[vvhitespace] / vv_interpreter.c

/*
 * (c) 2019 Aaron Taylor <ataylor at subgeniuskitty dot com>
 * All rights reserved.
 */

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>
#include <stdint.h>
#include <sys/select.h>
#include <getopt.h>
#include <termios.h>

#define VERSION 1

#define STACKSIZE 1024
#define HEAPSIZE  1024
#define RETURNSTACKSIZE 1024

void
print_usage(char ** argv)
{
    printf( "VVhitespace Interpreter v%d (www.subgeniuskitty.com)\n"
            "Usage: %s -i <file>\n"
            "  -h         Help (prints this message)\n"
            "  -i <file>  Specify a VVhitespace source file to interpret.\n"
            , VERSION, argv[0]
    );
}

int
stdin_empty(void)
{
    fd_set read_fds;
    FD_ZERO(&read_fds);
    FD_SET(STDIN_FILENO, &read_fds);

    struct timeval timeout;
    timeout.tv_sec = 0;
    timeout.tv_usec = 0;

    int retval = select(1, &read_fds, NULL, NULL, &timeout);
    /* retval could be -1. Ignoring that for now. */
    if (retval > 0) return 0;
    return 1;
}

void
set_terminal_mode(void)
{
    struct termios options;
    tcgetattr(STDIN_FILENO, &options);
    /* Create a cbreak-like environment through the following options. */
    options.c_lflag &= ~ECHO; /* Disable echoing of input characters. */
    options.c_lflag &= ~ICANON; /* Disable cooked/line-oriented mode. */
    options.c_cc[VMIN] = 1;
    options.c_cc[VTIME] = 0;
    tcsetattr(STDIN_FILENO, TCSANOW, &options);
}

void
unset_terminal_mode(void)
{
    struct termios options;
    tcgetattr(STDIN_FILENO, &options);
    /* Undo the changes made in set_terminal_mode(). */
    options.c_lflag |= ECHO; /* Enable echoing of input characters. */
    options.c_lflag |= ICANON; /* Enable cooked/line-oriented mode. */
    options.c_cc[VMIN] = 1; /* Default value from /usr/src/sys/sys/ttydefaults.h */
    options.c_cc[VTIME] = 0; /* Default value from /usr/src/sys/sys/ttydefaults.h */
    tcsetattr(STDIN_FILENO, TCSANOW, &options);
}

void
ws_die(size_t * pc, char * msg)
{
    printf("SIM_ERROR @ PC %lu: %s\n", *pc, msg);
    fflush(stdout);
    unset_terminal_mode();
    exit(EXIT_FAILURE);
}

void
stack_push(int32_t ** sp, int32_t word)
{
    *((*sp)++) = word;
}

int32_t
stack_pop(int32_t ** sp)
{
    return *(--(*sp));
}

int32_t
stack_peek(int32_t ** sp, size_t offset)
/* offset=0 peeks TOS, offset=1 peeks NOS, etc. */
{
    return *((*sp)-offset-1);
}

uint8_t
next_code_byte(uint8_t * code, size_t * pc)
{
    return code[(*pc)++];
}

/*
 * In addition to returning the parsed label, this function advances the PC to
 * the next instruction.
 */
uint16_t
parse_label(uint8_t * code, size_t * pc)
{
    uint16_t label = 0;
    uint8_t c;
    while ((c = code[(*pc)++]) != '\n') {
        label = label << 1;
        if (c == ' ') label++;
    }
    // TODO: Where should I handle attempts to access an unitialized label?
    //       For now, leave it undefined in a nasal demon sense.
    return label;
}

void
populate_labels(uint32_t * labels, uint8_t * code, size_t code_size)
{
    size_t cp = 0;
    while (cp <= code_size) {
        if (code[cp] == '\v') {
            uint16_t temp_label = parse_label(code, &cp);
            labels[temp_label] = cp;
        }
        cp++;
    }
}

void
process_imp_stack(uint8_t * code, size_t * pc, int32_t ** sp)
{
    switch (next_code_byte(code,pc)) {
        case ' ':
            /* Push number onto TOS. */
            {
                /* First, pick off the sign */
                int32_t sign = 0;
                switch (next_code_byte(code,pc)) {
                    case ' ' :  sign = 1;                       break;
                    case '\t':  sign = -1;                      break;
                    default  :  ws_die(pc, "expected sign");    break;
                }

