bitfiddle v0.1.1

bitfiddle

A simple toolkit for "bit-fiddling" operations

swizzle

A function that takes a string and a number and returns a new number or BigInt described by the bits in positions described by the string, in terms of 2-based little-endian indexing: 0 and 1 represent a literal 0 or 1.

Note that characters here are in parseInt's "base-36" order, ie. positions beyond 9 are described alphabetically, skipping no letters (not even I,l, or O as in Douglas Crockford's Base32).

In other words, the bits of a 32-bit value (right-justified) are counted thus:

XWVUTSRQ PONMLKJI HGFEDCBA 98765432

For convenience, you may use non-alphanumeric characters such as spaces to separate bit destination positions in the template string.

Example

Converting an 8-bit octet value into a 24-bit RGB value using rgbirgbi bit order:

const color = swizzle(byte, '95629562 84628462 73627362');
                          // rriirrii ggiiggii bbiibbii