/*
  * FLAC parser
  * Copyright (c) 2010 Michael Chinen
  *
  * This file is part of FFmpeg.
  *
  * FFmpeg is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
  * License as published by the Free Software Foundation; either
  * version 2.1 of the License, or (at your option) any later version.
  *
  * FFmpeg is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Lesser General Public License for more details.
  *
  * You should have received a copy of the GNU Lesser General Public
  * License along with FFmpeg; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
 /**
  * @file
  * FLAC parser
  *
  * The FLAC parser buffers input until FLAC_MIN_HEADERS has been found.
  * Each time it finds and verifies a CRC-8 header it sees which of the
  * FLAC_MAX_SEQUENTIAL_HEADERS that came before it have a valid CRC-16 footer
  * that ends at the newly found header.
  * Headers are scored by FLAC_HEADER_BASE_SCORE plus the max of it's crc-verified
  * children, penalized by changes in sample rate, frame number, etc.
  * The parser returns the frame with the highest score.
  **/
 
 #include "libavutil/crc.h"
 #include "libavutil/fifo.h"
 #include "bytestream.h"
 #include "parser.h"
 #include "flac.h"
 
 /** maximum number of adjacent headers that compare CRCs against each other   */
 #define FLAC_MAX_SEQUENTIAL_HEADERS 3
 /** minimum number of headers buffered and checked before returning frames    */
 #define FLAC_MIN_HEADERS 10

 /** estimate for average size of a FLAC frame                                 */
 #define FLAC_AVG_FRAME_SIZE 8192

 
 /** scoring settings for score_header */
 #define FLAC_HEADER_BASE_SCORE        10
 #define FLAC_HEADER_CHANGED_PENALTY   7
 #define FLAC_HEADER_CRC_FAIL_PENALTY  50
 #define FLAC_HEADER_NOT_PENALIZED_YET 100000
 #define FLAC_HEADER_NOT_SCORED_YET    -100000
 
 /** largest possible size of flac header */
 #define MAX_FRAME_HEADER_SIZE 16
 
 typedef struct FLACHeaderMarker {
     int offset;       /**< byte offset from start of FLACParseContext->buffer */
     int *link_penalty;  /**< pointer to array of local scores between this header
                            and the one at a distance equal array position     */
     int max_score;    /**< maximum score found after checking each child that
                            has a valid CRC                                    */
     FLACFrameInfo fi; /**< decoded frame header info                          */
     struct FLACHeaderMarker *next;       /**< next CRC-8 verified header that
                                               immediately follows this one in
                                               the bytestream                  */
     struct FLACHeaderMarker *best_child; /**< following frame header with
                                               which this frame has the best
                                               score with                      */
 } FLACHeaderMarker;
 
 typedef struct FLACParseContext {
     AVCodecContext *avctx;         /**< codec context pointer for logging     */
     FLACHeaderMarker *headers;     /**< linked-list that starts at the first
                                         CRC-8 verified header within buffer   */
     FLACHeaderMarker *best_header; /**< highest scoring header within buffer  */
     int nb_headers_found;          /**< number of headers found in the last
                                         flac_parse() call                     */

     int nb_headers_buffered;       /**< number of headers that are buffered   */

     int best_header_valid;         /**< flag set when the parser returns junk;
                                         if set return best_header next time   */
     AVFifoBuffer *fifo_buf;        /**< buffer to store all data until headers
                                         can be verified                       */
     int end_padded;                /**< specifies if fifo_buf's end is padded */
     uint8_t *wrap_buf;             /**< general fifo read buffer when wrapped */
     int wrap_buf_allocated_size;   /**< actual allocated size of the buffer   */
 } FLACParseContext;
 
 static int frame_header_is_valid(AVCodecContext *avctx, const uint8_t *buf,
                                  FLACFrameInfo *fi)
 {
     GetBitContext gb;
     init_get_bits(&gb, buf, MAX_FRAME_HEADER_SIZE * 8);
     return !ff_flac_decode_frame_header(avctx, &gb, fi, 127);
 }
 
