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/***
*read.c - read from a file handle** Copyright (c) 1989-2001, Microsoft Corporation. All rights reserved.**Purpose:* defines _read() - read from a file handle**Revision History:* 06-19-89 PHG Module created, based on asm version* 03-13-90 GJF Made calling type _CALLTYPE2 (for now), added #include* <cruntime.h> and fixed compiler warnings. Also, fixed* the copyright.* 04-03-90 GJF Now _CALLTYPE1.* 07-24-90 SBM Removed '32' from API names* 08-14-90 SBM Compiles cleanly with -W3* 10-01-90 GJF New-style function declarator.* 12-04-90 GJF Appended Win32 version onto the source with #ifdef-s.* It is enough different that there is little point in* trying to more closely merge the two versions.* 12-04-90 SRW Changed to include <oscalls.h> instead of <doscalls.h>* 12-06-90 SRW Changed to use _osfile and _osfhnd instead of _osfinfo* 12-28-90 SRW Added cast of void * to char * for Mips C Compiler* 01-16-91 GJF ANSI naming.* 01-29-91 SRW Changed to not read ahead on char devices [_WIN32_]* 02-01-91 SRW Changed to use ERROR_HANDLE_EOF error code (_WIN32_)* 02-25-91 MHL Adapt to ReadFile/WriteFile changes (_WIN32_)* 04-09-91 PNT Added _MAC_ conditional* 04-16-91 SRW Character device bug fix [_WIN32_]* 05-23-91 GJF Don't set FEOFLAG if handle corresponds to a device.* 10-24-91 GJF Added LPDWORD casts to make MIPS compiler happy.* ASSUMES THAT sizeof(int) == sizeof(DWORD).* 02-13-92 GJF Replaced _nfile by _nhandle for Win32.* 06-16-92 GJF Bug fix - if CR was the very last char read, and the* last char in the file, CRLF was getting written to* user's buffer.* 12-18-93 GJF Don't treat ERROR_BROKEN_PIPE as an error. Instead,* just return 0.* 04-06-93 SKS Replace _CRTAPI* with __cdecl* 08-10-94 GJF Don't check the caller's buffer for a LF if NOTHING* was actually read in!* 09-06-94 CFW Remove Cruiser support.* 09-06-94 CFW Replace MTHREAD with _MT.* 12-03-94 SKS Clean up OS/2 references* 01-04-95 GJF _WIN32_ -> _WIN32* 02-15-95 GJF Appended Mac version of source file (somewhat cleaned* up), with appropriate #ifdef-s.* 06-11-95 GJF Changed _osfile[], _osfhnd[] and _pipech[] to* _osfile(), _osfhnd() and _pipech(), which reference* __pioinfo[].* 06-27-95 GJF Added check that the file handle is open.* 07-09-96 GJF Replaced defined(_WIN32) with !defined(_MAC) and* defined(_M_M68K) || defined(_M_MPPC) with * defined(_MAC). Also, detab-ed and cleaned up the * format a bit.* 12-29-97 GJF Exception-safe locking.* 03-03-98 RKP Forced amount read to be int even with 64 bits* 05-17-99 PML Remove all Macintosh support.********************************************************************************/
#include <cruntime.h>
#include <oscalls.h>
#include <mtdll.h>
#include <io.h>
#include <internal.h>
#include <stdlib.h>
#include <errno.h>
#include <msdos.h>
#define LF 10 /* line feed */
#define CR 13 /* carriage return */
#define CTRLZ 26 /* ctrl-z means eof for text */
/***
*int _read(fh, buf, cnt) - read bytes from a file handle**Purpose:* Attempts to read cnt bytes from fh into a buffer.* If the file is in text mode, CR-LF's are mapped to LF's, thus* affecting the number of characters read. This does not* affect the file pointer.** NOTE: The stdio _IOCTRLZ flag is tied to the use of FEOFLAG.* Cross-reference the two symbols before changing FEOFLAG's use.**Entry:* int fh - file handle to read from* char *buf - buffer to read into* int cnt - number of bytes to read**Exit:* Returns number of bytes read (may be less than the number requested* if the EOF was reached or the file is in text mode).* returns -1 (and sets errno) if fails.**Exceptions:********************************************************************************/
#ifdef _MT
/* define normal version that locks/unlocks, validates fh */int __cdecl _read ( int fh, void *buf, unsigned cnt ){ int r; /* return value */
/* validate handle */ if ( ((unsigned)fh >= (unsigned)_nhandle) || !(_osfile(fh) & FOPEN) ) { /* out of range -- return error */ errno = EBADF; _doserrno = 0; /* not o.s. error */ return -1; }
_lock_fh(fh); /* lock file */
__try { if ( _osfile(fh) & FOPEN ) r = _read_lk(fh, buf, cnt); /* read bytes */ else { errno = EBADF; _doserrno = 0; r = -1; } } __finally { _unlock_fh(fh); /* unlock file */ }
return r;}
