[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 HEAPSIZE        1024    /* Size of heap in words        */
#define DATASTACKSIZE   1024    /* Size of stack in words       */
#define RETURNSTACKSIZE 1024    /* Max subroutine call depth    */

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(int64_t ** sp, int64_t word)
{
    *((*sp)++) = word;
}

int64_t
stack_pop(int64_t ** sp)
{
    return *(--(*sp));
}

int64_t
stack_peek(int64_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 == '\t') label++;
    }
    return label;
}

uint16_t
check_label(size_t * labels, uint16_t label, size_t * pc)
{
    if(!labels[label]) ws_die(pc, "uninitialized label (forgot an include?)");
    return label;
}

void
populate_labels(size_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;
        }
    }
}

void
process_imp_stack(uint8_t * code, size_t * pc, int64_t ** sp)
{
    switch (next_code_byte(code,pc)) {
        case ' ':
            /* Push number onto TOS. */
            {
                /* First, pick off the sign */
                int64_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. */
                int64_t number = 0;
                uint8_t temp;
                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':
                        {
                            int64_t t1 = stack_pop(sp);
                            int64_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, int64_t ** sp)
{
    int64_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, int64_t ** sp, size_t * labels,
                        size_t ** rsp)
{
    size_t temp_pc;
    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. */
                        temp_pc = labels[check_label(labels, parse_label(code, pc), pc)];
                        *((*rsp)++) = *pc;
                        *pc = temp_pc;
                        break;
                    case '\n':
                        /* Jump unconditionally to a label. */
                        *pc = labels[check_label(labels, parse_label(code, pc), 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 */
                        temp_pc = labels[check_label(labels, parse_label(code, pc), pc)];
                        if (stack_pop(sp) == 0) *pc = temp_pc;
                        break;
                    case '\t':
                        /* Jump to a label if TOS < 0. */
                        temp_pc = labels[check_label(labels, parse_label(code, pc), pc)];
                        if (stack_pop(sp) < 0) *pc = temp_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, int64_t ** sp, int64_t ** hp)
{
    switch (next_code_byte(code,pc)) {
        case ' ' :
            /* Store to heap */
            {
                int64_t value = stack_pop(sp);
                int64_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, int64_t ** sp, int64_t ** hp)
{
    switch (next_code_byte(code,pc)) {
        case ' ':
            /* Output */
            {
                switch (next_code_byte(code,pc)) {
                    case ' ' : /* Output char from TOS  */ printf("%c", (uint8_t) stack_pop(sp));     break;
                    case '\t': /* Output digit from TOS */ printf("%c", (uint8_t) 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, stripping comment characters.
     * 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.
     */
    int64_t * hp = malloc(HEAPSIZE*sizeof(int64_t));
    int64_t * sp = malloc(DATASTACKSIZE*sizeof(int64_t));

    /* 
     * Setup the return stack and the label array.
     */
    size_t * rsp = malloc(RETURNSTACKSIZE*sizeof(size_t));
    size_t labels[65536] = {0}; /* 65536 = 2^16 => Holds all possible labels.               */
                                /* Default value of zero indicates an uninitialized label.  */
    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();
        }

