[FFmpeg-cvslog] Implement Snappy decompression
Luca Barbato
git at videolan.org
Mon Jun 22 20:56:16 CEST 2015
ffmpeg | branch: master | Luca Barbato <lu_zero at gentoo.org> | Sun May 24 16:20:26 2015 +0200| [2ecfd451649c7a08cb633635df98e59f7c6e2140] | committer: Vittorio Giovara
Implement Snappy decompression
Signed-off-by: Vittorio Giovara <vittorio.giovara at gmail.com>
> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=2ecfd451649c7a08cb633635df98e59f7c6e2140
---
configure | 1 +
libavcodec/Makefile | 1 +
libavcodec/snappy.c | 173 +++++++++++++++++++++++++++++++++++++++++++++++++++
libavcodec/snappy.h | 51 +++++++++++++++
4 files changed, 226 insertions(+)
diff --git a/configure b/configure
index 90e5787..6d3fe62 100755
--- a/configure
+++ b/configure
@@ -1624,6 +1624,7 @@ CONFIG_EXTRA="
rtpdec
rtpenc_chain
sinewin
+ snappy
startcode
tpeldsp
videodsp
diff --git a/libavcodec/Makefile b/libavcodec/Makefile
index 6fda584..6e04ca6 100644
--- a/libavcodec/Makefile
+++ b/libavcodec/Makefile
@@ -91,6 +91,7 @@ OBJS-$(CONFIG_RANGECODER) += rangecoder.o
RDFT-OBJS-$(CONFIG_HARDCODED_TABLES) += sin_tables.o
OBJS-$(CONFIG_RDFT) += rdft.o $(RDFT-OBJS-yes)
OBJS-$(CONFIG_SINEWIN) += sinewin.o
+OBJS-$(CONFIG_SNAPPY) += snappy.o
OBJS-$(CONFIG_STARTCODE) += startcode.o
OBJS-$(CONFIG_TPELDSP) += tpeldsp.o
OBJS-$(CONFIG_VIDEODSP) += videodsp.o
diff --git a/libavcodec/snappy.c b/libavcodec/snappy.c
new file mode 100644
index 0000000..13ef1ec
--- /dev/null
+++ b/libavcodec/snappy.c
@@ -0,0 +1,173 @@
+/*
+ * Snappy decompression algorithm
+ * Copyright (c) 2015 Luca Barbato
+ *
+ * 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
+ */
+
+#include "libavutil/mem.h"
+
+#include "bytestream.h"
+#include "snappy.h"
+
+enum {
+ SNAPPY_LITERAL,
+ SNAPPY_COPY_1,
+ SNAPPY_COPY_2,
+ SNAPPY_COPY_4,
+};
+
+static int64_t bytestream2_get_levarint(GetByteContext *gb)
+{
+ uint64_t val = 0;
+ int shift = 0;
+ int tmp;
+
+ do {
+ tmp = bytestream2_get_byte(gb);
+ val |= (tmp & 127) << shift;
+ shift += 7;
+ } while (tmp & 128);
+
+ return val;
+}
+
+static int snappy_literal(GetByteContext *gb, uint8_t *p, int size, int val)
+{
+ unsigned int len = 1;
+
+ switch (val) {
+ case 63:
+ len += bytestream2_get_le32(gb);
+ break;
+ case 62:
+ len += bytestream2_get_le24(gb);
+ break;
+ case 61:
+ len += bytestream2_get_le16(gb);
+ break;
+ case 60:
+ len += bytestream2_get_byte(gb);
+ break;
+ default: // val < 60
+ len += val;
+ }
+
+ if (size < len)
+ return AVERROR_INVALIDDATA;
+
+ bytestream2_get_buffer(gb, p, len);
+
+ return len;
+}
+
+static int snappy_copy(uint8_t *start, uint8_t *p, int size,
+ unsigned int off, int len)
+{
+ uint8_t *q;
+ int i;
+ if (off > p - start || size < len)
+ return AVERROR_INVALIDDATA;
+
+ q = p - off;
+
+ for (i = 0; i < len; i++)
