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.

 */

/*

 * SvarCOM is a command-line interpreter.

 *

 * a little memory area is allocated as high as possible. it contains:

 *  - a signature (like XMS drivers do)

 *  - a routine for exec'ing programs

 *  - a "last command" buffer for input history

 *

 * when svarcom starts, it tries locating the routine in memory.

 *

 * if found:

 *   waits for user input and processes it. if execing something is required, set the "next exec" field in routine's memory and quit.

 *

 * if not found:

 *   installs it by creating a new PSP, set int 22 vector to the routine, set my "parent PSP" to the routine

 *   and quit.

 *

 * PSP structure

 * http://www.piclist.com/techref/dos/psps.htm

 *

 *

 *

 * === MCB ===

 *

 * each time that DOS allocates memory, it prefixes the allocated memory with

 * a 16-bytes structure called a "Memory Control Block" (MCB). This control

 * block has the following structure:

 *

 * Offset  Size     Description

 *   00h   byte     'M' =  non-last member of the MCB chain

 *                  'Z' = indicates last entry in MCB chain

 *                  other values cause "Memory Allocation Failure" on exit

 *   01h   word     PSP segment address of the owner (Process Id)

 *                  possible values:

 *                    0 = free

 *                    8 = Allocated by DOS before first user pgm loaded

 *                    other = Process Id/PSP segment address of owner

 *   03h  word      number of paragraphs related to this MCB (excluding MCB)

 *   05h  11 bytes  reserved

 *   10h  ...       start of actual allocated memory block

 */

#include <i86.h>

#include <dos.h>

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include <process.h>

#include "cmd.h"

#include "env.h"

#include "helpers.h"

#include "redir.h"

#include "rmodinit.h"

#include "sayonara.h"

#define FLAG_EXEC_AND_QUIT 1

struct config {

  unsigned char flags;

  char *execcmd;

  unsigned short envsiz;

};

/* parses command line the hard way (directly from PSP) */

static void parse_argv(struct config *cfg) {

  unsigned short i;

  const unsigned char *cmdlinelen = (unsigned char *)0x80;

  char *cmdline = (char *)0x81;

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

  /* set a NULL terminator on cmdline */

  cmdline[*cmdlinelen] = 0;

  for (i = 0;;) {

    /* skip over any leading spaces */

    for (;; i++) {

      if (cmdline[i] == 0) return;

      if (cmdline[i] != ' ') break;

    }

    if (cmdline[i] != '/') {

      output("Invalid parameter: ");

      outputnl(cmdline + i);

      /* exit(1); */

    } else {

      i++;        /* skip the slash */

      switch (cmdline[i]) {

        case 'c': /* /C = execute command and quit */

        case 'C':

          cfg->flags |= FLAG_EXEC_AND_QUIT;

          /* FALLTHRU */

        case 'k': /* /K = execute command and keep running */

        case 'K':

          cfg->execcmd = cmdline + i + 1;

          return;

        case 'e': /* preset the initial size of the environment block */

        case 'E':

          i++;

          if (cmdline[i] == ':') i++; /* could be /E:size */

          atous(&(cfg->envsiz), cmdline + i);

          if (cfg->envsiz < 64) cfg->envsiz = 0;

          break;

        case '?':

          outputnl("Starts the SvarCOM command interpreter");

          outputnl("");

          outputnl("COMMAND /E:nnn [/[C|K] command]");

          outputnl("");

          outputnl("/E:nnn     Sets the environment size to nnn bytes");

          outputnl("/C         Executes the specified command and returns");

          outputnl("/K         Executes the specified command and continues running");

          exit(1);

          break;

        default:

          output("Invalid switch:");

          output(" ");

          outputnl(cmdline + i);

          exit(1);

          break;

      }

    }

    /* move to next argument or quit processing if end of cmdline */

    for (i++; (cmdline[i] != 0) && (cmdline[i] != ' ') && (cmdline[i] != '/'); i++);

  }

}

static void buildprompt(char *s, unsigned short envseg) {

  /* locate the prompt variable or use the default pattern */

  const char far *fmt = env_lookup_val(envseg, "PROMPT");

  if ((fmt == NULL) || (*fmt == 0)) fmt = "$p$g"; /* fallback to default if empty */

  /* build the prompt string based on pattern */

  for (; *fmt != 0; fmt++) {

    if (*fmt != '$') {

      *s = *fmt;

      s++;

      continue;

    }

    /* escape code ($P, etc) */

    fmt++;

    switch (*fmt) {

      case 'Q':  /* $Q = = (equal sign) */

      case 'q':

