mysql的BASE64实现

mysql_base64.sql

delimiter |



DROP TABLE IF EXISTS base64_data |

CREATE TABLE base64_data (c CHAR(1) BINARY, val TINYINT) |

INSERT INTO base64_data VALUES 

    ('A',0), ('B',1), ('C',2), ('D',3), ('E',4), ('F',5), ('G',6), ('H',7), ('I',8), ('J',9),

    ('K',10), ('L',11), ('M',12), ('N',13), ('O',14), ('P',15), ('Q',16), ('R',17), ('S',18), ('T',19),

    ('U',20), ('V',21), ('W',22), ('X',23), ('Y',24), ('Z',25), ('a',26), ('b',27), ('c',28), ('d',29),

    ('e',30), ('f',31), ('g',32), ('h',33), ('i',34), ('j',35), ('k',36), ('l',37), ('m',38), ('n',39),

    ('o',40), ('p',41), ('q',42), ('r',43), ('s',44), ('t',45), ('u',46), ('v',47), ('w',48), ('x',49),

    ('y',50), ('z',51), ('0',52), ('1',53), ('2',54), ('3',55), ('4',56), ('5',57), ('6',58), ('7',59),

    ('8',60), ('9',61), ('+',62), ('/',63), ('=',0) |





DROP FUNCTION IF EXISTS BASE64_DECODE |

CREATE FUNCTION BASE64_DECODE (input BLOB)

    RETURNS BLOB

    CONTAINS SQL

    DETERMINISTIC

    SQL SECURITY INVOKER

BEGIN

    DECLARE ret BLOB DEFAULT '';

    DECLARE done TINYINT DEFAULT 0;



    IF input IS NULL THEN

        RETURN NULL;

    END IF;



each_block:

    WHILE NOT done DO BEGIN

        DECLARE accum_value BIGINT UNSIGNED DEFAULT 0;

        DECLARE in_count TINYINT DEFAULT 0;

        DECLARE out_count TINYINT DEFAULT 3;



each_input_char:

        WHILE in_count < 4 DO BEGIN

            DECLARE first_char CHAR(1);

    

            IF LENGTH(input) = 0 THEN

                RETURN ret;

            END IF;

    

            SET first_char = SUBSTRING(input,1,1);

            SET input = SUBSTRING(input,2);

    

            BEGIN

                DECLARE tempval TINYINT UNSIGNED;

                DECLARE error TINYINT DEFAULT 0;

                DECLARE base64_getval CURSOR FOR SELECT val FROM base64_data WHERE c = first_char;

                DECLARE CONTINUE HANDLER FOR SQLSTATE '02000' SET error = 1;

    

                OPEN base64_getval;

                FETCH base64_getval INTO tempval;

                CLOSE base64_getval;



                IF error THEN

                    ITERATE each_input_char;

                END IF;



                SET accum_value = (accum_value << 6) + tempval;

            END;



            SET in_count = in_count + 1;



            IF first_char = '=' THEN

                SET done = 1;

                SET out_count = out_count - 1;

            END IF;

        END; END WHILE;



        -- We've now accumulated 24 bits; deaccumulate into bytes



        -- We have to work from the left, so use the third byte position and shift left

        WHILE out_count > 0 DO BEGIN

            SET ret = CONCAT(ret,CHAR((accum_value & 0xff0000) >> 16));

            SET out_count = out_count - 1;

            SET accum_value = (accum_value << 8) & 0xffffff;

        END; END WHILE;

    

    END; END WHILE;



    RETURN ret;

END |



DROP FUNCTION IF EXISTS BASE64_ENCODE |

CREATE FUNCTION BASE64_ENCODE (input BLOB)

    RETURNS BLOB

    CONTAINS SQL

    DETERMINISTIC

    SQL SECURITY INVOKER

BEGIN

    DECLARE ret BLOB DEFAULT '';

    DECLARE done TINYINT DEFAULT 0;



    IF input IS NULL THEN

        RETURN NULL;

    END IF;



each_block:

    WHILE NOT done DO BEGIN

        DECLARE accum_value BIGINT UNSIGNED DEFAULT 0;

        DECLARE in_count TINYINT DEFAULT 0;

        DECLARE out_count TINYINT;



each_input_char:

        WHILE in_count < 3 DO BEGIN

            DECLARE first_char CHAR(1);

    

            IF LENGTH(input) = 0 THEN

                SET done = 1;

                SET accum_value = accum_value << (8 * (3 - in_count));

                LEAVE each_input_char;

            END IF;

    

            SET first_char = SUBSTRING(input,1,1);

            SET input = SUBSTRING(input,2);

    

            SET accum_value = (accum_value << 8) + ASCII(first_char);



            SET in_count = in_count + 1;

        END; END WHILE;



        -- We've now accumulated 24 bits; deaccumulate into base64 characters



        -- We have to work from the left, so use the third byte position and shift left

        CASE

            WHEN in_count = 3 THEN SET out_count = 4;

            WHEN in_count = 2 THEN SET out_count = 3;

            WHEN in_count = 1 THEN SET out_count = 2;

            ELSE RETURN ret;

        END CASE;



        WHILE out_count > 0 DO BEGIN

            BEGIN

                DECLARE out_char CHAR(1);

                DECLARE base64_getval CURSOR FOR SELECT c FROM base64_data WHERE val = (accum_value >> 18);



                OPEN base64_getval;

                FETCH base64_getval INTO out_char;

                CLOSE base64_getval;



                SET ret = CONCAT(ret,out_char);

                SET out_count = out_count - 1;

                SET accum_value = accum_value << 6 & 0xffffff;

            END;

        END; END WHILE;



        CASE

            WHEN in_count = 2 THEN SET ret = CONCAT(ret,'=');

            WHEN in_count = 1 THEN SET ret = CONCAT(ret,'==');

            ELSE BEGIN END;

        END CASE;

    

    END; END WHILE;



    RETURN ret;

END |