                /* Now, construct the number and push to TOS. */
                /* I'm assuming the numbers are read MSb first. */
                int32_t temp, number = 0;
                while ((temp = next_code_byte(code,pc)) != '\n') {
                    if (temp == '\v') ws_die(pc, "non-binary digit in number");
                    number <<= 1;
                    if (temp == '\t') number++;
                }
                stack_push(sp, number*sign);
            }
            break;
        case '\n':
            /* Stack sub-command */
            {
                switch (next_code_byte(code,pc)) {
                        /* Duplicate the TOS. */
                    case ' ':
                        stack_push(sp, stack_peek(sp,0));
                        break;
                        /* Swap TOS and NOS. */
                    case '\t':
                        {
                            int32_t t1 = stack_pop(sp);
                            int32_t t2 = stack_pop(sp);
                            stack_push(sp, t1);
                            stack_push(sp, t2);
                        }
                        break;
                        /* Discard TOS. */
                    case '\n':
                        stack_pop(sp);
                        break;
                    default:
                        ws_die(pc, "malformed stack IMP");
                        break;
                }
            }
            break;
        default: ws_die(pc, "malformed stack IMP"); break;
    }
}

void
process_imp_arithmetic(uint8_t * code, size_t * pc, int32_t ** sp)
{
    int32_t temp;
    switch (next_code_byte(code,pc)) {
        case ' ':
            {
                switch (next_code_byte(code,pc)) {
                    case ' ':
                        /* Addition */
                        stack_push(sp, stack_pop(sp)+stack_pop(sp));
                        break;
                    case '\t':
                        /* Subtraction */
                        temp = stack_pop(sp);
                        stack_push(sp, stack_pop(sp)-temp);
                        break;
                    case '\n':
                        /* Multiplication */
                        stack_push(sp, stack_pop(sp)*stack_pop(sp));
                        break;
                    default:
                        ws_die(pc, "malformed arithmetic IMP");
                        break;
                }
            }
            break;
        case '\t':
            {
                switch (next_code_byte(code,pc)) {
                    case ' ':
                        /* Division */
                        temp = stack_pop(sp);
                        stack_push(sp, stack_pop(sp)/temp);
                        break;
                    case '\t':
                        /* Modulo */
                        temp = stack_pop(sp);
                        stack_push(sp, stack_pop(sp)%temp);
                        break;
                    default: ws_die(pc, "malformed arithmetic IMP"); break;
                }
            }
            break;
        default: ws_die(pc, "malformed arithmetic IMP"); break;
    }
}

void
process_imp_flowcontrol(uint8_t * code, size_t * pc, int32_t ** sp, uint32_t * labels,
                        uint32_t ** rsp)
{
    switch (next_code_byte(code,pc)) {
        case '\n':
            /* Technically another LF is required but we ignore it. */
            fflush(stdout);
            unset_terminal_mode();
            exit(EXIT_SUCCESS);
        case ' ':
            {
                switch (next_code_byte(code,pc)) {
                    case ' ':
                        /* Mark a location in the program. */
                        if (next_code_byte(code,pc) != '\v') ws_die(pc,"expected vtab, "
                                "perhaps a whitespace program, rather than vvhitespace?");
                        /* Jump to next instruction since labels were parsed during startup. */
                        parse_label(code, pc);
                        break;
                    case '\t':
                        /* Call a subroutine. */
                        {
                            size_t temp_pc = labels[parse_label(code, pc)];
                            *((*rsp)++) = *pc;
                            *pc = temp_pc;
                        }
                        break;
                    case '\n':
                        /* Jump unconditionally to a label. */
                        *pc = labels[parse_label(code, pc)];
                        break;
                    default:
                        ws_die(pc, "malformed flow control IMP");
                        break;
                }
            }
            break;
        case '\t':
            {
                switch (next_code_byte(code,pc)) {
                    case ' ':
                        /* Jump to a label if TOS == 0 */
                        /* TODO: Does WS pop or peek the TOS? */
                        if (stack_peek(sp,0) == 0) *pc = labels[parse_label(code, pc)];
                        break;
                    case '\t':
                        /* Jump to a label if TOS < 0. */
                        /* TODO: Does WS pop or peek the TOS? */
                        if (stack_peek(sp,0) < 0) *pc = labels[parse_label(code, pc)];
                        break;
                    case '\n':
                        /* Return from subroutine. */
                        *pc = *(--(*rsp));
                        break;
                    default:
                        ws_die(pc, "malformed flow control IMP");
                        break;
                }
            }
            break;
        default:
            ws_die(pc, "malformed flow control IMP");
            break;
    }
}

