83 lines
2.5 KiB
C
83 lines
2.5 KiB
C
/* symtable.c: Symbol Table implementation
|
|
* Created: 2025-08-19
|
|
* Author: Aryadev Chavali
|
|
* License: See end of file
|
|
* Commentary:
|
|
*/
|
|
|
|
#include <alisp/symtable.h>
|
|
|
|
#include <malloc.h>
|
|
#include <string.h>
|
|
|
|
#define ENTRY_GET(TABLE, INDEX) (VEC_GET(&(TABLE)->entries, (INDEX), sv_t))
|
|
|
|
u64 djb2(sv_t string)
|
|
{
|
|
// magic number (see
|
|
// https://stackoverflow.com/questions/10696223/reason-for-the-number-5381-in-the-djb-hash-function)
|
|
u64 hash = 5381;
|
|
for (u64 i = 0; i < string.size; ++i)
|
|
hash = string.data[i] + (hash + (hash << 5));
|
|
return hash;
|
|
}
|
|
|
|
void sym_table_init(sym_table_t *table)
|
|
{
|
|
table->capacity = MAX(table->capacity, SYM_TABLE_INIT_SIZE);
|
|
table->count = 0;
|
|
vec_init(&table->entries, table->capacity * sizeof(sv_t));
|
|
}
|
|
|
|
char *sym_table_find(sym_table_t *table, sv_t sv)
|
|
{
|
|
// Initialise the table if it's not done already
|
|
if (table->entries.capacity == 0)
|
|
sym_table_init(table);
|
|
|
|
// TODO: Consider resizing table when count >= capacity / 2
|
|
u64 index = djb2(sv) & (table->capacity - 1);
|
|
|
|
// FIXME: Since we don't implement resizing currently, this will infinite loop
|
|
// when the table capacity SYM_TABLE_INIT_SIZE=(1 << 10)=1024 is filled.
|
|
for (sv_t comp = ENTRY_GET(table, index); comp.data;
|
|
index = (index + 1) & (table->capacity - 1),
|
|
comp = ENTRY_GET(table, index))
|
|
// If present in the table already, stop.
|
|
if (sv.size == comp.size && strncmp(sv.data, comp.data, sv.size) == 0)
|
|
return comp.data;
|
|
|
|
// Worst case: not present in the table already. Since index is certainly
|
|
// free (based on loop condition before) we can fill it.
|
|
ENTRY_GET(table, index) = sv_copy(sv);
|
|
++table->count;
|
|
return ENTRY_GET(table, index).data;
|
|
}
|
|
|
|
void sym_table_cleanup(sym_table_t *table)
|
|
{
|
|
// Iterate through the strings and free each of them.
|
|
sv_t current = {0};
|
|
for (u64 i = 0; i < table->capacity; ++i)
|
|
{
|
|
current = ENTRY_GET(table, i);
|
|
if (current.data)
|
|
free(current.data);
|
|
}
|
|
// Free the underlying container
|
|
vec_free(&table->entries);
|
|
memset(table, 0, sizeof(*table));
|
|
}
|
|
|
|
/* Copyright (C) 2025, 2026 Aryadev Chavali
|
|
|
|
* This program is distributed in the hope that it will be useful, but WITHOUT
|
|
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
|
|
* FOR A PARTICULAR PURPOSE. See the Unlicense for details.
|
|
|
|
* You may distribute and modify this code under the terms of the Unlicense,
|
|
* which you should have received a copy of along with this program. If not,
|
|
* please go to <https://unlicense.org/>.
|
|
|
|
*/
|