From dcc3f6227070fe8fecbcfe7849fb69f5e8b832f7 Mon Sep 17 00:00:00 2001 From: Andreas Rheinhardt Date: Fri, 11 Mar 2022 14:19:27 +0100 Subject: [PATCH] avcodec/flashsv: Avoid deflating data Currently priming the zlib decompressor involves compressing data directly after having decompressed it and decompressing it again in order to set the "dictionary" and to initialize the adler32-checksum. Yet this is wasteful and can be simplified by synthetizing the compressed data via non-compressed blocks. This reduced the amount of allocations for the decoding part of fate-vsynth1-flashsv2, namely from total heap usage: 9,135 allocs, 9,135 frees, 376,503,427 bytes allocated to total heap usage: 2,373 allocs, 2,373 frees, 14,144,083 bytes allocated Signed-off-by: Andreas Rheinhardt --- libavcodec/flashsv.c | 89 +++++++++++++++++++------------------------- 1 file changed, 38 insertions(+), 51 deletions(-) diff --git a/libavcodec/flashsv.c b/libavcodec/flashsv.c index 5f0bc0c6df..e284439972 100644 --- a/libavcodec/flashsv.c +++ b/libavcodec/flashsv.c @@ -63,11 +63,10 @@ typedef struct FlashSVContext { AVBufferRef *keyframedata_buf; uint8_t *keyframe; BlockInfo *blocks; - uint8_t *deflate_block; - int deflate_block_size; int color_depth; int zlibprime_curr, zlibprime_prev; int diff_start, diff_height; + uint8_t tmp[UINT16_MAX]; } FlashSVContext; static int decode_hybrid(const uint8_t *sptr, const uint8_t *sptr_end, uint8_t *dptr, int dx, int dy, @@ -141,41 +140,59 @@ static av_cold int flashsv_decode_init(AVCodecContext *avctx) static int flashsv2_prime(FlashSVContext *s, const uint8_t *src, int size) { - z_stream zs; int zret; // Zlib return code + static const uint8_t zlib_header[] = { 0x78, 0x01 }; + uint8_t *data = s->tmpblock; + unsigned remaining; if (!src) return AVERROR_INVALIDDATA; - zs.zalloc = NULL; - zs.zfree = NULL; - zs.opaque = NULL; - s->zstream.next_in = src; s->zstream.avail_in = size; - s->zstream.next_out = s->tmpblock; + s->zstream.next_out = data; s->zstream.avail_out = s->block_size * 3; inflate(&s->zstream, Z_SYNC_FLUSH); - - if (deflateInit(&zs, 0) != Z_OK) - return -1; - zs.next_in = s->tmpblock; - zs.avail_in = s->block_size * 3 - s->zstream.avail_out; - zs.next_out = s->deflate_block; - zs.avail_out = s->deflate_block_size; - deflate(&zs, Z_SYNC_FLUSH); - deflateEnd(&zs); + remaining = s->block_size * 3 - s->zstream.avail_out; if ((zret = inflateReset(&s->zstream)) != Z_OK) { av_log(s->avctx, AV_LOG_ERROR, "Inflate reset error: %d\n", zret); return AVERROR_UNKNOWN; } - s->zstream.next_in = s->deflate_block; - s->zstream.avail_in = s->deflate_block_size - zs.avail_out; - s->zstream.next_out = s->tmpblock; - s->zstream.avail_out = s->block_size * 3; + /* Create input for zlib that is equivalent to encoding the output + * from above and decoding it again (the net result of this is that + * the dictionary of past decoded data is correctly primed and + * the adler32 checksum is correctly initialized). + * This is accomplished by synthetizing blocks of uncompressed data + * out of the output from above. See section 3.2.4 of RFC 1951. */ + s->zstream.next_in = zlib_header; + s->zstream.avail_in = sizeof(zlib_header); inflate(&s->zstream, Z_SYNC_FLUSH); + while (remaining > 0) { + unsigned block_size = FFMIN(UINT16_MAX, remaining); + uint8_t header[5]; + /* Bit 0: Non-last-block, bits 1-2: BTYPE for uncompressed block */ + header[0] = 0; + /* Block size */ + AV_WL16(header + 1, block_size); + /* Block size (one's complement) */ + AV_WL16(header + 3, block_size ^ 0xFFFF); + s->zstream.next_in = header; + s->zstream.avail_in = sizeof(header); + s->zstream.next_out = s->tmp; + s->zstream.avail_out = sizeof(s->tmp); + zret = inflate(&s->zstream, Z_SYNC_FLUSH); + if (zret != Z_OK) + return AVERROR_UNKNOWN; + s->zstream.next_in = data; + s->zstream.avail_in = block_size; + zret = inflate(&s->zstream, Z_SYNC_FLUSH); + if (zret != Z_OK) + return AVERROR_UNKNOWN; + data += block_size; + remaining -= block_size; + } return 0; } @@ -248,22 +265,6 @@ static int flashsv_decode_block(AVCodecContext *avctx, const AVPacket *avpkt, return 0; } -static int calc_deflate_block_size(int tmpblock_size) -{ - z_stream zstream; - int size; - - zstream.zalloc = Z_NULL; - zstream.zfree = Z_NULL; - zstream.opaque = Z_NULL; - if (deflateInit(&zstream, 0) != Z_OK) - return -1; - size = deflateBound(&zstream, tmpblock_size); - deflateEnd(&zstream); - - return size; -} - static int flashsv_decode_frame(AVCodecContext *avctx, void *data, int *got_frame, AVPacket *avpkt) { @@ -322,19 +323,6 @@ static int flashsv_decode_frame(AVCodecContext *avctx, void *data, "Cannot allocate decompression buffer.\n"); return err; } - if (s->ver == 2) { - s->deflate_block_size = calc_deflate_block_size(tmpblock_size); - if (s->deflate_block_size <= 0) { - av_log(avctx, AV_LOG_ERROR, - "Cannot determine deflate buffer size.\n"); - return -1; - } - if ((err = av_reallocp(&s->deflate_block, s->deflate_block_size)) < 0) { - s->block_size = 0; - av_log(avctx, AV_LOG_ERROR, "Cannot allocate deflate buffer.\n"); - return err; - } - } } s->block_size = s->block_width * s->block_height; @@ -570,7 +558,6 @@ static av_cold int flashsv2_decode_end(AVCodecContext *avctx) av_buffer_unref(&s->keyframedata_buf); av_freep(&s->blocks); av_freep(&s->keyframe); - av_freep(&s->deflate_block); flashsv_decode_end(avctx); return 0;