 /**
  * Non-destructive fast fifo pointer fetching
  * Returns a pointer from the specified offset.
  * If possible the pointer points within the fifo buffer.
  * Otherwise (if it would cause a wrap around,) a pointer to a user-specified
  * buffer is used.
  * The pointer can be NULL.  In any case it will be reallocated to hold the size.
  * If the returned pointer will be used after subsequent calls to flac_fifo_read_wrap
  * then the subsequent calls should pass in a different wrap_buf so as to not
  * overwrite the contents of the previous wrap_buf.
  * This function is based on av_fifo_generic_read, which is why there is a comment
  * about a memory barrier for SMP.
  */
 static uint8_t* flac_fifo_read_wrap(FLACParseContext *fpc, int offset, int len,
                                uint8_t** wrap_buf, int* allocated_size)
 {
     AVFifoBuffer *f   = fpc->fifo_buf;
     uint8_t *start    = f->rptr + offset;
     uint8_t *tmp_buf;
 
     if (start >= f->end)
         start -= f->end - f->buffer;
     if (f->end - start >= len)
         return start;
 
     tmp_buf = av_fast_realloc(*wrap_buf, allocated_size, len);
 
     if (!tmp_buf) {
         av_log(fpc->avctx, AV_LOG_ERROR,
                "couldn't reallocate wrap buffer of size %d", len);
         return NULL;
     }
     *wrap_buf = tmp_buf;
     do {
         int seg_len = FFMIN(f->end - start, len);
         memcpy(tmp_buf, start, seg_len);
         tmp_buf = (uint8_t*)tmp_buf + seg_len;
 // memory barrier needed for SMP here in theory
 
         start += seg_len - (f->end - f->buffer);
         len -= seg_len;
     } while (len > 0);
 
     return *wrap_buf;
 }
 
 /**
  * Return a pointer in the fifo buffer where the offset starts at until
  * the wrap point or end of request.
  * len will contain the valid length of the returned buffer.
  * A second call to flac_fifo_read (with new offset and len) should be called
  * to get the post-wrap buf if the returned len is less than the requested.
  **/
 static uint8_t* flac_fifo_read(FLACParseContext *fpc, int offset, int *len)
 {
     AVFifoBuffer *f   = fpc->fifo_buf;
     uint8_t *start    = f->rptr + offset;
 
     if (start >= f->end)
         start -= f->end - f->buffer;
     *len = FFMIN(*len, f->end - start);
     return start;
 }
 
 static int find_headers_search_validate(FLACParseContext *fpc, int offset)
 {
     FLACFrameInfo fi;
     uint8_t *header_buf;
     int size = 0;
     header_buf = flac_fifo_read_wrap(fpc, offset,
                                      MAX_FRAME_HEADER_SIZE,
                                      &fpc->wrap_buf,
                                      &fpc->wrap_buf_allocated_size);
     if (frame_header_is_valid(fpc->avctx, header_buf, &fi)) {
         FLACHeaderMarker **end_handle = &fpc->headers;
         int i;
 
         size = 0;
         while (*end_handle) {
             end_handle = &(*end_handle)->next;
             size++;
         }
 
         *end_handle = av_mallocz(sizeof(FLACHeaderMarker));
         if (!*end_handle) {
             av_log(fpc->avctx, AV_LOG_ERROR,
                    "couldn't allocate FLACHeaderMarker\n");
             return AVERROR(ENOMEM);
         }
         (*end_handle)->fi           = fi;
         (*end_handle)->offset       = offset;
         (*end_handle)->link_penalty = av_malloc(sizeof(int) *
                                             FLAC_MAX_SEQUENTIAL_HEADERS);
         for (i = 0; i < FLAC_MAX_SEQUENTIAL_HEADERS; i++)
             (*end_handle)->link_penalty[i] = FLAC_HEADER_NOT_PENALIZED_YET;
 
         fpc->nb_headers_found++;
         size++;
     }
     return size;
 }
 
 static int find_headers_search(FLACParseContext *fpc, uint8_t *buf, int buf_size,
                                int search_start)
 
