Inside Macintosh: Operating System Utilities /

Chapter 3 - Mathematical and Logical Utilities

This chapter describes a number of utility routines that you can use to perform mathematical and logical operations supported directly by the Macintosh Operating System. In particular, this chapter discusses how you can

• perform low-level logical manipulation of bits and bytes when using a compiler that does not directly support such manipulations
• save disk space by using simple compression and decompression routines
• obtain a pseudorandom number
• perform mathematical operations with two fixed-point data types supported directly by the Operating System
• convert numeric variables of different types

You need to read this chapter only if you need access to any of these features. With the exception of the mathematical operations and conversions, the routines this chapter describes are intended for programmers who occasionally need to access some of these features and do not require that the algorithms used to implement them be sophisticated. For example, if you are developing an advanced mathematical application, the pseudorandom number generator built into the Operating System might be too simplistic to fit your needs. Similarly, if you wish to access individual bits of memory in a time-critical loop, the Operating System routines that perform these operations are probably too slow to be practical.

You do not need any prior knowledge of the Operating System to read this chapter, which begins by describing the building blocks of memory in any operating system: bits, bytes, words, and long words. After subsequent discussions of the built-in compression and decompression routines provided by the Operating System, this chapter illustrates how you can use the Operating System's Mathematical and Logical Utilities. The chapter concludes with a reference to all mathematical and logical routines supported by the Operating System. If you are an experienced programmer, you might be able to skip directly to that section to determine which routine you need.

This chapter does not describe the numeric data types supported by the Standard Apple Numerics Environment (SANE) that the Operating System does not support directly. For more information on such data types, consult the Apple Numerics Manual and Inside Macintosh: PowerPC Numerics.

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Chapter Contents

About the Mathematical and Logical Utilities

Bits, Bytes, Words, and Long Words

Bit Manipulation and Logical Operations

Reversed Bit-Numbering

Data Compression

Pseudorandom Number Generation

Fixed-Point Data Types

Angle-Slope Conversion

Using the Mathematical and Logical Utilities

Performing Low-Level Manipulation of Memory

Testing and Manipulating Bits

Performing Logical Operations on Long Words

Extracting a Word From a Long Word

Hardcoding Byte Values

Compressing Data

Obtaining Pseudorandom Numbers

Using Fixed-Point Data Types

Mathematical and Logical Utilities Reference

Data Structures

64-Bit Integer Record

Routines

Testing and Setting Bits

Performing Logical Operations

Getting and Setting Memory Values

Compressing and Decompressing Data

Obtaining a Pseudorandom Number

Converting Between Angle and Slope Values

Multiplying and Dividing Fixed-Point Numbers

Performing Calculations on Fixed-Point Numbers

Converting Among 32-Bit Numeric Types

Converting Between Fixed-Point and Floating-Point Values

Converting Between Fixed-Point and Integral Values

Multiplying 32-bit values

Summary of the Mathematical and Logical Utilities

Pascal Summary

Data Types

Routines

C Summary

Data Types

Routines

Global Variables