139 lines
3.5 KiB
Text
139 lines
3.5 KiB
Text
/* Require bison minimal version */
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%require "3.2"
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/* write out a header file containing the token defines */
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%header
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// Code for the header file generated by bison
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%code requires {
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#include <stdbool.h>
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typedef void* yyscan_t;
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struct parser_state {
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// for storing the most recently read 4 chars
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char buffer[4];
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// location tracker
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unsigned long loc;
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bool found_start;
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bool check_matrix[26];
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};
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}
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// Code for the c file
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%{
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#include <stdio.h>
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#include <stdlib.h>
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#include <stdbool.h>
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#include "parser.h"
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#include "lexer.h"
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void yyerror(struct parser_state* state, yyscan_t scanner, const char* msg) {
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(void)state;
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(void)scanner;
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fprintf(stderr, "\033[93mSyntax Error: %s\033[0m\n", msg);
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}
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%}
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// define a reentrant parser
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%define api.pure
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// enable parser tracing and detailed error messages (plus Lookahead Correction)
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%define parse.trace
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%define parse.error detailed
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%define parse.lac full
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%lex-param { yyscan_t scanner }
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%parse-param { struct parser_state* state }
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%parse-param { yyscan_t scanner }
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%union {
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char cval;
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}
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%start input
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%token NEWLINE
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%token <cval> CHAR
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%term END_OF_FILE
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%%
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input
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: msg blanks END_OF_FILE { return 0; }
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;
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blanks
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: NEWLINE blanks
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| NEWLINE
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;
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msg
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: bit msg
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| bit
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;
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bit
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: CHAR {
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if (!state->found_start) {
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state->loc++;
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// left shift existing data
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for (int i = 0; i < 3; i++) {
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state->buffer[i] = state->buffer[i+1];
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}
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state->buffer[3] = $1;
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// check whether condition is met
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// offset array indices by the base -- 'a'
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char offset = 'a';
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state->found_start = true;
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for (int i = 0; i < 4; i++) {
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if (!state->check_matrix[state->buffer[i] - offset]) {
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state->check_matrix[state->buffer[i] - offset] = true;
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} else {
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state->found_start = false;
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break;
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}
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}
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// housekeeping; reset the fields to false
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for (int i = 0; i < 4; i++) {
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state->check_matrix[state->buffer[i] - offset] = false;
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}
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}
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}
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;
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%%
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int main(void) {
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struct parser_state parser_state;
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for (int i = 0; i < 4; i++) {
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parser_state.buffer[i] = 'a';
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}
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parser_state.loc = 0;
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parser_state.found_start = false;
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yyscan_t scanner;
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if (yylex_init(&scanner)) {
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fprintf(stderr, "\033[91m[error] Could not initialize lexer\033[0m\n");
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return EXIT_FAILURE;
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}
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if (yyparse(&parser_state, scanner)) {
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// TODO: Error handling https://www.gnu.org/software/bison/manual/html_node/Parser-Function.html
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// error during parse occured
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return EXIT_FAILURE;
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}
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yylex_destroy(scanner);
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printf("First start-of-packet marker detected at: %lu\n", parser_state.loc);
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return 0;
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}
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