        /* 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 byte"); break;
        }
    }
}
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
eea0db3f AT	18	#define HEAPSIZE 1024 /* Size of heap in words */
	19	#define DATASTACKSIZE 1024 /* Size of stack in words */
	20	#define RETURNSTACKSIZE 1024 /* Max subroutine call depth */
1adfc4f4 AT	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
eea0db3f	86	stack_push(int64_t ** sp, int64_t word)
1adfc4f4 AT	87	{
	88	((sp)++) = word;
	89	}
	90
eea0db3f AT	91	int64_t
eea0db3f AT	92	stack_pop(int64_t ** sp)
1adfc4f4 AT	93	{
	94	return (--(sp));
	95	}
	96
eea0db3f AT	97	int64_t
eea0db3f AT	98	stack_peek(int64_t ** sp, size_t offset)
1adfc4f4 AT	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;
84c650ed	121	if (c == '\t') label++;
1adfc4f4	122	}
8d17aa41 AT	123	return label;
	124	}
	125
	126	uint16_t
	127	check_label(size_t * labels, uint16_t label, size_t * pc)
	128	{
	129	if(!labels[label]) ws_die(pc, "uninitialized label (forgot an include?)");
1adfc4f4 AT	130	return label;
	131	}
	132
bf43fa3f	133	void
eea0db3f	134	populate_labels(size_t * labels, uint8_t * code, size_t code_size)
bf43fa3f	135	{
9686c901 AT	136	size_t cp = 0;
9686c901 AT	137	while (cp <= code_size) {
84c650ed	138	if (code[cp++] == '\v') {
9686c901 AT	139	uint16_t temp_label = parse_label(code, &cp);
	140	labels[temp_label] = cp;
	141	}
9686c901	142	}
bf43fa3f AT	143	}
bf43fa3f AT	144
1adfc4f4	145	void
eea0db3f	146	process_imp_stack(uint8_t * code, size_t * pc, int64_t ** sp)
1adfc4f4 AT	147	{
	148	switch (next_code_byte(code,pc)) {
	149	case ' ':
	150	/* Push number onto TOS. */
	151	{
	152	/* First, pick off the sign */
eea0db3f	153	int64_t sign = 0;
1adfc4f4 AT	154	switch (next_code_byte(code,pc)) {
	155	case ' ' : sign = 1; break;
	156	case '\t': sign = -1; break;
bf43fa3f	157	default : ws_die(pc, "expected sign"); break;
1adfc4f4 AT	158	}
	159
	160	/* Now, construct the number and push to TOS. */
	161	/* I'm assuming the numbers are read MSb first. */
eea0db3f AT	162	int64_t number = 0;
eea0db3f AT	163	uint8_t temp;
1adfc4f4	164	while ((temp = next_code_byte(code,pc)) != '\n') {
bf43fa3f	165	if (temp == '\v') ws_die(pc, "non-binary digit in number");
1adfc4f4 AT	166	number <<= 1;
	167	if (temp == '\t') number++;
	168	}
	169	stack_push(sp, number*sign);
	170	}
	171	break;
	172	case '\n':
	173	/* Stack sub-command */
	174	{
	175	switch (next_code_byte(code,pc)) {
	176	/* Duplicate the TOS. */
	177	case ' ':
	178	stack_push(sp, stack_peek(sp,0));
	179	break;
	180	/* Swap TOS and NOS. */
	181	case '\t':
	182	{
eea0db3f AT	183	int64_t t1 = stack_pop(sp);
eea0db3f AT	184	int64_t t2 = stack_pop(sp);
1adfc4f4 AT	185	stack_push(sp, t1);
	186	stack_push(sp, t2);
	187	}
	188	break;
	189	/* Discard TOS. */
	190	case '\n':
	191	stack_pop(sp);
	192	break;
bf43fa3f AT	193	default:
	194	ws_die(pc, "malformed stack IMP");
	195	break;
1adfc4f4 AT	196	}
	197	}
	198	break;
bf43fa3f	199	default: ws_die(pc, "malformed stack IMP"); break;
1adfc4f4 AT	200	}
	201	}
	202
	203	void
eea0db3f	204	process_imp_arithmetic(uint8_t * code, size_t * pc, int64_t ** sp)
1adfc4f4	205	{
eea0db3f	206	int64_t temp;
1adfc4f4 AT	207	switch (next_code_byte(code,pc)) {
	208	case ' ':
	209	{
	210	switch (next_code_byte(code,pc)) {
	211	case ' ':
	212	/* Addition */
	213	stack_push(sp, stack_pop(sp)+stack_pop(sp));
	214	break;
	215	case '\t':
	216	/* Subtraction */
	217	temp = stack_pop(sp);
	218	stack_push(sp, stack_pop(sp)-temp);
	219	break;
	220	case '\n':
	221	/* Multiplication */
	222	stack_push(sp, stack_pop(sp)*stack_pop(sp));
	223	break;
bf43fa3f AT	224	default:
	225	ws_die(pc, "malformed arithmetic IMP");
	226	break;
1adfc4f4 AT	227	}
	228	}
	229	break;
	230	case '\t':
	231	{
