Update //third_party/protobuf to version 3.

third_party/protobuf/objectivec/GPBRootObject.m

+// 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