1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
|
/*
File: CFMLateImport.h
Contains: Interface to CFM late import library.
Written by: Quinn
Copyright: Copyright © 1999 by Apple Computer, Inc., all rights reserved.
You may incorporate this Apple sample source code into your program(s) without
restriction. This Apple sample source code has been provided "AS IS" and the
responsibility for its operation is yours. You are not permitted to redistribute
this Apple sample source code as "Apple sample source code" after having made
changes. If you're going to re-distribute the source, we require that you make
it clear in the source that the code was descended from Apple sample source
code, but that you've made changes.
Change History (most recent first):
<6> 21/9/01 Quinn Changes for CWPro7 Mach-O build.
<5> 19/9/01 Quinn Change comments to reflect the fact that an unpacked data
section is no longer required.
<4> 19/9/01 Quinn Simplified API and implementation after a suggestion by Eric
Grant. You no longer have to CFM export a dummy function; you
can just pass in the address of your fragment's init routine.
<3> 16/11/00 Quinn Allow symbol finding via a callback and use that to implement
CFBundle support.
<2> 18/10/99 Quinn Renamed CFMLateImport to CFMLateImportLibrary to allow for
possible future API expansion.
<1> 15/6/99 Quinn First checked in.
*/
#pragma once
/////////////////////////////////////////////////////////////////
// MoreIsBetter Setup
//#include "MoreSetup.h"
// Mac OS Interfaces
#if ! MORE_FRAMEWORK_INCLUDES
#include <MacTypes.h>
#include <CodeFragments.h>
#include <Devices.h>
#include <CFBundle.h>
#endif
/////////////////////////////////////////////////////////////////
#ifdef __cplusplus
extern "C" {
#endif
/* FAQ
---
Q: What does this library do?
A: It allows you to resolve a weak linked library at runtime,
by supply a CFM connection to the library that should substitute
for the weak linked one.
Q: Does the substituted library have to have the same name as the
weak linked library.
A: No.
Q: What's this useful for?
A: The most obvious example of where this is useful is when
you rely on shared libraries that the user might delete
or move. To can find the shared library (possibly even
using CatSearch), call GetDiskFragment to open a connection
to it, late import it using this library, and then the
rest of your code can continue to use the shared library
as if nothing had happened. No more defining thousands
of stub routines which call through routine pointers.
There are, however, numerous less obvious uses. You can
use this code to make a 'self repairing' application. If
the user removes your shared library from the Extensions
folder, the startup code for your application can offer
tor re-install it. If the user agrees, you can then
re-install your shared library, late import it, and then
continue running your application if nothing happened.
You can even use this code to free yourself from the
Extensions folder entirely. Say you have a suite of
applications that currently installs a dozen shared
libraries in the Extensions folder. You can move those
libraries to another folder entirely and each application's
startup code can track down the library (using an alias
in the Preferences file) and late import it.
An even cooler use is to provide easy abstraction layers.
Say you have a network code for both the MacTCP
API and the Open Transport API. Typically, you would be
force to do this by having an abstraction layer where every
routine contains a switch between MacTCP and OT. Your
OpenSocket routine might look like:
static int OpenSocket(void)
{
if (gOTAvailable) {
return OpenSocketOT();
} else {
return OpenSocketMacTCP();
}
}
With this code, you can avoid that entirely. Simply
weak link to a shared library that you know is never
going to be implemented ("crea;MySocketsDummy") and then,
at runtime, decide whether the system has MacTCP or OT
and late import the relevant real implementation
("crea;MySocketsMacTCP" or "crea;MySocketsOT").
One benefit of this approach is that only the MacTCP or
the OT code is resident in memory on any given system.
*/
typedef pascal OSStatus (*CFMLateImportLookupProc)(ConstStr255Param symName, CFragSymbolClass symClass,
void **symAddr, void *refCon);
// CFMLateImportLookupProc defines a callback for CFMLateImportCore.
// The routine is expected to look up the address of the symbol named
// symName and return it in *symAddr. The symbol should be of class
// symClass, although the callback decides whether a class mismatch is
// an error. refCon is an application defined value that was originally
// passed in to CFMLateImportCore.
//
// If this routine returns an error, a symbol address of 0 is assumed.
// If the symbol is marked as a weak import, the CFMLateImportCore will
// continue, otherwise the CFMLateImportCore routine will fail with the
// error.
extern pascal OSStatus CFMLateImportCore(const CFragSystem7DiskFlatLocator *fragToFixLocator,
CFragConnectionID fragToFixConnID,
CFragInitFunction fragToFixInitRoutine,
ConstStr255Param weakLinkedLibraryName,
CFMLateImportLookupProc lookup,
void *refCon);
// This routine will link you, at runtime, to some library
// that you were weak linked to and wasn't present when your
// fragment was prepared. As well as the obvious functionality
// of being able to resolve weak links after prepare time,
// this functionality can be put to a number of less obvious uses,
// some of which are discussed at the top of this header file.
//
// To call this routine, you need a number of pieces of information:
//
// 1. fragToFixLocator, fragToFixConnID: The location of your own
// code fragment on disk and the CFM connection ID to your own
// code fragment. Typically you get this information from your
// fragment's CFM init routine. You must ensure that
// fragToFixLocator->fileSpec points to an FSSpec of the
// file which holds your code fragment.
