  319.            as they are probably valid and this one follows it */
  320.  
  321.         expected_frame_num = expected_sample_num = header_fi->frame_or_sample_num;
  322.         curr = header;
  323.         while (curr != child) {
  324.             /* Ignore frames that failed all crc checks */
  325.             for (i = 0; i < FLAC_MAX_SEQUENTIAL_HEADERS; i++) {
  326.                 if (curr->link_penalty[i] < FLAC_HEADER_CRC_FAIL_PENALTY) {
  327.                     expected_frame_num++;
  328.                     expected_sample_num += curr->fi.blocksize;
  329.                     break;
  330.                 }
  331.             }
  332.             curr = curr->next;
  333.         }
  334.  
  335.         if (expected_frame_num  == child_fi->frame_or_sample_num ||
  336.             expected_sample_num == child_fi->frame_or_sample_num)
  337.             deduction_expected = deduction ? 0 : 1;
  338.  
  339.         deduction += FLAC_HEADER_CHANGED_PENALTY;
  340.         av_log(fpc->avctx, AV_LOG_WARNING + log_level_offset,
  341.                    "sample/frame number mismatch in adjacent frames\n");
  342.     }
  343.  
  344.     /* If we have suspicious headers, check the CRC between them */
  345.     if (deduction && !deduction_expected) {
  346.         FLACHeaderMarker *curr;
  347.         int read_len;
  348.         uint8_t *buf;
  349.         uint32_t crc = 1;
  350.         int inverted_test = 0;
  351.  
  352.         /* Since CRC is expensive only do it if we haven't yet.
  353.            This assumes a CRC penalty is greater than all other check penalties */
  354.         curr = header->next;
  355.         for (i = 0; i < FLAC_MAX_SEQUENTIAL_HEADERS && curr != child; i++)
  356.             curr = curr->next;
  357.  
  358.         if (header->link_penalty[i] < FLAC_HEADER_CRC_FAIL_PENALTY ||
  359.             header->link_penalty[i] == FLAC_HEADER_NOT_PENALIZED_YET) {
  360.             FLACHeaderMarker *start, *end;
  361.  
  362.             /* Although overlapping chains are scored, the crc should never
  363.                have to be computed twice for a single byte. */
  364.             start = header;
  365.             end   = child;
  366.             if (i > 0 &&
  367.                 header->link_penalty[i - 1] >= FLAC_HEADER_CRC_FAIL_PENALTY) {
  368.                 while (start->next != child)
  369.                     start = start->next;
  370.                 inverted_test = 1;
  371.             } else if (i > 0 &&
  372.                        header->next->link_penalty[i-1] >=
  373.                        FLAC_HEADER_CRC_FAIL_PENALTY ) {
  374.                 end = header->next;
  375.                 inverted_test = 1;
  376.             }
  377.  
  378.             read_len = end->offset - start->offset;
  379.             buf      = flac_fifo_read(fpc, start->offset, &read_len);
  380.             crc      = av_crc(av_crc_get_table(AV_CRC_16_ANSI), 0, buf, read_len);
  381.             read_len = (end->offset - start->offset) - read_len;
  382.  
  383.             if (read_len) {
  384.                 buf = flac_fifo_read(fpc, end->offset - read_len, &read_len);
  385.                 crc = av_crc(av_crc_get_table(AV_CRC_16_ANSI), crc, buf, read_len);
  386.             }
  387.         }
  388.  
  389.         if (!crc ^ !inverted_test) {
  390.             deduction += FLAC_HEADER_CRC_FAIL_PENALTY;
  391.             av_log(fpc->avctx, AV_LOG_WARNING + log_level_offset,
  392.                    "crc check failed from offset %i (frame %"PRId64") to %i (frame %"PRId64")\n",
  393.                    header->offset, header_fi->frame_or_sample_num,
  394.                    child->offset, child_fi->frame_or_sample_num);
  395.         }
  396.     }
  397.     return deduction;
  398. }
  399.  