        *s = '=';

        s++;

        break;

      case '$':  /* $$ = $ (dollar sign) */

        *s = '$';

        s++;

        break;

      case 'T':  /* $t = current time */

      case 't':

        s += sprintf(s, "00:00"); /* TODO */

        break;

      case 'D':  /* $D = current date */

      case 'd':

        s += sprintf(s, "1985-07-29"); /* TODO */

        break;

      case 'P':  /* $P = current drive and path */

      case 'p':

        _asm {

          mov ah, 0x19    /* DOS 1+ - GET CURRENT DRIVE */

          int 0x21

          mov bx, s

          mov [bx], al  /* AL = drive (00 = A:, 01 = B:, etc */

        }

        *s += 'A';

        s++;

        *s = ':';

        s++;

        *s = '\\';

        s++;

        _asm {

          mov ah, 0x47    /* DOS 2+ - CWD - GET CURRENT DIRECTORY */

          xor dl,dl       /* DL = drive number (00h = default, 01h = A:, etc) */

          mov si, s       /* DS:SI -> 64-byte buffer for ASCIZ pathname */

          int 0x21

        }

        while (*s != 0) s++; /* move ptr forward to end of pathname */

        break;

      case 'V':  /* $V = DOS version number */

      case 'v':

        s += sprintf(s, "VER"); /* TODO */

        break;

      case 'N':  /* $N = current drive */

      case 'n':

        _asm {

          mov ah, 0x19    /* DOS 1+ - GET CURRENT DRIVE */

          int 0x21

          mov bx, s

          mov [bx], al  /* AL = drive (00 = A:, 01 = B:, etc */

        }

        *s += 'A';

        s++;

        break;

      case 'G':  /* $G = > (greater-than sign) */

      case 'g':

        *s = '>';

        s++;

        break;

      case 'L':  /* $L = < (less-than sign) */

      case 'l':

        *s = '<';

        s++;

        break;

      case 'B':  /* $B = | (pipe) */

      case 'b':

        *s = '|';

        s++;

        break;

      case 'H':  /* $H = backspace (erases previous character) */

      case 'h':

        *s = '\b';

        s++;

        break;

      case 'E':  /* $E = Escape code (ASCII 27) */

      case 'e':

        *s = 27;

        s++;

        break;

      case '_':  /* $_ = CR+LF */

        *s = '\r';

        s++;

        *s = '\n';

        s++;

        break;

    }

  }

  *s = '$';

}

static void run_as_external(const char far *cmdline) {

  char buff[256];

  char const *argvlist[256];

  int i, n;

  /* copy buffer to a near var (incl. trailing CR), insert a space before

     every slash to make sure arguments are well separated */

  n = 0;

  i = 0;

  for (;;) {

    if (cmdline[i] == '/') buff[n++] = ' ';

    buff[n++] = cmdline[i++];

    if (buff[n] == 0) break;

  }

  cmd_explode(buff, cmdline, argvlist);

  /* for (i = 0; argvlist[i] != NULL; i++) printf("arg #%d = '%s'\r\n", i, argvlist[i]); */

  /* must be an external command then. this call should never return, unless

   * the other program failed to be executed. */

  execvp(argvlist[0], argvlist);

}

static void set_comspec_to_self(unsigned short envseg) {

  unsigned short *psp_envseg = (void *)(0x2c); /* pointer to my env segment field in the PSP */

  char far *myenv = MK_FP(*psp_envseg, 0);

  unsigned short varcount;

  char buff[256] = "COMSPEC=";

  char *buffptr = buff + 8;

  /* who am i? look into my own environment, at the end of it should be my EXEPATH string */

  while (*myenv != 0) {

    /* consume a NULL-terminated string */

    while (*myenv != 0) myenv++;

    /* move to next string */

    myenv++;

  }

  /* get next word, if 1 then EXEPATH follows */

  myenv++;

  varcount = *myenv;

  myenv++;

  varcount |= (*myenv << 8);

  myenv++;

  if (varcount != 1) return; /* NO EXEPATH FOUND */

  while (*myenv != 0) {

    *buffptr = *myenv;

    buffptr++;

    myenv++;

  }

  *buffptr = 0;

  /* printf("EXEPATH: '%s'\r\n", buff); */

  env_setvar(envseg, buff);

}

int main(void) {

  static struct config cfg;

  static unsigned short rmod_seg;

  static unsigned short far *rmod_envseg;

  static unsigned short far *lastexitcode;

  static unsigned char BUFFER[4096];

  parse_argv(&cfg);

  rmod_seg = rmod_find();

  if (rmod_seg == 0xffff) {

    rmod_seg = rmod_install(cfg.envsiz);

    if (rmod_seg == 0xffff) {

      outputnl("ERROR: rmod_install() failed");

      return(1);

