bit-arrays 1.0.1

Accessor words for bit arrays



BIT ARRAYS - Accessors for bit-packed arrays of bits for Forth

Robert Dickow <dickow@turbonet.com> Package bit-arrays Version 1.0.0 - 2018-02-25

This is a simple word lexicon for accessing arrays of bits.

The fetching words accept two values, the address of the buffer, and a bit-wise index. The storing words accept a bit value or a boolean value, the address of the buffer, and a bit-wise index. The buffer size should be at least 1 CELLS long.

Top level words:

BIT@ ( caddr n-index -- n0|1 ) \ given a buffer caddr at index n-index, returns a value of 1 or 0.

BIT! ( n caddr n-index -- ) \ given a TRUE|FALSE or 1|0 value for n, store the bit into buffer caddr at index n-index

BOOL@ ( caddr n-index -- ) \ fetch a TRUE|FALSE value given buffer caddr at index n-index

BOOL! ( n caddr n-index -- ) \ convenience word for BIT!, but accepts a value of TRUE as equally valid as a bit value 1.

Include file

bit_arrays.f

Dependencies

none

Internal public words:

2^ ( n -- 2^n ) \ calculates the nth power of 2, used by the ^2MASKS compiling word

^2MASKS \ a compiling word to build the bmask lookup table, used internally.

bmask \ a lookup table created by ^2MASKS, used internally in the top-level words

_BIT@ \ a shared code factoring, probably only useful in the top-level words

Usage Example

store a 0 into the 34th bit position in a 64 bit bit array.

\ **

DECIMAL

\ create the buffer:

CREATE bitbuffer 2 CELLS ALLOT

\ initialize buffer to all on bits:

4294967295 DUP bitbuffer DUP -ROT ! CELL+ !

\ store a bit at position 34

0 bitbuffer 34 BIT!

\ test it:

bitbuffer 2@ binary du. decimal \ displays: 1111111111111111111111111111111111011111111111111111111111111111

\ **

Bug Reports

Please send suggestions, comments, or bug reports Bob Dickow <dickow@turbonet.com>

Compatibility

This lexicon is thought to conform to most Forth standards. It was tested on SwiftForth 3.7.1

by Budsy

avatar of Budsy

Versions

3.0.2, 3.0.1, 3.0.0, 2.0.1, 1.0.3, 1.0.2, 1.0.1, 1.0.0

Download 1.0.1 as zip

Tags

gpl, arrays

Dependencies

None

Dependents

None