  400. /**
  401.  * Score a header.
  402.  *
  403.  * Give FLAC_HEADER_BASE_SCORE points to a frame for existing.
  404.  * If it has children, (subsequent frames of which the preceding CRC footer
  405.  * validates against this one,) then take the maximum score of the children,
  406.  * with a penalty of FLAC_HEADER_CHANGED_PENALTY applied for each change to
  407.  * bps, sample rate, channels, but not decorrelation mode, or blocksize,
  408.  * because it can change often.
  409.  **/
  410. static int score_header(FLACParseContext *fpc, FLACHeaderMarker *header)
  411. {
  412.     FLACHeaderMarker *child;
  413.     int dist = 0;
  414.     int child_score;
  415.     int base_score = FLAC_HEADER_BASE_SCORE;
  416.     if (header->max_score != FLAC_HEADER_NOT_SCORED_YET)
  417.         return header->max_score;
  418.  
  419.     /* Modify the base score with changes from the last output header */
  420.     if (fpc->last_fi_valid) {
  421.         /* Silence the log since this will be repeated if selected */
  422.         base_score -= check_header_fi_mismatch(fpc, &fpc->last_fi, &header->fi,
  423.                                                AV_LOG_DEBUG);
  424.     }
  425.  
  426.     header->max_score = base_score;
  427.  
  428.     /* Check and compute the children's scores. */
  429.     child = header->next;
  430.     for (dist = 0; dist < FLAC_MAX_SEQUENTIAL_HEADERS && child; dist++) {
  431.         /* Look at the child's frame header info and penalize suspicious
  432.            changes between the headers. */
  433.         if (header->link_penalty[dist] == FLAC_HEADER_NOT_PENALIZED_YET) {
  434.             header->link_penalty[dist] = check_header_mismatch(fpc, header,
  435.                                                                child, AV_LOG_DEBUG);
  436.         }
  437.         child_score = score_header(fpc, child) - header->link_penalty[dist];
  438.  
  439.         if (FLAC_HEADER_BASE_SCORE + child_score > header->max_score) {
  440.             /* Keep the child because the frame scoring is dynamic. */
  441.             header->best_child = child;
  442.             header->max_score  = base_score + child_score;
  443.         }
  444.         child = child->next;
  445.     }
  446.  
  447.     return header->max_score;
  448. }
  449.  
  450. static void score_sequences(FLACParseContext *fpc)
  451. {
  452.     FLACHeaderMarker *curr;
  453.     int best_score = 0;//FLAC_HEADER_NOT_SCORED_YET;
  454.     /* First pass to clear all old scores. */
  455.     for (curr = fpc->headers; curr; curr = curr->next)
  456.         curr->max_score = FLAC_HEADER_NOT_SCORED_YET;
  457.  
  458.     /* Do a second pass to score them all. */
  459.     for (curr = fpc->headers; curr; curr = curr->next) {
  460.         if (score_header(fpc, curr) > best_score) {
  461.             fpc->best_header = curr;
  462.             best_score       = curr->max_score;
  463.         }
  464.     }
  465. }
  466.  
  467. static int get_best_header(FLACParseContext* fpc, const uint8_t **poutbuf,
  468.                            int *poutbuf_size)
  469. {
  470.     FLACHeaderMarker *header = fpc->best_header;
  471.     FLACHeaderMarker *child  = header->best_child;
  472.     if (!child) {
  473.         *poutbuf_size = av_fifo_size(fpc->fifo_buf) - header->offset;
  474.     } else {
  475.         *poutbuf_size = child->offset - header->offset;
  476.  
  477.         /* If the child has suspicious changes, log them */
  478.         check_header_mismatch(fpc, header, child, 0);
  479.     }
  480.  
