331 lines
8.2 KiB
C
331 lines
8.2 KiB
C
#ifdef __LARGE64_FILES
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/*
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* Copyright (c) 1990 The Regents of the University of California.
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms are permitted
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* provided that the above copyright notice and this paragraph are
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* duplicated in all such forms and that any documentation,
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* advertising materials, and other materials related to such
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* distribution and use acknowledge that the software was developed
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* by the University of California, Berkeley. The name of the
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* University may not be used to endorse or promote products derived
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* from this software without specific prior written permission.
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* THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
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* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
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*/
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/*
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FUNCTION
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<<fseeko64>>---set file position for large file
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INDEX
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fseeko64
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ANSI_SYNOPSIS
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#include <stdio.h>
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int fseeko64(FILE *<[fp]>, _off64_t <[offset]>, int <[whence]>)
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TRAD_SYNOPSIS
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#include <stdio.h>
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int fseeko64(<[fp]>, <[offset]>, <[whence]>)
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FILE *<[fp]>;
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_off64_t <[offset]>;
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int <[whence]>;
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DESCRIPTION
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Objects of type <<FILE>> can have a ``position'' that records how much
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of the file your program has already read. Many of the <<stdio>> functions
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depend on this position, and many change it as a side effect.
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You can use <<fseeko64>> to set the position for the file identified by
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<[fp]> that was opened via <<fopen64>>. The value of <[offset]> determines
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the new position, in one of three ways selected by the value of <[whence]>
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(defined as macros in `<<stdio.h>>'):
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<<SEEK_SET>>---<[offset]> is the absolute file position (an offset
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from the beginning of the file) desired. <[offset]> must be positive.
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<<SEEK_CUR>>---<[offset]> is relative to the current file position.
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<[offset]> can meaningfully be either positive or negative.
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<<SEEK_END>>---<[offset]> is relative to the current end of file.
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<[offset]> can meaningfully be either positive (to increase the size
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of the file) or negative.
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See <<ftello64>> to determine the current file position.
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RETURNS
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<<fseeko64>> returns <<0>> when successful. On failure, the
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result is <<EOF>>. The reason for failure is indicated in <<errno>>:
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either <<ESPIPE>> (the stream identified by <[fp]> doesn't support
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repositioning or wasn't opened via <<fopen64>>) or <<EINVAL>>
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(invalid file position).
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PORTABILITY
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<<fseeko64>> is a glibc extension.
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Supporting OS subroutines required: <<close>>, <<fstat64>>, <<isatty>>,
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<<lseek64>>, <<read>>, <<sbrk>>, <<write>>.
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*/
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#include <stdio.h>
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#include <time.h>
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#include <fcntl.h>
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#include <stdlib.h>
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#include <errno.h>
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#include <sys/stat.h>
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#include "local64.h"
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#define POS_ERR (-(_fpos64_t)1)
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/*
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* Seek the given file to the given offset.
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* `Whence' must be one of the three SEEK_* macros.
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*/
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int
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fseeko64 (fp, offset, whence)
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register FILE *fp;
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_off64_t offset;
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int whence;
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{
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struct _reent *ptr;
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_fpos64_t _EXFUN ((*seekfn), (void *, _fpos64_t, int));
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_fpos64_t target, curoff;
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size_t n;
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struct stat st;
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int havepos;
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_flockfile(fp);
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/* Make sure stdio is set up. */
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CHECK_INIT (fp);
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ptr = fp->_data;
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/* If we've been doing some writing, and we're in append mode
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then we don't really know where the filepos is. */
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if (fp->_flags & __SAPP && fp->_flags & __SWR)
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{
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/* So flush the buffer and seek to the end. */
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fflush (fp);
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}
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/* Have to be able to seek. */
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if ((seekfn = fp->_seek64) == NULL || !(fp->_flags & __SL64))
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{
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ptr->_errno = ESPIPE; /* ??? */
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_funlockfile(fp);
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return EOF;
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}
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/*
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* Change any SEEK_CUR to SEEK_SET, and check `whence' argument.
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* After this, whence is either SEEK_SET or SEEK_END.
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*/
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switch (whence)
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{
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case SEEK_CUR:
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/*
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* In order to seek relative to the current stream offset,
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* we have to first find the current stream offset a la
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* ftell (see ftell for details).