 {
     int size = 0, mod_offset = (buf_size - 1) % 4, i, j;
     uint32_t x;
 
     for (i = 0; i < mod_offset; i++) {
         if ((AV_RB16(buf + i) & 0xFFFE) == 0xFFF8)
             size = find_headers_search_validate(fpc, search_start + i);
     }
 
     for (; i < buf_size - 1; i += 4) {
         x = AV_RB32(buf + i);
         if (((x & ~(x + 0x01010101)) & 0x80808080)) {
             for (j = 0; j < 4; j++) {
                 if ((AV_RB16(buf + i + j) & 0xFFFE) == 0xFFF8)
                     size = find_headers_search_validate(fpc, search_start + i + j);
             }
         }
     }
     return size;
 }
 
 static int find_new_headers(FLACParseContext *fpc, int search_start)
 {
     FLACHeaderMarker *end;
     int search_end, size = 0, read_len, temp;
     uint8_t *buf;
     fpc->nb_headers_found = 0;
 
     /* Search for a new header of at most 16 bytes. */
     search_end = av_fifo_size(fpc->fifo_buf) - (MAX_FRAME_HEADER_SIZE - 1);
     read_len   = search_end - search_start + 1;
     buf        = flac_fifo_read(fpc, search_start, &read_len);
     size       = find_headers_search(fpc, buf, read_len, search_start);
     search_start += read_len - 1;
 
     /* If fifo end was hit do the wrap around. */
     if (search_start != search_end) {
         uint8_t wrap[2];
 
         wrap[0]  = buf[read_len - 1];
         read_len = search_end - search_start + 1;
 
         /* search_start + 1 is the post-wrap offset in the fifo. */
         buf      = flac_fifo_read(fpc, search_start + 1, &read_len);
         wrap[1]  = buf[0];
 
         if ((AV_RB16(wrap) & 0xFFFE) == 0xFFF8) {
             temp = find_headers_search_validate(fpc, search_start);
             size = FFMAX(size, temp);
         }
         search_start++;
 
         /* Continue to do the last half of the wrap. */
         temp     = find_headers_search(fpc, buf, read_len, search_start);
         size     = FFMAX(size, temp);
         search_start += read_len - 1;
     }
 
     /* Return the size even if no new headers were found. */
     if (!size && fpc->headers)
         for (end = fpc->headers; end; end = end->next)
             size++;
     return size;
 }
 
 static int check_header_mismatch(FLACParseContext  *fpc,
                                  FLACHeaderMarker  *header,
                                  FLACHeaderMarker  *child,
                                  int                log_level_offset)
 {
     FLACFrameInfo  *header_fi = &header->fi, *child_fi = &child->fi;
     int deduction = 0, deduction_expected = 0, i;
     if (child_fi->samplerate != header_fi->samplerate) {
         deduction += FLAC_HEADER_CHANGED_PENALTY;
         av_log(fpc->avctx, AV_LOG_WARNING + log_level_offset,
                "sample rate change detected in adjacent frames\n");
     }
     if (child_fi->bps != header_fi->bps) {
         deduction += FLAC_HEADER_CHANGED_PENALTY;
         av_log(fpc->avctx, AV_LOG_WARNING + log_level_offset,
                "bits per sample change detected in adjacent frames\n");
     }
     if (child_fi->is_var_size != header_fi->is_var_size) {
         /* Changing blocking strategy not allowed per the spec */
         deduction += FLAC_HEADER_BASE_SCORE;
         av_log(fpc->avctx, AV_LOG_WARNING + log_level_offset,
                    "blocking strategy change detected in adjacent frames\n");
     }
     if (child_fi->channels != header_fi->channels) {
         deduction += FLAC_HEADER_CHANGED_PENALTY;
         av_log(fpc->avctx, AV_LOG_WARNING + log_level_offset,
                    "number of channels change detected in adjacent frames\n");
     }
     /* Check sample and frame numbers. */
     if ((child_fi->frame_or_sample_num - header_fi->frame_or_sample_num
          != header_fi->blocksize) &&
         (child_fi->frame_or_sample_num
          != header_fi->frame_or_sample_num + 1)) {
         FLACHeaderMarker *curr;
         int expected_frame_num, expected_sample_num;
         /* If there are frames in the middle we expect this deduction,
            as they are probably valid and this one follows it */
 
