Merge changes I3c72a2d8,I9905f3a8 into nextgenv2

* changes:
  Add pluggable bitwriters.
  Add pluggable bitreaders.

vp10/common/ans.h

@@ -16,6 +16,7 @@
 #include <assert.h>
 #include "./vpx_config.h"
 #include "vpx/vpx_integer.h"
+#include "vpx_dsp/prob.h"
 #include "vpx_ports/mem_ops.h"
 
 #define ANS_DIVIDE_BY_MULTIPLY 1
@@ -242,6 +243,18 @@ static INLINE int uabs_read_literal(struct AnsDecoder *ans, int bits) {
   return literal;
 }
 
+// TODO(aconverse): Replace trees with tokensets.
+static INLINE int uabs_read_tree(struct AnsDecoder *ans,
+                                 const vpx_tree_index *tree,
+                                 const AnsP8 *probs) {
+  vpx_tree_index i = 0;
+
+  while ((i = tree[i + uabs_read(ans, probs[i >> 1])]) > 0)
+    continue;
+
+  return -i;
+}
+
 struct rans_sym {
   AnsP8 prob;
   AnsP8 cum_prob;  // not-inclusive

vp10/decoder/bitreader.h

@@ -0,0 +1,38 @@
+/*
+ *  Copyright (c) 2016 The WebM project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+/* The purpose of this header is to provide compile time pluggable bit reader
+ * implementations with a common interface. */
+
+#ifndef VPX10_DECODER_BITREADER_H_
+#define VPX10_DECODER_BITREADER_H_
+
+#include "./vpx_config.h"
+
+#if CONFIG_ANS
+#include "vp10/common/ans.h"
+#include "vpx/vp8dx.h"  // for vp10_decrypt_cb
+#define vp10_reader struct AnsDecoder
+#define vp10_reader_has_error ans_reader_has_error
+#define vp10_read uabs_read
+#define vp10_read_bit uabs_read_bit
+#define vp10_read_literal uabs_read_literal
+#define vp10_read_tree uabs_read_tree
+#else
+#include "vpx_dsp/bitreader.h"
+#define vp10_reader vpx_reader
+#define vp10_reader_has_error vpx_reader_has_error
+#define vp10_read vpx_read
+#define vp10_read_bit vpx_read_bit
+#define vp10_read_literal vpx_read_literal
+#define vp10_read_tree vpx_read_tree
+#endif
+
+#endif  // VPX10_DECODER_BITREADER_H_

vp10/encoder/bitwriter.h

@@ -0,0 +1,35 @@
+/*
+ *  Copyright (c) 2016 The WebM project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+/* The purpose of this header is to provide compile time pluggable bit writer
+ * implementations with a common interface. */
+
+#ifndef VPX10_ENCODER_BITWRITER_H_
+#define VPX10_ENCODER_BITWRITER_H_
+
+#include "./vpx_config.h"
+#include "vpx_dsp/prob.h"
+
+#if CONFIG_ANS
+typedef struct BufAnsCoder BufAnsCoder;
+#include "vp10/encoder/buf_ans.h"
+#define vp10_writer BufAnsCoder
+#define vp10_write buf_uabs_write
+#define vp10_write_bit buf_uabs_write_bit
+#define vp10_write_literal buf_uabs_write_literal
+#else
+#include "vpx_dsp/bitwriter.h"
+#define vp10_writer vpx_writer
+#define vp10_write vpx_write
+#define vp10_write_bit vpx_write_bit
+#define vp10_write_literal vpx_write_literal
+#endif
+
+#endif  // VPX10_ENCODER_BITWRITER_H_

vp10/vp10cx.mk

@@ -18,6 +18,7 @@ VP10_CX_SRCS_REMOVE-no  += $(VP10_COMMON_SRCS_REMOVE-no)
 VP10_CX_SRCS-yes += vp10_cx_iface.c
 
 VP10_CX_SRCS-yes += encoder/bitstream.c
+VP10_CX_SRCS-yes += encoder/bitwriter.h
 VP10_CX_SRCS-yes += encoder/context_tree.c
 VP10_CX_SRCS-yes += encoder/context_tree.h
 VP10_CX_SRCS-yes += encoder/cost.h

vp10/vp10dx.mk

@@ -29,5 +29,6 @@ VP10_DX_SRCS-yes += decoder/decoder.c
 VP10_DX_SRCS-yes += decoder/decoder.h
 VP10_DX_SRCS-yes += decoder/dsubexp.c
 VP10_DX_SRCS-yes += decoder/dsubexp.h
+VP10_DX_SRCS-yes += decoder/bitreader.h
 
 VP10_DX_SRCS-yes := $(filter-out $(VP10_DX_SRCS_REMOVE-yes),$(VP10_DX_SRCS-yes))