Joshua Haberman
16 years ago
parent
2282d2489b
commit
71d82d06d1
10 changed files with 251 additions and 31 deletions
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/*
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* upb - a minimalist implementation of protocol buffers. |
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* |
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* Copyright (c) 2009 Joshua Haberman. See LICENSE for details. |
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* |
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* Only a very small part of upb is thread-safe. Notably, individual |
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* messages, arrays, and strings are *not* thread safe for mutating. |
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* However, we do make message *metadata* such as upb_msgdef and |
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* upb_context thread-safe, and their ownership is tracked via atomic |
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* refcounting. This header implements the small number of atomic |
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* primitives required to support this. The primitives we implement |
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* are: |
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* |
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* - a reader/writer lock (wrappers around platform-provided mutexes). |
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* - an atomic refcount. |
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*/ |
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#ifndef UPB_ATOMIC_H_ |
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#define UPB_ATOMIC_H_ |
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#include <stdbool.h> |
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#ifdef __cplusplus |
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extern "C" { |
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#endif |
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/* inline if possible, emit standalone code if required. */ |
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#ifndef INLINE |
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#define INLINE static inline |
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#endif |
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#ifdef UPB_THREAD_UNSAFE |
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/* Non-thread-safe implementations. ******************************************/ |
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typedef struct { |
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int val; |
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} upb_atomic_refcount_t; |
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INLINE void upb_atomic_refcount_init(upb_atomic_refcount_t *a, int val) { |
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a->val = val; |
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} |
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INLINE bool upb_atomic_ref(upb_atomic_refcount_t *a) { |
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return a->val++ == 0; |
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} |
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INLINE bool upb_atomic_unref(upb_atomic_refcount_t *a) { |
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return --a->val == 0; |
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} |
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typedef struct { |
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} upb_rwlock_t; |
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INLINE void upb_rwlock_init(upb_rwlock_t *l) { (void)l; } |
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INLINE void upb_rwlock_destroy(upb_rwlock_t *l) { (void)l; } |
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INLINE void upb_rwlock_rdlock(upb_rwlock_t *l) { (void)l; } |
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INLINE void upb_rwlock_wrlock(upb_rwlock_t *l) { (void)l; } |
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INLINE void upb_rwlock_unlock(upb_rwlock_t *l) { (void)l; } |
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#endif |
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/* Atomic refcount ************************************************************/ |
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#ifdef UPB_THREAD_UNSAFE |
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/* Already defined above. */ |
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#elif (__GNUC__ == 4 && __GNUC_MINOR__ >= 1) || __GNUC__ > 4 |
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/* GCC includes atomic primitives. */ |
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typedef struct { |
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volatile int val; |
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} upb_atomic_refcount_t; |
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INLINE void upb_atomic_refcount_init(upb_atomic_refcount_t *a, int val) { |
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a->val = val; |
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__sync_synchronize(); /* Ensure the initialized value is visible. */ |
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} |
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INLINE void upb_atomic_ref(upb_atomic_refcount_t *a) { |
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return __sync_fetch_and_add(&a->val) == 0; |
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} |
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INLINE bool upb_atomic_unref(upb_atomic_refcount_t *a) { |
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return __sync_sub_and_fetch(&a->val) == 0; |
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} |
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#elif defined(WIN32) |
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/* Windows defines atomic increment/decrement. */ |
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#include <Windows.h> |
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typedef struct { |
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volatile LONG val; |
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} upb_atomic_refcount_t; |
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INLINE void upb_atomic_refcount_init(upb_atomic_refcount_t *a, int val) { |
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InterlockedExchange(&a->val, val); |
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} |
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INLINE bool upb_atomic_ref(upb_atomic_refcount_t *a) { |
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return InterlockedIncrement(&a->val) == 1; |
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} |
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INLINE bool upb_atomic_unref(upb_atomic_refcount_t *a) { |
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return InterlockedDecrement(&a->val) == 0; |
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} |
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#else |
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#error Atomic primitives not defined for your platform/CPU. \ |
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Implement them or compile with UPB_THREAD_UNSAFE. |
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#endif |
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/* Reader/Writer lock. ********************************************************/ |
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#ifdef UPB_THREAD_UNSAFE |
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/* Already defined. */ |
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#elif defined(_POSIX_THREADS) |
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typedef struct { |
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pthread_rwlock_t lock; |
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} upb_rwlock_t; |
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INLINE void upb_rwlock_init(upb_rwlock_t *l) { |
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/* TODO: check return value. */ |
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pthread_rwlock_init(&l->lock); |
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} |
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INLINE void upb_rwlock_destroy(upb_rwlock_t *l) { |
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/* TODO: check return value. */ |
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pthread_rwlock_destroy(&l->lock); |
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} |
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INLINE void upb_rwlock_rdlock(upb_rwlock_t *l) { |
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/* TODO: check return value. */ |
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pthread_rwlock_rdlock(&l->lock); |
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} |
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INLINE void upb_rwlock_wrlock(upb_rwlock_t *l) { |
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/* TODO: check return value. */ |
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pthread_rwlock_wrlock(&l->lock); |
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} |
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INLINE void upb_rwlock_unlock(upb_rwlock_t *l) { |
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/* TODO: check return value. */ |
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pthread_rwlock_unlock(&l->lock); |
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} |
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#else |
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#error Reader/writer lock is not defined for your platform/CPU. \ |
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Implement it or compile with UPB_THREAD_UNSAFE. |
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#endif |
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#ifdef __cplusplus |
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} /* extern "C" */ |
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#endif |
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#endif /* UPB_ATOMIC_H_ */ |
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