         expected_frame_num = expected_sample_num = header_fi->frame_or_sample_num;
         curr = header;
         while (curr != child) {
             /* Ignore frames that failed all crc checks */
             for (i = 0; i < FLAC_MAX_SEQUENTIAL_HEADERS; i++) {
                 if (curr->link_penalty[i] < FLAC_HEADER_CRC_FAIL_PENALTY) {
                     expected_frame_num++;
                     expected_sample_num += curr->fi.blocksize;
                     break;
                 }
             }
             curr = curr->next;
         }
 
         if (expected_frame_num  == child_fi->frame_or_sample_num ||
             expected_sample_num == child_fi->frame_or_sample_num)
             deduction_expected = deduction ? 0 : 1;
 
         deduction += FLAC_HEADER_CHANGED_PENALTY;
         av_log(fpc->avctx, AV_LOG_WARNING + log_level_offset,
                    "sample/frame number mismatch in adjacent frames\n");
     }
 
     /* If we have suspicious headers, check the CRC between them */
     if (deduction && !deduction_expected) {
         FLACHeaderMarker *curr;
         int read_len;
         uint8_t *buf;
         uint32_t crc = 1;
         int inverted_test = 0;
 
         /* Since CRC is expensive only do it if we haven't yet.
            This assumes a CRC penalty is greater than all other check penalties */
         curr = header->next;
         for (i = 0; i < FLAC_MAX_SEQUENTIAL_HEADERS && curr != child; i++)
             curr = curr->next;
 
         if (header->link_penalty[i] < FLAC_HEADER_CRC_FAIL_PENALTY ||
             header->link_penalty[i] == FLAC_HEADER_NOT_PENALIZED_YET) {
             FLACHeaderMarker *start, *end;
 
             /* Although overlapping chains are scored, the crc should never
                have to be computed twice for a single byte. */
             start = header;
             end   = child;
             if (i > 0 &&
                 header->link_penalty[i - 1] >= FLAC_HEADER_CRC_FAIL_PENALTY) {
                 while (start->next != child)
                     start = start->next;
                 inverted_test = 1;
             } else if (i > 0 &&
                        header->next->link_penalty[i-1] >=
                        FLAC_HEADER_CRC_FAIL_PENALTY ) {
                 end = header->next;
                 inverted_test = 1;
             }
 
             read_len = end->offset - start->offset;
             buf      = flac_fifo_read(fpc, start->offset, &read_len);
             crc      = av_crc(av_crc_get_table(AV_CRC_16_ANSI), 0, buf, read_len);
             read_len = (end->offset - start->offset) - read_len;
 
             if (read_len) {
                 buf = flac_fifo_read(fpc, end->offset - read_len, &read_len);
                 crc = av_crc(av_crc_get_table(AV_CRC_16_ANSI), crc, buf, read_len);
             }
         }
 
         if (!crc ^ !inverted_test) {
             deduction += FLAC_HEADER_CRC_FAIL_PENALTY;
             av_log(fpc->avctx, AV_LOG_WARNING + log_level_offset,
                    "crc check failed from offset %i (frame %"PRId64") to %i (frame %"PRId64")\n",
                    header->offset, header_fi->frame_or_sample_num,
                    child->offset, child_fi->frame_or_sample_num);
         }
     }
     return deduction;
 }
 
