FreeBSD/Linux Kernel Cross Reference
sys/boot/common/interp_forth.c

     /*-
      * Copyright (c) 1998 Michael Smith <msmith@freebsd.org>
      * All rights reserved.
      *
      * Redistribution and use in source and binary forms, with or without
      * modification, are permitted provided that the following conditions
      * are met:
      * 1. Redistributions of source code must retain the above copyright
      *    notice, this list of conditions and the following disclaimer.
     * 2. Redistributions in binary form must reproduce the above copyright
     *    notice, this list of conditions and the following disclaimer in the
     *    documentation and/or other materials provided with the distribution.
     *
     * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
     * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
     * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     * SUCH DAMAGE.
     */
    
    #include <sys/cdefs.h>
    __FBSDID("$FreeBSD$");
    
    #include <sys/param.h>          /* to pick up __FreeBSD_version */
    #include <string.h>
    #include <stand.h>
    #include "bootstrap.h"
    #include "ficl.h"
    
    extern char bootprog_rev[];
    
    /* #define BFORTH_DEBUG */
    
    #ifdef BFORTH_DEBUG
    # define DEBUG(fmt, args...)    printf("%s: " fmt "\n" , __func__ , ## args)
    #else
    # define DEBUG(fmt, args...)
    #endif
    
    /*
     * Eventually, all builtin commands throw codes must be defined
     * elsewhere, possibly bootstrap.h. For now, just this code, used
     * just in this file, it is getting defined.
     */
    #define BF_PARSE 100
    
    /*
     * BootForth   Interface to Ficl Forth interpreter.
     */
    
    FICL_SYSTEM *bf_sys;
    FICL_VM *bf_vm;
    FICL_WORD *pInterp;
    
    /*
     * Shim for taking commands from BF and passing them out to 'standard'
     * argv/argc command functions.
     */
    static void
    bf_command(FICL_VM *vm)
    {
        char                        *name, *line, *tail, *cp;
        size_t                      len;
        struct bootblk_command      **cmdp;
        bootblk_cmd_t               *cmd;
        int                         nstrings, i;
        int                         argc, result;
        char                        **argv;
    
        /* Get the name of the current word */
        name = vm->runningWord->name;
        
        /* Find our command structure */
        cmd = NULL;
        SET_FOREACH(cmdp, Xcommand_set) {
            if (((*cmdp)->c_name != NULL) && !strcmp(name, (*cmdp)->c_name))
                cmd = (*cmdp)->c_fn;
        }
        if (cmd == NULL)
            panic("callout for unknown command '%s'", name);
       
        /* Check whether we have been compiled or are being interpreted */
        if (stackPopINT(vm->pStack)) {
            /*
             * Get parameters from stack, in the format:
             * an un ... a2 u2 a1 u1 n --
             * Where n is the number of strings, a/u are pairs of
             * address/size for strings, and they will be concatenated
             * in LIFO order.
             */
            nstrings = stackPopINT(vm->pStack);
            for (i = 0, len = 0; i < nstrings; i++)
                len += stackFetch(vm->pStack, i * 2).i + 1;
           line = malloc(strlen(name) + len + 1);
           strcpy(line, name);
   
           if (nstrings)
               for (i = 0; i < nstrings; i++) {
                   len = stackPopINT(vm->pStack);
                   cp = stackPopPtr(vm->pStack);
                   strcat(line, " ");
                   strncat(line, cp, len);
               }
       } else {
           /* Get remainder of invocation */
           tail = vmGetInBuf(vm);
           for (cp = tail, len = 0; cp != vm->tib.end && *cp != 0 && *cp != '\n'; cp++, len++)
               ;
       
           line = malloc(strlen(name) + len + 2);
           strcpy(line, name);
           if (len > 0) {
               strcat(line, " ");
               strncat(line, tail, len);
               vmUpdateTib(vm, tail + len);
           }
       }
       DEBUG("cmd '%s'", line);
       
       command_errmsg = command_errbuf;
       command_errbuf[0] = 0;
       if (!parse(&argc, &argv, line)) {
           result = (cmd)(argc, argv);
           free(argv);
       } else {
           result=BF_PARSE;
       }
       free(line);
       /* This is going to be thrown!!! */
       stackPushINT(vm->pStack,result);
   }
   