+ p[i] = q[i];
+
+ return len;
+}
+
+static int snappy_copy1(GetByteContext *gb, uint8_t *start, uint8_t *p,
+ int size, int val)
+{
+ int len = 4 + (val & 0x7);
+ unsigned int off = bytestream2_get_byte(gb) | (val & 0x38) << 5;
+
+ return snappy_copy(start, p, size, off, len);
+}
+
+static int snappy_copy2(GetByteContext *gb, uint8_t *start, uint8_t *p,
+ int size, int val)
+{
+ int len = 1 + val;
+ unsigned int off = bytestream2_get_le16(gb);
+
+ return snappy_copy(start, p, size, off, len);
+}
+
+static int snappy_copy4(GetByteContext *gb, uint8_t *start, uint8_t *p,
+ int size, int val)
+{
+ int len = 1 + val;
+ unsigned int off = bytestream2_get_le32(gb);
+
+ return snappy_copy(start, p, size, off, len);
+}
+
+static int64_t decode_len(GetByteContext *gb)
+{
+ int64_t len = bytestream2_get_levarint(gb);
+
+ if (len < 0 || len > UINT_MAX)
+ return AVERROR_INVALIDDATA;
+
+ return len;
+}
+
+int ff_snappy_uncompress(GetByteContext *gb, uint8_t **buf, int64_t *size)
+{
+ int64_t len = decode_len(gb);
+ int ret = 0;
+ uint8_t *p;
+
+ if (len < 0)
+ return len;
+
+ if ((ret = av_reallocp(buf, len)) < 0)
+ return AVERROR(ENOMEM);
+
+ *size = len;
+ p = *buf;
+
+ while (bytestream2_get_bytes_left(gb) > 0) {
+ uint8_t s = bytestream2_get_byte(gb);
+ int val = s >> 2;
+
+ switch (s & 0x03) {
+ case SNAPPY_LITERAL:
+ ret = snappy_literal(gb, p, len, val);
+ break;
+ case SNAPPY_COPY_1:
+ ret = snappy_copy1(gb, *buf, p, len, val);
+ break;
+ case SNAPPY_COPY_2:
+ ret = snappy_copy2(gb, *buf, p, len, val);
+ break;
+ case SNAPPY_COPY_4:
+ ret = snappy_copy4(gb, *buf, p, len, val);
+ break;
+ }
+
+ if (ret < 0)
+ return ret;
+
+ p += ret;
+ len -= ret;
+ }
+
+ return 0;
+}
diff --git a/libavcodec/snappy.h b/libavcodec/snappy.h
new file mode 100644
index 0000000..96666a8
--- /dev/null
+++ b/libavcodec/snappy.h
@@ -0,0 +1,51 @@
+/*
+ * Snappy module
+ * Copyright (c) Luca Barbato
+ *
+ * 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
+ * Snappy decompression
+ *
+ * Snappy is a compression/decompression algorithm that does not aim for
+ * maximum compression, but rather for very high speeds and reasonable
+ * compression.
+ *
+ * http://en.wikipedia.org/wiki/Snappy_%28software%29
+ */
+
+#ifndef AVCODEC_SNAPPY_H
+#define AVCODEC_SNAPPY_H
+
+#include <stdint.h>
+
+#include "bytestream.h"
+
+/**
+ * Decompress an input buffer using Snappy algorithm. Caller is
+ * responsible of freeing the memory allocated in buf.
+ *
+ * @param gb input GetByteContext.
+ * @param buf output buffer pointer.
+ * @param size output buffer size.
+ * @return 0 if success, AVERROR otherwise.
+ */
+int ff_snappy_uncompress(GetByteContext *gb, uint8_t **buf, int64_t *size);
+
+#endif /* AVCODEC_SNAPPY_H */
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