    }

/*    printf("rmod installed at seg 0x%04X\r\n", rmod_seg); */

  } else {

/*    printf("rmod found at seg 0x%04x\r\n", rmod_seg); */

  }

  rmod_envseg = MK_FP(rmod_seg, RMOD_OFFSET_ENVSEG);

  lastexitcode = MK_FP(rmod_seg, RMOD_OFFSET_LEXITCODE);

  /* make COMPSEC point to myself */

  set_comspec_to_self(*rmod_envseg);

/*  {

    unsigned short envsiz;

    unsigned short far *sizptr = MK_FP(*rmod_envseg - 1, 3);

    envsiz = *sizptr;

    envsiz *= 16;

    printf("rmod_inpbuff at %04X:%04X, env_seg at %04X:0000 (env_size = %u bytes)\r\n", rmod_seg, RMOD_OFFSET_INPBUFF, *rmod_envseg, envsiz);

  }*/

  do {

    char far *cmdline = MK_FP(rmod_seg, RMOD_OFFSET_INPBUFF + 2);

    unsigned char far *echostatus = MK_FP(rmod_seg, RMOD_OFFSET_ECHOFLAG);

    /* (re)load translation strings if needed */

    nls_langreload(BUFFER, *rmod_envseg);

    /* skip user input if I have a command to exec (/C or /K) */

    if (cfg.execcmd != NULL) {

      cmdline = cfg.execcmd;

      cfg.execcmd = NULL;

      goto EXEC_CMDLINE;

    }

    if (*echostatus != 0) outputnl(""); /* terminate the previous command with a CR/LF */

    SKIP_NEWLINE:

    /* print shell prompt (only if ECHO is enabled) */

    if (*echostatus != 0) {

      char *promptptr = BUFFER;

      buildprompt(promptptr, *rmod_envseg);

      _asm {

        push ax

        push dx

        mov ah, 0x09

        mov dx, promptptr

        int 0x21

        pop dx

        pop ax

      }

    }

    /* revert input history terminator to \r */

    if (cmdline[-1] != 0) {

      cmdline[(unsigned short)(cmdline[-1])] = '\r';

    }

    /* wait for user input */

    _asm {

      push ax

      push bx

      push cx

      push dx

      push ds

      /* is DOSKEY support present? (INT 2Fh, AX=4800h, returns non-zero in AL if present) */

      mov ax, 0x4800

      int 0x2f

      mov bl, al /* save doskey status in BL */

      /* set up buffered input */

      mov ax, rmod_seg

      push ax

      pop ds

      mov dx, RMOD_OFFSET_INPBUFF

      /* execute either DOS input or DOSKEY */

      test bl, bl /* zf set if no DOSKEY present */

      jnz DOSKEY

      mov ah, 0x0a

      int 0x21

      jmp short DONE

      DOSKEY:

      mov ax, 0x4810

      int 0x2f

      DONE:

      /* terminate command with a CR/LF */

      mov ah, 0x02 /* display character in dl */

      mov dl, 0x0d

      int 0x21

      mov dl, 0x0a

      int 0x21

      pop ds

      pop dx

      pop cx

      pop bx

      pop ax

    }

    /* if nothing entered, loop again (but without appending an extra CR/LF) */

    if (cmdline[-1] == 0) goto SKIP_NEWLINE;

    /* replace \r by a zero terminator */

    cmdline[(unsigned char)(cmdline[-1])] = 0;

    /* I jump here when I need to exec an initial command (/C or /K) */

    EXEC_CMDLINE:

    /* move pointer forward to skip over any leading spaces */

    while (*cmdline == ' ') cmdline++;

    /* update rmod's ptr to COMPSPEC so it is always up to date */

    rmod_updatecomspecptr(rmod_seg, *rmod_envseg);

    /* handle redirections (if any) */

    if (redir_parsecmd(cmdline, BUFFER) != 0) {

      outputnl("");

      continue;

    }

    /* try matching (and executing) an internal command */

    if (cmd_process(rmod_seg, *rmod_envseg, cmdline, BUFFER) >= -1) {

      /* internal command executed */

      redir_revert(); /* revert stdout (in case it was redirected) */

      continue;

    }

    /* if here, then this was not an internal command */

    run_as_external(cmdline);

    /* revert stdout (in case it was redirected) */

    redir_revert();

    /* execvp() replaces the current process by the new one

    if I am still alive then external command failed to execute */

    outputnl("Bad command or file name");

  } while ((cfg.flags & FLAG_EXEC_AND_QUIT) == 0);

  sayonara(rmod_seg);

  return(0);

}