diff options
Diffstat (limited to 'i386/dos/dos_open.c')
| -rw-r--r-- | i386/dos/dos_open.c | 158 |
1 files changed, 158 insertions, 0 deletions
diff --git a/i386/dos/dos_open.c b/i386/dos/dos_open.c new file mode 100644 index 0000000..7e6ef2b --- /dev/null +++ b/i386/dos/dos_open.c @@ -0,0 +1,158 @@ +/* + * Copyright (c) 1995-1994 The University of Utah and + * the Computer Systems Laboratory at the University of Utah (CSL). + * All rights reserved. + * + * Permission to use, copy, modify and distribute this software is hereby + * granted provided that (1) source code retains these copyright, permission, + * and disclaimer notices, and (2) redistributions including binaries + * reproduce the notices in supporting documentation, and (3) all advertising + * materials mentioning features or use of this software display the following + * acknowledgement: ``This product includes software developed by the + * Computer Systems Laboratory at the University of Utah.'' + * + * THE UNIVERSITY OF UTAH AND CSL ALLOW FREE USE OF THIS SOFTWARE IN ITS "AS + * IS" CONDITION. THE UNIVERSITY OF UTAH AND CSL DISCLAIM ANY LIABILITY OF + * ANY KIND FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE. + * + * CSL requests users of this software to return to csl-dist@cs.utah.edu any + * improvements that they make and grant CSL redistribution rights. + * + * Author: Bryan Ford, University of Utah CSL + */ + +#include <sys/types.h> +#include <sys/stat.h> +#include <fcntl.h> +#include <stdio.h> +#include <errno.h> + +#include "dos_io.h" +#include "vm_param.h" +#include "debug.h" + +int dos_open(const char *s, int flags, int mode, dos_fd_t *out_fh) +{ + struct real_call_data real_call_data; + int err = EINVAL; /*XXX*/ + vm_offset_t dos_buf_phys = (vm_offset_t)kvtophys(dos_buf); + + assert(dos_buf); assert(dos_buf_phys); + assert(dos_buf_phys < 0x100000); + + dos_init_rcd(&real_call_data); + + if (strlen(s)+1 > DOS_BUF_SIZE) + return E2BIG; + strcpy(dos_buf, s); + real_call_data.ds = dos_buf_phys >> 4; + real_call_data.edx = dos_buf_phys & 15; + + /* Possible situations: + + - 3d + C 3d || 3c + T 3d (ensure that it exists), close, 3c + CT 3c + X 3d + C X 3d (ensure that it doesn't exist), 3c + TX 3d (ensure that it exists), close, 3c + CTX 3d (ensure that it doesn't exist), 3c + */ + + if ((flags & (O_CREAT | O_EXCL | O_TRUNC)) != (O_CREAT | O_TRUNC)) + { + /* First try opening the file with function 0x3D. */ + real_call_data.eax = 0x3d40 | (flags & O_ACCMODE); + real_call_data.ecx = 0; + real_int(0x21, &real_call_data); + err = dos_check_err(&real_call_data); + if (!err) + *out_fh = real_call_data.eax & 0xffff; + } + + /* Now based on the result, determine what to do next. */ + switch (flags & (O_CREAT | O_EXCL | O_TRUNC)) + { + case 0: + case 0 | O_EXCL: + if (!err) + goto success; + else + return err; + case O_CREAT: + if (!err) + goto success; + else + break; + case O_CREAT | O_EXCL: + case O_CREAT | O_TRUNC | O_EXCL: + if (!err) + { + /* The file exists, but wasn't supposed to. + Close it and return an error. */ + dos_close(real_call_data.eax & 0xffff); + return EEXIST; + } + else + break; + case O_TRUNC: + case O_TRUNC | O_EXCL: + if (!err) + { + /* We've verified that the file exists - + now close it and reopen it with CREAT + so it'll be truncated as requested. */ + dos_close(real_call_data.eax & 0xffff); + break; + } + else + return err; + case O_CREAT | O_TRUNC: + /* This is the one case in which + we didn't try to open the file above at all. + Just fall on through and open it with CREAT. */ + break; + } + + /* Now try opening the file with DOS's CREAT call, + which truncates the file if it already exists. */ + real_call_data.eax = 0x3c00; + real_call_data.ecx = mode & S_IWUSR ? 0 : 1; + real_int(0x21, &real_call_data); + if (!(err = dos_check_err(&real_call_data))) + { + *out_fh = real_call_data.eax & 0xffff; + + /* We don't have to worry about O_APPEND here, + because we know the file starts out empty. */ + + return 0; + } + + return err; + + success: + + /* If the caller requested append access, + just seek to the end of the file once on open. + We can't implement full POSIX behavior here without help, + since DOS file descriptors don't have an append mode. + To get full POSIX behavior, + the caller must seek to the end of the file before every write. + However, seeking to the end only on open + is probably enough for most typical uses. */ + if (flags & O_APPEND) + { + vm_offset_t newpos; + err = dos_seek(*out_fh, 0, SEEK_END, &newpos); + if (err) + { + dos_close(*out_fh); + return err; + } + } + + return 0; +} + |