finished reorg of abstracted module interfaces

[dcpu16] / vm-dcpu16.c

#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <strings.h>
#include <signal.h>
#include <errno.h>
#include <assert.h>
#include <sysexits.h>
#include <time.h>
#include <sys/time.h>

#include <readline/readline.h>
#ifdef HAVE_LIBVNCSERVER
#include "rfb/rfb.h"
#endif /* HAVE_LIBVNCSERVER */

#include "dcpu16.h"
#include "common.h"

#include "hw_lem1802.h"
#include "hw_keyboard.h"

/*
 *  shell-like driver for dcpu16 core
 *  provides a basic interface to control a single emulation instance
 *  
 *  Justin Wind <justin.wind@gmail.com>
 *    2012 04 10 - implementation started
 *    2012 04 12 - cleanup, better shell loop
 *    2012 05 12 - support v1.7 style devices
 *
 *  TODO
 *    handle quotes in shell command parsing
 *    use readline/history.h, since we're using readline anyhow
 *    ncurses windowing or something, for future display capabilities
 */

static const char * const src_id_ = "$Id$";

/* global invocation options */
struct options {
    unsigned int verbose;
} opt_ = {
    .verbose = 0,
};

/* global run state, first sigint caught will drop out of run loop and back into shell */
static volatile unsigned int running_ = 0;
static
void sigint_handler_(int sig) {
    (void)sig;
    running_ = 0;
}

#define VERBOSE_PRINTF(...) do { if (opt_.verbose) printf(__VA_ARGS__); } while (0)

static
void usage_(char *prog, unsigned int full) {
    FILE *f = full ? stdout : stderr;
    char *x = strrchr(prog, '/');

    if (x && *(x + 1))
        prog = x + 1;

    if (full)
        fprintf(f, "%s -- dcpu16 emulator core shell\n\n",
                prog);

    fprintf(f, "Usage: %s [-v] [file]\n",
            prog);

    if (full) {
        fprintf(f, "\nOptions:\n"
                "\t [file] -- ram image to load initially\n"
                "\t -v -- prints slightly more information while operating\n"
                "\t -h -- this screen\n");

        fprintf(f, "\n%78s\n", src_id_);
    }
}


/* flense a buffer into a newly-allocated argument list */
static
int buf_tok_vect_(char ***v, int *c, char *buf) {
    const char *sep = " \t";
    const char *quot = "\"'`";
    const size_t v_grow = 32;
    size_t v_sz = 32;
    char *st, *qt;

    *c = 0;
    *v = malloc(v_sz * sizeof **v);
    if (*v == NULL) {
        fprintf(stderr, "%s():%s\n", "malloc", strerror(errno));
        return -1;
    }

    for ( (*v)[*c] = strqtok_r(buf, sep, '\\', quot, &qt, &st);
          (*v)[*c];
          (*v)[*c] = strqtok_r(NULL, sep, '\\', quot, &qt, &st)
        ) {
            (*c)++;

            if ((size_t)(*c) == v_sz) {
                void *tmp_ptr = realloc(*v, (v_sz + v_grow) * sizeof **v);
                if (tmp_ptr == NULL) {
                    fprintf(stderr, "%s():%s\n", "realloc", strerror(errno));
                    free(*v);
                    *v = NULL;
                    return -1;
                }
                v_sz += v_grow;
            }
    }

    return 0;
}

/*
    resets the vm if addr is zero then
    loads an image from filename into ram starting at addr
*/
static
int file_load_(struct dcpu16 *vm, char *filename, DCPU16_WORD addr) {
    FILE *f;
    size_t r;

    if (!addr)
        dcpu16_reset(vm);

    f = fopen(filename, "rb");
    if (f == NULL) {
        fprintf(stderr, "%s('%s'):%s\n", "fopen", filename, strerror(errno));
        return -1;
    }

    r = fread(vm->ram + addr, sizeof(DCPU16_WORD), DCPU16_RAM - addr, f);
    VERBOSE_PRINTF("read %zu words", r);
    if (addr) VERBOSE_PRINTF(" starting at 0x%04x", addr);
    VERBOSE_PRINTF("\n");

    if (ferror(f))
        fprintf(stderr, "%s('%s'):%s\n", "fread", filename, strerror(errno));

    fclose(f);
    return 0;
}


#ifdef HAVE_LIBVNCSERVER
static struct dynamic_array rfbScreens_;
/* wups, kbdAddEvent isn't null by default, so I guess track associations externally */
struct rfb_instance_ {
    rfbScreenInfoPtr screen;
    struct dcpu16_hw *attached_display;
    struct dcpu16_hw *attached_keyboard;
};