	232	switch (next_code_byte(code,pc)) {
	233	case ' ':
	234	/* Division */
	235	temp = stack_pop(sp);
	236	stack_push(sp, stack_pop(sp)/temp);
	237	break;
	238	case '\t':
	239	/* Modulo */
	240	temp = stack_pop(sp);
	241	stack_push(sp, stack_pop(sp)%temp);
	242	break;
bf43fa3f	243	default: ws_die(pc, "malformed arithmetic IMP"); break;
1adfc4f4 AT	244	}
	245	}
	246	break;
bf43fa3f	247	default: ws_die(pc, "malformed arithmetic IMP"); break;
1adfc4f4 AT	248	}
	249	}
	250
	251	void
eea0db3f AT	252	process_imp_flowcontrol(uint8_t * code, size_t * pc, int64_t ** sp, size_t * labels,
eea0db3f AT	253	size_t ** rsp)
1adfc4f4	254	{
84c650ed	255	size_t temp_pc;
1adfc4f4 AT	256	switch (next_code_byte(code,pc)) {
	257	case '\n':
	258	/* Technically another LF is required but we ignore it. */
1adfc4f4	259	fflush(stdout);
a2664738	260	unset_terminal_mode();
1adfc4f4 AT	261	exit(EXIT_SUCCESS);
	262	case ' ':
	263	{
	264	switch (next_code_byte(code,pc)) {
	265	case ' ':
	266	/* Mark a location in the program. */
9686c901 AT	267	if (next_code_byte(code,pc) != '\v') ws_die(pc,"expected vtab, "
	268	"perhaps a whitespace program, rather than vvhitespace?");
	269	/* Jump to next instruction since labels were parsed during startup. */
1e574f5b	270	parse_label(code, pc);
1adfc4f4 AT	271	break;
	272	case '\t':
	273	/* Call a subroutine. */
8d17aa41	274	temp_pc = labels[check_label(labels, parse_label(code, pc), pc)];
84c650ed AT	275	((rsp)++) = *pc;
84c650ed AT	276	*pc = temp_pc;
1adfc4f4 AT	277	break;
	278	case '\n':
	279	/* Jump unconditionally to a label. */
8d17aa41	280	*pc = labels[check_label(labels, parse_label(code, pc), pc)];
1adfc4f4	281	break;
bf43fa3f AT	282	default:
	283	ws_die(pc, "malformed flow control IMP");
	284	break;
1adfc4f4 AT	285	}
	286	}
	287	break;
	288	case '\t':
	289	{
	290	switch (next_code_byte(code,pc)) {
	291	case ' ':
	292	/* Jump to a label if TOS == 0 */
8d17aa41	293	temp_pc = labels[check_label(labels, parse_label(code, pc), pc)];
84c650ed	294	if (stack_pop(sp) == 0) *pc = temp_pc;
1adfc4f4 AT	295	break;
	296	case '\t':
	297	/* Jump to a label if TOS < 0. */
8d17aa41	298	temp_pc = labels[check_label(labels, parse_label(code, pc), pc)];
84c650ed	299	if (stack_pop(sp) < 0) *pc = temp_pc;
1adfc4f4 AT	300	break;
	301	case '\n':
	302	/* Return from subroutine. */
	303	pc = (--(*rsp));
	304	break;
bf43fa3f AT	305	default:
	306	ws_die(pc, "malformed flow control IMP");
	307	break;
1adfc4f4 AT	308	}
	309	}
	310	break;
bf43fa3f AT	311	default:
	312	ws_die(pc, "malformed flow control IMP");
	313	break;
1adfc4f4 AT	314	}
	315	}
	316
	317	void
eea0db3f	318	process_imp_heap(uint8_t * code, size_t * pc, int64_t sp, int64_t hp)
1adfc4f4 AT	319	{
1adfc4f4 AT	320	switch (next_code_byte(code,pc)) {
aea85838 AT	321	case ' ' :
	322	/* Store to heap */
	323	{
eea0db3f AT	324	int64_t value = stack_pop(sp);
eea0db3f AT	325	int64_t addr = stack_pop(sp);
aea85838 AT	326	(hp + addr) = value;
	327	}
	328	break;
	329	case '\t':
	330	/* Retrieve from heap */
	331	stack_push(sp, (hp + stack_pop(sp)));
	332	break;
	333	default:
	334	ws_die(pc, "malformed heap IMP");
	335	break;
1adfc4f4 AT	336	}
	337	}
	338
	339	void
eea0db3f	340	process_imp_io(uint8_t * code, size_t * pc, int64_t sp, int64_t hp)
1adfc4f4 AT	341	{
	342	switch (next_code_byte(code,pc)) {
	343	case ' ':
	344	/* Output */
	345	{
	346	switch (next_code_byte(code,pc)) {
eea0db3f AT	347	case ' ' : /* Output char from TOS */ printf("%c", (uint8_t) stack_pop(sp)); break;
eea0db3f AT	348	case '\t': /* Output digit from TOS */ printf("%c", (uint8_t) stack_pop(sp)+'0'); break;
9686c901	349	default : ws_die(pc, "malformed output IMP"); break;
1adfc4f4 AT	350	}
	351	fflush(stdout);
	352	}
	353	break;
	354	case '\t':
	355	/* Input */
	356	{
	357	while (stdin_empty()) continue;