  481.     if (header->fi.channels != fpc->avctx->channels ||
  482.         !fpc->avctx->channel_layout) {
  483.         fpc->avctx->channels = header->fi.channels;
  484.         ff_flac_set_channel_layout(fpc->avctx);
  485.     }
  486.     fpc->avctx->sample_rate = header->fi.samplerate;
  487.     fpc->pc->duration       = header->fi.blocksize;
  488.     *poutbuf = flac_fifo_read_wrap(fpc, header->offset, *poutbuf_size,
  489.                                         &fpc->wrap_buf,
  490.                                         &fpc->wrap_buf_allocated_size);
  491.  
  492.     fpc->best_header_valid = 0;
  493.     fpc->last_fi_valid = 1;
  494.     fpc->last_fi = header->fi;
  495.  
  496.     /* Return the negative overread index so the client can compute pos.
  497.        This should be the amount overread to the beginning of the child */
  498.     if (child)
  499.         return child->offset - av_fifo_size(fpc->fifo_buf);
  500.     return 0;
  501. }
  502.  
  503. static int flac_parse(AVCodecParserContext *s, AVCodecContext *avctx,
  504.                       const uint8_t **poutbuf, int *poutbuf_size,
  505.                       const uint8_t *buf, int buf_size)
  506. {
  507.     FLACParseContext *fpc = s->priv_data;
  508.     FLACHeaderMarker *curr;
  509.     int nb_headers;
  510.     const uint8_t *read_end   = buf;
  511.     const uint8_t *read_start = buf;
  512.  
  513.     if (s->flags & PARSER_FLAG_COMPLETE_FRAMES) {
  514.         FLACFrameInfo fi;
  515.         if (frame_header_is_valid(avctx, buf, &fi)) {
  516.             s->duration = fi.blocksize;
  517.             if (!avctx->sample_rate)
  518.                 avctx->sample_rate = fi.samplerate;
  519.         }
  520.         *poutbuf      = buf;
  521.         *poutbuf_size = buf_size;
  522.         return buf_size;
  523.     }
  524.  
  525.     fpc->avctx = avctx;
  526.     if (fpc->best_header_valid)
  527.         return get_best_header(fpc, poutbuf, poutbuf_size);
  528.  
  529.     /* If a best_header was found last call remove it with the buffer data. */
  530.     if (fpc->best_header && fpc->best_header->best_child) {
  531.         FLACHeaderMarker *temp;
  532.         FLACHeaderMarker *best_child = fpc->best_header->best_child;
  533.  
  534.         /* Remove headers in list until the end of the best_header. */
  535.         for (curr = fpc->headers; curr != best_child; curr = temp) {
  536.             if (curr != fpc->best_header) {
  537.                 av_log(avctx, AV_LOG_DEBUG,
  538.                        "dropping low score %i frame header from offset %i to %i\n",
  539.                        curr->max_score, curr->offset, curr->next->offset);
  540.             }
  541.             temp = curr->next;
  542.             av_freep(&curr->link_penalty);
  543.             av_free(curr);
  544.             fpc->nb_headers_buffered--;
  545.         }
  546.         /* Release returned data from ring buffer. */
  547.         av_fifo_drain(fpc->fifo_buf, best_child->offset);
  548.  
  549.         /* Fix the offset for the headers remaining to match the new buffer. */
  550.         for (curr = best_child->next; curr; curr = curr->next)
  551.             curr->offset -= best_child->offset;
  552.  
  553.         fpc->nb_headers_buffered--;
  554.         best_child->offset = 0;
  555.         fpc->headers       = best_child;
  556.         if (fpc->nb_headers_buffered >= FLAC_MIN_HEADERS) {
  557.             fpc->best_header = best_child;
  558.             return get_best_header(fpc, poutbuf, poutbuf_size);
  559.         }
  560.         fpc->best_header   = NULL;
  561.     } else if (fpc->best_header) {
  562.         /* No end frame no need to delete the buffer; probably eof */
  563.         FLACHeaderMarker *temp;
  564.  
