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#include "bu-parser.h"
void free_node(node *n) {
if (n->lhs) free_node(n->lhs);
if (n->rhs) free_node(n->rhs);
free(n);
}
struct expr_parser expr_parser_init(lexer_fn src, void* lex_data) {
return (struct expr_parser){
.lex = src,
.lex_data = lex_data,
.lahead = {0},
.st = PARSER_READY,
.stack = {0},
.stack_idx = 0,
};
}
void expr_parser_finish(struct expr_parser *ep) {
for (size_t i = 0; i < ep->stack_idx; i++) {
if (ep->stack[i].id == STACKMEMBER_EXPR)
free_node(ep->stack[i].expr);
}
}
struct stackmember stack_pos(struct expr_parser *ep, size_t pos) {
ssize_t npos = ep->stack_idx - pos;
if (npos < 0) {
fprintf(stderr, "bad stack idx");
return (struct stackmember)
{ .id = (enum stackmember_id)TOKEN_OOB, .expr = NULL };
}
return ep->stack[npos];
}
void shift(struct expr_parser *ep) {
ep->stack[ep->stack_idx] = (struct stackmember){
.id = (enum stackmember_id)ep->lahead.id,
.terminal = ep->lahead.c,
};
ep->stack_idx++;
ep->lahead = ep->lex(ep->lex_data);
}
void var_expr(struct expr_parser *ep) {
struct stackmember v = stack_pos(ep, 0);
if (v.id != TOKEN_VARIABLE) {
ep->st = PARSER_ERR;
fprintf(stderr, "%s: not a variable token", __func__);
return;
}
node *n = malloc(sizeof(node));
n->type = LTTR;
n->el = v.terminal;
struct stackmember newm = {
.id = STACKMEMBER_EXPR,
.expr = n,
};
ep->stack[ep->stack_idx] = newm;
}
void binary_expr(struct expr_parser *ep) {
struct stackmember rhs, op, lhs;
lhs = stack_pos(ep, 2);
op = stack_pos(ep, 1);
rhs = stack_pos(ep, 0);
if ( lhs.id != STACKMEMBER_EXPR
|| op.id != TOKEN_BINARY_OPERATOR
|| rhs.id != STACKMEMBER_EXPR
) {
ep->st = PARSER_ERR;
fprintf(stderr, "%s: incorrect token pattern", __func__);
return;
}
node *n = malloc(sizeof(node));
n->type = BIOP;
n->el = op.terminal;
n->lhs = lhs.expr;
n->rhs = rhs.expr;
struct stackmember newm = {
.id = STACKMEMBER_EXPR,
.expr = n,
};
ep->stack_idx -= 2;
ep->stack[ep->stack_idx] = newm;
}
void unary_expr(struct expr_parser *ep) {
struct stackmember op, val;
op = stack_pos(ep, 1);
val = stack_pos(ep, 0);
if ( op.id != TOKEN_UNARY_OPERATOR
|| val.id != STACKMEMBER_EXPR
) {
ep->st = PARSER_ERR;
fprintf(stderr, "%s: incorrect token pattern", __func__);
return;
}
node *n = malloc(sizeof(node));
n->type = UNOP;
n->el = op.terminal;
n->value = val.expr;
struct stackmember newm = {
.id = STACKMEMBER_EXPR,
.expr = n,
};
ep->stack_idx -= 1;
ep->stack[ep->stack_idx] = newm;
}
int expr_parser_run(struct expr_parser *ep) {
while (ep->st != PARSER_ERR) {
shift(ep);
struct stackmember top = stack_pos(ep, 0);
if (top.id == TOKEN_EOS) {
ep->st = PARSER_OK;
continue;
}
if (top.id == TOKEN_VARIABLE) {
var_expr(ep);
}
if (ep->st == PARSER_OR_OP || ep->st == PARSER_AND_OP) {
if (ep->st == PARSER_OR_OP) {
if (ep->lahead.c == '*') continue;
}
binary_expr(ep);
}
else if (ep->st == PARSER_NOT_OP) {
unary_expr(ep);
}
if (top.id == TOKEN_BINARY_OPERATOR || top.id == TOKEN_UNARY_OPERATOR) {
switch (top.terminal) {
case '+': ep->st = PARSER_OR_OP; break;
case '*': ep->st = PARSER_AND_OP; break;
case '!': ep->st = PARSER_NOT_OP; break;
default: break;
}
continue;
}
}
return ep->st;
}
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