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 <string.h> /* memset() */

#include "doserr.h"

#include "helpers.h"

#include "rmodinit.h"

#include "redir.h"

static unsigned short oldstdout = 0xffff;

/* parse commandline and performs necessary redirections. cmdline is

 * modified so all redirections are cut out. */

void redir_parsecmd(struct redir_data *d, char *cmdline) {

  unsigned short i;

  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;

  /* clear out the redir_data struct */

  memset(d, 0, sizeof(*d));

  /* parse the command line and fill struct with pointers */

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

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

      cmdline[i] = 0;

      if (cmdline[i + 1] == '>') {

        i++;

        d->stdout_openflag = 0x11;  /* used during int 21h,AH=6C */

      } else {

        d->stdout_openflag = 0x12;

      }

      d->stdoutfile = cmdline + i + 1;

      while (d->stdoutfile[0] == ' ') d->stdoutfile++;

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

      cmdline[i] = 0;

      d->stdinfile = cmdline + i + 1;

      while (d->stdinfile[0] == ' ') d->stdinfile++;

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

      cmdline[i] = 0;

      if (pipescount < REDIR_MAX_PIPES) {

        d->pipes[pipescount++] = cmdline + i + 1;

        while (d->pipes[pipescount][0] == ' ') d->pipes[pipescount]++;

      }

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

      break;

    }

  }

}

/* apply stdin/stdout redirections defined in redir_data, returns 0 on success */

int redir_apply(const struct redir_data *d) {

  if (d->stdinfile != NULL) {

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

    return(-1);

  }

  if (d->stdoutfile != NULL) {

    unsigned short openflag = d->stdout_openflag;

    unsigned short errcode = 0;

    unsigned short handle = 0;

    const char *myptr = d->stdoutfile;

    /* */

    _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, myptr      /* ASCIIZ filename */

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

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

      jnc JMPEOF

      mov errcode, ax

      jmp DONE

      JMPEOF:

      cmp openflag, word ptr 0x11

      jne DUPSTDOUT

      /* jump to the end of the file (required for >> redirections) */

      mov ax, 0x4202     /* jump to position EOF - CX:DX in handle BX */

      mov bx, handle

      xor cx, cx

      xor dx, dx

      int 0x21

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

      DUPSTDOUT:

      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

    /* close old handle (in bx already) */

    mov ah, 0x3e

    int 0x21

    mov [oldstdout], 0xffff

    DONE:

  }

}