/*

 * 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 its crc-verified

 * children, penalized by changes in sample rate, frame number, etc.

 * The parser returns the frame with the highest score.

 **/

#include "libavutil/attributes.h"

#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 4

/** 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[FLAC_MAX_SEQUENTIAL_HEADERS]; /**< 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 {

    AVCodecParserContext *pc;      /**< parent context                        */

    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   */

    FLACFrameInfo last_fi;         /**< last decoded frame header info        */

    int last_fi_valid;             /**< set if last_fi is valid               */

} FLACParseContext;

                                 FLACFrameInfo *fi)

{

    GetBitContext gb;

}

/**

 * 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.

 */

                                    uint8_t **wrap_buf, int *allocated_size)

{

    uint8_t *tmp_buf;

               "couldn't reallocate wrap buffer of size %d", len);

    }

    do {

// memory barrier needed for SMP here in theory

}

/**

 * 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.

 **/

{

}

{

    FLACFrameInfo fi;

    uint8_t *header_buf;

                                     MAX_FRAME_HEADER_SIZE,

                                     &fpc->wrap_buf,

                                     &fpc->wrap_buf_allocated_size);

        int i;

        }

                   "couldn't allocate FLACHeaderMarker\n");

        }

    }

}

                               int buf_size, int search_start)

{

    uint32_t x;

    }

            }

        }

    }

}

{

    FLACHeaderMarker *end;

    uint8_t *buf;

    /* Search for a new header of at most 16 bytes. */

    /* If fifo end was hit do the wrap around. */

        uint8_t wrap[2];

        /* search_start + 1 is the post-wrap offset in the fifo. */

        }

        /* Continue to do the last half of the wrap. */

    }

    /* Return the size even if no new headers were found. */

}

                                    FLACFrameInfo     *header_fi,

                                    FLACFrameInfo     *child_fi,

                                    int                log_level_offset)

{

               "sample rate change detected in adjacent frames\n");

    }

               "bits per sample change detected in adjacent frames\n");

    }

        /* Changing blocking strategy not allowed per the spec */

               "blocking strategy change detected in adjacent frames\n");

    }

               "number of channels change detected in adjacent frames\n");

    }

}

                                 FLACHeaderMarker  *header,

                                 FLACHeaderMarker  *child,

                                 int                log_level_offset)

{

                                         log_level_offset);

    /* Check sample and frame numbers. */

        FLACHeaderMarker *curr;

        int64_t 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 */

            /* Ignore frames that failed all crc checks */

                }

            }

        }

                   "sample/frame number mismatch in adjacent frames\n");

    }

    /* If we have suspicious headers, check the CRC between them */

        FLACHeaderMarker *curr;

        int read_len;

        uint8_t *buf;

        /* Since CRC is expensive only do it if we haven't yet.

           This assumes a CRC penalty is greater than all other check penalties */

            FLACHeaderMarker *start, *end;

            /* Although overlapping chains are scored, the crc should never

               have to be computed twice for a single byte. */

                       FLAC_HEADER_CRC_FAIL_PENALTY ) {

            }

            }

        }

                   "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);

        }

    }

}

/**

 * 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.

 **/

{

    FLACHeaderMarker *child;

    int child_score;

    /* Modify the base score with changes from the last output header */

        /* Silence the log since this will be repeated if selected */

                                               AV_LOG_DEBUG);

    }

    /* Check and compute the children's scores. */

        /* Look at the child's frame header info and penalize suspicious

           changes between the headers. */

                                                               child, AV_LOG_DEBUG);

        }

            /* Keep the child because the frame scoring is dynamic. */

        }

    }

}

{

    FLACHeaderMarker *curr;

    /* First pass to clear all old scores. */

    /* Do a second pass to score them all. */

        }

    }

                           int *poutbuf_size)

{

    } else {

        /* If the child has suspicious changes, log them */

    }

    }

                                        &fpc->wrap_buf,

                                        &fpc->wrap_buf_allocated_size);

    }

    /* Return the negative overread index so the client can compute pos.

       This should be the amount overread to the beginning of the child */

}

                      const uint8_t **poutbuf, int *poutbuf_size,

                      const uint8_t *buf, int buf_size)

{

    FLACHeaderMarker *curr;

    int nb_headers;

        FLACFrameInfo fi;

            }

        }

    }

    /* If a best_header was found last call remove it with the buffer data. */

        FLACHeaderMarker *temp;

        /* Remove headers in list until the end of the best_header. */

                       "dropping low score %i frame header from offset %i to %i\n",

            }

        }

        /* Release returned data from ring buffer. */

        /* Fix the offset for the headers remaining to match the new buffer. */

        }

        /* No end frame no need to delete the buffer; probably eof */

        FLACHeaderMarker *temp;

        }

    }

    /* Find and score new headers.                                     */

    /* buf_size is zero when flushing, so check for this since we do   */

    /* not want to try to read more input once we have found the end.  */

    /* Also note that buf can't be NULL.                               */

        int start_offset;

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

        } else {

            /* The maximum read size is the upper-bound of what the parser

               needs to have the required number of frames buffered */

                                              nb_desired * FLAC_AVG_FRAME_SIZE);

        }

            /* There is less than one valid flac header buffered for 20 headers

             * buffered. Therefore the fifo is most likely filled with invalid

             * data and the input is not a flac file. */

        }

        /* Fill the buffer. */

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

        }

        } else {

        }

        /* Tag headers and update sequences. */

                   "find_new_headers couldn't allocate FLAC header\n");

        }

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

            } else {

            }

        }

        /* If headers found, update the scores since we have longer chains. */

        /* restore the state pre-padding */

            /* HACK: drain the tail of the fifo */

            }

        }

    }

        }

    }

        // Only accept a bad header if there is no other option to continue

    }

            /* Output a junk frame. */

            /* Set duration to 0. It is unknown or invalid in a junk frame. */

                                                &fpc->wrap_buf,

                                                &fpc->wrap_buf_allocated_size);

        }

    }

}

{

    /* There will generally be FLAC_MIN_HEADERS buffered in the fifo before

       it drains.  This is allocated early to avoid slow reallocation. */

                "couldn't allocate fifo_buf\n");

    }

}

{

    }

AVCodecParser ff_flac_parser = {

    .codec_ids      = { AV_CODEC_ID_FLAC },

    .priv_data_size = sizeof(FLACParseContext),

    .parser_init    = flac_parse_init,

    .parser_parse   = flac_parse,

    .parser_close   = flac_parse_close,

};