  565.         for (curr = fpc->headers; curr != fpc->best_header; curr = temp) {
  566.             temp = curr->next;
  567.             av_freep(&curr->link_penalty);
  568.             av_free(curr);
  569.         }
  570.         fpc->headers = fpc->best_header->next;
  571.         av_freep(&fpc->best_header->link_penalty);
  572.         av_freep(&fpc->best_header);
  573.     }
  574.  
  575.     /* Find and score new headers.                                     */
  576.     /* buf_size is to zero when padding, so check for this since we do */
  577.     /* not want to try to read more input once we have found the end.  */
  578.     /* Note that as (non-modified) parameters, buf can be non-NULL,    */
  579.     /* while buf_size is 0.                                            */
  580.     while ((buf && buf_size && read_end < buf + buf_size &&
  581.             fpc->nb_headers_buffered < FLAC_MIN_HEADERS)
  582.            || ((!buf || !buf_size) && !fpc->end_padded)) {
  583.         int start_offset;
  584.  
  585.         /* Pad the end once if EOF, to check the final region for headers. */
  586.         if (!buf || !buf_size) {
  587.             fpc->end_padded      = 1;
  588.             buf_size = MAX_FRAME_HEADER_SIZE;
  589.             read_end = read_start + MAX_FRAME_HEADER_SIZE;
  590.         } else {
  591.             /* The maximum read size is the upper-bound of what the parser
  592.                needs to have the required number of frames buffered */
  593.             int nb_desired = FLAC_MIN_HEADERS - fpc->nb_headers_buffered + 1;
  594.             read_end       = read_end + FFMIN(buf + buf_size - read_end,
  595.                                               nb_desired * FLAC_AVG_FRAME_SIZE);
  596.         }
  597.  
  598.         /* Fill the buffer. */
  599.         if (   av_fifo_space(fpc->fifo_buf) < read_end - read_start
  600.             && av_fifo_realloc2(fpc->fifo_buf, (read_end - read_start) + 2*av_fifo_size(fpc->fifo_buf)) < 0) {
  601.             av_log(avctx, AV_LOG_ERROR,
  602.                    "couldn't reallocate buffer of size %td\n",
  603.                    (read_end - read_start) + av_fifo_size(fpc->fifo_buf));
  604.             goto handle_error;
  605.         }
  606.  
  607.         if (buf && buf_size) {
  608.             av_fifo_generic_write(fpc->fifo_buf, (void*) read_start,
  609.                                   read_end - read_start, NULL);
  610.         } else {
  611.             int8_t pad[MAX_FRAME_HEADER_SIZE] = { 0 };
  612.             av_fifo_generic_write(fpc->fifo_buf, (void*) pad, sizeof(pad), NULL);
  613.         }
  614.  
  615.         /* Tag headers and update sequences. */
  616.         start_offset = av_fifo_size(fpc->fifo_buf) -
  617.                        ((read_end - read_start) + (MAX_FRAME_HEADER_SIZE - 1));
  618.         start_offset = FFMAX(0, start_offset);
  619.         nb_headers   = find_new_headers(fpc, start_offset);
  620.  
  621.         if (nb_headers < 0) {
  622.             av_log(avctx, AV_LOG_ERROR,
  623.                    "find_new_headers couldn't allocate FLAC header\n");
  624.             goto handle_error;
  625.         }
  626.  
  627.         fpc->nb_headers_buffered = nb_headers;
  628.         /* Wait till FLAC_MIN_HEADERS to output a valid frame. */
  629.         if (!fpc->end_padded && fpc->nb_headers_buffered < FLAC_MIN_HEADERS) {
  630.             if (buf && read_end < buf + buf_size) {
  631.                 read_start = read_end;
  632.                 continue;
  633.             } else {
  634.                 goto handle_error;
  635.             }
  636.         }
  637.  
  638.         /* If headers found, update the scores since we have longer chains. */
  639.         if (fpc->end_padded || fpc->nb_headers_found)
  640.             score_sequences(fpc);
  641.  
