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/* Copyright (C) 2004 Manuel Novoa III <mjn3@codepoet.org>
*
* GNU Library General Public License (LGPL) version 2 or later.
*
* Dedicated to Toni. See uClibc/DEDICATION.mjn3 for details.
*/
#include "_stdio.h"
/* Both ftell() and fseek() (for SEEK_CUR) need to correct the stream's
* position to take into account buffered data and ungotten chars.
*
* If successful, store corrected position in *pos and return >= 0.
* Otherwise return < 0.
*
* If position is unrepresentable, set errno to EOVERFLOW.
*/
int attribute_hidden __stdio_adjust_position(register FILE * __restrict stream,
register __offmax_t *pos)
{
__offmax_t oldpos;
int corr;
if ((corr = stream->__modeflags & __MASK_READING) != 0) {
--corr; /* Correct for ungots. Assume narrow, and fix below. */
}
#ifdef __UCLIBC_HAS_WCHAR__
if (corr && __STDIO_STREAM_IS_WIDE(stream)) {
/* A wide stream and we have at least one ungotten wchar.
* If it is a user ungot, we need to fail since position
* is unspecified as per C99. */
if ((corr > 1) || stream->__ungot[1]) { /* User ungetwc, */
return -1; /* so position is undefined. */
}
corr -= (1 + stream->__ungot_width[1]);
if (stream->__state.__mask > 0) { /* Incomplete (bad?) mb char. */
corr -= stream->__ungot_width[0];
}
}
#endif
#ifdef __STDIO_BUFFERS
corr += (((__STDIO_STREAM_IS_WRITING(stream))
? stream->__bufstart : stream->__bufread)
- stream->__bufpos);
#endif
oldpos = *pos;
/* Range checking cases:
* (pos - corr > pos) && (corr > 0) : underflow? return -corr < 0
* (pos - corr > pos) && (corr < 0) : ok .. return -corr > 0
* (pos - corr <= pos) && (corr >= 0) : ok .. return corr > 0
* (pos - corr <= pos) && (corr < 0) : overflow .. return corr < 0
*/
if ((*pos -= corr) > oldpos) {
corr = -corr;
}
if (corr < 0) {
__set_errno(EOVERFLOW);
}
return corr;
}
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