void
process_imp_heap(uint8_t * code, size_t * pc, int32_t ** sp, int32_t ** hp)
{
    switch (next_code_byte(code,pc)) {
        case ' ' :
            /* Store to heap */
            {
                int32_t value = stack_pop(sp);
                int32_t addr = stack_pop(sp);
                *(*hp + addr) = value;
            }
            break;
        case '\t':
            /* Retrieve from heap */
            stack_push(sp, *(*hp + stack_pop(sp)));
            break;
        default:
            ws_die(pc, "malformed heap IMP");
            break;
    }
}

void
process_imp_io(uint8_t * code, size_t * pc, int32_t ** sp, int32_t ** hp)
{
    switch (next_code_byte(code,pc)) {
        case ' ':
            /* Output */
            {
                switch (next_code_byte(code,pc)) {
                    case ' ' : /* Output char from TOS  */ printf("%c", stack_pop(sp));     break;
                    case '\t': /* Output digit from TOS */ printf("%c", stack_pop(sp)+'0'); break;
                    default  : ws_die(pc, "malformed output IMP");                          break;
                }
                fflush(stdout);
            }
            break;
        case '\t':
            /* Input */
            {
                while (stdin_empty()) continue;
                char c = getchar();
                switch (next_code_byte(code,pc)) {
                    case '\t': /* Input digit     */ c -= '0';                /* fallthrough */
                    case ' ' : /* Input character */ *(*hp + *(--(*sp))) = c; break;
                    default  : ws_die(pc, "malformed input IMP");             break;
                }
            }
            break;
        default: ws_die(pc, "malformed i/o IMP"); break;
    }
}

int
main(int argc, char ** argv)
{
    /*
     * Process command line arguments
     */
    int c;
    FILE * input = NULL;
    while ((c = getopt(argc,argv,"i:h")) != -1) {
        switch (c) {
            case 'i':
                if ((input = fopen(optarg, "r")) == NULL) {
                    fprintf(stderr, "ERROR: %s: %s\n", optarg, strerror(errno));
                }
                break;
            case 'h':
                print_usage(argv);
                exit(EXIT_SUCCESS);
                break;
            default:
                break;
        }
    }
    if (input == NULL) {
        fprintf(stderr, "ERROR: Must specify a VVhitespace source file with -f flag.\n");
        print_usage(argv);
        exit(EXIT_FAILURE);
    }

    /*
     * Read just the VVhitespace source code into memory.
     * We will use the array indices as addresses for the virtual PC when jumping to labels.
     */
    size_t ws_code_size = 0;
    uint8_t temp_byte;
    while (fread(&temp_byte, 1, 1, input)) {
        if (temp_byte == ' ' || temp_byte == '\t' || temp_byte == '\n' || temp_byte == '\v') {
            ws_code_size++;
        }
    }
    rewind(input);
    uint8_t * ws_code_space = malloc(ws_code_size);
    ws_code_size = 0;
    while (fread(&temp_byte, 1, 1, input)) {
        if (temp_byte == ' ' || temp_byte == '\t' || temp_byte == '\n' || temp_byte == '\v') {
            ws_code_space[ws_code_size++] = temp_byte;
        }
    }
    fclose(input);

    /*
     * Setup a stack and heap.
     * Assume a 32-bit word size.
     */
    // TODO: Make everything 64-bit.
    int32_t * hp = malloc(HEAPSIZE*4);
    int32_t * sp = malloc(STACKSIZE*4);

