avcodec: move leb reading functions to its own header

Signed-off-by: James Almer <jamrial@gmail.com>

1 files changed, 70 insertions, 0 deletions

diff --git a/libavcodec/leb.h b/libavcodec/leb.h
new file mode 100644
index 0000000000..5159c434b1
--- /dev/null
+++ b/libavcodec/leb.h
@@ -0,0 +1,70 @@
+/*
+ * 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
+ * leb128 handling implementations
+ */
+
+#ifndef AVCODEC_LEB_H
+#define AVCODEC_LEB_H
+
+#include "get_bits.h"
+
+/**
+ * Read a unsigned integer coded as a variable number of up to eight
+ * little-endian bytes, where the MSB in a byte signals another byte
+ * must be read.
+ * All coded bits are read, but values > UINT_MAX are truncated.
+ */
+static inline unsigned get_leb(GetBitContext *s) {
+    int more, i = 0;
+    unsigned leb = 0;
+
+    do {
+        int byte = get_bits(s, 8);
+        unsigned bits = byte & 0x7f;
+        more = byte & 0x80;
+        if (i <= 4)
+            leb |= bits << (i * 7);
+        if (++i == 8)
+            break;
+    } while (more);
+
+    return leb;
+}
+
+/**
+ * Read a unsigned integer coded as a variable number of up to eight
+ * little-endian bytes, where the MSB in a byte signals another byte
+ * must be read.
+ */
+static inline int64_t get_leb128(GetBitContext *gb) {
+    int64_t ret = 0;
+
+    for (int i = 0; i < 8; i++) {
+        int byte = get_bits(gb, 8);
+        ret |= (int64_t)(byte & 0x7f) << (i * 7);
+        if (!(byte & 0x80))
+            break;
+    }
+
+    return ret;
+}
+
+#endif /* AVCODEC_LEB_H */