EXEMPLO_1212310 Database

Parameters

Name	Type	Mode
@input	varchar	IN
@hash	int	INOUT

Definition

CREATE PROCEDURE [dbo].[GetHashCode]
    @input tAppName,
    @hash int OUTPUT
AS
    /*
       This sproc is based on this C# hash function:
        int GetHashCode(string s)
        {
            int     hash = 5381;
            int     len = s.Length;
            for (int i = 0; i < len; i++) {
                int     c = Convert.ToInt32(s[i]);
                hash = ((hash << 5) + hash) ^ c;
            }
            return hash;
        }
        However, SQL 7 doesn't provide a 32-bit integer
        type that allows rollover of bits, we have to
        divide our 32bit integer into the upper and lower
        16 bits to do our calculation.
    */
    DECLARE @hi_16bit   int
    DECLARE @lo_16bit   int
    DECLARE @hi_t       int
    DECLARE @lo_t       int
    DECLARE @len        int
    DECLARE @i          int
    DECLARE @c          int
    DECLARE @carry      int
    SET @hi_16bit = 0
    SET @lo_16bit = 5381
    SET @len = DATALENGTH(@input)
    SET @i = 1
    WHILE (@i <= @len)
    BEGIN
        SET @c = ASCII(SUBSTRING(@input, @i, 1))
        /* Formula:
           hash = ((hash << 5) + hash) ^ c */
        /* hash << 5 */
        SET @hi_t = @hi_16bit * 32 /* high 16bits << 5 */
        SET @hi_t = @hi_t & 0xFFFF /* zero out overflow */
        SET @lo_t = @lo_16bit * 32 /* low 16bits << 5 */
        SET @carry = @lo_16bit & 0x1F0000 /* move low 16bits carryover to hi 16bits */
        SET @carry = @carry / 0x10000 /* >> 16 */
        SET @hi_t = @hi_t + @carry
        SET @hi_t = @hi_t & 0xFFFF /* zero out overflow */
        /* + hash */
        SET @lo_16bit = @lo_16bit + @lo_t
        SET @hi_16bit = @hi_16bit + @hi_t + (@lo_16bit / 0x10000)
        /* delay clearing the overflow */
        /* ^c */
        SET @lo_16bit = @lo_16bit ^ @c
        /* Now clear the overflow bits */
        SET @hi_16bit = @hi_16bit & 0xFFFF
        SET @lo_16bit = @lo_16bit & 0xFFFF
        SET @i = @i + 1
    END
    /* Do a sign extension of the hi-16bit if needed */
    IF (@hi_16bit & 0x8000 <> 0)
        SET @hi_16bit = 0xFFFF0000 | @hi_16bit
    /* Merge hi and lo 16bit back together */
    SET @hi_16bit = @hi_16bit * 0x10000 /* << 16 */
    SET @hash = @hi_16bit | @lo_16bit
    RETURN 0