Utils

Utils

Functions

• getUniqueId

getUniqueId

Description

Gets a unique id for the given value, ensuring there are no collisions with the given mapping table. Appends the given prefix to the start and truncates the md5 hash to the given length.

Definition

getUniqueId(any value, table? mappingTable, string? prefix, integer? md5Length)

Arguments

any	value	The value from which to make the unique id. Note that calling this function with the same value twice will give different ids.
table?	mappingTable	The optional table to check against for collisions. For each id that is generated, the table is checked. If the value with that key is anything other than nil; a new id is generated.
string?	prefix	The optional prefix to append to the front of the id.
integer?	md5Length	The optional length of the desired md5 hash, between 1 and 32. This length does not include the prefix. If this is nil, the full 32 characters will be used.

Return Values

integer?	uniqueId	The generated unique id.

Code

function Utils.getUniqueId(value, mappingTable, prefix, md5Length)

    -- Default the md5 length to nil if it is not valid.
        if type(md5Length) ~ = "number" or md5Length < = 0 or md5Length > = 32 then
            md5Length = nil
        end

        --#debug Assert.isNotNil(value, "Mapping value cannot be nil!")
        --#debug Assert.isNilOrType(mappingTable, "table", "Mapping table must be a table or nil!")
        --#debug Assert.isNilOrType(prefix, "string", "Prefix must be a string or nil!")

        -- Default the prefix to an empty string.
        prefix = prefix or ""

        -- Keep generating unique ids until one is found that does not collide.
        local uniqueId
        local i = 0
        repeat
        local md5 = getMD5( tostring(value) .. tostring(getTime()) .. tostring(i))
        if md5Length ~ = nil then
            uniqueId = prefix .. string.sub(md5, 1 , md5Length)
        else
                uniqueId = prefix .. md5
            end
            i = i + 1
            until mappingTable = = nil or mappingTable[uniqueId] = = nil

            -- Return the unique id.
            return uniqueId
        end