100 lines
2.6 KiB
C
100 lines
2.6 KiB
C
/* ****************************************************************************
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* stream/seek.c -- move in a stream.
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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 libcasio.
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* libcasio 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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* libcasio 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 libcasio; if not, see <http://www.gnu.org/licenses/>.
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* ************************************************************************* */
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#include "stream.h"
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/**
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* casio_seek:
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* Move in a stream.
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*
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* @arg stream the stream to move into.
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* @arg offset the offset.
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* @arg whence the whence.
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* @return the error code (0 if ok).
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*/
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int CASIO_EXPORT casio_seek(casio_stream_t *stream, casio_off_t offset,
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casio_whence_t whence)
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{
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int err;
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casio_stream_seek_t *s;
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if (whence != CASIO_SEEK_SET && whence != CASIO_SEEK_CUR
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&& whence != CASIO_SEEK_END) {
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err = casio_error_op;
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goto fail;
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}
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/* Check if the job isn't already done. */
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if ((whence == CASIO_SEEK_CUR && !offset)
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|| (whence == CASIO_SEEK_SET && offset == stream->casio_stream_offset))
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return (0);
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/* Try to seek using the dedicated function. */
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if ((s = stream->casio_stream_callbacks.casio_streamfuncs_seek)) {
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/* The callback exists, let's use it! */
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if ((err = (*s)(stream->casio_stream_cookie, &offset, whence)))
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goto fail;
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} else if (whence == CASIO_SEEK_CUR && offset > 0
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&& stream->casio_stream_mode & CASIO_OPENMODE_READ) {
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/* Fallback mehod for skipping bytes: read until N bytes have
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* been skipped. */
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{
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unsigned char buf[128];
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size_t to_skip = (size_t)offset;
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do {
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size_t rd = min(to_skip, 128);
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/* Read that much from the stream. */
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if ((err = casio_read(stream, buf, rd, 0)))
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goto fail;
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to_skip -= rd;
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} while (to_skip);
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}
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} else {
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err = casio_error_op;
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goto fail;
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}
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stream->casio_stream_offset = offset;
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err = 0;
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fail:
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stream->casio_stream_lasterr = err;
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return (err);
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}
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/**
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* casio_tell:
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* Tell the position in a stream.
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*
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* @arg stream the stream to get the position of.
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* @return the position.
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*/
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casio_off_t CASIO_EXPORT casio_tell(casio_stream_t *stream)
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{
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return (stream->casio_stream_offset);
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}
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