Class: WordArray

• Inheritance
• Description
• Related information
• Class protocol
  • queries
• Instance protocol
  • accessing

Inheritance:

   Object
   |
   +--Collection
      |
      +--SequenceableCollection
         |
         +--ArrayedCollection
            |
            +--UninterpretedBytes
               |
               +--AbstractNumberVector
                  |
                  +--UnboxedIntegerArray
                     |
                     +--WordArray

Package:

stx:libbasic

Category:

Collections-Arrayed

Version:

rev: 1.3 date: 2019/03/24 11:26:53

user: cg

file: WordArray.st directory: libbasic

module: stx stc-classLibrary: libbasic

Author:

Claus Gittinger

Description:

WordArrays store integers in the range 0..16rFFFF.
In contrast to normal arrays (which store pointers to their elements),
wordArrays store the values in a dense & compact way. 
Since the representation fits the underlying C-language systems representation
of unsigned int16's, this is also useful to pass bulk data to c primitive code.

WordArrays can be used to hold bulk integer data in a more compact way.
    For example:
        Array new:100000 withAll:1
    requires 400k of object memory;

    in contrast,
        WordArray new:100000 withAll:1
    only requires half of it.

[memory requirements:]
    OBJ-HEADER + (size * 2)


[caveat:]
    should probably be renamed to UnsignedInt16Array

Related information:

    ByteArray
    BooleanArray
    FloatArray
    DoubleArray
    Array
    SignedWordArray

Class protocol:

 elementByteSize

for bit-like containers, return the number of bytes stored per element.
Here, 2 is returned

 maxVal

the maximum value which can be stored in instances of me.
For WordArrays, this is 16rFFFF (largest 16bit unsigned int)

 minVal

the minimum value which can be stored in instances of me.
For WordArrays, this is 0

Instance protocol:

 unsignedInt16At: index MSB: msb

return the 2-bytes starting at index as an (unsigned) Integer.
The index is a smalltalk index (i.e. 1-based).
The value is retrieved MSB (high 8 bits at lower index) if msb is true;
LSB-first (i.e. low 8-bits at lower byte index) if it's false.
Notice:
the index is a byte index; thus, this allows for unaligned access to
words on any boundary