//
// IMPORTANT:
// The fact that you pass in a CFragSystem7DiskFlatLocator as the
// fragToFixLocator implies that the fragment to be fixed up must
// be in the data fork of a file. The code could be modified
// to remove this requirement, but on disk code fragments are the most
// common case.
//
// IMPORTANT:
// The fragment to fix may have a packed data section. Packing the
// data section will reduce the size of your fragment on disk, but it
// will significantly increase the memory needed by this routine
// (it increases memory usage by the sum of the sizes of the packed
// and unpacked data section). See below for instructions on how to
// create an unpacked data section.
//
// 2. fragToFixInitRoutine: A pointer to your own code fragment's
// fragment initialiser routine. You necessarily have one of these
// because you need it to get values for the fragToFixLocator and
// fragToFixConnID parameters. Just pass its address in as a parameter
// as well.
//
// 3. weakLinkedLibraryName: The name of the weak linked library which
// failed to link. You must have weak linked to this library.
// It is oxymoric for you to pass a strong linked library here,
// because your code would not have prepared if a strong linked
// library failed to prepare, and so you couldn't supply a valid
/// fragToFix.
//
// 4. lookup, refCon: A pointer to a callback function that the
// routine calls to look up the address of a symbol, and a refCon
// for that callback routine.
//
// Note:
// The fragToFixLocator and fragToFixInitRoutine parameters
// are artifacts of the way in which this functionality is implemented.
// In an ideal world, where CFM exported decent introspection APIs
// to third party developers, these parameters would not be necessary.
// If you're using this code inside Apple, you probably should investigate
// using the CFM private APIs for getting at the information these
// parameters are needed for. See the comments inside the implementation
// for more details.
//
// Note:
// The extra memory taken when you use a packed data section is also an
// artifact of my workaround for the lack of CFM introspection APIs. In
// my opinion it's better to use an unpacked data section and consume more
// space on disk while saving memory. In CodeWarrior you can switch to an
// unpacked data section by checking the "Expand Uninitialized Data"
// checkbox in the "PPC PEF" settings panel. In MPW, specified the
// "-packdata off" option to PPCLink.
//
// When the routine returns, any symbols that you imported from the
// library named weakLinkedLibraryName will be resolved to the address
// of the symbol provided by the "lookup" callback routine.
//
// It is possible for an unresolved import to remain unresolved after
// this routine returns. If the symbol import is marked as weak (as
// opposed to the library, which *must* be marked as weak) and the symbol
// is not found by the "lookup" callback, the routine will simple skip
// that symbol. If the symbol isn't marked as weak, the routine will fail
// in that case.
//
// Most of the possible error results are co-opted CFM errors. These
// include:
//
// cfragFragmentFormatErr -- The fragment to fix is is an unknown format.
// cfragNoSectionErr -- Could not find the loader section in the fragment to fix.
// cfragNoLibraryErr -- The fragment to fix is not weak linked to weakLinkedLibraryName.
// cfragFragmentUsageErr -- The fragment to fix doesn't have a data section.
// -- The fragment to fix is strong linked to weakLinkedLibraryName.
// -- The fragment doesn't have an init routine.
// cfragFragmentCorruptErr -- Encountered an undefined relocation opcode.
// unimpErr -- Encountered an unimplement relocation opcode. The
// relocation engine only implements a subset of the CFM
// relocation opcodes, the subset most commonly used by
// MPW and CodeWarrior PEF containers. If you encounter
// this error, you'll probably have to add the weird
// relocation opcode to the engine, which shouldn't be
// be too hard.
// memFullErr -- It's likely that this error is triggered by the memory
// needed to unpack your data section. Either make your
// data section smaller, or unpack it (see above).
// errors returned by FindSymbol
// errors returned by Memory Manager
//
// The routine needs enough memory to hold the loader section of the fragment
// to fix in memory. It allocates that memory using NewPtr and dispsoses of
// it before it returns. You may want to change the memory allocator, which
// is very simple.
extern pascal OSStatus CFMLateImportLibrary(const CFragSystem7DiskFlatLocator *fragToFixLocator,
CFragConnectionID fragToFixConnID,
CFragInitFunction fragToFixInitRoutine,
ConstStr255Param weakLinkedLibraryName,
CFragConnectionID connIDToImport);
// A wrapper around CFMLateImportCore that looks up symbols by calling
// FindSymbol on a connection to a CFM library (connIDToImport).
// You can get this connection ID through any standard CFM API, for example
// GetSharedLibrary, GetDiskFragment, or GetMemFragment.
//
// IMPORTANT:
// The fragment name for connIDToImport *does not* have to match
// weakLinkedLibraryName. This is part of the power of this library.
extern pascal OSStatus CFMLateImportBundle(const CFragSystem7DiskFlatLocator *fragToFixLocator,
CFragConnectionID fragToFixConnID,
CFragInitFunction fragToFixInitRoutine,
ConstStr255Param weakLinkedLibraryName,
CFBundleRef bundleToImport);
// A wrapper around CFMLateImportCore that looks up symbols by calling
// CFBundleGetFunctionPointerForName on a reference to a Core Foundation
// bundle (bundleToImport). You can get this reference through any
// Core Foundation bundle API, for example CFBundleCreate.
#ifdef __cplusplus
}
#endif
|
