61 lines
1.8 KiB
C
61 lines
1.8 KiB
C
/*
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* Copyright (c) 2013 The WebM project authors. All Rights Reserved.
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*
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* Use of this source code is governed by a BSD-style license
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* that can be found in the LICENSE file in the root of the source
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* tree. An additional intellectual property rights grant can be found
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* in the file PATENTS. All contributing project authors may
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* be found in the AUTHORS file in the root of the source tree.
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*/
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#ifndef VP9_READ_BIT_BUFFER_
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#define VP9_READ_BIT_BUFFER_
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#include <limits.h>
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#include "vpx/vpx_integer.h"
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typedef void (*vp9_rb_error_handler)(void *data, size_t bit_offset);
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struct vp9_read_bit_buffer {
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const uint8_t *bit_buffer;
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const uint8_t *bit_buffer_end;
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size_t bit_offset;
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void *error_handler_data;
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vp9_rb_error_handler error_handler;
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};
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static size_t vp9_rb_bytes_read(struct vp9_read_bit_buffer *rb) {
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return rb->bit_offset / CHAR_BIT + (rb->bit_offset % CHAR_BIT > 0);
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}
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static int vp9_rb_read_bit(struct vp9_read_bit_buffer *rb) {
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const size_t off = rb->bit_offset;
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const size_t p = off / CHAR_BIT;
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const int q = CHAR_BIT - 1 - (int)off % CHAR_BIT;
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if (rb->bit_buffer + p >= rb->bit_buffer_end) {
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rb->error_handler(rb->error_handler_data, rb->bit_offset);
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return 0;
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} else {
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const int bit = (rb->bit_buffer[p] & (1 << q)) >> q;
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rb->bit_offset = off + 1;
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return bit;
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}
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}
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static int vp9_rb_read_literal(struct vp9_read_bit_buffer *rb, int bits) {
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int value = 0, bit;
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for (bit = bits - 1; bit >= 0; bit--)
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value |= vp9_rb_read_bit(rb) << bit;
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return value;
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}
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static int vp9_rb_read_signed_literal(struct vp9_read_bit_buffer *rb,
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int bits) {
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const int value = vp9_rb_read_literal(rb, bits);
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return vp9_rb_read_bit(rb) ? -value : value;
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}
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#endif // VP9_READ_BIT_BUFFER_
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