[FFmpeg-devel] [PATCH 3/9] avformat/aviobuf: add ffio_read_leb() and ffio_write_leb()

[James Almer]

Signed-off-by: James Almer <jamrial at gmail.com>
---
 libavformat/avio_internal.h |  4 ++++
 libavformat/aviobuf.c       | 37 +++++++++++++++++++++++++++++++++++++
 2 files changed, 41 insertions(+)

diff --git a/libavformat/avio_internal.h b/libavformat/avio_internal.h
index bd58499b64..6b6cd6e8b3 100644
--- a/libavformat/avio_internal.h
+++ b/libavformat/avio_internal.h
@@ -146,6 +146,10 @@ int ffio_rewind_with_probe_data(AVIOContext *s, unsigned char **buf, int buf_siz
 
 uint64_t ffio_read_varlen(AVIOContext *bc);
 
+unsigned int ffio_read_leb(AVIOContext *s);
+
+void ffio_write_leb(AVIOContext *s, unsigned val);
+
 /**
  * Read size bytes from AVIOContext into buf.
  * Check that exactly size bytes have been read.
diff --git a/libavformat/aviobuf.c b/libavformat/aviobuf.c
index 2899c75521..cdd1528155 100644
--- a/libavformat/aviobuf.c
+++ b/libavformat/aviobuf.c
@@ -971,6 +971,43 @@ uint64_t ffio_read_varlen(AVIOContext *bc){
     return val;
 }
 
+unsigned int ffio_read_leb(AVIOContext *s) {
+    int more, i = 0;
+    unsigned leb = 0;
+
+    do {
+        int byte = avio_r8(s);
+        unsigned bits = byte & 0x7f;
+        more = byte & 0x80;
+        if (i <= 3 || (i == 4 && bits < (1 << 4)))
+            leb |= bits << (i * 7);
+        else if (bits) { // leb > UINT_MAX
+            leb |= (bits & 0xF) << (i * 7);
+            break;
+        }
+        if (++i == 8 && more)
+            break; // invalid leb
+    } while (more);
+
+    return leb;
+}
+
+void ffio_write_leb(AVIOContext *s, unsigned val)
+{
+    int len;
+    uint8_t byte;
+
+    len = (av_log2(val) + 7) / 7;
+
+    for (int i = 0; i < len; i++) {
+        byte = val >> (7 * i) & 0x7f;
+        if (i < len - 1)
+            byte |= 0x80;
+
+        avio_w8(s, byte);
+    }
+}
+
 int ffio_fdopen(AVIOContext **s, URLContext *h)
 {
     uint8_t *buffer = NULL;
-- 
2.42.1