mirror of
https://github.com/darlinghq/darling-objc4.git
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126 lines
2.7 KiB
C++
126 lines
2.7 KiB
C++
/*
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* Copyright (c) 2019 Apple Inc. All Rights Reserved.
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*
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* @APPLE_LICENSE_HEADER_START@
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*
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* This file contains Original Code and/or Modifications of Original Code
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* as defined in and that are subject to the Apple Public Source License
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* Version 2.0 (the 'License'). You may not use this file except in
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* compliance with the License. Please obtain a copy of the License at
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* http://www.opensource.apple.com/apsl/ and read it before using this
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* file.
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*
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* The Original Code and all software distributed under the License are
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* distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
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* EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
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* INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
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* Please see the License for the specific language governing rights and
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* limitations under the License.
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*
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* @APPLE_LICENSE_HEADER_END@
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*/
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/**
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* @file objc-zalloc.h
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*
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* "zone allocator" for objc.
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*
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* Provides packed allocation for data structures the runtime
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* almost never frees.
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*/
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#ifndef _OBJC_ZALLOC_H
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#define _OBJC_ZALLOC_H
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#include <cstdint>
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#include <atomic>
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#include <cstdlib>
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namespace objc {
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// Darwin malloc always aligns to 16 bytes
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#define MALLOC_ALIGNMENT 16
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class AtomicQueue {
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#if __LP64__
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using pair_t = __int128_t;
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#else
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using pair_t = uint64_t;
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#endif
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static constexpr auto relaxed = std::memory_order_relaxed;
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static constexpr auto release = std::memory_order_release;
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struct Entry {
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struct Entry *next;
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};
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union {
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struct {
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Entry *head;
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unsigned long gen;
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};
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std::atomic<pair_t> atomic_pair;
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pair_t pair;
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};
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public:
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void *pop();
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void push_list(void *_head, void *_tail);
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inline void push(void *head)
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{
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push_list(head, head);
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}
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};
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template<class T, bool useMalloc>
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class Zone {
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};
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template<class T>
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class Zone<T, false> {
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struct Element {
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Element *next;
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char buf[sizeof(T) - sizeof(void *)];
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} __attribute__((packed));
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static AtomicQueue _freelist;
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static T *alloc_slow();
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public:
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static T *alloc();
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static void free(T *);
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};
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template<class T>
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class Zone<T, true> {
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public:
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static inline T *alloc() {
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return reinterpret_cast<T *>(::calloc(sizeof(T), 1));
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}
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static inline void free(T *ptr) {
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::free(ptr);
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}
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};
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/*
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* This allocator returns always zeroed memory,
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* and the template needs to be instantiated in objc-zalloc.mm
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*/
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template<class T>
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T *zalloc()
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{
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return Zone<T, sizeof(T) % MALLOC_ALIGNMENT == 0>::alloc();
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}
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template<class T>
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void zfree(T *e)
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{
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Zone<T, sizeof(T) % MALLOC_ALIGNMENT == 0>::free(e);
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}
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};
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#endif
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