  642.         /* restore the state pre-padding */
  643.         if (fpc->end_padded) {
  644.             int warp = fpc->fifo_buf->wptr - fpc->fifo_buf->buffer < MAX_FRAME_HEADER_SIZE;
  645.             /* HACK: drain the tail of the fifo */
  646.             fpc->fifo_buf->wptr -= MAX_FRAME_HEADER_SIZE;
  647.             fpc->fifo_buf->wndx -= MAX_FRAME_HEADER_SIZE;
  648.             if (warp) {
  649.                 fpc->fifo_buf->wptr += fpc->fifo_buf->end -
  650.                     fpc->fifo_buf->buffer;
  651.             }
  652.             buf_size = 0;
  653.             read_start = read_end = NULL;
  654.         }
  655.     }
  656.  
  657.     curr = fpc->headers;
  658.     for (curr = fpc->headers; curr; curr = curr->next) {
  659.         if (curr->max_score > 0 &&
  660.             (!fpc->best_header || curr->max_score > fpc->best_header->max_score)) {
  661.             fpc->best_header = curr;
  662.         }
  663.     }
  664.  
  665.     if (fpc->best_header) {
  666.         fpc->best_header_valid = 1;
  667.         if (fpc->best_header->offset > 0) {
  668.             /* Output a junk frame. */
  669.             av_log(avctx, AV_LOG_DEBUG, "Junk frame till offset %i\n",
  670.                    fpc->best_header->offset);
  671.  
  672.             /* Set duration to 0. It is unknown or invalid in a junk frame. */
  673.             s->duration = 0;
  674.             *poutbuf_size     = fpc->best_header->offset;
  675.             *poutbuf          = flac_fifo_read_wrap(fpc, 0, *poutbuf_size,
  676.                                                     &fpc->wrap_buf,
  677.                                                     &fpc->wrap_buf_allocated_size);
  678.             return buf_size ? (read_end - buf) : (fpc->best_header->offset -
  679.                                            av_fifo_size(fpc->fifo_buf));
  680.         }
  681.         if (!buf_size)
  682.             return get_best_header(fpc, poutbuf, poutbuf_size);
  683.     }
  684.  
  685. handle_error:
  686.     *poutbuf      = NULL;
  687.     *poutbuf_size = 0;
  688.     return read_end - buf;
  689. }
  690.  
  691. static av_cold int flac_parse_init(AVCodecParserContext *c)
  692. {
  693.     FLACParseContext *fpc = c->priv_data;
  694.     fpc->pc = c;
  695.     /* There will generally be FLAC_MIN_HEADERS buffered in the fifo before
  696.        it drains.  This is allocated early to avoid slow reallocation. */
  697.     fpc->fifo_buf = av_fifo_alloc(FLAC_AVG_FRAME_SIZE * (FLAC_MIN_HEADERS + 3));
  698.     if (!fpc->fifo_buf)
  699.         return AVERROR(ENOMEM);
  700.     return 0;
  701. }
  702.  
  703. static void flac_parse_close(AVCodecParserContext *c)
  704. {
  705.     FLACParseContext *fpc = c->priv_data;
  706.     FLACHeaderMarker *curr = fpc->headers, *temp;
  707.  
  708.     while (curr) {
  709.         temp = curr->next;
  710.         av_freep(&curr->link_penalty);
  711.         av_free(curr);
  712.         curr = temp;
  713.     }
  714.     av_fifo_free(fpc->fifo_buf);
  715.     av_free(fpc->wrap_buf);
  716. }
  717.  
  718. AVCodecParser ff_flac_parser = {
  719.     .codec_ids      = { AV_CODEC_ID_FLAC },
  720.     .priv_data_size = sizeof(FLACParseContext),
  721.     .parser_init    = flac_parse_init,
  722.     .parser_parse   = flac_parse,
  723.     .parser_close   = flac_parse_close,
  724. };
  725.