Implement Snappy decompression

Signed-off-by: Vittorio Giovara <vittorio.giovara@gmail.com>

1 files changed, 173 insertions, 0 deletions

diff --git a/libavcodec/snappy.c b/libavcodec/snappy.c
new file mode 100644
index 0000000000..13ef1ec137
--- /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;
+}