    /* 
     * Setup the return stack and the label array.
     */
    uint32_t * rsp = malloc(RETURNSTACKSIZE*4);
    uint32_t labels[65536] = {0};
    populate_labels(labels, ws_code_space, ws_code_size);

    /*
     * Main Loop
     */
    set_terminal_mode();
    size_t pc = 0; /* Virtual program counter. Operates in the ws_code_space[] address space. */
    while (1) {
        if (pc >= ws_code_size) {
            fprintf(stderr, "SIM_ERROR: PC Overrun\n    Requested PC: %lu\n    Max Address: %lu\n",
                pc, ws_code_size-1);
            exit(EXIT_FAILURE);
            unset_terminal_mode();
        }
// TODO: Have the SIGTERM signal handler and normal term point return the value
// on TOS so I can do rudimentary automated tests.

        /* Decode the IMPs */
        switch (ws_code_space[pc++]) {
            case ' ':
                /* Stack Manipulation */
                process_imp_stack(ws_code_space, &pc, &sp);
                break;
            case '\n':
                /* Flow Control */
                process_imp_flowcontrol(ws_code_space, &pc, &sp, labels, &rsp);
                break;
            case '\t':
                /* Arithmetic, Heap Access, or I/O */
                {
                    switch (ws_code_space[pc++]) {
                        case ' ':
                            /* Arithmetic */
                            process_imp_arithmetic(ws_code_space, &pc, &sp);
                            break;
                        case '\t':
                            /* Heap Access */
                            process_imp_heap(ws_code_space, &pc, &sp, &hp);
                            break;
                        case '\n':
                            /* I/O */
                            process_imp_io(ws_code_space, &pc, &sp, &hp);
                            break;
                    }
                }
                break;
            default: ws_die(&pc, "unexpected VTab"); break;
        }
    }

    printf("\n");
    printf("Program executed.\n");

