Airsequel / double-x-encoding

Encoding scheme to encode any Unicode string with only [0-9a-zA-Z_]. Similar to URL percent-encoding. Especially useful for GraphQL ID generation.

Double X Encoding

Encoding scheme to encode any Unicode string with only characters from [0-9a-zA-Z_]. Therefore it's quite similar to URL percent-encoding. It's especially useful for GraphQL ID generation.

Constraints for the encoding scheme:

1. Common IDs like file_format, fileFormat, FileFormat, FILE_FORMAT, __file_format__, … must not be altered
2. Support all Unicode characters
3. Characters of the ASCII range must lead to shorter encodings
4. Optional support for encoding leading digits (like in 1_file_format) to fulfill constraints of some ID schemes (e.g. GraphQL's).

Examples

Input	Output
camelCaseId	camelCaseId
snake_case_id	snake_case_id
__Schema	__Schema
doxxing	doxxing
DOXXING	DOXXXXXXING
id with spaces	idXX0withXX0spaces
id-with.special$chars!	idXXDwithXXEspecialXX4charsXX1
id_with_ümläutß	id_with_XXaaapmmlXXaaaoeutXXaaanp
Emoji: 😅	EmojiXXGXX0XXbpgaf
Multi Byte Emoji: 👨‍🦲	MultiXX0ByteXX0EmojiXXGXX0XXbpegiXXacaanXXbpjlc
\u{100000}	XXYbaaaaa
\u{10ffff}	XXYbapppp

With encoding of leading digit and double underscore activated (necessary for GraphQL ID generation):

Input	Output
1FileFormat	XXZ1FileFormat
__index__	XXRXXRindexXXRXXR

Explanation

The encoding scheme is based on the following rules:

1. All characters in [0-9A-Za-z_] except for XX are encoded as is
2. XX is encoded as XXXXXX
3. All other printable characters inside the ASCII range are encoded as a sequence of 3 characters: XX[0-9A-W]
4. All other Unicode code points until U+fffff (e.g. Emojis) are encoded as a sequence of 7 characters: XX[a-p]{5}, where the 5 characters are the hexadecimal representation with an alternative hex alphabet ranging from a to p instead of 0 to f.
5. All Unicode code points in the Supplementary Private Use Area-B (U+100000 to U+10ffff) are encoded as a sequence of 9 characters: XXY[a-p]{6}

If the optional leading digit encoding is enabled, a leading digit is encoded as XXZ[0-9].

If the optional double underscore encoding is enabled, double underscores are encoded as XXRXXR.

Installation

The code is not yet available via common package managers. Please copy the code into your project for the time being.