/* now define version that doesn't lock/unlock, validate fh */int __cdecl _read_lk ( int fh, void *buf, unsigned cnt ){ int bytes_read; /* number of bytes read */ char *buffer; /* buffer to read to */ int os_read; /* bytes read on OS call */ char *p, *q; /* pointers into buffer */ char peekchr; /* peek-ahead character */ ULONG filepos; /* file position after seek */ ULONG dosretval; /* o.s. return value */
#else
/* now define normal version */int __cdecl _read ( int fh, void *buf, unsigned cnt ){ int bytes_read; /* number of bytes read */ char *buffer; /* buffer to read to */ int os_read; /* bytes read on OS call */ char *p, *q; /* pointers into buffer */ char peekchr; /* peek-ahead character */ ULONG filepos; /* file position after seek */ ULONG dosretval; /* o.s. return value */
/* validate fh */ if ( ((unsigned)fh >= (unsigned)_nhandle) || !(_osfile(fh) & FOPEN) ) { /* bad file handle */ errno = EBADF; _doserrno = 0; /* not o.s. error */ return -1; }
#endif
bytes_read = 0; /* nothing read yet */ buffer = buf;
if (cnt == 0 || (_osfile(fh) & FEOFLAG)) { /* nothing to read or at EOF, so return 0 read */ return 0; }
if ((_osfile(fh) & (FPIPE|FDEV)) && _pipech(fh) != LF) { /* a pipe/device and pipe lookahead non-empty: read the lookahead
* char */ *buffer++ = _pipech(fh); ++bytes_read; --cnt; _pipech(fh) = LF; /* mark as empty */ }
/* read the data */
if ( !ReadFile( (HANDLE)_osfhnd(fh), buffer, cnt, (LPDWORD)&os_read, NULL ) ) { /* ReadFile has reported an error. recognize two special cases.
* * 1. map ERROR_ACCESS_DENIED to EBADF * * 2. just return 0 if ERROR_BROKEN_PIPE has occurred. it * means the handle is a read-handle on a pipe for which * all write-handles have been closed and all data has been * read. */
if ( (dosretval = GetLastError()) == ERROR_ACCESS_DENIED ) { /* wrong read/write mode should return EBADF, not EACCES */ errno = EBADF; _doserrno = dosretval; return -1; } else if ( dosretval == ERROR_BROKEN_PIPE ) { return 0; } else { _dosmaperr(dosretval); return -1; } }
bytes_read += os_read; /* update bytes read */
if (_osfile(fh) & FTEXT) { /* now must translate CR-LFs to LFs in the buffer */
/* set CRLF flag to indicate LF at beginning of buffer */ if ( (os_read != 0) && (*(char *)buf == LF) ) _osfile(fh) |= FCRLF; else _osfile(fh) &= ~FCRLF;
/* convert chars in the buffer: p is src, q is dest */ p = q = buf; while (p < (char *)buf + bytes_read) { if (*p == CTRLZ) { /* if fh is not a device, set ctrl-z flag */ if ( !(_osfile(fh) & FDEV) ) _osfile(fh) |= FEOFLAG; break; /* stop translating */ } else if (*p != CR) *q++ = *p++; else { /* *p is CR, so must check next char for LF */ if (p < (char *)buf + bytes_read - 1) { if (*(p+1) == LF) { p += 2; *q++ = LF; /* convert CR-LF to LF */ } else *q++ = *p++; /* store char normally */ } else { /* This is the hard part. We found a CR at end of
buffer. We must peek ahead to see if next char is an LF. */ ++p;
dosretval = 0; if ( !ReadFile( (HANDLE)_osfhnd(fh), &peekchr, 1, (LPDWORD)&os_read, NULL ) ) dosretval = GetLastError();
if (dosretval != 0 || os_read == 0) { /* couldn't read ahead, store CR */ *q++ = CR; } else { /* peekchr now has the extra character -- we now
have several possibilities: 1. disk file and char is not LF; just seek back and copy CR 2. disk file and char is LF; seek back and discard CR 3. disk file, char is LF but this is a one-byte read: store LF, don't seek back 4. pipe/device and char is LF; store LF. 5. pipe/device and char isn't LF, store CR and put char in pipe lookahead buffer. */ if (_osfile(fh) & (FDEV|FPIPE)) { /* non-seekable device */ if (peekchr == LF) *q++ = LF; else { *q++ = CR; _pipech(fh) = peekchr; } } else { /* disk file */ if (q == buf && peekchr == LF) { /* nothing read yet; must make some
progress */ *q++ = LF; } else { /* seek back */ filepos = _lseek_lk(fh, -1, FILE_CURRENT); if (peekchr != LF) *q++ = CR; } } } } } }
/* we now change bytes_read to reflect the true number of chars
in the buffer */ bytes_read = (int)(q - (char *)buf); }
return bytes_read; /* and return */}
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