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-rw-r--r--media/libvpx/vp8/decoder/dboolhuff.h141
1 files changed, 141 insertions, 0 deletions
diff --git a/media/libvpx/vp8/decoder/dboolhuff.h b/media/libvpx/vp8/decoder/dboolhuff.h
new file mode 100644
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+++ b/media/libvpx/vp8/decoder/dboolhuff.h
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+/*
+ * Copyright (c) 2010 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 VP8_DECODER_DBOOLHUFF_H_
+#define VP8_DECODER_DBOOLHUFF_H_
+
+#include <stddef.h>
+#include <limits.h>
+
+#include "vpx_config.h"
+#include "vpx_ports/mem.h"
+#include "vpx/vp8dx.h"
+#include "vpx/vpx_integer.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+typedef size_t VP8_BD_VALUE;
+
+#define VP8_BD_VALUE_SIZE ((int)sizeof(VP8_BD_VALUE)*CHAR_BIT)
+
+/*This is meant to be a large, positive constant that can still be efficiently
+ loaded as an immediate (on platforms like ARM, for example).
+ Even relatively modest values like 100 would work fine.*/
+#define VP8_LOTS_OF_BITS (0x40000000)
+
+typedef struct
+{
+ const unsigned char *user_buffer_end;
+ const unsigned char *user_buffer;
+ VP8_BD_VALUE value;
+ int count;
+ unsigned int range;
+ vpx_decrypt_cb decrypt_cb;
+ void *decrypt_state;
+} BOOL_DECODER;
+
+DECLARE_ALIGNED(16, extern const unsigned char, vp8_norm[256]);
+
+int vp8dx_start_decode(BOOL_DECODER *br,
+ const unsigned char *source,
+ unsigned int source_sz,
+ vpx_decrypt_cb decrypt_cb,
+ void *decrypt_state);
+
+void vp8dx_bool_decoder_fill(BOOL_DECODER *br);
+
+
+static int vp8dx_decode_bool(BOOL_DECODER *br, int probability) {
+ unsigned int bit = 0;
+ VP8_BD_VALUE value;
+ unsigned int split;
+ VP8_BD_VALUE bigsplit;
+ int count;
+ unsigned int range;
+
+ split = 1 + (((br->range - 1) * probability) >> 8);
+
+ if(br->count < 0)
+ vp8dx_bool_decoder_fill(br);
+
+ value = br->value;
+ count = br->count;
+
+ bigsplit = (VP8_BD_VALUE)split << (VP8_BD_VALUE_SIZE - 8);
+
+ range = split;
+
+ if (value >= bigsplit)
+ {
+ range = br->range - split;
+ value = value - bigsplit;
+ bit = 1;
+ }
+
+ {
+ register unsigned int shift = vp8_norm[range];
+ range <<= shift;
+ value <<= shift;
+ count -= shift;
+ }
+ br->value = value;
+ br->count = count;
+ br->range = range;
+
+ return bit;
+}
+
+static int vp8_decode_value(BOOL_DECODER *br, int bits)
+{
+ int z = 0;
+ int bit;
+
+ for (bit = bits - 1; bit >= 0; bit--)
+ {
+ z |= (vp8dx_decode_bool(br, 0x80) << bit);
+ }
+
+ return z;
+}
+
+static int vp8dx_bool_error(BOOL_DECODER *br)
+{
+ /* Check if we have reached the end of the buffer.
+ *
+ * Variable 'count' stores the number of bits in the 'value' buffer, minus
+ * 8. The top byte is part of the algorithm, and the remainder is buffered
+ * to be shifted into it. So if count == 8, the top 16 bits of 'value' are
+ * occupied, 8 for the algorithm and 8 in the buffer.
+ *
+ * When reading a byte from the user's buffer, count is filled with 8 and
+ * one byte is filled into the value buffer. When we reach the end of the
+ * data, count is additionally filled with VP8_LOTS_OF_BITS. So when
+ * count == VP8_LOTS_OF_BITS - 1, the user's data has been exhausted.
+ */
+ if ((br->count > VP8_BD_VALUE_SIZE) && (br->count < VP8_LOTS_OF_BITS))
+ {
+ /* We have tried to decode bits after the end of
+ * stream was encountered.
+ */
+ return 1;
+ }
+
+ /* No error. */
+ return 0;
+}
+
+#ifdef __cplusplus
+} // extern "C"
+#endif
+
+#endif // VP8_DECODER_DBOOLHUFF_H_