/* locate or allocate the next display with an un-occupied framebuffer */
static
struct rfb_instance_ *rfbScreen_next_available_display_(struct dynamic_array *rfbScreens, int argc, char *argv[]) {
    size_t i;
    struct rfb_instance_ new_instance, *s;
    struct packed_args_ {
        int argc;
        char **argv;
    } parg = { argc, argv };

    fprintf(stderr, "DEBUG: rfbScreens->entries:%zu\n", rfbScreens->entries);

    for (i = 0; i < rfbScreens->entries; i++) {
        s = (struct rfb_instance_ *)DYNARRAY_ITEM(*rfbScreens, i);
        if (s->attached_display == NULL)
            return s;
    }

    if (dcpu16_hw_module_lem1802.ctl(NULL, "new_rfbScreen", &parg, &new_instance.screen)) {
        fprintf(stderr, "failed to allocate new rfbScreen");
        return NULL;
    }

    new_instance.attached_display = NULL;
    new_instance.attached_keyboard = NULL;
    s = dynarray_add(rfbScreens, &new_instance);
    return s;
}

/* locate or allocate the next display with an un-occupied keyboard */
static
struct rfb_instance_ *rfbScreen_next_available_keyboard_(struct dynamic_array *rfbScreens, int argc, char *argv[]) {
    size_t i;
    struct rfb_instance_ new_instance, *s;
    struct packed_args_ {
        int argc;
        char **argv;
    } parg = { argc, argv };

    for (i = 0; i < rfbScreens->entries; i++) {
        s = (struct rfb_instance_ *)DYNARRAY_ITEM(*rfbScreens, i);
        if (s->attached_keyboard == NULL)
            return s;
    }

    if (dcpu16_hw_module_lem1802.ctl(NULL, "new_rfbScreen", &parg, &new_instance.screen)) {
        fprintf(stderr, "failed to allocate new rfbScreen");
        return NULL;
    }

    new_instance.attached_display = NULL;
    new_instance.attached_keyboard = NULL;
    s = dynarray_add(rfbScreens, &new_instance);
    return s;
}

/* begin serving a screen */
void rfbScreen_start(rfbScreenInfoPtr s) {
    rfbInitServer(s);
    rfbRunEventLoop(s, -1, TRUE);
}
#endif /* HAVE_LIBVNCSERVER */

/*
    Here follows the various commands the shell can execute.

    At invocation, a command function will have already had its
    number of arguments vetted, but will need command-specific
    argument verifications done.

    The arg_vector contains the command as the first entry, and
    as such, arg_count will always be at least 1.
    However, the args_min and args_max entries in struct command_
    only refer to the counts of arguments, not the entries in the
    argv.
*/

struct command_ {
    char *name;
    int args_min;
    int args_max;
    int (*func)(struct dcpu16 *, int c, char **v);
    void (*help)(FILE *f, unsigned int);
};

#define COMMAND_IMPL(x) static int command_##x##_(struct dcpu16 *vm, int arg_count, char **arg_vector)
#define COMMAND_HELP(x) static void command_##x##_help_(FILE *f, unsigned int summary)
#define COMMAND_ENTRY(x, y, z) { #x, y, z, command_##x##_, command_##x##_help_ }


COMMAND_IMPL(quit) {
    (void)vm, (void)arg_count, (void)arg_vector;

    return -1;
}
COMMAND_HELP(quit) {
    fprintf(f, "\tquit\n");
    if (summary) return;

    fprintf(f, "Exits the emulator.\n");
}


COMMAND_IMPL(reset) {
    (void)arg_count, (void)arg_vector;

    dcpu16_reset(vm);
    printf("initialized\n");
    return 0;
}
COMMAND_HELP(reset) {
    fprintf(f, "\treset\n");
    if (summary) return;

    fprintf(f, "Clears and reinitializes emulator.\n");
}


COMMAND_IMPL(load) {
    int addr = 0;

    if (arg_count > 2) {
        addr = str_to_word(arg_vector[2]);
        if (addr < 0) {
            fprintf(stderr, "address '%s' is not a valid word: %s\n", arg_vector[2], strerror(errno));
            return 0;
        }
    }