    exit(EXIT_SUCCESS);
    unset_terminal_mode();
}
Commit	Line	Data
1adfc4f4 AT	1	/*
	2	* (c) 2019 Aaron Taylor <ataylor at subgeniuskitty dot com>
	3	* All rights reserved.
	4	*/
	5
	6	#include <stdio.h>
	7	#include <stdlib.h>
	8	#include <unistd.h>
	9	#include <string.h>
	10	#include <errno.h>
	11	#include <stdint.h>
	12	#include <sys/select.h>
	13	#include <getopt.h>
a2664738	14	#include <termios.h>
1adfc4f4 AT	15
	16	#define VERSION 1
	17
	18	#define STACKSIZE 1024
	19	#define HEAPSIZE 1024
	20	#define RETURNSTACKSIZE 1024
	21
	22	void
	23	print_usage(char ** argv)
	24	{
bf43fa3f	25	printf( "VVhitespace Interpreter v%d (www.subgeniuskitty.com)\n"
1adfc4f4 AT	26	"Usage: %s -i <file>\n"
1adfc4f4 AT	27	" -h Help (prints this message)\n"
bf43fa3f	28	" -i <file> Specify a VVhitespace source file to interpret.\n"
1adfc4f4 AT	29	, VERSION, argv[0]
	30	);
	31	}
	32
	33	int
	34	stdin_empty(void)
	35	{
	36	fd_set read_fds;
	37	FD_ZERO(&read_fds);
	38	FD_SET(STDIN_FILENO, &read_fds);
	39
	40	struct timeval timeout;
	41	timeout.tv_sec = 0;
	42	timeout.tv_usec = 0;
	43
	44	int retval = select(1, &read_fds, NULL, NULL, &timeout);
	45	/* retval could be -1. Ignoring that for now. */
	46	if (retval > 0) return 0;
	47	return 1;
	48	}
	49
a2664738 AT	50	void
	51	set_terminal_mode(void)
	52	{
	53	struct termios options;
	54	tcgetattr(STDIN_FILENO, &options);
	55	/* Create a cbreak-like environment through the following options. */
	56	options.c_lflag &= ~ECHO; /* Disable echoing of input characters. */
	57	options.c_lflag &= ~ICANON; /* Disable cooked/line-oriented mode. */
	58	options.c_cc[VMIN] = 1;
	59	options.c_cc[VTIME] = 0;
	60	tcsetattr(STDIN_FILENO, TCSANOW, &options);
	61	}
	62
	63	void
	64	unset_terminal_mode(void)
	65	{
	66	struct termios options;
	67	tcgetattr(STDIN_FILENO, &options);
	68	/* Undo the changes made in set_terminal_mode(). */
	69	options.c_lflag \|= ECHO; /* Enable echoing of input characters. */
	70	options.c_lflag \|= ICANON; /* Enable cooked/line-oriented mode. */
	71	options.c_cc[VMIN] = 1; /* Default value from /usr/src/sys/sys/ttydefaults.h */
	72	options.c_cc[VTIME] = 0; /* Default value from /usr/src/sys/sys/ttydefaults.h */
	73	tcsetattr(STDIN_FILENO, TCSANOW, &options);
	74	}
	75
1adfc4f4 AT	76	void
	77	ws_die(size_t * pc, char * msg)
	78	{
1adfc4f4 AT	79	printf("SIM_ERROR @ PC %lu: %s\n", *pc, msg);
1adfc4f4 AT	80	fflush(stdout);
a2664738	81	unset_terminal_mode();
1adfc4f4 AT	82	exit(EXIT_FAILURE);
	83	}
	84
	85	void
	86	stack_push(int32_t ** sp, int32_t word)
	87	{
	88	((sp)++) = word;
	89	}
	90
	91	int32_t
	92	stack_pop(int32_t ** sp)
	93	{
	94	return (--(sp));
	95	}
	96
	97	int32_t
	98	stack_peek(int32_t ** sp, size_t offset)
	99	/* offset=0 peeks TOS, offset=1 peeks NOS, etc. */
	100	{
	101	return ((sp)-offset-1);
	102	}
	103
	104	uint8_t
	105	next_code_byte(uint8_t * code, size_t * pc)
	106	{
	107	return code[(*pc)++];
	108	}
	109
9686c901 AT	110	/*
	111	* In addition to returning the parsed label, this function advances the PC to
	112	* the next instruction.
	113	*/
1adfc4f4 AT	114	uint16_t
	115	parse_label(uint8_t * code, size_t * pc)
	116	{
	117	uint16_t label = 0;
	118	uint8_t c;
	119	while ((c = code[(*pc)++]) != '\n') {
	120	label = label << 1;
	121	if (c == ' ') label++;
	122	}
9686c901 AT	123	// TODO: Where should I handle attempts to access an unitialized label?
