migemo function for sqlite3

migemo.c

/*
 * Written by Alexey Tourbin <at@altlinux.org>.
 *
 * The author has dedicated the code to the public domain.  Anyone is free
 * to copy, modify, publish, use, compile, sell, or distribute the original
 * code, either in source code form or as a compiled binary, for any purpose,
 * commercial or non-commercial, and by any means.
 */
#include <assert.h>
#include <stdlib.h>
#include <string.h>
#include <pcre.h>
#include <sqlite3ext.h>
#include "migemo.h"
SQLITE_EXTENSION_INIT1

typedef struct {
	char *s;
	pcre *p;
	pcre_extra *e;
} cache_entry;

#ifndef CACHE_SIZE
#define CACHE_SIZE 16
#endif

	static
void func_migemo(sqlite3_context *ctx, int argc, sqlite3_value **argv)
{
	const char *re, *str;
	pcre *p;
	pcre_extra *e;

	assert(argc == 2);

	re = (const char *) sqlite3_value_text(argv[0]);
	if (!re) {
		sqlite3_result_error(ctx, "no word", -1);
		return;
	}

	str = (const char *) sqlite3_value_text(argv[1]);
	if (!str) {
		str = "";
	}

	/* simple LRU cache */
	{
		int i;
		int found = 0;
		cache_entry *cache = sqlite3_user_data(ctx);

		assert(cache);

		for (i = 0; i < CACHE_SIZE && cache[i].s; i++)
			if (strcmp(re, cache[i].s) == 0) {
				found = 1;
				break;
			}
		if (found) {
			if (i > 0) {
				cache_entry c = cache[i];
				memmove(cache + 1, cache, i * sizeof(cache_entry));
				cache[0] = c;
			}
		}
		else {
			cache_entry c;
			const char *err;
			int pos;

			migemo *m;
			m = migemo_open("/usr/local/opt/cmigemo/share/migemo/utf-8/migemo-dict");
			unsigned char *migemo_pattern;
			migemo_pattern = migemo_query(m, (const unsigned char*)re);

			c.p = pcre_compile((char*)migemo_pattern, 0, &err, &pos, NULL);

			migemo_release(m, migemo_pattern);
			migemo_close(m);

			if (!c.p) {
				char *e2 = sqlite3_mprintf("%s: %s (offset %d)", re, err, pos);
				sqlite3_result_error(ctx, e2, -1);
				sqlite3_free(e2);
				return;
			}
			c.e = pcre_study(c.p, 0, &err);
			c.s = strdup(re);
			if (!c.s) {
				sqlite3_result_error(ctx, "strdup: ENOMEM", -1);
				pcre_free(c.p);
				pcre_free(c.e);
				return;
			}
			i = CACHE_SIZE - 1;
			if (cache[i].s) {
				free(cache[i].s);
				assert(cache[i].p);
				pcre_free(cache[i].p);
				pcre_free(cache[i].e);
			}
			memmove(cache + 1, cache, i * sizeof(cache_entry));
			cache[0] = c;
		}
		p = cache[0].p;
		e = cache[0].e;
	}

	{
		int rc;
		assert(p);
		rc = pcre_exec(p, e, str, strlen(str), 0, 0, NULL, 0);
		sqlite3_result_int(ctx, rc >= 0);
		return;
	}
}

int sqlite3_extension_init(sqlite3 *db, char **err, const sqlite3_api_routines *api)
{
	SQLITE_EXTENSION_INIT2(api)
		cache_entry *cache = calloc(CACHE_SIZE, sizeof(cache_entry));
	if (!cache) {
		*err = "calloc: ENOMEM";
		return 1;
	}
	sqlite3_create_function(db, "migemo", 2, SQLITE_UTF8, cache, func_migemo, NULL, NULL);
	return 0;
}