Inside Macintosh: PowerPC System Software /

Chapter 3 - Code Fragment Manager

This chapter describes the Code Fragment Manager, the part of the Macintosh system software that loads fragments into memory and prepares them for execution. A fragment can be an application, an import library, a system extension, or any other block of executable code and its associated data.

The Code Fragment Manager is intended to operate transparently to most applications and other software. You need to use the Code Fragment Manager explicitly only if

• you need to load code modules dynamically during the execution of your application or other software
• you want to unload code modules before the termination of your application
• you want to obtain information about the symbols exported by a fragment

For example, if your application supports dynamic loading of tools, filters, or other software modules contained in fragments, you'll need to use the Code Fragment Manager to load and prepare them for execution.

This chapter also describes the format of the code fragment resource, which defines information about a fragment. You need to create a code fragment resource (a resource
of type 'cfrg') for each application or import library you create. For information on doing this, see "Creating a Code Fragment Resource" on page 3-12.

To use this chapter, you should already be generally familiar with the Macintosh Operating System. See the books Inside Macintosh: Processes and Inside Macintosh: Memory for information about the run-time architecture of the 680x0 environment. You also need to be familiar with the run-time architecture of PowerPC processor-based Macintosh computers, as explained in the chapter "Introduction to PowerPC System Software." That chapter describes the general nature and structure of fragments.

This chapter begins by describing the capabilities of the Code Fragment Manager. Then it describes how the Code Fragment Manager searches for the appropriate versions of import libraries. In general, you need to know these details about searching and version checking only if you are creating updated versions of an existing import library. The section "Using the Code Fragment Manager" beginning on page 3-10 provides code samples illustrating how to use some of the routines provided by the Code Fragment Manager. The section "Code Fragment Manager Reference" beginning on page 3-15 is a complete reference to the Code Fragment Manager.

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Chapter Contents

About the Code Fragment Manager

Fragments

Import Library Searching

Version Checking

Using the Code Fragment Manager

Loading Code Fragments

Creating a Code Fragment Resource

Getting Information About Exported Symbols

Code Fragment Manager Reference

Data Structures

Fragment Initialization Block

Fragment Location Record

Memory Location Record

Disk Location Record

Segment Location Record

Code Fragment Manager Routines

Loading Fragments

Unloading Fragments

Finding Symbols

Fragment-Defined Routines

Resources

The Code Fragment Resource

Summary of the Code Fragment Manager

C Summary

Constants

Data Types

Code Fragment Manager Routines

Fragment-Defined Routines

Result Codes