png: add a standalone parser

Useful for reading png images from a pipe.

1 files changed, 124 insertions, 0 deletions

diff --git a/libavcodec/png_parser.c b/libavcodec/png_parser.c
new file mode 100644
index 0000000000..00cbb82071
--- /dev/null
+++ b/libavcodec/png_parser.c
@@ -0,0 +1,124 @@
+/*
+ * PNG parser
+ * Copyright (c) 2009 Peter Holik
+ *
+ * This file is part of Libav.
+ *
+ * Libav 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.
+ *
+ * Libav 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 Libav; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+/**
+ * @file
+ * PNG parser
+ */
+
+#include "libavutil/intreadwrite.h"
+#include "libavutil/common.h"
+
+#include "parser.h"
+
+#define PNG_SIGNATURE UINT64_C(0x89504e470d0a1a0a)
+#define MNG_SIGNATURE UINT64_C(0x8a4d4e470d0a1a0a)
+
+typedef struct PNGParseContext {
+    ParseContext pc;
+
+    int chunk_pos;          ///< position inside current chunk
+    int chunk_length;       ///< length of the current chunk
+    int remaining_size;     ///< remaining size of the current chunk
+} PNGParseContext;
+
+static int png_parse(AVCodecParserContext *s, AVCodecContext *avctx,
+                     const uint8_t **poutbuf, int *poutbuf_size,
+                     const uint8_t *buf, int buf_size)
+{
+    PNGParseContext *ppc = s->priv_data;
+    int next = END_NOT_FOUND;
+    int i = 0;
+
+    *poutbuf_size = 0;
+    if (buf_size == 0)
+        return 0;
+
+    if (!ppc->pc.frame_start_found) {
+        uint64_t state64 = ppc->pc.state64;
+        for (; i < buf_size; i++) {
+            state64 = (state64 << 8) | buf[i];
+            if (state64 == PNG_SIGNATURE ||
+                state64 == MNG_SIGNATURE) {
+                i++;
+                ppc->pc.frame_start_found = 1;
+                break;
+            }
+        }
+        ppc->pc.state64 = state64;
+    } else if (ppc->remaining_size) {
+        i = FFMIN(ppc->remaining_size, buf_size);
+        ppc->remaining_size -= i;
+        if (ppc->remaining_size)
+            goto flush;
+        if (ppc->chunk_pos == -1) {
+            next = i;
+            goto flush;
+        }
+    }
+
+    for (; ppc->pc.frame_start_found && i < buf_size; i++) {
+        ppc->pc.state = (ppc->pc.state << 8) | buf[i];
+        if (ppc->chunk_pos == 3) {
+            ppc->chunk_length = AV_RL32(&ppc->pc.state);
+            if (ppc->chunk_length > 0x7fffffff) {
+                ppc->chunk_pos = ppc->pc.frame_start_found = 0;
+                goto flush;
+            }
+            ppc->chunk_length += 4;
+        } else if (ppc->chunk_pos == 7) {
+            if (ppc->chunk_length >= buf_size - i)
+                ppc->remaining_size = ppc->chunk_length - buf_size + i + 1;
+            if (AV_RB32(&ppc->pc.state) == MKTAG('I', 'E', 'N', 'D')) {
+                if (ppc->remaining_size)
+                    ppc->chunk_pos = -1;
+                else
+                    next = ppc->chunk_length + i + 1;
+                break;
+            } else {
+                ppc->chunk_pos = 0;
+                if (ppc->remaining_size)
+                    break;
+                else
+                    i += ppc->chunk_length;
+                continue;
+            }
+        }
+        ppc->chunk_pos++;
+    }
+
+flush:
+    if (ff_combine_frame(&ppc->pc, next, &buf, &buf_size) < 0)
+        return buf_size;
+
+    ppc->chunk_pos = ppc->pc.frame_start_found = 0;
+
+    *poutbuf      = buf;
+    *poutbuf_size = buf_size;
+    return next;
+}
+
+AVCodecParser ff_png_parser = {
+    .codec_ids      = { AV_CODEC_ID_PNG },
+    .priv_data_size = sizeof(PNGParseContext),
+    .parser_parse   = png_parse,
+    .parser_close   = ff_parse_close,
+};