igen/lexer.c


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#include <stddef.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "lexer.h"
#include "misc.h"
#include "preprocessor.h"

stmt *lex_stmt(source *src, int dbg);

char *skip_seperators(source *src, whitespace *wspace, int preserve_src, int dbg) {
	char *text = NULL;
	char *tmp = src->text;

	src->text = max(src->text, text);

	src->text = skip_whitespace(src, wspace, 1, 1, dbg);
	src->text = skip_comment(src, wspace, NULL, dbg);

	text = src->text;
	if (preserve_src) {
		src->text = tmp;
	}
	return text;
}

cond_stmt *lex_cond_stmt(source *src, int dbg) {
	const keyword *cond_keywords[] = {
		&(const keyword) {"do", COND_DO, NULL},
		&(const keyword) {"for", COND_FOR, NULL},
		&(const keyword) {"if", COND_IF, NULL},
		&(const keyword) {"while", COND_WHILE, NULL},
	};
	char *text = src->text;
	char *key = NULL;
	size_t key_len = 0;
	cond_type type = COND_NONE;
	whitespace wsp = {0};

	text = skip_seperators(src, &wsp, 1, dbg);
	key_len = strcspn(text, " \t\v\b");

	key = calloc(key_len+1, sizeof(char));
	memcpy(key, text, key_len);
	type = find_keyword(key, (keyword **)cond_keywords, NULL, NULL, dbg);
	free(key);

	text += key_len+1;

	if (type >= COND_NONE) {
		cond_stmt *cond = calloc(1, sizeof(cond_stmt));
		cond->type = type;

		src->text = text;
		src->cur.column += key_len+1;

		if (type != COND_DO) {
			cond->expr = lex_expr(src, dbg);
		}

		cond->stmt = lex_stmt(src, dbg);

		if (type == COND_DO) {
			text = skip_seperators(src, &wsp, 1, dbg);
			key_len = strcspn(text, " \t\v\b");

			key = calloc(key_len+1, sizeof(char));
			memcpy(key, text, key_len);

			if (!strcmp(key, "while")) {
				text += key_len+1;

				src->text = text;
				src->cur.column += key_len+1;

				cond->expr = lex_expr(src, dbg);

				text = skip_seperators(src, &wsp, 1, dbg);

				if (*text++ != ';') {
					--text;
					throw_error(src, 1, "Missing \';\' after do while statement.");
				} else {
					src->text = text;
					++src->cur.column;
				}
			} else {
				throw_error(src, 1, "Missing \'while\' after do while statement.");
			}
			free(key);
		}
		return cond;
	}

}

stmt *lex_comp_stmt(source *src, int dbg) {
	char *text = NULL;
	whitespace wsp = {0};

	text = skip_seperators(src, &wsp, 0, dbg);

	if (*text++ == '{') {
		stmt *s;

		src->text = text;
		++src->cur.column;

		for (s = lex_stmt(src, dbg); *src->text != '}' && *src->text != '\0'; s = s->next) {
			s->wsp = wsp;
			s->next = lex_stmt(src, dbg);
			text = skip_seperators(src, &wsp, 1, dbg);
		}

		text = src->text;

		if (*text++ == '}') {
			++src->cur.column;
		} else {
			--text;
			throw_error(src, 1, "Missing terminating \'}\' in compound statement.");
		}
		src->text = text;
		return s;
	}
	return NULL;
}

stmt *lex_stmt(source *src, int dbg) {
	char *text = src->text;
	const alt_stmt alts[] = {
		{STMT_FUNC, offsetof(stmt, func), (lex_func *)lex_func},
		{STMT_EXPR, offsetof(stmt, expr), (lex_func *)lex_exprs},
		{STMT_COND, offsetof(stmt, cond_stmt), (lex_func *)lex_cond_stmt},
		{STMT_COMP, offsetof(stmt, down), (lex_func *)lex_comp_stmt},
	};

	for (int i = 0; i < NUM_STMTS; ++i) {
		src->text = text;
		void *data = alts[i].lex(src, dbg);
		if (data != NULL) {
			stmt *s = calloc(1, sizeof(stmt));
			char *stmt = (char *)s;
			*(void **)(stmt+alts[i].offset) = data;
			return s;
		}
	}

	src->text = text;
	return NULL;
}

void lex_library(source *src, int dbg) {
	src->root = lex_stmt(src, dbg);
	src->last = (src->last != NULL) ? src->last : src->root;
	for (stmt *s = src->root; s != NULL; s = lex_stmt(src, dbg)) {
		src->last->next = s;
		src->last = s;
	}
};

int lex(source *src, int dbg) {
	char *text = src->text;

	lex_library(src, dbg);
	src->text = text;

	return (src->root != NULL && src->last != NULL);
}