diff options
| -rwxr-xr-x | lib/system/atomics.nim | 34 |
1 files changed, 34 insertions, 0 deletions
diff --git a/lib/system/atomics.nim b/lib/system/atomics.nim index 127a8637f..623f8d0d2 100755 --- a/lib/system/atomics.nim +++ b/lib/system/atomics.nim @@ -40,3 +40,37 @@ proc atomicDec(memLoc: var int, x: int = 1): int = dec(memLoc, x) result = memLoc + +# atomic compare and swap (CAS) funcitons to implement lock-free algorithms + +when (defined(gcc) or defined(llvm_gcc)) and hasThreadSupport: + proc compareAndSwap*[T: ptr|ref|pointer](mem: var T, expected: T, newValue: T): bool {.nodecl, + importc: " __sync_bool_compare_and_swap".} + ## Returns true if successfully set value at mem to newValue when value + ## at mem == expected + +elif defined(windows) and hasThreadSupport: + proc InterlockedCompareExchangePointer(mem: ptr pointer, + newValue: pointer, comparand: pointer) : pointer {.nodecl, + importc: "InterlockedCompareExchangePointer", header:"windows.h".} + + + proc compareAndSwap*[T: ptr|ref|pointer](mem: var T, + expected: T, newValue: T): bool {.inline.}= + ## Returns true if successfully set value at mem to newValue when value + ## at mem == expected + return InterlockedCompareExchangePointer(addr(mem), + newValue, expected) == expected + +elif not hasThreadSupport: + proc compareAndSwap*[T: ptr|ref|pointer](mem: var T, + expected: T, newValue: T): bool {.inline.} = + ## Returns true if successfully set value at mem to newValue when value + ## at mem == expected + var oldval = mem + if oldval == expected: + mem = newValue + return true + return false + + |