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Annotation of Gnu-Mach/i386/dos/dos_open.c, revision 1.1

1.1     ! root        1: /* 
        !             2:  * Copyright (c) 1995-1994 The University of Utah and
        !             3:  * the Computer Systems Laboratory at the University of Utah (CSL).
        !             4:  * All rights reserved.
        !             5:  *
        !             6:  * Permission to use, copy, modify and distribute this software is hereby
        !             7:  * granted provided that (1) source code retains these copyright, permission,
        !             8:  * and disclaimer notices, and (2) redistributions including binaries
        !             9:  * reproduce the notices in supporting documentation, and (3) all advertising
        !            10:  * materials mentioning features or use of this software display the following
        !            11:  * acknowledgement: ``This product includes software developed by the
        !            12:  * Computer Systems Laboratory at the University of Utah.''
        !            13:  *
        !            14:  * THE UNIVERSITY OF UTAH AND CSL ALLOW FREE USE OF THIS SOFTWARE IN ITS "AS
        !            15:  * IS" CONDITION.  THE UNIVERSITY OF UTAH AND CSL DISCLAIM ANY LIABILITY OF
        !            16:  * ANY KIND FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
        !            17:  *
        !            18:  * CSL requests users of this software to return to [email protected] any
        !            19:  * improvements that they make and grant CSL redistribution rights.
        !            20:  *
        !            21:  *      Author: Bryan Ford, University of Utah CSL
        !            22:  */
        !            23: 
        !            24: #include <sys/types.h>
        !            25: #include <sys/stat.h>
        !            26: #include <fcntl.h>
        !            27: #include <stdio.h>
        !            28: #include <errno.h>
        !            29: 
        !            30: #include "dos_io.h"
        !            31: #include "vm_param.h"
        !            32: #include "debug.h"
        !            33: 
        !            34: int dos_open(const char *s, int flags, int mode, dos_fd_t *out_fh)
        !            35: {
        !            36:        struct real_call_data real_call_data;
        !            37:        int err = EINVAL; /*XXX*/
        !            38:        vm_offset_t dos_buf_phys = (vm_offset_t)kvtophys(dos_buf);
        !            39: 
        !            40:        assert(dos_buf); assert(dos_buf_phys);
        !            41:        assert(dos_buf_phys < 0x100000);
        !            42: 
        !            43:        dos_init_rcd(&real_call_data);
        !            44: 
        !            45:        if (strlen(s)+1 > DOS_BUF_SIZE)
        !            46:                return E2BIG;
        !            47:        strcpy(dos_buf, s);
        !            48:        real_call_data.ds = dos_buf_phys >> 4;
        !            49:        real_call_data.edx = dos_buf_phys & 15;
        !            50: 
        !            51:        /* Possible situations:
        !            52: 
        !            53:        -       3d
        !            54:        C       3d || 3c
        !            55:         T      3d (ensure that it exists), close, 3c
        !            56:        CT      3c
        !            57:          X     3d
        !            58:        C X     3d (ensure that it doesn't exist), 3c
        !            59:         TX     3d (ensure that it exists), close, 3c
        !            60:        CTX     3d (ensure that it doesn't exist), 3c
        !            61:        */
        !            62: 
        !            63:        if ((flags & (O_CREAT | O_EXCL | O_TRUNC)) != (O_CREAT | O_TRUNC))
        !            64:        {
        !            65:                /* First try opening the file with function 0x3D.  */
        !            66:                real_call_data.eax = 0x3d40 | (flags & O_ACCMODE);
        !            67:                real_call_data.ecx = 0;
        !            68:                real_int(0x21, &real_call_data);
        !            69:                err = dos_check_err(&real_call_data);
        !            70:                if (!err)
        !            71:                        *out_fh = real_call_data.eax & 0xffff;
        !            72:        }
        !            73: 
        !            74:        /* Now based on the result, determine what to do next.  */
        !            75:        switch (flags & (O_CREAT | O_EXCL | O_TRUNC))
        !            76:        {
        !            77:                case 0:
        !            78:                case 0 | O_EXCL:
        !            79:                        if (!err)
        !            80:                                goto success;
        !            81:                        else
        !            82:                                return err;
        !            83:                case O_CREAT:
        !            84:                        if (!err)
        !            85:                                goto success;
        !            86:                        else
        !            87:                                break;
        !            88:                case O_CREAT | O_EXCL:
        !            89:                case O_CREAT | O_TRUNC | O_EXCL:
        !            90:                        if (!err)
        !            91:                        {
        !            92:                                /* The file exists, but wasn't supposed to.
        !            93:                                   Close it and return an error.  */
        !            94:                                dos_close(real_call_data.eax & 0xffff);
        !            95:                                return EEXIST;
        !            96:                        }
        !            97:                        else
        !            98:                                break;
        !            99:                case O_TRUNC:
        !           100:                case O_TRUNC | O_EXCL:
        !           101:                        if (!err)
        !           102:                        {
        !           103:                                /* We've verified that the file exists -
        !           104:                                   now close it and reopen it with CREAT
        !           105:                                   so it'll be truncated as requested.  */
        !           106:                                dos_close(real_call_data.eax & 0xffff);
        !           107:                                break;
        !           108:                        }
        !           109:                        else
        !           110:                                return err;
        !           111:                case O_CREAT | O_TRUNC:
        !           112:                        /* This is the one case in which
        !           113:                           we didn't try to open the file above at all.
        !           114:                           Just fall on through and open it with CREAT.  */
        !           115:                        break;
        !           116:        }
        !           117: 
        !           118:        /* Now try opening the file with DOS's CREAT call,
        !           119:           which truncates the file if it already exists.  */
        !           120:        real_call_data.eax = 0x3c00;
        !           121:        real_call_data.ecx = mode & S_IWUSR ? 0 : 1;
        !           122:        real_int(0x21, &real_call_data);
        !           123:        if (!(err = dos_check_err(&real_call_data)))
        !           124:        {
        !           125:                *out_fh = real_call_data.eax & 0xffff;
        !           126: 
        !           127:                /* We don't have to worry about O_APPEND here,
        !           128:                   because we know the file starts out empty.  */
        !           129: 
        !           130:                return 0;
        !           131:        }
        !           132: 
        !           133:        return err;
        !           134: 
        !           135:        success:
        !           136: 
        !           137:        /* If the caller requested append access,
        !           138:           just seek to the end of the file once on open.
        !           139:           We can't implement full POSIX behavior here without help,
        !           140:           since DOS file descriptors don't have an append mode.
        !           141:           To get full POSIX behavior,
        !           142:           the caller must seek to the end of the file before every write.
        !           143:           However, seeking to the end only on open
        !           144:           is probably enough for most typical uses.  */
        !           145:        if (flags & O_APPEND)
        !           146:        {
        !           147:                vm_offset_t newpos;
        !           148:                err = dos_seek(*out_fh, 0, SEEK_END, &newpos);
        !           149:                if (err)
        !           150:                {
        !           151:                        dos_close(*out_fh);
        !           152:                        return err;
        !           153:                }
        !           154:        }
        !           155: 
        !           156:        return 0;
        !           157: }
        !           158: 

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