84 lines
2.8 KiB
C
84 lines
2.8 KiB
C
/*
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* parser.c - Unlambda parser
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*
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* Copyright (C) 2020 CismonX <admin@cismon.net>
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <https://www.gnu.org/licenses/>.
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*/
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#include "parser.h"
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#include "logging.h"
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#include <stdlib.h>
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static const char* err_parse = "parse error";
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static const char* info_parse = "parse";
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bool
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u6a_parse(struct u6a_token* token_arr, uint32_t token_len, struct u6a_ast_node** ast_arr) {
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const uint32_t ast_size = (token_len + 2) * sizeof(struct u6a_ast_node);
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// The array stores the pre-order traversal of AST nodes
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struct u6a_ast_node* ast = calloc(1, ast_size);
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if (UNLIKELY(ast == NULL)) {
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u6a_err_bad_alloc(err_parse, ast_size);
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return false;
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}
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// Add an explicit `e` function as a guard, to ensure proper exit of the program.
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U6A_AN_FN(ast) = u6a_tf_app;
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U6A_AN_FN(U6A_AN_LEFT(ast)) = u6a_tf_e;
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U6A_AN_LEFT(ast)->sibling = 2;
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const uint32_t pstack_size = (token_len + 1) * sizeof(struct u6a_ast_node*);
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struct u6a_ast_node** pstack = malloc(pstack_size);
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if (UNLIKELY(pstack == NULL)) {
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u6a_err_bad_alloc(err_parse, pstack_size);
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goto parse_failed;
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}
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pstack[0] = ast;
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uint32_t pstack_idx = 0;
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// LL(0) parser
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for (uint32_t token_idx = 0; token_idx < token_len; ++token_idx) {
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struct u6a_token* current_token = token_arr + token_idx;
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struct u6a_ast_node* child;
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if (UNLIKELY(pstack_idx == UINT32_MAX)) {
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u6a_err_bad_syntax(err_parse);
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goto parse_failed;
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}
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struct u6a_ast_node* top = pstack[pstack_idx];
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if (!U6A_AN_FN(U6A_AN_LEFT(top))) {
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child = U6A_AN_LEFT(top);
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} else {
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U6A_AN_LEFT(top)->sibling = token_idx + 2;
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child = U6A_AN_RIGHT(top, ast);
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--pstack_idx;
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}
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child->value = *current_token;
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if (current_token->fn == u6a_tf_app) {
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pstack[++pstack_idx] = child;
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}
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}
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if (UNLIKELY(pstack_idx != UINT32_MAX)) {
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u6a_err_bad_syntax(err_parse);
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goto parse_failed;
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}
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free(pstack);
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*ast_arr = ast;
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u6a_info_verbose(info_parse, "completed");
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return true;
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parse_failed:
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free(pstack);
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free(ast);
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return false;
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}
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