[FFmpeg-devel] [PATCH] avcodec: add a WebP parser

[James Almer]

Based on code from the BMP parser.

Addresses ticket #8574

Signed-off-by: James Almer <jamrial at gmail.com>
---
 libavcodec/Makefile      |   1 +
 libavcodec/parsers.c     |   1 +
 libavcodec/webp_parser.c | 112 +++++++++++++++++++++++++++++++++++++++
 3 files changed, 114 insertions(+)
 create mode 100644 libavcodec/webp_parser.c

diff --git a/libavcodec/Makefile b/libavcodec/Makefile
index 1970ff027f..88944d9a3a 100644
--- a/libavcodec/Makefile
+++ b/libavcodec/Makefile
@@ -1084,6 +1084,7 @@ OBJS-$(CONFIG_VC1_PARSER)              += vc1_parser.o vc1.o vc1data.o  \
 OBJS-$(CONFIG_VP3_PARSER)              += vp3_parser.o
 OBJS-$(CONFIG_VP8_PARSER)              += vp8_parser.o
 OBJS-$(CONFIG_VP9_PARSER)              += vp9_parser.o
+OBJS-$(CONFIG_WEBP_PARSER)             += webp_parser.o
 OBJS-$(CONFIG_XMA_PARSER)              += xma_parser.o
 
 # bitstream filters
diff --git a/libavcodec/parsers.c b/libavcodec/parsers.c
index 33a71de8a0..9fbf182594 100644
--- a/libavcodec/parsers.c
+++ b/libavcodec/parsers.c
@@ -66,6 +66,7 @@ extern AVCodecParser ff_vorbis_parser;
 extern AVCodecParser ff_vp3_parser;
 extern AVCodecParser ff_vp8_parser;
 extern AVCodecParser ff_vp9_parser;
+extern AVCodecParser ff_webp_parser;
 extern AVCodecParser ff_xma_parser;
 
 #include "libavcodec/parser_list.c"
diff --git a/libavcodec/webp_parser.c b/libavcodec/webp_parser.c
new file mode 100644
index 0000000000..98e7988555
--- /dev/null
+++ b/libavcodec/webp_parser.c
@@ -0,0 +1,112 @@
+/*
+ * WebP parser
+ *
+ * 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
+ * WebP parser
+ */
+
+#include "libavutil/bswap.h"
+#include "libavutil/common.h"
+
+#include "parser.h"
+
+typedef struct WebPParseContext {
+    ParseContext pc;
+    uint32_t fsize;
+    uint32_t remaining_size;
+} WebPParseContext;
+
+static int webp_parse(AVCodecParserContext *s, AVCodecContext *avctx,
+                      const uint8_t **poutbuf, int *poutbuf_size,
+                      const uint8_t *buf, int buf_size)
+{
+    WebPParseContext *ctx = s->priv_data;
+    uint64_t state = ctx->pc.state64;
+    int next = END_NOT_FOUND;
+    int i = 0;
+
+    *poutbuf      = NULL;
+    *poutbuf_size = 0;
+
+restart:
+    if (ctx->pc.frame_start_found <= 8) {
+        for (; i < buf_size; i++) {
+            state = (state << 8) | buf[i];
+            if (ctx->pc.frame_start_found == 0) {
+                if ((state >> 32) == (('R' << 24) | ('I' << 16) | ('F' << 8) | 'F')) {
+                    ctx->fsize = av_bswap32(state);
+                    if (ctx->fsize > 15 && ctx->fsize <= UINT32_MAX - 10) {
+                        ctx->pc.frame_start_found = 1;
+                        ctx->fsize += 8;
+                    }
+                }
+            } else if (ctx->pc.frame_start_found == 8) {
+                if ((state >> 32) != (('W' << 24) | ('E' << 16) | ('B' << 8) | 'P')) {
+                    ctx->pc.frame_start_found = 0;
+                    continue;
+                }
+                ctx->pc.frame_start_found++;
+                ctx->remaining_size = ctx->fsize + i - 15;
+                if (ctx->pc.index + i > 15) {
+                    next = i - 15;
+                    state = 0;
+                    break;
+                } else {
+                    ctx->pc.state64 = 0;
+                    goto restart;
+                }
+            } else if (ctx->pc.frame_start_found)
+                ctx->pc.frame_start_found++;
+        }
+        ctx->pc.state64 = state;
+    } else {
+        if (ctx->remaining_size) {
+            i = FFMIN(ctx->remaining_size, buf_size);
+            ctx->remaining_size -= i;
+            if (ctx->remaining_size)
+                goto flush;
+
+            ctx->pc.frame_start_found = 0;
+            goto restart;
+        }
+    }
+
+flush:
+    if (ff_combine_frame(&ctx->pc, next, &buf, &buf_size) < 0)
+        return buf_size;
+
+    if (next != END_NOT_FOUND && next < 0)
+        ctx->pc.frame_start_found = FFMAX(ctx->pc.frame_start_found - i - 1, 0);
+    else
+        ctx->pc.frame_start_found = 0;
+
+    *poutbuf      = buf;
+    *poutbuf_size = buf_size;
+
+    return next;
+}
+
+AVCodecParser ff_webp_parser = {
+    .codec_ids      = { AV_CODEC_ID_WEBP },
+    .priv_data_size = sizeof(WebPParseContext),
+    .parser_parse   = webp_parse,
+    .parser_close   = ff_parse_close,
+};
-- 
2.26.0