    if (file_load_(vm, arg_vector[1], addr)) {
        fprintf(stderr, "failed to load '%s'\n", arg_vector[1]);
        return 0;
    }
    printf("loaded '%s'", arg_vector[1]);
    if (addr) printf(" starting at 0x%04x", addr);
    printf("\n");

    return 0;
}
COMMAND_HELP(load) {
    fprintf(f, "\tload file [addr]\n");
    if (summary) return;

    fprintf(f, "Load binary image from 'file' into ram.\n");
}


COMMAND_IMPL(dump) {
    int addr[2];
    int i;

    for (i = 1; i < arg_count; i++) {
        addr[i-1] = str_to_word(arg_vector[i]);
        if (addr[i-1] < 0) {
            fprintf(stderr, "address '%s' is not a valid word: %s\n", arg_vector[i], strerror(errno));
            return 0;
        }
    }
    if (arg_count < 2) addr[0] = vm->reg[DCPU16_REG_PC];
    if (arg_count < 3) addr[1] = addr[0];

    if (addr[1] < addr[0]) {
        fprintf(stderr, "\t'addr_start' must be before addr_end\n");
        return 0;
    }

    dcpu16_dump_ram(vm, addr[0], addr[1]);

    return 0;
}
COMMAND_HELP(dump) {
    fprintf(f, "\tdump [addr_start [addr_end]]\n");
    if (summary) return;

    fprintf(f, "Displays contents of ram from addr_start to addr_end.\n");
}


COMMAND_IMPL(disassemble) {
    int addr[2];
    int i;

    for (i = 1; i < arg_count; i++) {
        addr[i-1] = str_to_word(arg_vector[i]);
        if (addr[i-1] < 0) {
            fprintf(stderr, "address '%s' is not a valid word: %s\n", arg_vector[i], strerror(errno));
            return 0;
        }
    }
    if (arg_count < 2) addr[0] = vm->reg[DCPU16_REG_PC];
    if (arg_count < 3) addr[1] = addr[0];

    if (addr[1] < addr[0]) {
        fprintf(stderr, "\t'addr_start' must be before addr_end\n");
        return 0;
    }

    for (i = addr[0]; i <= addr[1]; /* */ ) {
        printf("0x%04x: ", i);
        i += dcpu16_disassemble_print(vm, i);
        printf("\n");
    }

    return 0;
}
COMMAND_HELP(disassemble) {
    fprintf(f, "\tdisassemble [addr_start [addr_end]]\n");
    if (summary) return;

    fprintf(f, "Displays contents of ram parsed into instructions.\n");
}


COMMAND_IMPL(step) {
    unsigned long count = 1;
    char *ep;

    if (arg_count == 2) {
        errno = 0;
        count = strtoul(arg_vector[1], &ep, 0);
        if (errno
        ||  !(*arg_vector[1] && *ep == '\0') ) {
            fprintf(stderr, "count '%s' is not a valid number: %s\n", arg_vector[1], strerror(errno));
            return 0;
        }

        if (count <= 0) {
            fprintf(stderr, "count must be positive\n");
            return 0;
        }
    }

    while (count--) {
        dcpu16_disassemble_print(vm, vm->reg[DCPU16_REG_PC]);
        printf("\n");
        dcpu16_step(vm);

        if (count > 1 && opt_.verbose)
            dcpu16_state_print(vm);
    }

    return 0;
}
COMMAND_HELP(step) {
    fprintf(f, "\tstep [count]\n");
    if (summary) return;

    fprintf(f, "Executes the next instruction, or the next count instructions.\n");
}


COMMAND_IMPL(set) {
    int addr, value;
    DCPU16_WORD *v;

    (void)arg_count;

    /* check if addr is a register */
    for (addr = 0; dcpu16_reg_names[addr]; addr++) {
        if (strcasecmp(arg_vector[1], dcpu16_reg_names[addr]) == 0)
            break;
    }
    if (addr < DCPU16_REG__NUM) {
        v = vm->reg + addr;
    } else {
        addr = str_to_word(arg_vector[1]);
        if (addr < 0) {
            fprintf(stderr, "address '%s' is not a valid word: %s\n", arg_vector[1], strerror(errno));
            return 0;
        }
        v = vm->ram + addr;
    }

    value = str_to_word(arg_vector[2]);
    if (value < 0) {
        fprintf(stderr, "address '%s' is not a valid word: %s\n", arg_vector[2], strerror(errno));
        return 0;
    }

