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Atomic: cleanup and add more operations
Cleanup: * Remove volatile keyword, it is of no use at all. [1] * Remove the enable_if stuff. It had no use either. The most likely explanation why the enable_if stuff was there is that it was used as something like a STATIC_ASSERT to verify that sizeof(T) is not larger than sizeof(void *). This check however is not just misplaced in a place where we already use a lock, it isn't needed at all, as gcc will just generate a call to to the runtime if it compiles for platforms that don't support atomic instructions. The runtime will then most likely use locks. Code style fixes: * Prefix name of the mutex * Line everything up nicely, where it makes things look nice * Filling \ continuations with spaces is code style rule Added operations on the atomic var: * Compare and swap * Swap The second point of the cleanup also fixes the Android build of the next commit. [1]: http://stackoverflow.com/q/2484980
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@ -29,64 +29,83 @@ with this program; if not, write to the Free Software Foundation, Inc.,
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#define GCC_VERSION (__GNUC__ * 100 + __GNUC_MINOR__)
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#define CLANG_VERSION (__clang_major__ * 100 + __clang_minor__)
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#if GCC_VERSION >= 407 || CLANG_VERSION >= 302
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#define ATOMIC_LOAD(T, v) return __atomic_load_n(&(v), __ATOMIC_SEQ_CST)
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#define ATOMIC_STORE(T, v, x) __atomic_store (&(v), &(x), __ATOMIC_SEQ_CST); return x
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#define ATOMIC_ADD_EQ(T, v, x) return __atomic_add_fetch(&(v), (x), __ATOMIC_SEQ_CST)
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#define ATOMIC_SUB_EQ(T, v, x) return __atomic_sub_fetch(&(v), (x), __ATOMIC_SEQ_CST)
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#define ATOMIC_POST_INC(T, v) return __atomic_fetch_add(&(v), 1, __ATOMIC_SEQ_CST)
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#define ATOMIC_POST_DEC(T, v) return __atomic_fetch_sub(&(v), 1, __ATOMIC_SEQ_CST)
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#define ATOMIC_LOAD(T, v) return __atomic_load_n (&(v), __ATOMIC_SEQ_CST)
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#define ATOMIC_STORE(T, v, x) __atomic_store (&(v), &(x), __ATOMIC_SEQ_CST); return x
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#define ATOMIC_EXCHANGE(T, v, x) return __atomic_exchange_n(&(v), (x), __ATOMIC_SEQ_CST)
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#define ATOMIC_ADD_EQ(T, v, x) return __atomic_add_fetch (&(v), (x), __ATOMIC_SEQ_CST)
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#define ATOMIC_SUB_EQ(T, v, x) return __atomic_sub_fetch (&(v), (x), __ATOMIC_SEQ_CST)
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#define ATOMIC_POST_INC(T, v) return __atomic_fetch_add (&(v), 1, __ATOMIC_SEQ_CST)
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#define ATOMIC_POST_DEC(T, v) return __atomic_fetch_sub (&(v), 1, __ATOMIC_SEQ_CST)
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#define ATOMIC_CAS(T, v, e, d) return __atomic_compare_exchange_n(&(v), &(e), (d), \
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false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST)
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#else
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#define ATOMIC_USE_LOCK
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#include "threading/mutex.h"
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#define ATOMIC_LOCK_OP(T, op) do { \
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mutex.lock(); \
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T _val = (op); \
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mutex.unlock(); \
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return _val; \
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m_mutex.lock(); \
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T _val = (op); \
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m_mutex.unlock(); \
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return _val; \
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} while (0)
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#define ATOMIC_LOAD(T, v) \
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#define ATOMIC_LOCK_CAS(T, v, e, d) do { \
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m_mutex.lock(); \
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bool _eq = (v == e); \
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if (_eq) \
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v = d; \
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m_mutex.unlock(); \
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return _eq; \
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} while (0)
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#define ATOMIC_LOAD(T, v) \
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if (sizeof(T) <= sizeof(void*)) return v; \
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else ATOMIC_LOCK_OP(T, v);
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#define ATOMIC_STORE(T, v, x) \
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#define ATOMIC_STORE(T, v, x) \
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if (sizeof(T) <= sizeof(void*)) return v = x; \
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else ATOMIC_LOCK_OP(T, v = x);
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# if GCC_VERSION >= 401