9686c901 AT	124	// For now, leave it undefined in a nasal demon sense.
1adfc4f4 AT	125	return label;
	126	}
	127
bf43fa3f AT	128	void
	129	populate_labels(uint32_t * labels, uint8_t * code, size_t code_size)
	130	{
9686c901 AT	131	size_t cp = 0;
	132	while (cp <= code_size) {
	133	if (code[cp] == '\v') {
	134	uint16_t temp_label = parse_label(code, &cp);
	135	labels[temp_label] = cp;
	136	}
	137	cp++;
	138	}
bf43fa3f AT	139	}
bf43fa3f AT	140
1adfc4f4 AT	141	void
	142	process_imp_stack(uint8_t * code, size_t * pc, int32_t ** sp)
	143	{
	144	switch (next_code_byte(code,pc)) {
	145	case ' ':
	146	/* Push number onto TOS. */
	147	{
	148	/* First, pick off the sign */
	149	int32_t sign = 0;
	150	switch (next_code_byte(code,pc)) {
	151	case ' ' : sign = 1; break;
	152	case '\t': sign = -1; break;
bf43fa3f	153	default : ws_die(pc, "expected sign"); break;
1adfc4f4 AT	154	}
	155
	156	/* Now, construct the number and push to TOS. */
	157	/* I'm assuming the numbers are read MSb first. */
	158	int32_t temp, number = 0;
	159	while ((temp = next_code_byte(code,pc)) != '\n') {
bf43fa3f	160	if (temp == '\v') ws_die(pc, "non-binary digit in number");
1adfc4f4 AT	161	number <<= 1;
	162	if (temp == '\t') number++;
	163	}
	164	stack_push(sp, number*sign);
	165	}
	166	break;
	167	case '\n':
	168	/* Stack sub-command */
	169	{
	170	switch (next_code_byte(code,pc)) {
	171	/* Duplicate the TOS. */
	172	case ' ':
	173	stack_push(sp, stack_peek(sp,0));
	174	break;
	175	/* Swap TOS and NOS. */
	176	case '\t':
	177	{
	178	int32_t t1 = stack_pop(sp);
	179	int32_t t2 = stack_pop(sp);
	180	stack_push(sp, t1);
	181	stack_push(sp, t2);
	182	}
	183	break;
	184	/* Discard TOS. */
	185	case '\n':
	186	stack_pop(sp);
	187	break;
bf43fa3f AT	188	default:
	189	ws_die(pc, "malformed stack IMP");
	190	break;
1adfc4f4 AT	191	}
	192	}
	193	break;
bf43fa3f	194	default: ws_die(pc, "malformed stack IMP"); break;
1adfc4f4 AT	195	}
	196	}
	197
	198	void
	199	process_imp_arithmetic(uint8_t * code, size_t * pc, int32_t ** sp)
	200	{
	201	int32_t temp;
	202	switch (next_code_byte(code,pc)) {
	203	case ' ':
	204	{
	205	switch (next_code_byte(code,pc)) {
	206	case ' ':
	207	/* Addition */
	208	stack_push(sp, stack_pop(sp)+stack_pop(sp));
	209	break;
	210	case '\t':
	211	/* Subtraction */
	212	temp = stack_pop(sp);
	213	stack_push(sp, stack_pop(sp)-temp);
	214	break;
	215	case '\n':
	216	/* Multiplication */
	217	stack_push(sp, stack_pop(sp)*stack_pop(sp));
	218	break;
bf43fa3f AT	219	default:
	220	ws_die(pc, "malformed arithmetic IMP");
	221	break;
1adfc4f4 AT	222	}
	223	}
	224	break;
	225	case '\t':
	226	{
	227	switch (next_code_byte(code,pc)) {
	228	case ' ':
	229	/* Division */
	230	temp = stack_pop(sp);
	231	stack_push(sp, stack_pop(sp)/temp);
	232	break;
	233	case '\t':
	234	/* Modulo */
	235	temp = stack_pop(sp);
	236	stack_push(sp, stack_pop(sp)%temp);
	237	break;
bf43fa3f	238	default: ws_die(pc, "malformed arithmetic IMP"); break;
1adfc4f4 AT	239	}
	240	}
	241	break;
bf43fa3f	242	default: ws_die(pc, "malformed arithmetic IMP"); break;
1adfc4f4 AT	243	}
	244	}
	245
	246	void
	247	process_imp_flowcontrol(uint8_t * code, size_t * pc, int32_t ** sp, uint32_t * labels,
	248	uint32_t ** rsp)
	249	{
	250	switch (next_code_byte(code,pc)) {
	251	case '\n':
	252	/* Technically another LF is required but we ignore it. */