    *v = value;

    return 0;
}

COMMAND_HELP(set) {
    fprintf(f, "\tset addr value\n");
    if (summary) return;

    fprintf(f, "Sets addr to value.");
}

#define MICROSECONDS_PER_CYCLE 10
COMMAND_IMPL(run) {
    struct sigaction act;
    struct timeval run_start_tv, run_stop_tv;
    long long run_cycle_start;
    struct timeval start_tv, now_tv, diff_tv;
    long long cycle_start, cycles_to_wait;
    struct timespec sleep_time, rem_time;
    long long run_usec;

    (void)arg_count, (void)arg_vector;

    running_ = 1;
    gettimeofday(&run_start_tv, NULL);
    run_cycle_start = vm->cycle_;

    memset(&act, 0, sizeof act);
    act.sa_handler = sigint_handler_;
    act.sa_flags = SA_RESETHAND;

    if (sigaction(SIGINT, &act, NULL)) {
        fprintf(stderr, "%s():%s\n", "sigaction", strerror(errno));
        return -1;
    }

    while (running_) {
        gettimeofday(&start_tv, NULL);
        cycle_start = vm->cycle_;

        dcpu16_step(vm);
        if (opt_.verbose > 1)
            dcpu16_state_print(vm);
        else if (opt_.verbose) {
            dcpu16_disassemble_print(vm, vm->reg[DCPU16_REG_PC]);
            printf("\n");
        }

        /* how many cycles did this instr use? */
        cycles_to_wait = vm->cycle_ - cycle_start;

        if (cycles_to_wait == 0)
            continue;

        /* each cycle wants 10 microseconds */

        /* how much of that did we spend already */
        gettimeofday(&now_tv, NULL);
        timeval_subtract(&diff_tv, &now_tv, &start_tv);
        /* do we have time to kill? */
        if (cycles_to_wait * MICROSECONDS_PER_CYCLE > diff_tv.tv_usec) {
            sleep_time.tv_sec = diff_tv.tv_sec;
            /* this is not accurate.. */
            sleep_time.tv_nsec = 250 * ( (cycles_to_wait * MICROSECONDS_PER_CYCLE) - diff_tv.tv_usec);

            /* nanosleep doesn't interfere with libvncserver, unlike usleep */
            while ( nanosleep(&sleep_time, &rem_time) ) {
                sleep_time = rem_time;
                fprintf(stderr, "rem:%ld %ld\n", rem_time.tv_sec, rem_time.tv_nsec);
            }
        }
    }

    gettimeofday(&run_stop_tv, NULL);
    timeval_subtract(&diff_tv, &run_stop_tv, &run_start_tv);
    run_usec = diff_tv.tv_sec * 1000000;
    run_usec += diff_tv.tv_usec;
    fprintf(stderr, "ran %llu cycles in %lds %dus (%lldus)\n",
            vm->cycle_ - run_cycle_start,
            diff_tv.tv_sec,
            diff_tv.tv_usec,
            run_usec);

    printf("interrupted...\n");

    return 0;
}
COMMAND_HELP(run) {
    fprintf(f, "\trun\n");
    if (summary) return;

    fprintf(f, "Begins executing continuously.\n"
               "May be interrupted with SIGINT.\n");
}

static const char * const display_filename_default_ =
#ifdef HAVE_LIBPNG
    "dcpu16-display.png"
#else /* HAVE_LIBPNG */
    "dcpu16-display.pnm"
#endif /* HAVE_LIBPNG */
;
COMMAND_IMPL(display) {
    struct dcpu16_hw *hw;
    const char *renderer = arg_vector[1];
    const char *renderer_arg = NULL;
    void *renderer_data;

    if (arg_count == 3)
        renderer_arg = arg_vector[2];

    hw = dcpu16_hw_new(vm, &dcpu16_hw_module_lem1802, NULL);
    if (hw == NULL) {
        fprintf(stderr, "failed to initialize new display\n");
        return 0;
    }

    /* handle per-renderer setup of data.. */
    /* FIXME: these are awkward */
    if (strcmp(renderer, "pnm") == 0) {
        renderer_data = (void *)(renderer_arg ? renderer_arg : display_filename_default_);
    }

#ifdef HAVE_LIBPNG
    if (strcmp(renderer, "png") == 0) {
        renderer_data = (void *)(renderer_arg ? renderer_arg : display_filename_default_);
    }
#endif /* HAVE_LIBPNG */

