Updating some terminology and variable names. Also updated readme to include more information about extending the package and fixed some spelling errors

src/res/levenshtein.sql

@@ -0,0 +1,42 @@
+DELIMITER $$
+DROP FUNCTION IF EXISTS levenshtein $$
+CREATE FUNCTION levenshtein( s1 VARCHAR(255), s2 VARCHAR(255), sensitivity INT )
+RETURNS INT
+DETERMINISTIC
+BEGIN
+DECLARE s1_len, s2_len, i, j, c, c_temp, cost INT;
+DECLARE s1_char CHAR;
+-- max strlen=255
+DECLARE cv0, cv1 VARBINARY(256);
+SET s1_len = CHAR_LENGTH(s1), s2_len = CHAR_LENGTH(s2), cv1 = 0x00, j = 1, i = 1, c = 0;
+IF s1 = s2 THEN
+  RETURN 0;
+ELSEIF s1_len = 0 THEN
+  RETURN s2_len;
+ELSEIF s2_len = 0 THEN
+  RETURN s1_len;
+ELSE
+  WHILE j <= s2_len DO
+    SET cv1 = CONCAT(cv1, UNHEX(HEX(j))), j = j + 1;
+  END WHILE;
+  WHILE i <= s1_len DO
+    SET s1_char = SUBSTRING(s1, i, 1), c = i, cv0 = UNHEX(HEX(i)), j = 1;
+    WHILE j <= s2_len DO
+      SET c = c + 1;
+      IF s1_char = SUBSTRING(s2, j, 1) THEN
+        SET cost = 0; ELSE SET cost = 1;
+      END IF;
+      SET c_temp = CONV(HEX(SUBSTRING(cv1, j, 1)), 16, 10) + cost;
+      IF c > c_temp THEN SET c = c_temp; END IF;
+      SET c_temp = CONV(HEX(SUBSTRING(cv1, j+1, 1)), 16, 10) + 1;
+      IF c > c_temp THEN
+        SET c = c_temp;
+      END IF;
+      SET cv0 = CONCAT(cv0, UNHEX(HEX(c))), j = j + 1;
+    END WHILE;
+    SET cv1 = cv0, i = i + 1;
+ END WHILE;
+END IF;
+RETURN c;
+END$$
+DELIMITER ;