Merge "Add a placeholder forward buffered ANS coder." into nextgenv2

vp10/encoder/buf_ans.h

+/*
+ *  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.
+ */
+
+#ifndef VP10_ENCODER_BUF_ANS_H_
+#define VP10_ENCODER_BUF_ANS_H_
+// Buffered forward ANS writer.
+// Symbols are written to the writer in forward (decode) order and serialzed
+// backwards due to ANS's stack like behavior.
+
+#include <assert.h>
+#include "./vpx_config.h"
+#include "vpx/vpx_integer.h"
+#include "vpx_ports/mem_ops.h"
+#include "vp10/common/ans.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif  // __cplusplus
+
+#define ANS_METHOD_UABS 0
+#define ANS_METHOD_RANS 1
+
+struct buffered_ans_symbol {
+  uint8_t method;    // one of ANS_METHOD_UABS or ANS_METHOD_RANS
+  // TODO(aconverse): Should be possible to write this interms of start for ABS
+  AnsP8 val_start;  // Boolean value for ABS, start in symbol cycle for Rans
+  AnsP8 prob;  // Probability of this symbol
+};
+
+struct BufAnsCoder {
+  struct buffered_ans_symbol *buf;
+  int size;
+  int offset;
+};
+
+static INLINE void buf_ans_write_init(struct BufAnsCoder *const c,
+                                      struct buffered_ans_symbol *sym_arr,
+                                      int size) {
+  c->buf = sym_arr;
+  c->size = size;
+  c->offset = 0;
+}
+
+static INLINE void buf_uabs_write(struct BufAnsCoder *const c,
+                             uint8_t val, AnsP8 prob) {
+  assert(c->offset < c->size);
+  c->buf[c->offset].method = ANS_METHOD_UABS;
+  c->buf[c->offset].val_start = val;
+  c->buf[c->offset].prob = prob;
+  ++c->offset;
+}
+
+static INLINE void buf_rans_write(struct BufAnsCoder *const c,
+                                  const struct rans_sym *const sym) {
+  assert(c->offset < c->size);
+  c->buf[c->offset].method = ANS_METHOD_RANS;
+  c->buf[c->offset].val_start = sym->cum_prob;
+  c->buf[c->offset].prob = sym->prob;
+  ++c->offset;
+}
+
+static INLINE void buf_ans_flush(const struct BufAnsCoder *const c,
+                                 struct AnsCoder *ans) {
+  int offset;
+  for (offset = c->offset - 1; offset >= 0; --offset) {
+    if (c->buf[offset].method == ANS_METHOD_RANS) {
+      struct rans_sym sym;
+      sym.prob = c->buf[offset].prob;
+      sym.cum_prob = c->buf[offset].val_start;
+      rans_write(ans, &sym);
+    } else {
+      uabs_write(ans, c->buf[offset].val_start, c->buf[offset].prob);
+    }
+  }
+}
+
+#ifdef __cplusplus
+}  // extern "C"
+#endif  // __cplusplus
+#endif  // VP10_ENCODER_BUF_ANS_H_