81 lines
2.4 KiB
C
81 lines
2.4 KiB
C
/* from http://rosettacode.org/wiki/Execute_Brain****#C */
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/* This is the Neutron brainfuck interpreter.
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* It's rather small and dense, but still readable, more or less.
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*
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* Robert de Bath -- 2013.
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*/
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#include <am.h>
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#include <klib.h>
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const char *prog =
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#include "mandelbrot.h"
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;
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struct bfi { char cmd; struct bfi *next, *jmp; };
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struct mem { char val; struct mem *next, *prev; };
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int main() {
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int ch;
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struct bfi *p=0, *n=0, *j=0, *pgm = 0;
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struct mem *m = malloc(sizeof(*m));
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/*
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* For each character, if it's a valid BF command add it onto the
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* end of the program. If the input is stdin use the '!' character
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* to mark the end of the program and the start of the data, but
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* only if we have a complete program. The 'j' variable points
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* at the list of currently open '[' commands, one is matched off
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* by each ']'. A ']' without a matching '[' is not a legal BF
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* command and so is ignored. If there are any '[' commands left
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* over at the end they are not valid BF commands and so are ignored.
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*/
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const char *s = prog;
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while((ch = *(s ++)) != '\0') {
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if (ch == '<' || ch == '>' || ch == '+' || ch == '-' ||
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ch == ',' || ch == '.' || ch == '[' || (ch == ']' && j)) {
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if ((n = malloc(sizeof(*n))) == NULL) {
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printf("malloc failed! exiting...\n");
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return 1;
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}
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if (p) p->next = n; else pgm = n;
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n->cmd = ch; p = n;
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if (n->cmd == '[') { n->jmp=j; j = n; }
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else if (n->cmd == ']') {
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n->jmp = j; j = j->jmp; n->jmp->jmp = n;
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}
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}
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}
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/* Ignore any left over '[' commands */
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while(j) { p = j; j = j->jmp; p->jmp = 0; p->cmd = ' '; }
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/* Execute the loaded BF program */
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for(n=pgm; n; n=n->next) {
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switch(n->cmd) {
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case '+': m->val++; break;
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case '-': m->val--; break;
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case '.': putch(m->val); break;
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case ',': if((ch=*(s ++))!='\0') m->val=ch; break;
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case '[': if (m->val == 0) n=n->jmp; break;
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case ']': if (m->val != 0) n=n->jmp; break;
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case '<':
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if (!(m=m->prev)) {
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printf("Hit start of tape\n");
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return 1;
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}
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break;
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case '>':
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if (m->next == 0) {
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if ((m->next = malloc(sizeof(*m))) == NULL) {
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printf("malloc failed! exiting...\n");
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return 1;
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}
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m->next->prev = m;
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}
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m=m->next;
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break;
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}
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}
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return 0;
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}
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