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*/
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fflush(fp); /* may adjust seek offset on append stream */
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if (fp->_flags & __SOFF)
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curoff = fp->_offset;
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else
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{
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curoff = (*seekfn) (fp->_cookie, (_fpos64_t) 0, SEEK_CUR);
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if (curoff == -1L)
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{
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_funlockfile(fp);
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return EOF;
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}
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}
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if (fp->_flags & __SRD)
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{
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curoff -= fp->_r;
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if (HASUB (fp))
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curoff -= fp->_ur;
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}
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else if (fp->_flags & __SWR && fp->_p != NULL)
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curoff += fp->_p - fp->_bf._base;
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offset += curoff;
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whence = SEEK_SET;
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havepos = 1;
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break;
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case SEEK_SET:
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case SEEK_END:
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havepos = 0;
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break;
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default:
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ptr->_errno = EINVAL;
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_funlockfile(fp);
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return (EOF);
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}
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/*
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* Can only optimise if:
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* reading (and not reading-and-writing);
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* not unbuffered; and
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* this is a `regular' Unix file (and hence seekfn==__sseek).
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* We must check __NBF first, because it is possible to have __NBF
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* and __SOPT both set.
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*/
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if (fp->_bf._base == NULL)
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__smakebuf (fp);
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if (fp->_flags & (__SWR | __SRW | __SNBF | __SNPT))
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goto dumb;
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if ((fp->_flags & __SOPT) == 0)
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{
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if (seekfn != __sseek64
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|| fp->_file < 0
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|| _fstat64_r (ptr, fp->_file, &st)
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|| (st.st_mode & S_IFMT) != S_IFREG)
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{
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fp->_flags |= __SNPT;
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goto dumb;
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}
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#ifdef HAVE_BLKSIZE
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fp->_blksize = st.st_blksize;
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#else
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fp->_blksize = 1024;
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#endif
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fp->_flags |= __SOPT;
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}
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/*
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* We are reading; we can try to optimise.
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* Figure out where we are going and where we are now.
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*/
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if (whence == SEEK_SET)
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target = offset;
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else
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{
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if (_fstat64_r (ptr, fp->_file, &st))
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goto dumb;
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target = st.st_size + offset;
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}
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if (!havepos)
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{
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if (fp->_flags & __SOFF)
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curoff = fp->_offset;
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else
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{
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curoff = (*seekfn) (fp->_cookie, (_fpos64_t)0, SEEK_CUR);
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if (curoff == POS_ERR)
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goto dumb;
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}
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curoff -= fp->_r;
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if (HASUB (fp))
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curoff -= fp->_ur;
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}
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/*
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* Compute the number of bytes in the input buffer (pretending
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* that any ungetc() input has been discarded). Adjust current
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* offset backwards by this count so that it represents the
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* file offset for the first byte in the current input buffer.
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*/
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if (HASUB (fp))
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{
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curoff += fp->_r; /* kill off ungetc */
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n = fp->_up - fp->_bf._base;
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curoff -= n;
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n += fp->_ur;
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}
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else
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{
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n = fp->_p - fp->_bf._base;
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curoff -= n;
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n += fp->_r;
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}
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/*
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* If the target offset is within the current buffer,
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* simply adjust the pointers, clear EOF, undo ungetc(),
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* and return. (If the buffer was modified, we have to
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* skip this; see fgetline.c.)
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*/
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if ((fp->_flags & __SMOD) == 0 &&
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target >= curoff && target < curoff + n)
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{
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register int o = target - curoff;
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fp->_p = fp->_bf._base + o;
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fp->_r = n - o;
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if (HASUB (fp))
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FREEUB (fp);
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fp->_flags &= ~__SEOF;
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_funlockfile(fp);
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return 0;
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}
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/*
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* The place we want to get to is not within the current buffer,
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* but we can still be kind to the kernel copyout mechanism.
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* By aligning the file offset to a block boundary, we can let
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* the kernel use the VM hardware to map pages instead of
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* copying bytes laboriously. Using a block boundary also
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* ensures that we only read one block, rather than two.
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*/
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curoff = target & ~((_fpos64_t)(fp->_blksize - 1));
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if ((*seekfn) (fp->_cookie, curoff, SEEK_SET) == POS_ERR)
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goto dumb;
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fp->_r = 0;
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fp->_p = fp->_bf._base;
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if (HASUB (fp))
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FREEUB (fp);
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fp->_flags &= ~__SEOF;
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n = target - curoff;
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if (n)
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{
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if (__srefill (fp) || fp->_r < n)
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goto dumb;
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fp->_p += n;
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fp->_r -= n;
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}
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_funlockfile(fp);
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return 0;
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/*
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* We get here if we cannot optimise the seek ... just
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* do it. Allow the seek function to change fp->_bf._base.
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*/
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dumb:
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if (fflush (fp) || (*seekfn) (fp->_cookie, offset, whence) == POS_ERR)
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{
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_funlockfile(fp);
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return EOF;
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}
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/* success: clear EOF indicator and discard ungetc() data */
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if (HASUB (fp))
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FREEUB (fp);
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fp->_p = fp->_bf._base;
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fp->_r = 0;
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/* fp->_w = 0; *//* unnecessary (I think...) */
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fp->_flags &= ~__SEOF;
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_funlockfile(fp);
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return 0;
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}
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#endif /* __LARGE64_FILES */
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