shithub: dav1d

Info  •  Files  •  Log  •  Branches

get_bits: Factor out leb parsing to  dav1d_get_uleb128()

--- a/src/getbits.c

+++ b/src/getbits.c

@@ -79,6 +79,27 @@

     return res >> shift;

 }

+unsigned dav1d_get_uleb128(GetBits *c) {

+    unsigned val = 0, more, i = 0;

+

+    do {

+        more = dav1d_get_bits(c, 1);

+        unsigned bits = dav1d_get_bits(c, 7);

+        if (i <= 3 || (i == 4 && bits < (1 << 4)))

+            val |= bits << (i * 7);

+        else if (bits) {

+            c->error = 1;

+            return 0;

+        }

+        if (more && ++i == 8) {

+            c->error = 1;

+            return 0;

+        }

+    } while (more);

+

+    return val;

+}

+

 unsigned dav1d_get_uniform(GetBits *const c, const unsigned max) {

     // Output in range [0..max-1]

     // max must be > 1, or else nothing is read from the bitstream

--- a/src/getbits.h

+++ b/src/getbits.h

@@ -41,6 +41,7 @@

 void dav1d_init_get_bits(GetBits *c, const uint8_t *data, size_t sz);

 unsigned dav1d_get_bits(GetBits *c, unsigned n);

 int dav1d_get_sbits(GetBits *c, unsigned n);

+unsigned dav1d_get_uleb128(GetBits *c);

 // Output in range 0..max-1

 unsigned dav1d_get_uniform(GetBits *c, unsigned max);

--- a/src/obu.c

+++ b/src/obu.c

@@ -1187,17 +1187,9 @@

     }

     // obu length field

-    unsigned len = 0, more, i = 0;

+    unsigned len = 0;

     if (has_length_field)

-        do {

-            more = dav1d_get_bits(&gb, 1);

-            unsigned bits = dav1d_get_bits(&gb, 7);

-            if (i <= 3 || (i == 4 && bits < (1 << 4)))

-                len |= bits << (i * 7);

-            else if (bits)

-                goto error;

-            if (more && ++i == 8) goto error;

-        } while (more);

+        len = dav1d_get_uleb128(&gb);

     else

         len = (int) in->sz - 1 - has_extension;

     if (gb.error) goto error;