int
_unit_bksp(unit *cup)
{
int errn;
unsigned char tbuf[TBUFSZB], *tp;
struct ffsw fst;
int first_read;
if (cup->useq == 0) /* If direct access file */
return(FEBKSPIV); /* BACKSPACE invalid on dir. acc.*/
/*
* Wait for completion of a preceding asynchronous BUFFER IN/OUT.
*/
WAITIO(cup, return(cup->uffsw.sw_error));
if (cup->uwrt) {
if (cup->utrunc) {
/*
* Truncate file after last sequential write before
* this BACKSPACE.
*/
errn = _unit_trunc(cup);
if (errn != 0)
return(errn);
}
cup->uwrt = 0;
}
/*
* According to the file structure make the appropriate request to
* backspace one logical record.
*/
switch( cup->ufs ) {
case FS_FDC:
if ((cup->uend != LOGICAL_ENDFILE) || (cup->uspcproc==1)) {
errn = XRCALL(cup->ufp.fdc, backrtn) cup->ufp.fdc,
&fst);
if (errn < 0)
return(fst.sw_error);
}
break;
case FS_TEXT:
case STD:
/*
* Can't backspace pipes. sockets, ttys.
*/
if (!cup->useek)
return(FENOBKPI); /* can't backspace pipe */
if (!cup->ufmt) /* if not formatted */
return(FENOBKSP); /* can't backspace unblocked files */
if (cup->uend) goto ok;
first_read = 1;
for ( ; ; ) {
ssize_t i;
size_t ret;
_ftelltype x, y;
y = LIBFTELL(cup->ufp.std);
#ifdef KEY /* Bug 1678 */
if (((_ftelltype) -1) == y) {
return FEINTUNK;
}
#endif /* KEY Bug 1678 */
x = y;
if (x < TBUFSZB)
x = 0;
else
x -= TBUFSZB;
#ifdef KEY /* Bug 1678 */
if (LIBFSEEK(cup->ufp.std, x, 0)) {
return FEINTUNK;
}
#else /* KEY Bug 1678 */
(void) LIBFSEEK(cup->ufp.std, x, 0);
#endif /* KEY Bug 1678 */
/*
* starting at the current character position
* minus 2 chars, search backwards for a newline
* character.
*/
ret = fread(tbuf, 1,(size_t)(y - x), cup->ufp.std);
if (ret < (y-x) && ferror(cup->ufp.std))
return(FEBSPNRD);
/* only the first time fread, we need to skip the
* first 2 chars
*/
if (first_read) i = ret - 2;
else i = ret;
first_read = 0;
tp = tbuf;
for ( ; i >= 0; i--) {
if ( *(tp+i) != '\n') continue;
#ifdef KEY /* Bug 1678 */
if (LIBFSEEK(cup->ufp.std, (_ftelltype)i+1-ret,
1)) {
return FEINTUNK;
}
#else /* KEY Bug 1678 */
(void) LIBFSEEK(cup->ufp.std, (_ftelltype)i+1-ret, 1);
#endif /* KEY Bug 1678 */
goto ok;
}
if (x == 0) {
#ifdef KEY /* Bug 1678 */
if (LIBFSEEK(cup->ufp.std, FTELLZERO, 0)) {
return FEINTUNK;
}
#else /* KEY Bug 1678 */
(void) LIBFSEEK(cup->ufp.std, FTELLZERO, 0);
#endif /* KEY Bug 1678 */
goto ok;
}
else
if (ret <= 0) /* Should never occur */
return(FEINTUNK);
#ifdef KEY /* Bug 1678 */
if (LIBFSEEK(cup->ufp.std, x, 0)) {
return FEINTUNK;
}
#else /* KEY Bug 1678 */
(void) LIBFSEEK(cup->ufp.std, x, 0);
#endif /* KEY Bug 1678 */
}
case FS_BIN:
return(FENOBKSP);
case FS_AUX:
errn = FEMIXAUX; /* BACKSPACE not allowed on a WAIO,
* MSIO, DRIO, or AQIO file. */
break;
default:
return(FEINTFST);
}
/*
* _unit_trunc()
*
* Truncate a file at its current position.
*
* Return value
*
* 0 for OK
* error code if an error is encountered
*/
int
_unit_trunc(unit *cup)
{
_ftelltype flength;
FILE *iop;
if (cup->useq == 0) /* If direct access file */
return(0); /* Don't truncate direct access files */
switch(cup->ufs) {
case FS_TEXT:
case STD:
/*
* Truncate the file with trunc(2) if the file is a a regular
* file. The trunc(2) system call is not allowed on terminal
* files, FIFO piped files, "/dev/null", or sockets.
*/
if (cup->useek) {
iop = cup->ufp.std;
/*
* If stream is in O_APPEND mode (as when 'a.out>>ofil')
* we call fseek to current position. Turns out that on
* SysV systems, ftell does not flush the buffer. Thus
* the file offset does not get bumped to EOF as the
* result of the flush.
*/
if (LIBFSEEK(iop, 0, SEEK_CUR) != 0)
return(errno);
flength = LIBFTELL(iop); /* get current position */
/* position fd to the location of the truncation */
if (LIBFSEEK(iop, flength, SEEK_SET) != 0)
return(errno);
#ifdef _UNICOS
if (trunc(fileno(iop)) == -1L)
#else
if (LIBFTRUNC(fileno(iop), flength) == -1)
#endif
return(errno);
#ifdef KEY /* Bug 5386 */
/* Until Fedora Core 3, this code never encountered
* a Unix system that required an "fflush" here. But
* without it, the FC3 stdio code doesn't notice that
* we've bypassed stdio and truncated the file, and
* to be honest, it seems like blind dumb luck that
* other systems haven't encountered a problem here.
*/
fflush(iop);
#endif /* KEY Bug 5386 */
}
break;
case FS_FDC:
if (XRCALL(cup->ufp.fdc, weodrtn)cup->ufp.fdc,
&cup->uffsw) < 0)
return(cup->uffsw.sw_error);
break;
default:
return(FEINTFST);
}
return(0);
}
