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/* 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"
struct config {
unsigned char flags; /* command.com flags, as defined in rmodinit.h */
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 'p': /* permanent shell (can't exit) */
case 'P':
cfg->flags |= FLAG_PERMANENT;
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("/P Makes the new command interpreter permanent (can't exit)");
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];
static struct rmod_props far *rmod;
parse_argv(&cfg);
rmod = rmod_find();
if (rmod == NULL) {
rmod = rmod_install(cfg.envsiz);
if (rmod == NULL) {
outputnl("ERROR: rmod_install() failed");
return(1);
}
/* copy flags to rmod's storage */
rmod->flags = cfg.flags;
/* printf("rmod installed at seg 0x%04X\r\n", rmod_seg); */
} else {
/* printf("rmod found at seg 0x%04x\r\n", rmod_seg); */
}
rmod_seg = rmod->rmodseg;
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, *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 ((rmod->flags & FLAG_EXEC_AND_QUIT) == 0);
sayonara(rmod);
return(0);
}