objc_cache

Performance optimization for method calls. Contains pointers to recently used methods.

Declaration 宣言

struct objc_cache
{
unsigned int mask;
unsigned int occupied;
Method buckets[1];
};

Overview 概要

To limit the need to perform linear searches of method lists for the definitions of frequently accessed methods—an operation that can considerably slow down method lookup—the Objective-C runtime functions store pointers to the definitions of the most recently called method of the class in an objc_cache data structure.

Topics 話題

Fields

mask

An integer specifying the total number of allocated cache buckets (minus one). During method lookup, the Objective-C runtime uses this field to determine the index at which to begin a linear search of the buckets array. A pointer to a method’s selector is masked against this field using a logical AND operation (index = (mask & selector)). This serves as a simple hashing algorithm.

occupied

An integer specifying the total number of occupied cache buckets.

buckets

An array of pointers to Method data structures. This array may contain no more than mask + 1 items. Note that pointers may be NULL, indicating that the cache bucket is unoccupied, and occupied buckets may not be contiguous. This array may grow over time.

objc_cache

Declaration 宣言

Overview 概要

Topics 話題

Fields

See Also 参照

Class-Definition Data Structures