// Protocol Buffers - Google's data interchange format
// Copyright 2008 Google Inc. All rights reserved.
// https://developers.google.com/protocol-buffers/
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
// * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#import "GPBRootObject_PackagePrivate.h"
#import <objc/runtime.h>
#import <CoreFoundation/CoreFoundation.h>
#import "GPBDescriptor.h"
#import "GPBExtensionRegistry.h"
#import "GPBUtilities_PackagePrivate.h"
@interface GPBExtensionDescriptor (GPBRootObject)
// Get singletonName as a c string.
- (const char *)singletonNameC;
@end
@implementation GPBRootObject
// Taken from http://www.burtleburtle.net/bob/hash/doobs.html
// Public Domain
static uint32_t jenkins_one_at_a_time_hash(const char *key) {
uint32_t hash = 0;
for (uint32_t i = 0; key[i] != '\0'; ++i) {
hash += key[i];
hash += (hash << 10);
hash ^= (hash >> 6);
}
hash += (hash << 3);
hash ^= (hash >> 11);
hash += (hash << 15);
return hash;
}
// Key methods for our custom CFDictionary.
// Note that the dictionary lasts for the lifetime of our app, so no need
// to worry about deallocation. All of the items are added to it at
// startup, and so the keys don't need to be retained/released.
// Keys are NULL terminated char *.
static const void *GPBRootExtensionKeyRetain(CFAllocatorRef allocator,
const void *value) {
#pragma unused(allocator)
return value;
}
static void GPBRootExtensionKeyRelease(CFAllocatorRef allocator,
const void *value) {
#pragma unused(allocator)
#pragma unused(value)
}
static CFStringRef GPBRootExtensionCopyKeyDescription(const void *value) {
const char *key = (const char *)value;
return CFStringCreateWithCString(kCFAllocatorDefault, key,
kCFStringEncodingUTF8);
}
static Boolean GPBRootExtensionKeyEqual(const void *value1,
const void *value2) {
const char *key1 = (const char *)value1;
const char *key2 = (const char *)value2;
return strcmp(key1, key2) == 0;
}
static CFHashCode GPBRootExtensionKeyHash(const void *value) {
const char *key = (const char *)value;
return jenkins_one_at_a_time_hash(key);
}
// NOTE: OSSpinLock may seem like a good fit here but Apple engineers have
// pointed out that they are vulnerable to live locking on iOS in cases of
// priority inversion:
// http://mjtsai.com/blog/2015/12/16/osspinlock-is-unsafe/
// https://lists.swift.org/pipermail/swift-dev/Week-of-Mon-20151214/000372.html
static dispatch_semaphore_t gExtensionSingletonDictionarySemaphore;
static CFMutableDictionaryRef gExtensionSingletonDictionary = NULL;
static GPBExtensionRegistry *gDefaultExtensionRegistry = NULL;
+ (void)initialize {
// Ensure the global is started up.
if (!gExtensionSingletonDictionary) {
gExtensionSingletonDictionarySemaphore = dispatch_semaphore_create(1);
CFDictionaryKeyCallBacks keyCallBacks = {
// See description above for reason for using custom dictionary.
0,
GPBRootExtensionKeyRetain,
GPBRootExtensionKeyRelease,
GPBRootExtensionCopyKeyDescription,
GPBRootExtensionKeyEqual,
GPBRootExtensionKeyHash,
};
gExtensionSingletonDictionary =
CFDictionaryCreateMutable(kCFAllocatorDefault, 0, &keyCallBacks,
&kCFTypeDictionaryValueCallBacks);
gDefaultExtensionRegistry = [[GPBExtensionRegistry alloc] init];
}
if ([self superclass] == [GPBRootObject class]) {
// This is here to start up all the per file "Root" subclasses.
// This must be done in initialize to enforce thread safety of start up of
// the protocol buffer library.
[self extensionRegistry];
}
}
+ (GPBExtensionRegistry *)extensionRegistry {
// Is overridden in all the subclasses that provide extensions to provide the
// per class one.
return gDefaultExtensionRegistry;
}
+ (void)globallyRegisterExtension:(GPBExtensionDescriptor *)field {
const char *key = [field singletonNameC];
dispatch_semaphore_wait(gExtensionSingletonDictionarySemaphore,
DISPATCH_TIME_FOREVER);
CFDictionarySetValue(gExtensionSingletonDictionary, key, field);
dispatch_semaphore_signal(gExtensionSingletonDictionarySemaphore);
}
static id ExtensionForName(id self, SEL _cmd) {
// Really fast way of doing "classname_selName".
// This came up as a hotspot (creation of NSString *) when accessing a
// lot of extensions.
const char *selName = sel_getName(_cmd);
if (selName[0] == '_') {
return nil; // Apple internal selector.
}
size_t selNameLen = 0;
while (1) {
char c = selName[selNameLen];
if (c == '\0') { // String end.
break;
}
if (c == ':') {
return nil; // Selector took an arg, not one of the runtime methods.
}
++selNameLen;
}
const char *className = class_getName(self);
size_t classNameLen = strlen(className);
char key[classNameLen + selNameLen + 2];
memcpy(key, className, classNameLen);
key[classNameLen] = '_';
memcpy(&key[classNameLen + 1], selName, selNameLen);
key[classNameLen + 1 + selNameLen] = '\0';
// NOTE: Even though this method is called from another C function,
// gExtensionSingletonDictionarySemaphore and gExtensionSingletonDictionary
// will always be initialized. This is because this call flow is just to
// lookup the Extension, meaning the code is calling an Extension class
// message on a Message or Root class. This guarantees that the class was
// initialized and Message classes ensure their Root was also initialized.
NSAssert(gExtensionSingletonDictionary, @"Startup order broken!");
dispatch_semaphore_wait(gExtensionSingletonDictionarySemaphore,
DISPATCH_TIME_FOREVER);
id extension = (id)CFDictionaryGetValue(gExtensionSingletonDictionary, key);
if (extension) {
// The method is getting wired in to the class, so no need to keep it in
// the dictionary.
CFDictionaryRemoveValue(gExtensionSingletonDictionary, key);
}
dispatch_semaphore_signal(gExtensionSingletonDictionarySemaphore);
return extension;
}
BOOL GPBResolveExtensionClassMethod(Class self, SEL sel) {
// Another option would be to register the extensions with the class at
// globallyRegisterExtension:
// Timing the two solutions, this solution turned out to be much faster
// and reduced startup time, and runtime memory.
// The advantage to globallyRegisterExtension is that it would reduce the
// size of the protos somewhat because the singletonNameC wouldn't need
// to include the class name. For a class with a lot of extensions it
// can add up. You could also significantly reduce the code complexity of this
// file.
id extension = ExtensionForName(self, sel);
if (extension != nil) {
const char *encoding =
GPBMessageEncodingForSelector(@selector(getClassValue), NO);
Class metaClass = objc_getMetaClass(class_getName(self));
IMP imp = imp_implementationWithBlock(^(id obj) {
#pragma unused(obj)
return extension;
});
if (class_addMethod(metaClass, sel, imp, encoding)) {
return YES;
}
}
return NO;
}
+ (BOOL)resolveClassMethod:(SEL)sel {
if (GPBResolveExtensionClassMethod(self, sel)) {
return YES;
}
return [super resolveClassMethod:sel];
}
@end