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Diffstat (limited to 'private/crt32/stdio/ungetc.c')
| -rw-r--r-- | private/crt32/stdio/ungetc.c | 174 |
1 files changed, 174 insertions, 0 deletions
diff --git a/private/crt32/stdio/ungetc.c b/private/crt32/stdio/ungetc.c new file mode 100644 index 000000000..e8b912ffe --- /dev/null +++ b/private/crt32/stdio/ungetc.c @@ -0,0 +1,174 @@ +/*** +*ungetc.c - unget a character from a stream +* +* Copyright (c) 1985-1993, Microsoft Corporation. All rights reserved. +* +*Purpose: +* defines ungetc() - pushes a character back onto an input stream +* +*Revision History: +* 09-02-83 RN initial version +* 04-16-87 JCR added support for _IOUNGETC flag +* 08-04-87 JCR (1) Added _IOSTRG check before setting _IOUNGETC flag. +* (2) Allow an ugnetc() before a read has occurred (get a +* buffer (ANSI). [MSC only] +* 09-28-87 JCR Corrected _iob2 indexing (now uses _iob_index() macro). +* 11-04-87 JCR Multi-thread support +* 12-11-87 JCR Added "_LOAD_DS" to declaration +* 05-25-88 JCR Allow an ungetc() before read for file opened "r+". +* 05-31-88 PHG Merged DLL and normal versions +* 06-06-88 JCR Optimized _iob2 references +* 06-15-88 JCR Near reference to _iob[] entries; improve REG variables +* 08-25-88 GJF Don't use FP_OFF() macro for the 386 +* 04-11-89 JCR Removed _IOUNGETC flag, fseek() no longer needs it +* 08-17-89 GJF Clean up, now specific to OS/2 2.0 (i.e., 386 flat +* model). Also fixed copyright and indents. +* 02-16-90 GJF Fixed copyright +* 03-20-90 GJF Made calling type _CALLTYPE1, added #include +* <cruntime.h> and removed #include <register.h>. +* 07-23-90 SBM Replaced <assertm.h> by <assert.h> +* 08-13-90 SBM Compiles cleanly with -W3 +* 10-03-90 GJF New-style function declarators. +* 11-07-92 SRW Dont modify buffer if stream opened by sscanf +* 04-26-93 CFW Wide char enable. +* 04-30-93 CFW Remove wide char support to ungetwc.c. +* +*******************************************************************************/ + +#include <cruntime.h> +#include <stdio.h> +#include <file2.h> +#include <assert.h> +#include <internal.h> +#include <os2dll.h> + +#ifdef MTHREAD /* multi-thread; define both ungetc and _lk_ungetc */ + +/*** +*int ungetc(ch, stream) - put a character back onto a stream +* +*Purpose: +* Guaranteed one char pushback on a stream as long as open for reading. +* More than one char pushback in a row is not guaranteed, and will fail +* if it follows an ungetc which pushed the first char in buffer. Failure +* causes return of EOF. +* +*Entry: +* char ch - character to push back +* FILE *stream - stream to push character onto +* +*Exit: +* returns ch +* returns EOF if tried to push EOF, stream not opened for reading or +* or if we have already ungetc'd back to beginning of buffer. +* +*Exceptions: +* +*******************************************************************************/ + +int _CRTAPI1 ungetc ( + REG2 int ch, + REG1 FILE *stream + ) +{ + int retval; + int index; + + assert(stream != NULL); + + index = _iob_index(stream); + + _lock_str(index); + + retval = _ungetc_lk (ch, stream); + + _unlock_str(index); + + return(retval); +} + +/*** +*_ungetc_lk() - Ungetc() core routine (locked version) +* +*Purpose: +* Core ungetc() routine; assumes stream is already locked. +* +* [See ungetc() above for more info.] +* +*Entry: [See ungetc()] +* +*Exit: [See ungetc()] +* +*Exceptions: +* +*******************************************************************************/ + +int _CRTAPI1 _ungetc_lk ( + REG2 int ch, + FILE *str + ) + +{ + +#else /* non multi-thread; just define ungetc */ + +int _CRTAPI1 ungetc ( + REG2 int ch, + FILE *str + ) + +{ + +#endif /* rejoin common code */ + + REG1 FILE *stream; + + assert(str != NULL); + + /* Init stream pointer and file descriptor */ + stream = str; + + /* Stream must be open for read and can NOT be currently in write mode. + Also, ungetc() character cannot be EOF. */ + + if ( + (ch == EOF) || + !( + (stream->_flag & _IOREAD) || + ((stream->_flag & _IORW) && !(stream->_flag & _IOWRT)) + ) + ) + return(EOF); + + /* If stream is unbuffered, get one. */ + + if (stream->_base == NULL) + _getbuf(stream); + + /* now we know _base != NULL; since file must be buffered */ + + if (stream->_ptr == stream->_base) { + if (stream->_cnt) + /* my back is against the wall; i've already done + * ungetc, and there's no room for this one + */ + return(EOF); + + stream->_ptr++; + } + + if (stream->_flag & _IOSTRG) { + /* If stream opened by sscanf do not modify buffer */ + if (*--stream->_ptr != (char)ch) { + ++stream->_ptr; + return(EOF); + } + } else + *--stream->_ptr = (char)ch; + + stream->_cnt++; + stream->_flag &= ~_IOEOF; + stream->_flag |= _IOREAD; /* may already be set */ + + return(0xff & ch); +} |