Crimpua

Crimpua is an implementation of Crimp in Lua.

Please see the bbc-news/crimp repo for more details.

Implementations

Installation

Crimpua can be installed with Luarocks from GitHub:

luarocks install https://raw.githubusercontent.com/BBC-News/crimpua/v1.0.0-0/crimp-1.0.0-0.rockspec

Usage

local Crimp = require("crimp")
print(Crimp.signature({a = {b = 1}})) -- prints "ac13c15d07e5fa3992fc6b15113db900"

Lua implementation details

Lua doesn't distinguish between an array and a hash. They're both tables, but an array is indexed with numbers.

letters = {'a', 'b', 'c', 'd'}
print(letters) -- prints "table: 0x2119ef0"
print(letters[1]) -- prints "a"

We distinguish between an array and a hash by inspecting table[1] which returns the first element for an array and nil for a hash.

You'll see why we have mentioned the use of tables in the next section.

Implementation Details

Under the hood Crimp annotates the passed data structure to a nested array of primitives (strings, numbers, booleans, nils, etc.) and a single byte to indicate the type of the primitive:

Type	Byte
String	S
Number	N
Boolean	B
nil	_
Array	A
Hash	H

You can verify it using the #notation function:

Crimp.notation({a=1})
"1NaSAH"

Before signing Crimpua, uses the #notation function to transform the return value of a table to a string. However the terminal strips away quotes when using LuaJIT (Just-In-Time-Compiler).

Crimp.notation({ a: { b: 'c' } })
"aSbScSAHAH"

Please note the Arrays and Hash keys are sorted before signing.

Crimp.notation({3, 1, 2})
"1N2N3NA"

key/value tuples get sorted as well.

Crimp.notation({ b: 3 })
"3NbSAH"

Changelog

1.0.0-0

Initial release.

Testing

For testing we use busted.

luarocks install crimp-1.0.0-0.rockspec --only-deps
luarocks test