Data¶

The data module is encoding, hashing, compression and byte packing. None of it touches the screen, so you can use it anywhere.

Base64 and hex¶

encode turns bytes or a string into base64, or into hex when you pass hex = true. decode gives you back the bytes, and decodeString gives back a string for when you know the payload was text.

let s = encode("hello")               # (1)!
let h = encode("hello", hex = true)   # (2)!
let back = decodeString(s)            # (3)!

Encodes the string as base64.
Encodes as hex instead by passing hex = true.
Decodes the base64 back to the original string.

Hashing¶

digest returns the hash of a string or bytes as lowercase hex. The function is the first argument: hfMD5, hfSHA1, hfSHA256 or hfSHA512. digestRaw gives the raw bytes instead.

echo digest(hfSHA256, "hello")

The proc is called digest rather than hash so it does not clash with the standard library's hash when you import both.

Compression¶

compress shrinks bytes or a string, and decompress expands them again. The format is compZlib, compGzip or compDeflate, and an optional level runs from 1 for fastest to 9 for smallest, with -1 as a sensible middle. decompressString gives back a string.

let packed = compress(bigText, compZlib)        # (1)!
let text = decompressString(packed, compZlib)   # (2)!

Shrinks the text with zlib, the chosen format.
Expands it back to a string using the same format.

Use the same format for decompress that you used to compress. Deflate has no header to detect, so it has to match.

Packing¶

pack writes integers into bytes following a small format string, and unpack reads them back. The codes are b and B for one byte, h and H for two, i and I for four, and l and L for eight, with the lowercase ones signed. A < switches to little-endian and a > to big-endian, with little-endian the default, and spaces in the format are ignored.

let bytes = pack("<i h b", 70000, 513, -3)   # (1)!
let values = unpack("<i h b", bytes)         # (2)!

Packs three little-endian integers, four bytes then two then one.
Reads them back in the same format, giving @[70000, 513, -3].