 /**
  * Score a header.
  *
  * Give FLAC_HEADER_BASE_SCORE points to a frame for existing.
  * If it has children, (subsequent frames of which the preceding CRC footer
  * validates against this one,) then take the maximum score of the children,
  * with a penalty of FLAC_HEADER_CHANGED_PENALTY applied for each change to
  * bps, sample rate, channels, but not decorrelation mode, or blocksize,
  * because it can change often.
  **/
 static int score_header(FLACParseContext *fpc, FLACHeaderMarker *header)
 {
     FLACHeaderMarker *child;
     int dist = 0;
     int child_score;
 
     if (header->max_score != FLAC_HEADER_NOT_SCORED_YET)
         return header->max_score;
 
     header->max_score = FLAC_HEADER_BASE_SCORE;
 
     /* Check and compute the children's scores. */
     child = header->next;
     for (dist = 0; dist < FLAC_MAX_SEQUENTIAL_HEADERS && child; dist++) {
         /* Look at the child's frame header info and penalize suspicious
            changes between the headers. */
         if (header->link_penalty[dist] == FLAC_HEADER_NOT_PENALIZED_YET) {
             header->link_penalty[dist] = check_header_mismatch(fpc, header,
                                                                child, AV_LOG_DEBUG);
         }
         child_score = score_header(fpc, child) - header->link_penalty[dist];
 
         if (FLAC_HEADER_BASE_SCORE + child_score > header->max_score) {
             /* Keep the child because the frame scoring is dynamic. */
             header->best_child = child;
             header->max_score  = FLAC_HEADER_BASE_SCORE + child_score;
         }
         child = child->next;
     }
 
     return header->max_score;
 }
 
 static void score_sequences(FLACParseContext *fpc)
 {
     FLACHeaderMarker *curr;
     int best_score = FLAC_HEADER_NOT_SCORED_YET;
     /* First pass to clear all old scores. */
     for (curr = fpc->headers; curr; curr = curr->next)
         curr->max_score = FLAC_HEADER_NOT_SCORED_YET;
 
     /* Do a second pass to score them all. */
     for (curr = fpc->headers; curr; curr = curr->next) {
         if (score_header(fpc, curr) > best_score) {
             fpc->best_header = curr;
             best_score       = curr->max_score;
         }
     }
 }
 
 static int get_best_header(FLACParseContext* fpc, const uint8_t **poutbuf,
                            int *poutbuf_size)
 {
     FLACHeaderMarker *header = fpc->best_header;
     FLACHeaderMarker *child  = header->best_child;
     if (!child) {
         *poutbuf_size = av_fifo_size(fpc->fifo_buf) - header->offset;
     } else {
         *poutbuf_size = child->offset - header->offset;
 
         /* If the child has suspicious changes, log them */
         check_header_mismatch(fpc, header, child, 0);
     }
 
     fpc->avctx->sample_rate = header->fi.samplerate;
     fpc->avctx->channels    = header->fi.channels;
     fpc->avctx->frame_size  = header->fi.blocksize;
     *poutbuf = flac_fifo_read_wrap(fpc, header->offset, *poutbuf_size,
                                         &fpc->wrap_buf,
                                         &fpc->wrap_buf_allocated_size);
 
     fpc->best_header_valid = 0;
     /* Return the negative overread index so the client can compute pos.
        This should be the amount overread to the beginning of the child */
     if (child)
         return child->offset - av_fifo_size(fpc->fifo_buf);
     return 0;
 }
 
 static int flac_parse(AVCodecParserContext *s, AVCodecContext *avctx,
                       const uint8_t **poutbuf, int *poutbuf_size,
                       const uint8_t *buf, int buf_size)
 {
     FLACParseContext *fpc = s->priv_data;
     FLACHeaderMarker *curr;
     int nb_headers;

     const uint8_t *read_end   = buf;
     const uint8_t *read_start = buf;

 
     if (s->flags & PARSER_FLAG_COMPLETE_FRAMES) {
         FLACFrameInfo fi;
         if (frame_header_is_valid(avctx, buf, &fi))
             avctx->frame_size = fi.blocksize;
         *poutbuf      = buf;
         *poutbuf_size = buf_size;
         return buf_size;
     }
 
     fpc->avctx = avctx;
     if (fpc->best_header_valid)
         return get_best_header(fpc, poutbuf, poutbuf_size);
 
