mirror of
https://github.com/pnx/m16vm
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121 lines
2.9 KiB
C
121 lines
2.9 KiB
C
/* symtab.c
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*
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* Copyright (C) 2018-2019 Henrik Hautakoski <henrik.hautakoski@gmail.com>
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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 2 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, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
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* MA 02110-1301, USA.
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*/
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#include <stdlib.h>
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#include <string.h>
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#include "symtab.h"
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// TODO: Right now, the symtab is implemented as a simple dynamic growing array.
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// This is fine for now, but for lookup speed. A hashtable is more efficient.
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// How much memory that should be allocated each time.
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// Note: this should be defined as number of `struct symbol` objects, not bytes.
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#define BLOCK_SIZE 32
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// Helper macro to calculate number of bytes the table need.
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#define __M_SIZE(t) \
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((t)->size * sizeof(struct symbol))
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struct symbol {
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// The label associated with the location.
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char label[SYMTAB_LABEL_MAXLEN];
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// Location (program adress)
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uint16_t loc;
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};
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// Symbol table structure.
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struct symtab {
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// Array of symbols.
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struct symbol *data;
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// Number of symbols in the array.
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size_t num;
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// Total number of symbols the array can hold.
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size_t size;
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};
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symtab_t* symtab_init() {
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struct symtab *table = malloc(sizeof(struct symtab));
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table->num = 0;
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table->size = BLOCK_SIZE;
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table->data = malloc(__M_SIZE(table));
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return table;
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}
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void symtab_free(symtab_t *table) {
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if (!table)
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return;
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if (table->data)
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free(table->data);
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memset(table, 0, sizeof(struct symtab));
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free(table);
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}
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int symtab_set(symtab_t *table, const char *label, uint16_t loc) {
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// Check if it exist first.
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int index = symtab_get(table, label, NULL);
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// Entry did not exists. Insert
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if (index < 0) {
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struct symbol *sym;
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// We have one more.
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table->num += 1;
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// Make sure we resize the memory.
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if (table->num > table->size) {
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table->size += BLOCK_SIZE;
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table->data = realloc(table->data, __M_SIZE(table));
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}
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// insert the symbol at the end.
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sym = table->data + (table->num - 1);
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strncpy(sym->label, label, SYMTAB_LABEL_MAXLEN);
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sym->loc = loc;
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return 0;
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}
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// Could not insert. return as error.
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return -1;
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}
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int symtab_get(symtab_t *table, const char *label, uint16_t *loc) {
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// Linear search here for simplicity.
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for(size_t i = 0; i < table->num; i++) {
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struct symbol *sym = table->data + i;
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if (!strncmp(sym->label, label, SYMTAB_LABEL_MAXLEN)) {
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if (loc) *loc = sym->loc;
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return i;
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}
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}
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return -1;
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}
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