Fill buffer speed up

Eliminates the byte by byte read from bool decoder,  by reading
in a size_t and then shifting it into place.

Change-Id: Id89241977103fc3b973e4ed172a5cbf246998e5d

1 files changed, 37 insertions, 13 deletions

diff --git a/vp9/decoder/vp9_reader.c b/vp9/decoder/vp9_reader.c
index 2c96f74f4..9a46cd717 100644
--- a/vp9/decoder/vp9_reader.c
+++ b/vp9/decoder/vp9_reader.c
@@ -7,12 +7,24 @@
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
+#include <stdlib.h>
 
 #include "vpx_ports/mem.h"
 #include "vpx_mem/vpx_mem.h"
 
+#include "./vpx_config.h"
 #include "vp9/decoder/vp9_reader.h"
 
+#include "vpx_util/endian_inl.h"
+
+#if CONFIG_BIG_ENDIAN
+#define BIGENDIFY64(X) (X)
+#define BIGENDIFY32(X) (X)
+#else
+#define BIGENDIFY64(X) BSwap64(X)
+#define BIGENDIFY32(X) BSwap32(X)
+#endif
+
 int vp9_reader_init(vp9_reader *r,
                     const uint8_t *buffer,
                     size_t size,
@@ -39,11 +51,9 @@ void vp9_reader_fill(vp9_reader *r) {
   const uint8_t *buffer_start = buffer;
   BD_VALUE value = r->value;
   int count = r->count;
-  int shift = BD_VALUE_SIZE - CHAR_BIT - (count + CHAR_BIT);
-  int loop_end = 0;
   const size_t bytes_left = buffer_end - buffer;
   const size_t bits_left = bytes_left * CHAR_BIT;
-  const int x = (int)(shift + CHAR_BIT - bits_left);
+  int shift = BD_VALUE_SIZE - CHAR_BIT - (count + CHAR_BIT);
 
   if (r->decrypt_cb) {
     size_t n = MIN(sizeof(r->clear_buffer), bytes_left);
@@ -51,17 +61,31 @@ void vp9_reader_fill(vp9_reader *r) {
     buffer = r->clear_buffer;
     buffer_start = r->clear_buffer;
   }
+  if (bits_left > BD_VALUE_SIZE) {
+#if UINTPTR_MAX == 0xffffffffffffffff
+      BD_VALUE big_endian_values = BIGENDIFY64(*((const BD_VALUE *) buffer));
+#else
+      BD_VALUE big_endian_values = BIGENDIFY32(*((const BD_VALUE *) buffer));
+#endif
+      const int bits = (shift & 0xfffffff8) + CHAR_BIT;
+      const BD_VALUE nv = big_endian_values >> (BD_VALUE_SIZE - bits);
+      count += bits;
+      buffer += (bits >> 3);
+      value = r->value | (nv << (shift & 0x7));
+  } else {
+    const int bits_over = (int)(shift + CHAR_BIT - bits_left);
+    int loop_end = 0;
+    if (bits_over >= 0) {
+      count += LOTS_OF_BITS;
+      loop_end = bits_over;
+    }
 
-  if (x >= 0) {
-    count += LOTS_OF_BITS;
-    loop_end = x;
-  }
-
-  if (x < 0 || bits_left) {
-    while (shift >= loop_end) {
-      count += CHAR_BIT;
-      value |= (BD_VALUE)*buffer++ << shift;
-      shift -= CHAR_BIT;
+    if (bits_over < 0 || bits_left) {
+      while (shift >= loop_end) {
+        count += CHAR_BIT;
+        value |= (BD_VALUE)*buffer++ << shift;
+        shift -= CHAR_BIT;
+      }
     }
   }