1adfc4f4	253	fflush(stdout);
a2664738	254	unset_terminal_mode();
1adfc4f4 AT	255	exit(EXIT_SUCCESS);
	256	case ' ':
	257	{
	258	switch (next_code_byte(code,pc)) {
	259	case ' ':
	260	/* Mark a location in the program. */
9686c901 AT	261	if (next_code_byte(code,pc) != '\v') ws_die(pc,"expected vtab, "
	262	"perhaps a whitespace program, rather than vvhitespace?");
	263	/* Jump to next instruction since labels were parsed during startup. */
1e574f5b	264	parse_label(code, pc);
1adfc4f4 AT	265	break;
	266	case '\t':
	267	/* Call a subroutine. */
519b6ab4 AT	268	{
	269	size_t temp_pc = labels[parse_label(code, pc)];
	270	((rsp)++) = *pc;
	271	*pc = temp_pc;
	272	}
1adfc4f4 AT	273	break;
	274	case '\n':
	275	/* Jump unconditionally to a label. */
	276	*pc = labels[parse_label(code, pc)];
	277	break;
bf43fa3f AT	278	default:
	279	ws_die(pc, "malformed flow control IMP");
	280	break;
1adfc4f4 AT	281	}
	282	}
	283	break;
	284	case '\t':
	285	{
	286	switch (next_code_byte(code,pc)) {
	287	case ' ':
	288	/* Jump to a label if TOS == 0 */
519b6ab4	289	/* TODO: Does WS pop or peek the TOS? */
1adfc4f4 AT	290	if (stack_peek(sp,0) == 0) *pc = labels[parse_label(code, pc)];
	291	break;
	292	case '\t':
	293	/* Jump to a label if TOS < 0. */
519b6ab4	294	/* TODO: Does WS pop or peek the TOS? */
1adfc4f4 AT	295	if (stack_peek(sp,0) < 0) *pc = labels[parse_label(code, pc)];
	296	break;
	297	case '\n':
	298	/* Return from subroutine. */
	299	pc = (--(*rsp));
	300	break;
bf43fa3f AT	301	default:
	302	ws_die(pc, "malformed flow control IMP");
	303	break;
1adfc4f4 AT	304	}
	305	}
	306	break;
bf43fa3f AT	307	default:
	308	ws_die(pc, "malformed flow control IMP");
	309	break;
1adfc4f4 AT	310	}
	311	}
	312
	313	void
	314	process_imp_heap(uint8_t * code, size_t * pc, int32_t sp, int32_t hp)
	315	{
	316	switch (next_code_byte(code,pc)) {
aea85838 AT	317	case ' ' :
	318	/* Store to heap */
	319	{
	320	int32_t value = stack_pop(sp);
	321	int32_t addr = stack_pop(sp);
	322	(hp + addr) = value;
	323	}
	324	break;
	325	case '\t':
	326	/* Retrieve from heap */
	327	stack_push(sp, (hp + stack_pop(sp)));
	328	break;
	329	default:
	330	ws_die(pc, "malformed heap IMP");
	331	break;
1adfc4f4 AT	332	}
	333	}
	334
	335	void
	336	process_imp_io(uint8_t * code, size_t * pc, int32_t sp, int32_t hp)
	337	{
	338	switch (next_code_byte(code,pc)) {
	339	case ' ':
	340	/* Output */
	341	{
	342	switch (next_code_byte(code,pc)) {
1e574f5b AT	343	case ' ' : /* Output char from TOS */ printf("%c", stack_pop(sp)); break;
1e574f5b AT	344	case '\t': /* Output digit from TOS */ printf("%c", stack_pop(sp)+'0'); break;
9686c901	345	default : ws_die(pc, "malformed output IMP"); break;
1adfc4f4 AT	346	}
	347	fflush(stdout);
	348	}
	349	break;
	350	case '\t':
	351	/* Input */
	352	{
	353	while (stdin_empty()) continue;
	354	char c = getchar();
	355	switch (next_code_byte(code,pc)) {
	356	case '\t': /* Input digit / c -= '0'; / fallthrough */
a2664738	357	case ' ' : /* Input character / (hp + (--(*sp))) = c; break;
9686c901	358	default : ws_die(pc, "malformed input IMP"); break;
1adfc4f4 AT	359	}
	360	}
	361	break;
bf43fa3f	362	default: ws_die(pc, "malformed i/o IMP"); break;
1adfc4f4 AT	363	}
	364	}
	365
1adfc4f4 AT	366	int
	367	main(int argc, char ** argv)
	368	{
	369	/*
	370	* Process command line arguments
	371	*/
	372	int c;
	373	FILE * input = NULL;