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#define ATOMIC_ADD_EQ(T, v, x) return __sync_add_and_fetch(&(v), (x))
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#define ATOMIC_SUB_EQ(T, v, x) return __sync_sub_and_fetch(&(v), (x))
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#define ATOMIC_POST_INC(T, v) return __sync_fetch_and_add(&(v), 1)
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#define ATOMIC_POST_DEC(T, v) return __sync_fetch_and_sub(&(v), 1)
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# else
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#define ATOMIC_ADD_EQ(T, v, x) ATOMIC_LOCK_OP(T, v += x)
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#define ATOMIC_SUB_EQ(T, v, x) ATOMIC_LOCK_OP(T, v -= x)
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#define ATOMIC_POST_INC(T, v) ATOMIC_LOCK_OP(T, v++)
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#define ATOMIC_POST_DEC(T, v) ATOMIC_LOCK_OP(T, v--)
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# endif
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#define ATOMIC_EXCHANGE(T, v, x) do { \
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m_mutex.lock(); \
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T _val = v; \
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v = x; \
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m_mutex.unlock(); \
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return _val; \
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} while (0)
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#if GCC_VERSION >= 401
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#define ATOMIC_ADD_EQ(T, v, x) return __sync_add_and_fetch(&(v), (x))
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#define ATOMIC_SUB_EQ(T, v, x) return __sync_sub_and_fetch(&(v), (x))
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#define ATOMIC_POST_INC(T, v) return __sync_fetch_and_add(&(v), 1)
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#define ATOMIC_POST_DEC(T, v) return __sync_fetch_and_sub(&(v), 1)
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#define ATOMIC_CAS(T, v, e, d) return __sync_bool_compare_and_swap(&(v), &(e), (d))
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#else
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#define ATOMIC_ADD_EQ(T, v, x) ATOMIC_LOCK_OP(T, v += x)
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#define ATOMIC_SUB_EQ(T, v, x) ATOMIC_LOCK_OP(T, v -= x)
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#define ATOMIC_POST_INC(T, v) ATOMIC_LOCK_OP(T, v++)
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#define ATOMIC_POST_DEC(T, v) ATOMIC_LOCK_OP(T, v--)
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#define ATOMIC_CAS(T, v, e, d) ATOMIC_LOCK_CAS(T, v, e, d)
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#endif
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#endif
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template<typename T>
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class Atomic
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{
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// Like C++11 std::enable_if, but defaults to char since C++03 doesn't support SFINAE
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template<bool B, typename T_ = void> struct enable_if { typedef char type; };
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template<typename T_> struct enable_if<true, T_> { typedef T_ type; };
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class Atomic {
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public:
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Atomic(const T &v=0) : val(v) {}
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Atomic(const T &v = 0) : val(v) {}
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operator T () { ATOMIC_LOAD(T, val); }
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T operator = (T x) { ATOMIC_STORE(T, val, x); }
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T exchange(T x) { ATOMIC_EXCHANGE(T, val, x); }
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bool compare_exchange_strong(T &expected, T desired) { ATOMIC_CAS(T, val, expected, desired); }
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T operator = (T x) { ATOMIC_STORE(T, val, x); }
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T operator += (T x) { ATOMIC_ADD_EQ(T, val, x); }
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T operator -= (T x) { ATOMIC_SUB_EQ(T, val, x); }
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T operator ++ () { return *this += 1; }
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T operator -- () { return *this -= 1; }
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T operator ++ () { return *this += 1; }
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T operator -- () { return *this -= 1; }
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T operator ++ (int) { ATOMIC_POST_INC(T, val); }
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T operator -- (int) { ATOMIC_POST_DEC(T, val); }
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private:
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volatile T val;
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T val;
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#ifdef ATOMIC_USE_LOCK
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typename enable_if<sizeof(T) <= sizeof(void*), Mutex>::type mutex;
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Mutex m_mutex;
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#endif
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};
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