Hexabecimal turn to Decimal custom functions

The following is a Hexadecimal turn to Decimal system custom functions.

wrote by Jimmy on Mar 18th 2011

use master
GO

drop function [dbo].[Jimmy_HexadecimalToDecimal]
go

create function [dbo].[Jimmy_HexadecimalToDecimal]
(
    @hec    varchar(50)
)
returns int
as
begin
    declare    @dec int,@count int,@bigbit int,@strone int
 
    set @bigbit = 0
    set @count = 1
    set @dec = 0
    
   --get the number of hexadecimal digits 
    while @bigbit < len(@hec)
    begin
        set    @strone = ascii(lower(substring(@hec,@count,1)))
        if    (@strone >= 48 and    @strone <= 57) 
           or
            (@strone >= 97 and @strone <= 102)
        begin
                set @bigbit = @bigbit + 1
                set    @count = @count + 1
                continue
        end
        else
            break
    end    
    
    set @count = 1

    while @bigbit > 0
    begin
        set    @strone =ascii(lower(substring(@hec,@count,1)))
        select @dec = @dec +
                    cast(
                        case when @strone >=48 and @strone <= 57 then @strone-48
                        when @strone = 97  then 10
                        when @strone = 98  then 11
                        when @strone = 99  then 12
                        when @strone = 100 then 13
                        when @strone = 101 then 14
                        when @strone = 102 then 15
                        end
                     as int)*power(16,@bigbit-1)
        set @count = @count + 1
        set @bigbit = @bigbit - 1
    end

    return @dec
end
go
----------------------
select [master].[dbo].[Jimmy_HexadecimalToDecimal] ('ab') as '十六进制转十进制' --171
go