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/*
* Stupid C parser, version 1e-6.
*
* Let's see how hard this is to do.
*/
#include <stdarg.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <ctype.h>
#include <unistd.h>
#include <fcntl.h>
#include "token.h"
#include "parse.h"
void show_expression(struct expression *expr)
{
if (!expr)
return;
switch (expr->type) {
case EXPR_IDENT:
printf("%s", show_token(expr->token));
break;
case EXPR_BINOP:
printf("<");
show_expression(expr->left);
printf(" %s ", show_special(expr->op));
show_expression(expr->right);
printf(">");
break;
case EXPR_UNARY:
printf("(");
show_expression(expr->unop);
printf(")");
break;
default:
printf("WTF");
}
}
static struct expression *alloc_expression(struct token *token, int type)
{
struct expression *expr = malloc(sizeof(struct expression));
if (!expr)
die("Unable to allocate expression");
memset(expr, 0, sizeof(*expr));
expr->type = type;
expr->token = token;
return expr;
}
struct token *cast_expression(struct token *token, struct expression **tree)
{
struct expression *expr = NULL;
if (token) {
switch (token->value.type) {
case TOKEN_IDENT:
expr = alloc_expression(token, EXPR_IDENT);
token = token->next;
break;
case TOKEN_SPECIAL:
if (token->value.special == '(') {
expr = alloc_expression(token, EXPR_UNARY);
expr->op = '(';
token = parse_expression(token->next, &expr->unop);
if (!token || token->value.type != TOKEN_SPECIAL || token->value.special != ')')
warn(token, "Expected ')'");
else
token = token->next;
break;
}
default:
warn(token, "Syntax error");
}
}
*tree = expr;
return token;
}
/* Generic left-to-right binop parsing */
struct token *lr_binop_expression(struct token *token, struct expression **tree,
struct token *(*inner)(struct token *, struct expression **), ...)
{
struct expression *left = NULL;
struct token * next = inner(token, &left);
if (left) {
while (next && next->value.type == TOKEN_SPECIAL) {
struct expression *top, *right = NULL;
int op = next->value.special;
va_list args;
va_start(args, inner);
for (;;) {
int nextop = va_arg(args, int);
if (!nextop)
goto out;
if (op == nextop)
break;
}
va_end(args);
top = alloc_expression(next, EXPR_BINOP);
next = inner(next->next, &right);
if (!right) {
warn(token, "Syntax error");
break;
}
top->op = op;
top->left = left;
top->right = right;
left = top;
}
}
out:
*tree = left;
return next;
}
struct token *multiplicative_expression(struct token *token, struct expression **tree)
{
return lr_binop_expression(token, tree, cast_expression, '*', '/', '%', 0);
}
struct token *additive_expression(struct token *token, struct expression **tree)
{
return lr_binop_expression(token, tree, multiplicative_expression, '+', '-', 0);
}
struct token *shift_expression(struct token *token, struct expression **tree)
{
return lr_binop_expression(token, tree, additive_expression, SPECIAL_LEFTSHIFT, SPECIAL_RIGHTSHIFT, 0);
}
struct token *relational_expression(struct token *token, struct expression **tree)
{
return lr_binop_expression(token, tree, shift_expression, '<', '>', SPECIAL_LTE, SPECIAL_GTE, 0);
}
struct token *equality_expression(struct token *token, struct expression **tree)
{
return lr_binop_expression(token, tree, relational_expression, SPECIAL_EQUAL, SPECIAL_NOTEQUAL, 0);
}
struct token *bitwise_and_expression(struct token *token, struct expression **tree)
{
return lr_binop_expression(token, tree, equality_expression, '&', 0);
}
struct token *bitwise_xor_expression(struct token *token, struct expression **tree)
{
return lr_binop_expression(token, tree, bitwise_and_expression, '^', 0);
}
struct token *bitwise_or_expression(struct token *token, struct expression **tree)
{
return lr_binop_expression(token, tree, bitwise_xor_expression, '|', 0);
}
struct token *logical_and_expression(struct token *token, struct expression **tree)
{
return lr_binop_expression(token, tree, bitwise_or_expression, SPECIAL_LOGICAL_AND, 0);
}
struct token *logical_or_expression(struct token *token, struct expression **tree)
{
return lr_binop_expression(token, tree, logical_and_expression, SPECIAL_LOGICAL_OR, 0);
}
struct token *parse_expression(struct token *token, struct expression **tree)
{
return logical_or_expression(token,tree);
}
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