bit-arrays 2.0.1

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 2.0.1 - 2018-03-02

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 expect a bit value of 1 or 0 or TRUE or FALSE value, the address of the buffer, and a bit-wise offset. The buffer size should be at least 1 CELLS long.

Top level words:

BIT@ ( caddr n-index -- n0|1 ) \ given a buffer caddr at offset 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 offset n-index

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

^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

_HANDLE0 \ an internal word to BIT!

Usage Example (32 bit CELL machines)

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 ROT ! CELL+ !

\ store a bit at position 34 0 bitbuffer 34 BIT!

\ test it: (DU. is unsigned double print ) bitbuffer 2@ BINARY DU. DECIMAL \ displays: 1111111111111111111111111111111111011111111111111111111111111111

\ **

Changes

Fixed bug in which ( 0 addr BIT! ) simply toggled the bit if executed a second time. Simplified code a little bit. Stack comments and other minor typographical changes.

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 2.0.1 as zip

Tags

gpl, arrays

Dependencies

None

Dependents

None