100 lines
2.6 KiB
C
100 lines
2.6 KiB
C
/* ----------------------------------------------------------------------- *
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*
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* Copyright 2004-2008 H. Peter Anvin - All Rights Reserved
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*
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* Permission is hereby granted, free of charge, to any person
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* obtaining a copy of this software and associated documentation
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* files (the "Software"), to deal in the Software without
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* restriction, including without limitation the rights to use,
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* copy, modify, merge, publish, distribute, sublicense, and/or
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* sell copies of the Software, and to permit persons to whom
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* the Software is furnished to do so, subject to the following
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* conditions:
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*
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* The above copyright notice and this permission notice shall
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* be included in all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
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* OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
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* HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
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* WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
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* OTHER DEALINGS IN THE SOFTWARE.
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*
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* ----------------------------------------------------------------------- */
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/*
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* read.c
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*
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* Reading from a file
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*/
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#include <errno.h>
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#include <string.h>
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#include <com32.h>
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#include <pmapi.h>
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#include <syslinux/pmapi.h>
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#include <minmax.h>
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#include "file.h"
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int __file_get_block(struct file_info *fp)
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{
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ssize_t bytes_read;
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bytes_read = pmapi_read_file(&fp->i.fd.handle, fp->i.buf,
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MAXBLOCK >> fp->i.fd.blocklg2);
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if (!bytes_read) {
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errno = EIO;
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return -1;
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}
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fp->i.nbytes = bytes_read;
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fp->i.datap = fp->i.buf;
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return 0;
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}
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ssize_t __file_read(struct file_info * fp, void *buf, size_t count)
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{
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char *bufp = buf;
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ssize_t n = 0;
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size_t ncopy;
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while (count) {
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if (fp->i.nbytes == 0) {
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if (fp->i.offset >= fp->i.fd.size || !fp->i.fd.handle)
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return n; /* As good as it gets... */
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if (count > MAXBLOCK) {
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/* Large transfer: copy directly, without buffering */
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ncopy = pmapi_read_file(&fp->i.fd.handle, bufp,
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count >> fp->i.fd.blocklg2);
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if (!ncopy) {
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errno = EIO;
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return n ? n : -1;
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}
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goto got_data;
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} else {
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if (__file_get_block(fp))
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return n ? n : -1;
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}
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}
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ncopy = min(count, fp->i.nbytes);
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memcpy(bufp, fp->i.datap, ncopy);
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fp->i.datap += ncopy;
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fp->i.offset += ncopy;
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fp->i.nbytes -= ncopy;
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got_data:
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n += ncopy;
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bufp += ncopy;
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count -= ncopy;
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}
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return n;
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}
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