shithub: libvpx

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Optimize bit_read_buffer.

Change-Id: Iee43c34909deec9787b29c1c33672213b9f049df

--- a/vp9/decoder/vp9_read_bit_buffer.c

+++ b/vp9/decoder/vp9_read_bit_buffer.c

@@ -10,20 +10,20 @@

 #include "vp9/decoder/vp9_read_bit_buffer.h"

 size_t vp9_rb_bytes_read(struct vp9_read_bit_buffer *rb) {

-  return (rb->bit_offset + CHAR_BIT - 1) / CHAR_BIT;

+  return (rb->bit_offset + 7) >> 3;

 }

 int vp9_rb_read_bit(struct vp9_read_bit_buffer *rb) {

   const size_t off = rb->bit_offset;

-  const size_t p = off / CHAR_BIT;

-  const int q = CHAR_BIT - 1 - (int)off % CHAR_BIT;

-  if (rb->bit_buffer + p >= rb->bit_buffer_end) {

-    rb->error_handler(rb->error_handler_data);

-    return 0;

-  } else {

-    const int bit = (rb->bit_buffer[p] & (1 << q)) >> q;

+  const size_t p = off >> 3;

+  const int q = 7 - (int)(off & 0x7);

+  if (rb->bit_buffer + p < rb->bit_buffer_end) {

+    const int bit = (rb->bit_buffer[p] >> q) & 1;

     rb->bit_offset = off + 1;

     return bit;

+  } else {

+    rb->error_handler(rb->error_handler_data);

+    return 0;

   }

 }