ref: 52d350febfc19ec5a1783789c183af2397bf5b20
dir: /vp9/decoder/vp9_dboolhuff.c/
/* * 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; const unsigned char *bufend; VP9_BD_VALUE value; int count; bufend = br->user_buffer_end; bufptr = br->user_buffer; value = br->value; count = br->count; VP9DX_BOOL_DECODER_FILL(count, value, bufptr, bufend); 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; }