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/* Copyright(c) 1986 Association of Universities for Research in Astronomy Inc.
*/
#define import_spp
#define import_libc
#define import_stdio
#define import_fset
#include <iraf.h>
/* FSEEK -- Seek on a file opened under stdio. The seek functions do not
** completely emulate the UNIX seek functions. The following restrictions
** apply:
**
** - It is only permissible to seek to the beginning of a line if the
** actual file is a text file. The seek offset must have been
** obtained by a prior call to FTELL, which returns the seek offset
** of the next line to be read or written. Seek offsets cannot be
** manufactured, e.g., as physical char offsets in the file, as is
** the case for binary files. These restrictions apply because text
** files are record structured on many systems, rather than simple
** byte stream files as in UNIX.
**
** - It is permissible to randomly seek about on a binary file, but
** seeks must be aligned on XCHAR word boundaries in the file. This
** can be guaranteed by structuring the application so that it always
** reads and writes binary data records that are an integral number
** of integers in size. If this is done the program is portable to
** any IRAF machine as well as to UNIX. Seek offsets are specified
** in units of bytes and are zero-indexed, as in C.
*/
int
fseek (
FILE *fp, /* operand file */
long offset, /* offset in file */
int mode /* 0=absolute, 1=relative, 2=from EOF */
)
{
register XINT fd = fileno(fp);
int text_file, stat;
text_file = (c_fstati (fd, F_TYPE) == TEXT_FILE);
fp->_fflags &= ~_FEOF;
if (text_file) {
switch (mode) {
case 0:
if (offset == 0L)
stat = c_seek (fd, BOFL);
else
stat = c_seek (fd, offset);
break;
case 2:
if (offset == 0L) {
stat = c_seek (fd, EOFL);
fp->_fflags |= _FEOF;
} else
stat = ERR;
break;
default:
stat = ERR;
break;
}
} else {
/* Random seeks on (non-streaming) binary files are permitted,
* but the seek must be to an XCHAR offset. This is checked
* by c_seek, which takes a zero-indexed byte offset as argument.
*/
switch (mode) {
case 0:
stat = c_seek (fd, offset);
break;
case 1:
stat = c_seek (fd, c_note(fd) + offset);
break;
case 2:
if ((stat = c_seek (fd, EOFL)) != ERR) {
if (offset == 0L)
fp->_fflags |= _FEOF;
else
stat = c_seek (fd, c_note(fd) - offset);
}
break;
default:
stat = ERR;
}
}
return (stat);
}
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