	358	char c = getchar();
	359	switch (next_code_byte(code,pc)) {
	360	case '\t': /* Input digit / c -= '0'; / fallthrough */
a2664738	361	case ' ' : /* Input character / (hp + (--(*sp))) = c; break;
9686c901	362	default : ws_die(pc, "malformed input IMP"); break;
1adfc4f4 AT	363	}
	364	}
	365	break;
bf43fa3f	366	default: ws_die(pc, "malformed i/o IMP"); break;
1adfc4f4 AT	367	}
	368	}
	369
1adfc4f4 AT	370	int
	371	main(int argc, char ** argv)
	372	{
	373	/*
	374	* Process command line arguments
	375	*/
	376	int c;
	377	FILE * input = NULL;
	378	while ((c = getopt(argc,argv,"i:h")) != -1) {
	379	switch (c) {
	380	case 'i':
	381	if ((input = fopen(optarg, "r")) == NULL) {
	382	fprintf(stderr, "ERROR: %s: %s\n", optarg, strerror(errno));
	383	}
	384	break;
	385	case 'h':
	386	print_usage(argv);
	387	exit(EXIT_SUCCESS);
	388	break;
	389	default:
	390	break;
	391	}
	392	}
	393	if (input == NULL) {
bf43fa3f	394	fprintf(stderr, "ERROR: Must specify a VVhitespace source file with -f flag.\n");
1adfc4f4 AT	395	print_usage(argv);
	396	exit(EXIT_FAILURE);
	397	}
	398
	399	/*
eea0db3f	400	* Read just the VVhitespace source code into memory, stripping comment characters.
1adfc4f4 AT	401	* We will use the array indices as addresses for the virtual PC when jumping to labels.
	402	*/
	403	size_t ws_code_size = 0;
	404	uint8_t temp_byte;
	405	while (fread(&temp_byte, 1, 1, input)) {
bf43fa3f AT	406	if (temp_byte == ' ' \|\| temp_byte == '\t' \|\| temp_byte == '\n' \|\| temp_byte == '\v') {
	407	ws_code_size++;
	408	}
1adfc4f4 AT	409	}
	410	rewind(input);
	411	uint8_t * ws_code_space = malloc(ws_code_size);
	412	ws_code_size = 0;
	413	while (fread(&temp_byte, 1, 1, input)) {
bf43fa3f AT	414	if (temp_byte == ' ' \|\| temp_byte == '\t' \|\| temp_byte == '\n' \|\| temp_byte == '\v') {
	415	ws_code_space[ws_code_size++] = temp_byte;
	416	}
1adfc4f4 AT	417	}
	418	fclose(input);
	419
	420	/*
	421	* Setup a stack and heap.
1adfc4f4	422	*/
eea0db3f AT	423	int64_t * hp = malloc(HEAPSIZE*sizeof(int64_t));
eea0db3f AT	424	int64_t * sp = malloc(DATASTACKSIZE*sizeof(int64_t));
1adfc4f4 AT	425
	426	/*
	427	* Setup the return stack and the label array.
	428	*/
eea0db3f AT	429	size_t * rsp = malloc(RETURNSTACKSIZE*sizeof(size_t));
	430	size_t labels[65536] = {0}; /* 65536 = 2^16 => Holds all possible labels. */
	431	/* Default value of zero indicates an uninitialized label. */
bf43fa3f	432	populate_labels(labels, ws_code_space, ws_code_size);
1adfc4f4 AT	433
	434	/*
	435	* Main Loop
	436	*/
a2664738	437	set_terminal_mode();
1adfc4f4 AT	438	size_t pc = 0; /* Virtual program counter. Operates in the ws_code_space[] address space. */
	439	while (1) {
	440	if (pc >= ws_code_size) {
bf43fa3f AT	441	fprintf(stderr, "SIM_ERROR: PC Overrun\n Requested PC: %lu\n Max Address: %lu\n",
bf43fa3f AT	442	pc, ws_code_size-1);
1adfc4f4	443	exit(EXIT_FAILURE);
a2664738	444	unset_terminal_mode();
1adfc4f4 AT	445	}
	446
	447	/* Decode the IMPs */
	448	switch (ws_code_space[pc++]) {
	449	case ' ':
	450	/* Stack Manipulation */
	451	process_imp_stack(ws_code_space, &pc, &sp);
	452	break;
	453	case '\n':
	454	/* Flow Control */
	455	process_imp_flowcontrol(ws_code_space, &pc, &sp, labels, &rsp);
	456	break;
	457	case '\t':
	458	/* Arithmetic, Heap Access, or I/O */
	459	{
	460	switch (ws_code_space[pc++]) {
	461	case ' ':
	462	/* Arithmetic */
	463	process_imp_arithmetic(ws_code_space, &pc, &sp);
	464	break;
	465	case '\t':
	466	/* Heap Access */
	467	process_imp_heap(ws_code_space, &pc, &sp, &hp);
	468	break;
	469	case '\n':
	470	/* I/O */
	471	process_imp_io(ws_code_space, &pc, &sp, &hp);
	472	break;
	473	}
	474	}
	475	break;
eea0db3f	476	default: ws_die(&pc, "unexpected byte"); break;
1adfc4f4 AT	477	}
1adfc4f4 AT	478	}
1adfc4f4	479	}