[libav-devel] [PATCH 1/2] lavc: Add a lzf decompressor

Vittorio Giovara vittorio.giovara at gmail.com
Wed Aug 26 11:31:40 CEST 2015


From: Luca Barbato <lu_zero at gentoo.org>

Signed-off-by: Vittorio Giovara <vittorio.giovara at gmail.com>
---
 configure           |  1 +
 libavcodec/Makefile |  1 +
 libavcodec/lzf.c    | 90 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 libavcodec/lzf.h    | 29 +++++++++++++++++
 4 files changed, 121 insertions(+)
 create mode 100644 libavcodec/lzf.c
 create mode 100644 libavcodec/lzf.h

diff --git a/configure b/configure
index 1334480..c2d38cf 100755
--- a/configure
+++ b/configure
@@ -1613,6 +1613,7 @@ CONFIG_EXTRA="
     libx262
     lgplv3
     lpc
+    lzf
     me_cmp
     mpeg_er
     mpegaudio
diff --git a/libavcodec/Makefile b/libavcodec/Makefile
index a6e88c7..e229b2f 100644
--- a/libavcodec/Makefile
+++ b/libavcodec/Makefile
@@ -68,6 +68,7 @@ OBJS-$(CONFIG_JPEGTABLES)              += jpegtables.o
 OBJS-$(CONFIG_LIBXVID)                 += libxvid_rc.o
 OBJS-$(CONFIG_LPC)                     += lpc.o
 OBJS-$(CONFIG_LSP)                     += lsp.o
+OBJS-$(CONFIG_LZF)                     += lzf.o
 OBJS-$(CONFIG_MDCT)                    += mdct_fixed.o mdct_float.o
 OBJS-$(CONFIG_ME_CMP)                  += me_cmp.o
 OBJS-$(CONFIG_MPEG_ER)                 += mpeg_er.o
diff --git a/libavcodec/lzf.c b/libavcodec/lzf.c
new file mode 100644
index 0000000..35b932b
--- /dev/null
+++ b/libavcodec/lzf.c
@@ -0,0 +1,90 @@
+/*
+ * lzf 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
+ */
+
+/**
+ * @file
+ * lzf decompression
+ *
+ * LZF is a fast compression/decompression algorithm that takes very little
+ * code space and working memory, ideal for real-time and block compression.
+ *
+ * https://en.wikibooks.org/wiki/Data_Compression/Dictionary_compression#LZF
+ */
+
+#include "libavutil/mem.h"
+
+#include "bytestream.h"
+#include "lzf.h"
+
+#define LZF_LITERAL_MAX (1 << 5)
+#define LZF_LONG_BACKREF 7 + 2
+
+int ff_lzf_uncompress(GetByteContext *gb, uint8_t **buf, int64_t *size)
+{
+    int ret     = 0;
+    uint8_t *p  = *buf;
+    int64_t len = 0;
+
+    while (bytestream2_get_bytes_left(gb) > 2) {
+        uint8_t s = bytestream2_get_byte(gb);
+
+        if (s < LZF_LITERAL_MAX) {
+            s++;
+            if (s > *size - len) {
+                *size += *size /2;
+                ret = av_reallocp(buf, *size);
+                if (ret < 0)
+                    return ret;
+            }
+
+            bytestream2_get_buffer(gb, p, s);
+            p   += s;
+            len += s;
+        } else {
+            int l   = 2 + (s >> 5);
+            int off = ((s & 0x1f) << 8) + 1;
+
+            if (l == LZF_LONG_BACKREF)
+                l += bytestream2_get_byte(gb);
+
+            off += bytestream2_get_byte(gb);
+
+            if (off > len)
+                return AVERROR_INVALIDDATA;
+
+            if (l > *size - len) {
+                *size += *size / 2;
+                ret = av_reallocp(buf, *size);
+                if (ret < 0)
+                    return ret;
+            }
+
+            av_memcpy_backptr(p, off, l);
+
+            p   += l;
+            len += l;
+        }
+    }
+
+    *size = len;
+
+    return 0;
+}
diff --git a/libavcodec/lzf.h b/libavcodec/lzf.h
new file mode 100644
index 0000000..4951f25
--- /dev/null
+++ b/libavcodec/lzf.h
@@ -0,0 +1,29 @@
+/*
+ * lzf 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
+ */
+
+#ifndef AVCODEC_LZF_H
+#define AVCODEC_LZF_H
+
+#include "bytestream.h"
+
+int ff_lzf_uncompress(GetByteContext *gb, uint8_t **buf, int64_t *size);
+
+#endif /* AVCODEC_LZF_H */
-- 
1.9.5 (Apple Git-50.3)



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