#ifdef HAVE_LIBVNCSERVER
    if (strcmp(renderer, "vnc") == 0) {
        int argc = 1;
        char *argv[] = { "vm-dcpu16", NULL };
        struct rfb_instance_ *s;

        s = rfbScreen_next_available_display_(&rfbScreens_, argc, argv);
        if (s == NULL) {
            fprintf(stderr, "failed to initialize vnc\n");
            dcpu16_hw_del(&hw);
            return 0;
        }

        if (dcpu16_hw_ctl(hw, "associate_rfbScreen", s->screen, NULL)) {
            fprintf(stderr, "failed to configure display/vnc");
            dcpu16_hw_del(&hw);
            return 0;
        }
        s->attached_display = hw;
        rfbScreen_start(s->screen);
        renderer_data = s->screen;
    }
#endif /* HAVE_LIBVNCSERVER */

    dcpu16_hw_ctl(hw, "renderer", (char *)renderer, NULL);
    dcpu16_hw_ctl(hw, "renderer_data", renderer_data, NULL);

    if (dcpu16_hw_attach(vm, hw)) {
        fprintf(stderr, "failed to attach new display\n");
        dcpu16_hw_del(&hw);
        return 0;
    }

    return 0;
}
COMMAND_HELP(display) {
    struct renderer_ {
        char *name;
        char *args;
    } renderer;
    void *iter;

    fprintf(f, "\tdisplay renderer [renderer data]\n");
    if (summary) return;

    fprintf(f, "Attaches new display unit, using 'renderer' as back-end output.\n"
            );

    fprintf(f, "Supported renderers:\n");

    iter = NULL;
    do {
        if (dcpu16_hw_module_lem1802.ctl(NULL, "renderers_iter", &iter, &renderer)) {
            fprintf(stderr, "error fetching next renderer\n");
            break;
        }
        if (iter == NULL || renderer.name == NULL)
            break;

        fprintf(f, "\t%s %s\n", renderer.name, renderer.args);
    } while (iter);
}

COMMAND_IMPL(keyboard) {
    struct dcpu16_hw *hw;

    (void)arg_count, (void)arg_vector;

    hw = dcpu16_hw_new(vm, &dcpu16_hw_module_keyboard, NULL);
    if (hw == NULL) {
        fprintf(stderr, "failed to initialize new keyboard\n");
        return 0;
    }

#ifdef HAVE_LIBVNCSERVER
    struct rfb_instance_ *s;
    int argc = 1;
    char *argv[] = { "vm-dcpu16", NULL };

    s = rfbScreen_next_available_keyboard_(&rfbScreens_, argc, argv);
    if (s == NULL) {
        fprintf(stderr, "failed to initialize vnc\n");
        dcpu16_hw_del(&hw);
        return 0;
    }
    if (dcpu16_hw_ctl(hw, "associate_rfbScreen", s->screen, NULL)) {
        fprintf(stderr, "failed to configure keyboard/vnc\n");
        dcpu16_hw_del(&hw);
        return 0;
    }
    s->attached_keyboard = hw;

    if (dcpu16_hw_attach(vm, hw)) {
        fprintf(stderr, "failed to attach new keyboard\n");
        dcpu16_hw_del(&hw);
        return 0;
    }
#endif /* HAVE_LIBVNCSERVER */

    return 0;
}
COMMAND_HELP(keyboard) {
    fprintf(f, "\tkeyboard\n");
    if (summary) return;

    fprintf(f, "Attaches new keyboard unit.\n");
}

/* gather all these together into a searchable table */

/* help command gets some assistance in declarations */
COMMAND_IMPL(help);
COMMAND_HELP(help);

static struct command_ command_table_[] = {
    COMMAND_ENTRY(help, 0, -1),
    COMMAND_ENTRY(quit, 0, -1),
    COMMAND_ENTRY(load, 1, 2),
    COMMAND_ENTRY(dump, 0, 2),
    COMMAND_ENTRY(disassemble, 0, 2),
    COMMAND_ENTRY(step, 0, 1),
    COMMAND_ENTRY(run, 0, 0),
    COMMAND_ENTRY(set, 2, 2),
    COMMAND_ENTRY(reset, 0, 0),
    COMMAND_ENTRY(display, 1, 2),
    COMMAND_ENTRY(keyboard, 0, 0),
    { NULL, 0, 0, NULL, NULL }
};

