test_levenshtein.js

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/* This Source Code Form is subject to the terms of the Mozilla Public

 * License, v. 2.0. If a copy of the MPL was not distributed with this

 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

// This file tests the Levenshtein Distance function we've registered.

function createUtf16Database() {

  print("Creating the in-memory UTF-16-encoded database.");

  let conn = Services.storage.openSpecialDatabase("memory");

  conn.executeSimpleSQL("PRAGMA encoding = 'UTF-16'");

  print("Make sure the encoding was set correctly and is now UTF-16.");

  let stmt = conn.createStatement("PRAGMA encoding");

  Assert.ok(stmt.executeStep());

  let enc = stmt.getString(0);

  stmt.finalize();

  // The value returned will actually be UTF-16le or UTF-16be.

  Assert.ok(enc === "UTF-16le" || enc === "UTF-16be");

  return conn;

function check_levenshtein(db, s, t, expectedDistance) {

  var stmt = db.createStatement("SELECT levenshteinDistance(:s, :t) AS result");

  stmt.params.s = s;

  stmt.params.t = t;

  try {

    Assert.ok(stmt.executeStep());

    Assert.equal(expectedDistance, stmt.row.result);

  } finally {

    stmt.reset();

    stmt.finalize();

function testLevenshtein(db) {

  // Basic tests.

  check_levenshtein(db, "", "", 0);

  check_levenshtein(db, "foo", "", 3);

  check_levenshtein(db, "", "bar", 3);

  check_levenshtein(db, "yellow", "hello", 2);

  check_levenshtein(db, "gumbo", "gambol", 2);

  check_levenshtein(db, "kitten", "sitten", 1);

  check_levenshtein(db, "sitten", "sittin", 1);

  check_levenshtein(db, "sittin", "sitting", 1);

  check_levenshtein(db, "kitten", "sitting", 3);

  check_levenshtein(db, "Saturday", "Sunday", 3);

  check_levenshtein(db, "YHCQPGK", "LAHYQQKPGKA", 6);

  // Test SQL NULL handling.

  check_levenshtein(db, "foo", null, null);

  check_levenshtein(db, null, "bar", null);

  check_levenshtein(db, null, null, null);

  // The levenshteinDistance function allocates temporary memory on the stack

  // if it can.  Test some strings long enough to force a heap allocation.

  var dots1000 = Array(1001).join(".");

  var dashes1000 = Array(1001).join("-");

  check_levenshtein(db, dots1000, dashes1000, 1000);

function run_test() {

  testLevenshtein(getOpenedDatabase());

  testLevenshtein(createUtf16Database());