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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.
*/
#include "vp9/decoder/vp9_dboolhuff.h"
#include "vpx_ports/mem.h"
#include "vpx_mem/vpx_mem.h"
int vp9_start_decode(BOOL_DECODER *br,
const unsigned char *source,
unsigned int source_sz) {
br->user_buffer_end = source + source_sz;
br->user_buffer = source;
br->value = 0;
br->count = -8;
br->range = 255;
if (source_sz && !source)
return 1;
/* Populate the buffer */
vp9_bool_decoder_fill(br);
return 0;
}
void vp9_bool_decoder_fill(BOOL_DECODER *br) {
const unsigned char *bufptr = br->user_buffer;
const unsigned char *bufend = br->user_buffer_end;
VP9_BD_VALUE value = br->value;
int count = br->count;
int shift = VP9_BD_VALUE_SIZE - 8 - (count + 8);
int loop_end = 0;
int bits_left = (int)((bufend - bufptr)*CHAR_BIT);
int x = shift + CHAR_BIT - bits_left;
if (x >= 0) {
count += VP9_LOTS_OF_BITS;
loop_end = x;
}
if (x < 0 || bits_left) {
while (shift >= loop_end) {
count += CHAR_BIT;
value |= (VP9_BD_VALUE)*bufptr++ << shift;
shift -= CHAR_BIT;
}
}
br->user_buffer = bufptr;
br->value = value;
br->count = count;
}
static int get_unsigned_bits(unsigned num_values) {
int cat = 0;
if ((num_values--) <= 1) return 0;
while (num_values > 0) {
cat++;
num_values >>= 1;
}
return cat;
}
int vp9_inv_recenter_nonneg(int v, int m) {
if (v > (m << 1)) return v;
else if ((v & 1) == 0) return (v >> 1) + m;
else return m - ((v + 1) >> 1);
}
int vp9_decode_uniform(BOOL_DECODER *br, int n) {
int v;
int l = get_unsigned_bits(n);
int m = (1 << l) - n;
if (!l) return 0;
v = decode_value(br, l - 1);
if (v < m)
return v;
else
return (v << 1) - m + decode_value(br, 1);
}
int vp9_decode_term_subexp(BOOL_DECODER *br, int k, int num_syms) {
int i = 0, mk = 0, word;
while (1) {
int b = (i ? k + i - 1 : k);
int a = (1 << b);
if (num_syms <= mk + 3 * a) {
word = vp9_decode_uniform(br, num_syms - mk) + mk;
break;
} else {
if (decode_value(br, 1)) {
i++;
mk += a;
} else {
word = decode_value(br, b) + mk;
break;
}
}
}
return word;
}
int vp9_decode_unsigned_max(BOOL_DECODER *br, int max) {
int data = 0, bit = 0, lmax = max;
while (lmax) {
data |= decode_bool(br, 128) << bit++;
lmax >>= 1;
}
if (data > max)
return max;
return data;
}
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