消息查找小知识

OC runtime 消息查找的时候 如果 方法数组

    int methodListIsFixedUp = mlist->isFixedUp();
    int methodListHasExpectedSize = mlist->entsize() == sizeof(method_t);
    //如果是修正过的数组。使用 二分查找 如果不是 使用 线性查找
    if (fastpath(methodListIsFixedUp && methodListHasExpectedSize)) {
        return findMethodInSortedMethodList(sel, mlist);
    } else {
        // Linear search of unsorted method list
        for (auto& meth : *mlist) {
            if (meth.name == sel) return &meth;
        }
    }

那么 FixedUp 是在什么时候呢。 如何进行的FixedUp 呢。

//对MethodList 进行FixedUp 如果sort 为true 则进行排序
static void 
fixupMethodList(method_list_t *mlist, bool bundleCopy, bool sort)
{
    runtimeLock.assertLocked();
    ASSERT(!mlist->isFixedUp());

    // fixme lock less in attachMethodLists ?
    // dyld3 may have already uniqued, but not sorted, the list
    if (!mlist->isUniqued()) {
        mutex_locker_t lock(selLock);
    
        // Unique selectors in list.
        for (auto& meth : *mlist) {
            const char *name = sel_cname(meth.name);
            meth.name = sel_registerNameNoLock(name, bundleCopy);
        }
    }

    // Sort by selector address.//排序 必须是稳定的排序
    if (sort) {
        method_t::SortBySELAddress sorter;
        std::stable_sort(mlist->begin(), mlist->end(), sorter);
    }
    
    // Mark method list as uniqued and sorted
    mlist->setFixedUp();
}

准备数组

static void 
prepareMethodLists(Class cls, method_list_t **addedLists, int addedCount,
                   bool baseMethods, bool methodsFromBundle)
{
    runtimeLock.assertLocked();

    if (addedCount == 0) return;

    // There exist RR/AWZ/Core special cases for some class's base methods.
    // But this code should never need to scan base methods for RR/AWZ/Core:
    // default RR/AWZ/Core cannot be set before setInitialized().
    // Therefore we need not handle any special cases here.
    if (baseMethods) {
        ASSERT(cls->hasCustomAWZ() && cls->hasCustomRR() && cls->hasCustomCore());
    }

    // Add method lists to array.
    // Reallocate un-fixed method lists.
    // The new methods are PREPENDED to the method list array.

    for (int i = 0; i < addedCount; i++) {
        method_list_t *mlist = addedLists[i];
        ASSERT(mlist);

        // Fixup selectors if necessary
        if (!mlist->isFixedUp()) {
            fixupMethodList(mlist, methodsFromBundle, true/*sort*/);
        }
    }

    // If the class is initialized, then scan for method implementations
    // tracked by the class's flags. If it's not initialized yet,
    // then objc_class::setInitialized() will take care of it.
    if (cls->isInitialized()) {
        objc::AWZScanner::scanAddedMethodLists(cls, addedLists, addedCount);
        objc::RRScanner::scanAddedMethodLists(cls, addedLists, addedCount);
        objc::CoreScanner::scanAddedMethodLists(cls, addedLists, addedCount);
    }
}

* Fixes up cls's method list, protocol list, and property list.
* Attaches any outstanding categories.
* Locking: runtimeLock must be held by the caller
static void methodizeClass(Class cls, Class previously)

/***********************************************************************
* realizeClassWithoutSwift
* Performs first-time initialization on class cls, 
* including allocating its read-write data.
* Does not perform any Swift-side initialization.
* Returns the real class structure for the class. 
* Locking: runtimeLock must be write-locked by the caller
**********************************************************************/
static Class realizeClassWithoutSwift(Class cls, Class previously)

/***********************************************************************
* objc_readClassPair()
* Read a class and metaclass as written by a compiler.
* Assumes the class and metaclass are not referenced by other things 
* that might need to be fixed up (such as categories and subclasses).
* Does not call +load.
* Returns the class pointer, or nil.
*
* Locking: runtimeLock acquired by map_images
**********************************************************************/
Class objc_readClassPair(Class bits, const struct objc_image_info *info)

think
1， 一个类中如果方法过多是会影响启动速度吗？
2， 通过runtime 添加的方法 是怎么处理的呢。