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July 14, 2024 17:59
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| // Ref: https://old.reddit.com/r/C_Programming/comments/1e30ce8/ | |
| #include <stddef.h> | |
| #include <stdio.h> | |
| #define S(s) (str){s, sizeof(s)-1} | |
| typedef struct { | |
| char *data; | |
| ptrdiff_t len; | |
| } str; | |
| static str span(char *beg, char *end) | |
| { | |
| str r = {0}; | |
| r.data = beg; | |
| r.len = beg ? end - beg : 0; | |
| return r; | |
| } | |
| typedef enum { TOK_EOF, TOK_DATA, TOK_OR, TOK_AND } tok; | |
| typedef struct { | |
| str token; | |
| str input; | |
| tok type; | |
| } result; | |
| static result parse(str input) | |
| { | |
| result r = {0}; | |
| if (!input.len) { | |
| return r; | |
| } | |
| r.type = TOK_DATA; | |
| char *beg = input.data; | |
| char *cut = beg; | |
| char *end = input.data + input.len; | |
| for (int ands = 0; cut < end; cut++) { | |
| switch (*cut) { | |
| case '|': if (cut == beg) { | |
| r.type = TOK_OR; | |
| cut++; // consume | | |
| } | |
| goto done; | |
| case '&': switch (ands) { | |
| case 0: ands = 1; | |
| break; | |
| case 1: cut--; // back off to first & | |
| if (cut == beg) { | |
| r.type = TOK_AND; | |
| cut += 2; // consume && | |
| } | |
| goto done; | |
| } | |
| break; | |
| default : ands = 0; | |
| } | |
| } | |
| done: | |
| r.token = span(beg, cut); | |
| r.input = span(cut, end); | |
| return r; | |
| } | |
| int main(void) | |
| { | |
| result r = {0}; | |
| r.input = S("Hello, I am | a && human"); | |
| for (;;) { | |
| r = parse(r.input); | |
| if (r.type == TOK_EOF) break; | |
| printf("%-4s = \"%.*s\"\n", | |
| (char *[]){"EOF", "DATA", "OR", "AND"}[r.type], | |
| (int)r.token.len, r.token.data); | |
| } | |
| return 0; | |
| } |
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