132 lines
4.5 KiB
Plaintext
132 lines
4.5 KiB
Plaintext
// Copyright (c) 2011 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#import "base/mac/objc_property_releaser.h"
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#import <objc/runtime.h>
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#include <stdlib.h>
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#include <string>
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#include "base/logging.h"
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namespace base {
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namespace mac {
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namespace {
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// Returns the name of the instance variable backing the property, if known,
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// if the property is marked "retain" or "copy". If the instance variable name
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// is not known (perhaps because it was not automatically associated with the
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// property by @synthesize) or if the property is not "retain" or "copy",
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// returns an empty string.
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std::string ReleasableInstanceName(objc_property_t property) {
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// TODO(mark): Starting in newer system releases, the Objective-C runtime
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// provides a function to break the property attribute string into
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// individual attributes (property_copyAttributeList), as well as a function
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// to look up the value of a specific attribute
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// (property_copyAttributeValue). When the SDK defining that interface is
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// final, this function should be adapted to walk the attribute list as
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// returned by property_copyAttributeList when that function is available in
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// preference to scanning through the attribute list manually.
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// The format of the string returned by property_getAttributes is documented
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// at
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// http://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/ObjCRuntimeGuide/Articles/ocrtPropertyIntrospection.html#//apple_ref/doc/uid/TP40008048-CH101-SW6
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const char* property_attributes = property_getAttributes(property);
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std::string instance_name;
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bool releasable = false;
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while (*property_attributes) {
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char name = *property_attributes;
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const char* value = ++property_attributes;
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while (*property_attributes && *property_attributes != ',') {
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++property_attributes;
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}
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switch (name) {
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// It might seem intelligent to check the type ('T') attribute to verify
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// that it identifies an NSObject-derived type (the attribute value
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// begins with '@'.) This is a bad idea beacuse it fails to identify
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// CFTypeRef-based properties declared as __attribute__((NSObject)),
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// which just show up as pointers to their underlying CFType structs.
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//
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// Quoting
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// http://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/ObjectiveC/Chapters/ocProperties.html#//apple_ref/doc/uid/TP30001163-CH17-SW27
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//
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// > In Mac OS X v10.6 and later, you can use the __attribute__ keyword
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// > to specify that a Core Foundation property should be treated like
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// > an Objective-C object for memory management:
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// > @property(retain) __attribute__((NSObject)) CFDictionaryRef
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// > myDictionary;
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case 'C': // copy
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case '&': // retain
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releasable = true;
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break;
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case 'V': // instance variable name
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// 'V' is specified as the last attribute to occur in the
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// documentation, but empirically, it's not always the last. In
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// GC-supported or GC-required code, the 'P' (GC-eligible) attribute
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// occurs after 'V'.
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instance_name.assign(value, property_attributes - value);
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break;
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}
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if (*property_attributes) {
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++property_attributes;
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}
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}
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if (releasable) {
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return instance_name;
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}
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return std::string();
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}
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} // namespace
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void ObjCPropertyReleaser::Init(id object, Class classy) {
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DCHECK(!object_);
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DCHECK(!class_);
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CHECK([object isKindOfClass:classy]);
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object_ = object;
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class_ = classy;
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}
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void ObjCPropertyReleaser::ReleaseProperties() {
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DCHECK(object_);
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DCHECK(class_);
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unsigned int property_count = 0;
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objc_property_t* properties = class_copyPropertyList(class_, &property_count);
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for (unsigned int property_index = 0;
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property_index < property_count;
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++property_index) {
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objc_property_t property = properties[property_index];
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std::string instance_name = ReleasableInstanceName(property);
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if (!instance_name.empty()) {
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id instance_value = nil;
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Ivar instance_variable =
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object_getInstanceVariable(object_, instance_name.c_str(),
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(void**)&instance_value);
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DCHECK(instance_variable);
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[instance_value release];
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}
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}
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free(properties);
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// Clear object_ and class_ in case this ObjCPropertyReleaser will live on.
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// It's only expected to release the properties it supervises once per Init.
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object_ = nil;
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class_ = nil;
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}
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} // namespace mac
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} // namespace base
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