     /* If a best_header was found last call remove it with the buffer data. */
     if (fpc->best_header && fpc->best_header->best_child) {
         FLACHeaderMarker *temp;
         FLACHeaderMarker *best_child = fpc->best_header->best_child;
 
         /* Remove headers in list until the end of the best_header. */
         for (curr = fpc->headers; curr != best_child; curr = temp) {
             if (curr != fpc->best_header) {
                 av_log(avctx, AV_LOG_DEBUG,
                        "dropping low score %i frame header from offset %i to %i\n",
                        curr->max_score, curr->offset, curr->next->offset);
             }
             temp = curr->next;
             av_freep(&curr->link_penalty);
             av_free(curr);

             fpc->nb_headers_buffered--;

         }
         /* Release returned data from ring buffer. */
         av_fifo_drain(fpc->fifo_buf, best_child->offset);
 
         /* Fix the offset for the headers remaining to match the new buffer. */
         for (curr = best_child->next; curr; curr = curr->next)
             curr->offset -= best_child->offset;
 

         fpc->nb_headers_buffered--;

         best_child->offset = 0;
         fpc->headers       = best_child;

         if (fpc->nb_headers_buffered >= FLAC_MIN_HEADERS) {
             fpc->best_header = best_child;
             return get_best_header(fpc, poutbuf, poutbuf_size);
         }

         fpc->best_header   = NULL;
     } else if (fpc->best_header) {
         /* No end frame no need to delete the buffer; probably eof */
         FLACHeaderMarker *temp;
 
         for (curr = fpc->headers; curr != fpc->best_header; curr = temp) {
             temp = curr->next;
             av_freep(&curr->link_penalty);
             av_free(curr);
         }
         fpc->headers = fpc->best_header->next;
         av_freep(&fpc->best_header->link_penalty);
         av_freep(&fpc->best_header);
     }
 
     /* Find and score new headers. */

     while ((buf && read_end < buf + buf_size &&
             fpc->nb_headers_buffered < FLAC_MIN_HEADERS)
            || (!buf && !fpc->end_padded)) {

         int start_offset;
 
         /* Pad the end once if EOF, to check the final region for headers. */

         if (!buf) {

             fpc->end_padded      = 1;

             buf_size = MAX_FRAME_HEADER_SIZE;
             read_end = read_start + MAX_FRAME_HEADER_SIZE;

         } else {
             /* The maximum read size is the upper-bound of what the parser
                needs to have the required number of frames buffered */
             int nb_desired = FLAC_MIN_HEADERS - fpc->nb_headers_buffered + 1;

             read_end       = read_end + FFMIN(buf + buf_size - read_end,
                                               nb_desired * FLAC_AVG_FRAME_SIZE);

         }
 
         /* Fill the buffer. */
         if (av_fifo_realloc2(fpc->fifo_buf,

                              (read_end - read_start) + av_fifo_size(fpc->fifo_buf)) < 0) {

             av_log(avctx, AV_LOG_ERROR,

                    "couldn't reallocate buffer of size %td\n",

                    (read_end - read_start) + av_fifo_size(fpc->fifo_buf));

             goto handle_error;
         }
 
         if (buf) {

             av_fifo_generic_write(fpc->fifo_buf, (void*) read_start,
                                   read_end - read_start, NULL);

         } else {
             int8_t pad[MAX_FRAME_HEADER_SIZE];
             memset(pad, 0, sizeof(pad));
             av_fifo_generic_write(fpc->fifo_buf, (void*) pad, sizeof(pad), NULL);
         }
 
         /* Tag headers and update sequences. */
         start_offset = av_fifo_size(fpc->fifo_buf) -

