GCC Code Coverage Report
Directory: ../../../ffmpeg/ Exec Total Coverage
File: src/libavcodec/rangecoder.c Lines: 53 55 96.4 %
Date: 2021-04-14 23:45:22 Branches: 23 24 95.8 %

Line Branch Exec Source
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/*
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 * Range coder
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 * Copyright (c) 2004 Michael Niedermayer <michaelni@gmx.at>
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 *
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 * This file is part of FFmpeg.
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 *
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 * FFmpeg is free software; you can redistribute it and/or
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 * modify it under the terms of the GNU Lesser General Public
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 * License as published by the Free Software Foundation; either
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 * version 2.1 of the License, or (at your option) any later version.
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 *
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 * FFmpeg is distributed in the hope that it will be useful,
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 * but WITHOUT ANY WARRANTY; without even the implied warranty of
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 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
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 * Lesser General Public License for more details.
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 *
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 * You should have received a copy of the GNU Lesser General Public
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 * License along with FFmpeg; if not, write to the Free Software
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 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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 */
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/**
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 * @file
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 * Range coder.
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 * based upon
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 *    "Range encoding: an algorithm for removing redundancy from a digitised
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 *                     message.
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 *     G. N. N. Martin                  Presented in March 1979 to the Video &
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 *                                      Data Recording Conference,
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 *     IBM UK Scientific Center         held in Southampton July 24-27 1979."
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 */
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#include <string.h>
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#include "libavutil/attributes.h"
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#include "libavutil/avassert.h"
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#include "libavutil/intreadwrite.h"
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#include "avcodec.h"
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#include "rangecoder.h"
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av_cold void ff_init_range_encoder(RangeCoder *c, uint8_t *buf, int buf_size)
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{
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15276
    c->bytestream_start  =
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    c->bytestream        = buf;
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    c->bytestream_end    = buf + buf_size;
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    c->low               = 0;
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    c->range             = 0xFF00;
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    c->outstanding_count = 0;
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    c->outstanding_byte  = -1;
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}
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av_cold void ff_init_range_decoder(RangeCoder *c, const uint8_t *buf,
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                                   int buf_size)
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{
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    /* cast to avoid compiler warning */
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7673
    ff_init_range_encoder(c, (uint8_t *)buf, buf_size);
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    c->low         = AV_RB16(c->bytestream);
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    c->bytestream += 2;
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    c->overread    = 0;
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    if (c->low >= 0xFF00) {
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        c->low = 0xFF00;
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        c->bytestream_end = c->bytestream;
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    }
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}
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void ff_build_rac_states(RangeCoder *c, int factor, int max_p)
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{
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5948
    const int64_t one = 1LL << 32;
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    int64_t p;
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    int last_p8, p8, i;
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    memset(c->zero_state, 0, sizeof(c->zero_state));
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    memset(c->one_state, 0, sizeof(c->one_state));
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    last_p8 = 0;
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    p       = one / 2;
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    for (i = 0; i < 128; i++) {
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        p8 = (256 * p + one / 2) >> 32; // FIXME: try without the one
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        if (p8 <= last_p8)
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            p8 = last_p8 + 1;
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        if (last_p8 && last_p8 < 256 && p8 <= max_p)
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            c->one_state[last_p8] = p8;
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        p      += ((one - p) * factor + one / 2) >> 32;
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        last_p8 = p8;
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    }
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    for (i = 256 - max_p; i <= max_p; i++) {
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        if (c->one_state[i])
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            continue;
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        p  = (i * one + 128) >> 8;
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        p += ((one - p) * factor + one / 2) >> 32;
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        p8 = (256 * p + one / 2) >> 32; // FIXME: try without the one
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        if (p8 <= i)
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            p8 = i + 1;
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        if (p8 > max_p)
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            p8 = max_p;
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        c->one_state[i] = p8;
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    }
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    for (i = 1; i < 255; i++)
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        c->zero_state[i] = 256 - c->one_state[256 - i];
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}
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/* Return the number of bytes written. */
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int ff_rac_terminate(RangeCoder *c, int version)
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{
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    if (version == 1)
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        put_rac(c, (uint8_t[]) { 129 }, 0);
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    c->range = 0xFF;
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    c->low  += 0xFF;
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    renorm_encoder(c);
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    c->range = 0xFF;
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    renorm_encoder(c);
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    av_assert1(c->low   == 0);
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    av_assert1(c->range >= 0x100);
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    return c->bytestream - c->bytestream_start;
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}