62 lines
1.9 KiB
C
62 lines
1.9 KiB
C
/* *****************************************************************************
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* utils/skip.c -- skip some bytes (useful for debugging).
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* Copyright (C) 2017 Thomas "Cakeisalie5" Touhey <thomas@touhey.fr>
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*
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* This file is part of libg1m.
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* libg1m is free software; you can redistribute it and/or modify it
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* under the terms of the GNU Lesser General Public License as published by
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* the Free Software Foundation; either version 3.0 of the License,
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* or (at your option) any later version.
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*
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* libg1m 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.
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* See the GNU 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 License
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* along with libg1m; if not, see <http://www.gnu.org/licenses/>.
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* ************************************************************************** */
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#include <libg1m/internals.h>
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/**
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* g1m_skip:
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* Skip some bytes.
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*
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* I've made two loops to avoid conditions in each loop iteration
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* when checksum is not calculated. Yeah, I know. #YOLO.
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*
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* @arg buffer the buffer from which to read.
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* @arg size the size to skip.
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* @arg checksum pointer to the checksum variable if there is one.
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*/
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int g1m_skip(g1m_buffer_t *buffer, size_t size, uint_fast32_t *checksum)
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{
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uint8_t buf[1024]; int err;
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size_t rd = 0; uint_fast32_t add = 0;
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while (1) {
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/* if no size left, exit */
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if (!size) break;
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/* read that much */
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{
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size_t curlen = min(size, 1024);
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if ((err = (*buffer->read)(buffer->cookie, buf, curlen))) {
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log_error("Skipping has failed after %zu bytes", size);
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return (err);
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}
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rd += curlen;
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/* feed the checksum */
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add = g1m_checksum32(buf, curlen, add);
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}
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}
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/* add to checksum */
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if (checksum) *checksum += add;
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/* no error */
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return (0);
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}
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