Subversion Repositories SvarDOS

/* This file is part of the SvarCOM project and is published under the terms

 * of the MIT license.

 *

 * Copyright (C) 2021 Mateusz Viste

 *

 * Permission is hereby granted, free of charge, to any person obtaining a

 * copy of this software and associated documentation files (the "Software"),

 * to deal in the Software without restriction, including without limitation

 * the rights to use, copy, modify, merge, publish, distribute, sublicense,

 * and/or sell copies of the Software, and to permit persons to whom the

 * Software is furnished to do so, subject to the following conditions:

 *

 * The above copyright notice and this permission notice shall be included in

 * all copies or substantial portions of the Software.

 *

 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR

 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,

 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE

 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER

 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING

 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER

 * DEALINGS IN THE SOFTWARE.

 */

#include "doserr.h"

#include "helpers.h"

#include "redir.h"

static unsigned short oldstdout = 0xffff;

/* parse commandline and performs necessary redirections. cmdline is

 * modified so all redirections are cut out.

 * returns 0 on success, non-zero otherwise */

int redir_parsecmd(char *cmdline, char *BUFFER) {

  unsigned short i;

  unsigned short rediroffset_stdin = 0;

  unsigned short rediroffset_stdout = 0;

  unsigned short pipesoffsets[16];

  unsigned short pipescount = 0;

  /* NOTE:

   *

   * 1. while it is possible to type a command with multiple

   *    redirections, MSDOS executes only the last redirection.

   *

   * 2. the order in which >, < and | are provided on the command line does

   *    not seem to matter for MSDOS. piped commands are executed first (in

   *    the order they appear) and the result of the last one is redirected to

   *    whenever the last > points at.

   */

  /* preset oldstdout to 0xffff in case no redirection is required */

  oldstdout = 0xffff;

  for (i = 0;; i++) {

    if (cmdline[i] == '>') {

      cmdline[i] = 0;

      rediroffset_stdout = i + 1;

    } else if (cmdline[i] == '<') {

      cmdline[i] = 0;

      rediroffset_stdin = i + 1;

    } else if (cmdline[i] == '|') {

      cmdline[i] = 0;

      pipesoffsets[pipescount++] = i + 1;

    } else if (cmdline[i] == 0) {

      break;

    }

  }

  if (rediroffset_stdin != 0) {

    outputnl("ERROR: stdin redirection is not supported yet");

    return(-1);

  }

  if (pipescount != 0) {

    outputnl("ERROR: pipe redirections are not supported yet");

    return(-1);

  }

  if (rediroffset_stdout != 0) {

    unsigned short openflag = 0x12;  /* used during the int 21h,ah=6c call */

    unsigned short errcode = 0;

    unsigned short handle = 0;

    char *ptr;

    /* append? */

    if (cmdline[rediroffset_stdout] == '>') {

      openflag = 0x11;

      rediroffset_stdout++;

    }

    /* copy dst file to BUFFER */

    ptr = cmdline + rediroffset_stdout;

    while (*ptr == ' ') ptr++; /* skip leading white spaces */

    for (i = 0;; i++) {

      BUFFER[i] = ptr[i];

      if ((BUFFER[i] == ' ') || (BUFFER[i] == 0)) break;

    }

    BUFFER[i] = 0;

    /* */

    _asm {

      push ax

      push bx

      push cx

      push dx

      push si

      mov ax, 0x6c00     /* Extended Open/Create */

      mov bx, 1          /* access mode (0=read, 1=write, 2=r+w */

      xor cx, cx         /* attributes when(if) creating the file (0=normal) */

      mov dx, [openflag] /* action if file exists (0x11=open, 0x12=truncate)*/

      mov si, BUFFER     /* ASCIIZ filename */

      int 0x21           /* AX=handle on success (CF clear), otherwise dos err */

      mov [handle], ax   /* save the file handler */

      jnc DUPSTDOUT

      mov [errcode], ax

      jmp DONE

      DUPSTDOUT:

      /* save (duplicate) current stdout so I can revert it later */

      mov ah, 0x45       /* duplicate file handle */

      mov bx, 1          /* handle to dup (1=stdout) */

      int 0x21           /* ax = new file handle */

      mov [oldstdout], ax

      /* redirect the stdout handle */

      mov bx, [handle]   /* dst handle */

      mov cx, 1          /* src handle (1=stdout) */

      mov ah, 0x46       /* redirect a handle */

      int 0x21

      /* close the original file handle (no longer needed) */

      mov ah, 0x3e       /* close a file handle (handle in BX) */

      int 0x21

      DONE:

      pop si

      pop dx

      pop cx

      pop bx

      pop ax

    }

    if (errcode != 0) {

      outputnl(doserr(errcode));

      return(-1);

    }

  }

  return(0);

}

/* restores previous stdout/stdin handlers if they have been redirected */

void redir_revert(void) {

  _asm {

    /* if oldstdout is 0xffff then not redirected */

    cmp word ptr [oldstdout], 0xffff

    je DONE

    /* redirect the stdout handle */

    mov bx, [oldstdout] /* dst handle */

    mov cx, 1           /* src handle (1=stdout) */

    mov ah, 0x46        /* redirect a handle */

    int 0x21

    mov [oldstdout], 0xffff

    DONE:

  }

}