COMMAND_IMPL(help) {
    struct command_ *c;
    (void)vm;

    if (arg_count == 2) {
        for (c = command_table_; c->func; c++) {
            if (strcasecmp(arg_vector[1], c->name) == 0) {
                if (c->help)
                    c->help(stdout, 0);
                break;
            }
        }
        return 0;
    }

    for (c = command_table_; c->func; c++) {
        if (c->help)
            c->help(stdout, 1);
    }
    return 0;
}
COMMAND_HELP(help) {
        fprintf(f, "\thelp [command]\n");
        if (summary) return;

    fprintf(f, "Displays a list of available commands, or detailed help on a specific command.\n");
}


int main(int argc, char **argv) {
    const char prompt_fmt[] = "PC:%04x> ";
    char prompt[32];
    struct dcpu16 *vm;
    char *line, *line_prev;
    char **tok_v, **tok_v_prev;
    int tok_c, tok_c_prev;
    int c;

    while ( (c = getopt(argc, argv, "hv")) != EOF) {
        switch (c) {
            case 'v':
                opt_.verbose++;
                break;

            case 'h':
                usage_(argv[0], 1);
                exit(EX_OK);

            default:
                usage_(argv[0], 0);
                exit(EX_USAGE);
        }
    }
    if (opt_.verbose < 1) {
        dcpu16_warn_cb_set(NULL);
        dcpu16_trace_cb_set(NULL);
    } else if (opt_.verbose < 2) {
        dcpu16_trace_cb_set(NULL);
    }
    argc -= optind;
    argv += optind;

    if ((vm = dcpu16_new()) == NULL) {
        fprintf(stderr, "could not allocate new dcpu16 instance\n");
        exit(EX_UNAVAILABLE);
    }

#ifdef HAVE_LIBVNCSERVER
    if (dynarray_init(&rfbScreens_, sizeof(struct rfb_instance_), 4)) {
        fprintf(stderr, "could not allocate rfb container\n");
        exit(EX_UNAVAILABLE);
    }
#endif /* HAVE_LIBVNCSERVER */

    if (argc) {
        if (file_load_(vm, *argv, 0)) {
            fprintf(stderr, "couldn't load '%s'\n", *argv);
            exit(EX_NOINPUT);
        }
    }

    /* show state, read commands */
    for (line = line_prev = NULL,
         tok_v = tok_v_prev = NULL,
         tok_c = tok_c_prev= 0,
         snprintf(prompt, sizeof prompt, prompt_fmt, vm->reg[DCPU16_REG_PC]),
         dcpu16_state_print(vm);

         (line = readline(prompt));

         printf("\n"),
         snprintf(prompt, sizeof prompt, prompt_fmt, vm->reg[DCPU16_REG_PC]),
         dcpu16_state_print(vm)) {
        const char whitespace[] = " \t";
        char *line_start;
        struct command_ *c;
        int r = 0;

        /* skip whitespaces */
        line_start = line + strspn(line, whitespace);

        if (*line_start) {
            /* a new command, remember previous for possible repetition */

            /* turn new line into new arg array */
            if (buf_tok_vect_(&tok_v, &tok_c, line_start)) {
                fprintf(stderr, "failed to process command\n");
                continue;
            }

            /* and keep track if it all for the next time around */
            if (line_prev) free(line_prev);
            line_prev = line;

            if (tok_v_prev) free(tok_v_prev);
            tok_v_prev = tok_v;
            tok_c_prev = tok_c;
        } else {
            /* blank new command, but no prior command to repeat? ask again */
            if (tok_v_prev == NULL || tok_v_prev[0] == NULL || *(tok_v_prev[0]) == '\0') {
                free(line);
                continue;
            }

            /* otherwise discard new line and promote prior */
            free(line);
            tok_v = tok_v_prev;
            tok_c = tok_c_prev;
            line = line_prev;
        }

        /* look up command */
        for (c = command_table_; c->name; c++) {
            if (strcasecmp(tok_v[0], c->name) == 0) {
                if (c->args_min > tok_c - 1) {
                    fprintf(stderr, "%s: not enough arguments\n", c->name);
                    c->help(stderr, 1);
                    break;
                }

                if (c->args_max > 0
                &&  tok_c - 1 > c->args_max) {
                    fprintf(stderr, "%s: too many arguments\n", c->name);
                    c->help(stderr, 1);
                    break;
                }

                r = c->func(vm, tok_c, tok_v);
                break;
            }
        }
        if (r)
            break;

        if (!c->func)
            fprintf(stderr, "didn't recognize '%s'\n", tok_v[0]);
    }

    printf("\nfinished\n");

    dcpu16_delete(&vm);

    exit(EX_OK);
}