                        ((read_end - read_start) + (MAX_FRAME_HEADER_SIZE - 1));

         start_offset = FFMAX(0, start_offset);
         nb_headers   = find_new_headers(fpc, start_offset);
 

         if (nb_headers < 0) {
             av_log(avctx, AV_LOG_ERROR,
                    "find_new_headers couldn't allocate FLAC header\n");
             goto handle_error;
         }
 
         fpc->nb_headers_buffered = nb_headers;

         /* Wait till FLAC_MIN_HEADERS to output a valid frame. */

         if (!fpc->end_padded && fpc->nb_headers_buffered < FLAC_MIN_HEADERS) {
             if (buf && read_end < buf + buf_size) {
                 read_start = read_end;
                 continue;
             } else {
                 goto handle_error;
             }
         }

 
         /* If headers found, update the scores since we have longer chains. */
         if (fpc->end_padded || fpc->nb_headers_found)
             score_sequences(fpc);
 
         /* restore the state pre-padding */
         if (fpc->end_padded) {
             /* HACK: drain the tail of the fifo */
             fpc->fifo_buf->wptr -= MAX_FRAME_HEADER_SIZE;
             fpc->fifo_buf->wndx -= MAX_FRAME_HEADER_SIZE;
             if (fpc->fifo_buf->wptr < 0) {
                 fpc->fifo_buf->wptr += fpc->fifo_buf->end -
                     fpc->fifo_buf->buffer;
             }

             buf_size = 0;
             read_start = read_end = NULL;

         }
     }
 
     curr = fpc->headers;
     for (curr = fpc->headers; curr; curr = curr->next)
         if (!fpc->best_header || curr->max_score > fpc->best_header->max_score)
             fpc->best_header = curr;
 
     if (fpc->best_header) {
         fpc->best_header_valid = 1;
         if (fpc->best_header->offset > 0) {
             /* Output a junk frame. */
             av_log(avctx, AV_LOG_DEBUG, "Junk frame till offset %i\n",
                    fpc->best_header->offset);
 
             /* Set frame_size to 0. It is unknown or invalid in a junk frame. */
             avctx->frame_size = 0;
             *poutbuf_size     = fpc->best_header->offset;
             *poutbuf          = flac_fifo_read_wrap(fpc, 0, *poutbuf_size,
                                                     &fpc->wrap_buf,
                                                     &fpc->wrap_buf_allocated_size);

             return buf_size ? (read_end - buf) : (fpc->best_header->offset -

                                            av_fifo_size(fpc->fifo_buf));

         }
         if (!buf_size)
             return get_best_header(fpc, poutbuf, poutbuf_size);
     }
 
 handle_error:
     *poutbuf      = NULL;
     *poutbuf_size = 0;

     return read_end - buf;

 }
 
 static int flac_parse_init(AVCodecParserContext *c)
 {
     FLACParseContext *fpc = c->priv_data;
     /* There will generally be FLAC_MIN_HEADERS buffered in the fifo before

        it drains.  This is allocated early to avoid slow reallocation. */
     fpc->fifo_buf = av_fifo_alloc(FLAC_AVG_FRAME_SIZE * (FLAC_MIN_HEADERS + 3));

     return 0;
 }
 
 static void flac_parse_close(AVCodecParserContext *c)
 {
     FLACParseContext *fpc = c->priv_data;
     FLACHeaderMarker *curr = fpc->headers, *temp;
 
     while (curr) {
         temp = curr->next;
         av_freep(&curr->link_penalty);
         av_free(curr);
         curr = temp;
     }
     av_fifo_free(fpc->fifo_buf);
     av_free(fpc->wrap_buf);
 }
 

 AVCodecParser ff_flac_parser = {

     .codec_ids      = { CODEC_ID_FLAC },
     .priv_data_size = sizeof(FLACParseContext),
     .parser_init    = flac_parse_init,
     .parser_parse   = flac_parse,
     .parser_close   = flac_parse_close,

 };