Add a skia method to perform an atomic add.

Complements sk_atomic_inc for when you want to increase by more than one.

This time, use the correct atomic add function on Windows.

Reviewed at https://codereview.appspot.com/6399050/

Review URL: https://codereview.appspot.com/6407048

git-svn-id: http://skia.googlecode.com/svn/trunk@4623 2bbb7eff-a529-9590-31e7-b0007b416f81

3 files changed, 26 insertions, 1 deletions

diff --git a/src/ports/SkThread_none.cpp b/src/ports/SkThread_none.cpp
index 56bbbae3b3..1122c959d3 100644
--- a/src/ports/SkThread_none.cpp
+++ b/src/ports/SkThread_none.cpp
@@ -16,6 +16,12 @@ int32_t sk_atomic_inc(int32_t* addr) {
     return value;
 }
 
+int32_t sk_atomic_add(int32_t* addr, int32_t inc) {
+    int32_t value = *addr;
+    *addr = value + inc;
+    return value;
+}
+
 int32_t sk_atomic_dec(int32_t* addr) {
     int32_t value = *addr;
     *addr = value - 1;
diff --git a/src/ports/SkThread_pthread.cpp b/src/ports/SkThread_pthread.cpp
index d0bb3acbad..ad243b9e3a 100644
--- a/src/ports/SkThread_pthread.cpp
+++ b/src/ports/SkThread_pthread.cpp
@@ -35,6 +35,11 @@ int32_t sk_atomic_inc(int32_t* addr)
     return __sync_fetch_and_add(addr, 1);
 }
 
+int32_t sk_atomic_add(int32_t* addr, int32_t inc)
+{
+    return __sync_fetch_and_add(addr, inc);
+}
+
 int32_t sk_atomic_dec(int32_t* addr)
 {
     return __sync_fetch_and_add(addr, -1);
@@ -74,6 +79,15 @@ int32_t sk_atomic_inc(int32_t* addr)
     return value;
 }
 
+int32_t sk_atomic_add(int32_t* addr, int32_t inc)
+{
+    SkAutoMutexAcquire ac(gAtomicMutex);
+    
+    int32_t value = *addr;
+    *addr = value + inc;
+    return value;
+}
+
 int32_t sk_atomic_dec(int32_t* addr)
 {
     SkAutoMutexAcquire ac(gAtomicMutex);
diff --git a/src/ports/SkThread_win.cpp b/src/ports/SkThread_win.cpp
index e833314843..91a5ceb7ec 100644
--- a/src/ports/SkThread_win.cpp
+++ b/src/ports/SkThread_win.cpp
@@ -16,7 +16,7 @@
 //intrinsic, include intrin.h and put the function in a #pragma intrinsic
 //directive.
 //The pragma appears to be unnecessary, but doesn't hurt.
-#pragma intrinsic(_InterlockedIncrement, _InterlockedDecrement)
+#pragma intrinsic(_InterlockedIncrement, _InterlockedExchangeAdd, _InterlockedDecrement)
 #pragma intrinsic(_InterlockedCompareExchange)
 
 int32_t sk_atomic_inc(int32_t* addr) {
@@ -24,6 +24,11 @@ int32_t sk_atomic_inc(int32_t* addr) {
     return _InterlockedIncrement(reinterpret_cast<LONG*>(addr)) - 1;
 }
 
+int32_t sk_atomic_add(int32_t* addr, int32_t inc) {
+    return _InterlockedExchangeAdd(reinterpret_cast<LONG*>(addr),
+                                   static_cast<LONG>(inc));
+}
+
 int32_t sk_atomic_dec(int32_t* addr) {
     return _InterlockedDecrement(reinterpret_cast<LONG*>(addr)) + 1;
 }