	374	while ((c = getopt(argc,argv,"i:h")) != -1) {
	375	switch (c) {
	376	case 'i':
	377	if ((input = fopen(optarg, "r")) == NULL) {
	378	fprintf(stderr, "ERROR: %s: %s\n", optarg, strerror(errno));
	379	}
	380	break;
	381	case 'h':
	382	print_usage(argv);
	383	exit(EXIT_SUCCESS);
	384	break;
	385	default:
	386	break;
	387	}
	388	}
	389	if (input == NULL) {
bf43fa3f	390	fprintf(stderr, "ERROR: Must specify a VVhitespace source file with -f flag.\n");
1adfc4f4 AT	391	print_usage(argv);
	392	exit(EXIT_FAILURE);
	393	}
	394
	395	/*
bf43fa3f	396	* Read just the VVhitespace source code into memory.
1adfc4f4 AT	397	* We will use the array indices as addresses for the virtual PC when jumping to labels.
	398	*/
	399	size_t ws_code_size = 0;
	400	uint8_t temp_byte;
	401	while (fread(&temp_byte, 1, 1, input)) {
bf43fa3f AT	402	if (temp_byte == ' ' \|\| temp_byte == '\t' \|\| temp_byte == '\n' \|\| temp_byte == '\v') {
	403	ws_code_size++;
	404	}
1adfc4f4 AT	405	}
	406	rewind(input);
	407	uint8_t * ws_code_space = malloc(ws_code_size);
	408	ws_code_size = 0;
	409	while (fread(&temp_byte, 1, 1, input)) {
bf43fa3f AT	410	if (temp_byte == ' ' \|\| temp_byte == '\t' \|\| temp_byte == '\n' \|\| temp_byte == '\v') {
	411	ws_code_space[ws_code_size++] = temp_byte;
	412	}
1adfc4f4 AT	413	}
	414	fclose(input);
	415
	416	/*
	417	* Setup a stack and heap.
	418	* Assume a 32-bit word size.
	419	*/
bf43fa3f	420	// TODO: Make everything 64-bit.
1adfc4f4 AT	421	int32_t * hp = malloc(HEAPSIZE*4);
	422	int32_t * sp = malloc(STACKSIZE*4);
	423
	424	/*
	425	* Setup the return stack and the label array.
	426	*/
	427	uint32_t * rsp = malloc(RETURNSTACKSIZE*4);
bf43fa3f AT	428	uint32_t labels[65536] = {0};
bf43fa3f AT	429	populate_labels(labels, ws_code_space, ws_code_size);
1adfc4f4 AT	430
	431	/*
	432	* Main Loop
	433	*/
a2664738	434	set_terminal_mode();
1adfc4f4 AT	435	size_t pc = 0; /* Virtual program counter. Operates in the ws_code_space[] address space. */
	436	while (1) {
	437	if (pc >= ws_code_size) {
bf43fa3f AT	438	fprintf(stderr, "SIM_ERROR: PC Overrun\n Requested PC: %lu\n Max Address: %lu\n",
bf43fa3f AT	439	pc, ws_code_size-1);
1adfc4f4	440	exit(EXIT_FAILURE);
a2664738	441	unset_terminal_mode();
1adfc4f4	442	}
9686c901 AT	443	// TODO: Have the SIGTERM signal handler and normal term point return the value
9686c901 AT	444	// on TOS so I can do rudimentary automated tests.
1adfc4f4 AT	445
	446	/* Decode the IMPs */
	447	switch (ws_code_space[pc++]) {
	448	case ' ':
	449	/* Stack Manipulation */
	450	process_imp_stack(ws_code_space, &pc, &sp);
	451	break;
	452	case '\n':
	453	/* Flow Control */
	454	process_imp_flowcontrol(ws_code_space, &pc, &sp, labels, &rsp);
	455	break;
	456	case '\t':
	457	/* Arithmetic, Heap Access, or I/O */
	458	{
	459	switch (ws_code_space[pc++]) {
	460	case ' ':
	461	/* Arithmetic */
	462	process_imp_arithmetic(ws_code_space, &pc, &sp);
	463	break;
	464	case '\t':
	465	/* Heap Access */
	466	process_imp_heap(ws_code_space, &pc, &sp, &hp);
	467	break;
	468	case '\n':
	469	/* I/O */
	470	process_imp_io(ws_code_space, &pc, &sp, &hp);
	471	break;
	472	}
	473	}
	474	break;
9686c901	475	default: ws_die(&pc, "unexpected VTab"); break;
1adfc4f4 AT	476	}
	477	}
	478
	479	printf("\n");
	480	printf("Program executed.\n");
	481
	482	exit(EXIT_SUCCESS);
a2664738	483	unset_terminal_mode();
1adfc4f4	484	}