   /*
    * Replace a word definition (a builtin command) with another
    * one that:
    *
    *        - Throw error results instead of returning them on the stack
    *        - Pass a flag indicating whether the word was compiled or is
    *          being interpreted.
    *
    * There is one major problem with builtins that cannot be overcome
    * in anyway, except by outlawing it. We want builtins to behave
    * differently depending on whether they have been compiled or they
    * are being interpreted. Notice that this is *not* the interpreter's
    * current state. For example:
    *
    * : example ls ; immediate
    * : problem example ;          \ "ls" gets executed while compiling
    * example                      \ "ls" gets executed while interpreting
    *
    * Notice that, though the current state is different in the two
    * invocations of "example", in both cases "ls" has been
    * *compiled in*, which is what we really want.
    *
    * The problem arises when you tick the builtin. For example:
    *
    * : example-1 ['] ls postpone literal ; immediate
    * : example-2 example-1 execute ; immediate
    * : problem example-2 ;
    * example-2
    *
    * We have no way, when we get EXECUTEd, of knowing what our behavior
    * should be. Thus, our only alternative is to "outlaw" this. See RFI
    * 0007, and ANS Forth Standard's appendix D, item 6.7 for a related
    * problem, concerning compile semantics.
    *
    * The problem is compounded by the fact that "' builtin CATCH" is valid
    * and desirable. The only solution is to create an intermediary word.
    * For example:
    *
    * : my-ls ls ;
    * : example ['] my-ls catch ;
    *
    * So, with the below implementation, here is a summary of the behavior
    * of builtins:
    *
    * ls -l                                \ "interpret" behavior, ie,
    *                                      \ takes parameters from TIB
    * : ex-1 s" -l" 1 ls ;                 \ "compile" behavior, ie,
    *                                      \ takes parameters from the stack
    * : ex-2 ['] ls catch ; immediate      \ undefined behavior
    * : ex-3 ['] ls catch ;                \ undefined behavior
    * ex-2 ex-3                            \ "interpret" behavior,
    *                                      \ catch works
    * : ex-4 ex-2 ;                        \ "compile" behavior,
    *                                      \ catch does not work
    * : ex-5 ex-3 ; immediate              \ same as ex-2
    * : ex-6 ex-3 ;                        \ same as ex-3
    * : ex-7 ['] ex-1 catch ;              \ "compile" behavior,
    *                                      \ catch works
    * : ex-8 postpone ls ; immediate       \ same as ex-2
    * : ex-9 postpone ls ;                 \ same as ex-3
    *
    * As the definition below is particularly tricky, and it's side effects
    * must be well understood by those playing with it, I'll be heavy on
    * the comments.
    *
    * (if you edit this definition, pay attention to trailing spaces after
    *  each word -- I warned you! :-) )
    */
   #define BUILTIN_CONSTRUCTOR \
   ": builtin: "           \
     ">in @ "              /* save the tib index pointer */ \
     "' "                  /* get next word's xt */ \
     "swap >in ! "         /* point again to next word */ \
     "create "             /* create a new definition of the next word */ \
     ", "                  /* save previous definition's xt */ \
     "immediate "          /* make the new definition an immediate word */ \
                           \
     "does> "              /* Now, the *new* definition will: */ \
     "state @ if "         /* if in compiling state: */ \
       "1 postpone literal "       /* pass 1 flag to indicate compile */ \
       "@ compile, "               /* compile in previous definition */ \
       "postpone throw "           /* throw stack-returned result */ \
     "else "               /* if in interpreting state: */ \
       "0 swap "                   /* pass 0 flag to indicate interpret */ \
       "@ execute "                /* call previous definition */ \
       "throw "                    /* throw stack-returned result */ \
     "then ; "
   
   /*
    * Initialise the Forth interpreter, create all our commands as words.
    */
   void
   bf_init(void)
   {
       struct bootblk_command      **cmdp;
       char create_buf[41];        /* 31 characters-long builtins */
       int fd;
      
       bf_sys = ficlInitSystem(10000);     /* Default dictionary ~4000 cells */
       bf_vm = ficlNewVM(bf_sys);
   
       /* Put all private definitions in a "builtins" vocabulary */
       ficlExec(bf_vm, "vocabulary builtins also builtins definitions");
   
       /* Builtin constructor word  */
       ficlExec(bf_vm, BUILTIN_CONSTRUCTOR);
   
       /* make all commands appear as Forth words */
       SET_FOREACH(cmdp, Xcommand_set) {
           ficlBuild(bf_sys, (char *)(*cmdp)->c_name, bf_command, FW_DEFAULT);
           ficlExec(bf_vm, "forth definitions builtins");
           sprintf(create_buf, "builtin: %s", (*cmdp)->c_name);
           ficlExec(bf_vm, create_buf);
           ficlExec(bf_vm, "builtins definitions");
       }
       ficlExec(bf_vm, "only forth definitions");
   
       /* Export some version numbers so that code can detect the loader/host version */
       ficlSetEnv(bf_sys, "FreeBSD_version", __FreeBSD_version);
       ficlSetEnv(bf_sys, "loader_version", 
                  (bootprog_rev[0] - '') * 10 + (bootprog_rev[2] - ''));
   
       /* try to load and run init file if present */
       if ((fd = open("/boot/boot.4th", O_RDONLY)) != -1) {
           (void)ficlExecFD(bf_vm, fd);
           close(fd);
       }
   
       /* Do this last, so /boot/boot.4th can change it */
       pInterp = ficlLookup(bf_sys, "interpret");
   }
   
   /*
    * Feed a line of user input to the Forth interpreter
    */
   int
   bf_run(char *line)
   {
       int         result;
   
       result = ficlExec(bf_vm, line);
   
       DEBUG("ficlExec '%s' = %d", line, result);
       switch (result) {
       case VM_OUTOFTEXT:
       case VM_ABORTQ:
       case VM_QUIT:
       case VM_ERREXIT:
           break;
       case VM_USEREXIT:
           printf("No where to leave to!\n");
           break;
       case VM_ABORT:
           printf("Aborted!\n");
           break;
       case BF_PARSE:
           printf("Parse error!\n");
           break;
       default:
           /* Hopefully, all other codes filled this buffer */
           printf("%s\n", command_errmsg);
       }
       
       if (result == VM_USEREXIT)
           panic("interpreter exit");
       setenv("interpret", bf_vm->state ? "" : "OK", 1);
   
       return result;
   }

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