1 files changed, 63 insertions, 0 deletions
diff --git a/vp8/decoder/treereader.h b/vp8/decoder/treereader.h
new file mode 100644
index 000000000..eb10e2460
--- /dev/null
+++ b/vp8/decoder/treereader.h
@@ -0,0 +1,63 @@
+/*
+ *  Copyright (c) 2010 The VP8 project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license and patent
+ *  grant that can be found in the LICENSE file in the root of the source
+ *  tree. All contributing project authors may be found in the AUTHORS
+ *  file in the root of the source tree.
+ */
+
+
+#ifndef tree_reader_h
+#define tree_reader_h 1
+
+#include "treecoder.h"
+
+#include "dboolhuff.h"
+
+typedef BOOL_DECODER vp8_reader;
+
+#define vp8_read vp8dx_decode_bool
+#define vp8_read_literal vp8_decode_value
+#define vp8_read_bit( R) vp8_read( R, vp8_prob_half)
+
+
+/* Intent of tree data structure is to make decoding trivial. */
+
+static int vp8_treed_read(
+    vp8_reader *const r,        /* !!! must return a 0 or 1 !!! */
+    vp8_tree t,
+    const vp8_prob *const p
+)
+{
+    register vp8_tree_index i = 0;
+
+    while ((i = t[ i + vp8_read(r, p[i>>1])]) > 0) ;
+
+    return -i;
+}
+
+
+/* Variant reads a binary number given distributions on each bit.
+   Note that tree is arbitrary; probability of decoding a zero
+   may or may not depend on previously decoded bits. */
+
+static int vp8_treed_read_num(
+    vp8_reader *const r,        /* !!! must return a 0 or 1 !!! */
+    vp8_tree t,
+    const vp8_prob *const p
+)
+{
+    vp8_tree_index i = 0;
+    int v = 0, b;
+
+    do
+    {
+        b = vp8_read(r, p[i>>1]);
+        v = (v << 1) + b;
+    }
+    while ((i = t[i+b]) > 0);
+
+    return v;
+}
+#endif /* tree_reader_h */