murify: Efficient in-memory compression for URLs

This header-only C++ library converts URLs into a fully reversible compact representation. While general-purpose compression algorithms (e.g. GZIP or ZSTD) may not operate efficiently on URLs, URL compaction may reduce URL string length by as much as 75%, at low CPU cost. This may save substantial space when millions of URLs have to be kept in memory simultaneously.

Compaction is accomplished with a combination of several techniques:

• Decimal integers are represented as their binary equivalent, packed into minimum width. For example, the character string 123 of length 3 becomes the hexadecimal value 0x7B and is persisted in a single byte. The character string 4294967295 of length 10 becomes the hexadecimal value 0xFFFFFFFF and is persisted in 4 bytes.
• Frequently occurring strings (such as components in a path, or keys in a query string) are interned, and only the index in the lookup table is stored, packed into minimum width. A long but frequent path component such as management may become an index stored in a single byte.
• UUID strings (typically 36 characters) are parsed into a 16-byte array.
• When Base64-encoded data is encountered (e.g. a JWT or a user identifier), it's decoded and the raw representation is persisted, resulting in savings of 25%.
• Type is identified with a control byte. Integer width, string length or lookup table index is packed into the control byte whenever possible.
• Composite types such as URL path or query string are persisted as a combination of length and series of values, separators (e.g. /, & or =) are not stored.