Add a skia method to perform an atomic add.

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

Review URL: https://codereview.appspot.com/6350106

git-svn-id: http://skia.googlecode.com/svn/trunk@4614 2bbb7eff-a529-9590-31e7-b0007b416f81

7 files changed, 104 insertions, 3 deletions

diff --git a/gyp/tests.gyp b/gyp/tests.gyp
index c6e2786f05..8ea4ee8411 100644
--- a/gyp/tests.gyp
+++ b/gyp/tests.gyp
@@ -18,6 +18,7 @@
       'sources': [
         '../tests/AAClipTest.cpp',
         '../tests/AnnotationTest.cpp',
+        '../tests/AtomicTest.cpp',
         '../tests/BitmapCopyTest.cpp',
         '../tests/BitmapGetColorTest.cpp',
         '../tests/BitSetTest.cpp',
diff --git a/include/core/SkThread.h b/include/core/SkThread.h
index 2fd5052b06..5b1fc1c213 100644
--- a/include/core/SkThread.h
+++ b/include/core/SkThread.h
@@ -16,6 +16,7 @@
 /****** SkThread_platform needs to define the following...
 
 int32_t sk_atomic_inc(int32_t*);
+int32_t sk_atomic_add(int32_t*, int32_t);
 int32_t sk_atomic_dec(int32_t*);
 int32_t sk_atomic_conditional_inc(int32_t*);
 
diff --git a/include/core/SkThread_platform.h b/include/core/SkThread_platform.h
index cb05c50f3a..19fcd4a743 100644
--- a/include/core/SkThread_platform.h
+++ b/include/core/SkThread_platform.h
@@ -23,6 +23,10 @@ static inline __attribute__((always_inline)) int32_t sk_atomic_inc(int32_t *addr
     return __sync_fetch_and_add(addr, 1);
 }
 
+static inline __attribute__((always_inline)) int32_t sk_atomic_add(int32_t *addr, int32_t value) {
+    return __sync_fetch_and_add(addr, value);
+}
+
 static inline __attribute__((always_inline)) int32_t sk_atomic_dec(int32_t *addr) {
     return __sync_fetch_and_add(addr, -1);
 }
@@ -54,8 +58,9 @@ static inline __attribute__((always_inline)) void sk_membar_aquire__after_atomic
  */
 #include <utils/Atomic.h>
 
-#define sk_atomic_inc(addr)     android_atomic_inc(addr)
-#define sk_atomic_dec(addr)     android_atomic_dec(addr)
+#define sk_atomic_inc(addr)         android_atomic_inc(addr)
+#define sk_atomic_add(addr, value)  android_atomic_add(value, addr)
+#define sk_atomic_dec(addr)         android_atomic_dec(addr)
 void sk_membar_aquire__after_atomic_dec() {
     //HACK: Android is actually using full memory barriers.
     //      Should this change, uncomment below.
@@ -92,6 +97,14 @@ void sk_membar_aquire__after_atomic_conditional_inc() {
 */
 SK_API int32_t sk_atomic_inc(int32_t* addr);
 
+/** Implemented by the porting layer, this function adds value to the int
+ specified by the address (in a thread-safe manner), and returns the
+ previous value.
+ No additional memory barrier is required.
+ This must act as a compiler barrier.
+ */
+SK_API int32_t sk_atomic_add(int32_t* addr, int32_t value);
+
 /** Implemented by the porting layer, this function subtracts one from the int
     specified by the address (in a thread-safe manner), and returns the
     previous value.
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..a1c7b24f66 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 value)
+{
+    return __sync_fetch_and_add(addr, value);
+}
+
 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..7d091d2a67 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, _InterlockedAdd, _InterlockedDecrement)
 #pragma intrinsic(_InterlockedCompareExchange)
 
 int32_t sk_atomic_inc(int32_t* addr) {
@@ -24,6 +24,12 @@ 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) {
+    // InterlockedAdd returns the new value, we want to return the old.
+    LONG value = reinterpret_cast<LONG>(inc);
+    return _InterlockedAdd(reinterpret_cast<LONG*>(addr), value) - value;
+}
+
 int32_t sk_atomic_dec(int32_t* addr) {
     return _InterlockedDecrement(reinterpret_cast<LONG*>(addr)) + 1;
 }
diff --git a/tests/AtomicTest.cpp b/tests/AtomicTest.cpp
new file mode 100644
index 0000000000..a9ab8d2279
--- /dev/null
+++ b/tests/AtomicTest.cpp
@@ -0,0 +1,60 @@
+/*
+ * Copyright 2012 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SkThread.h"
+#include "SkThreadUtils.h"
+#include "SkTypes.h"
+#include "Test.h"
+
+struct AddInfo {
+    int32_t valueToAdd;
+    int timesToAdd;
+    unsigned int processorAffinity;
+};
+
+static int32_t base = 0;
+
+static AddInfo gAdds[] = {
+    { 3, 100, 23 },
+    { 2, 200, 2 },
+    { 7, 150, 17 },
+};
+
+static void addABunchOfTimes(void* data) {
+    AddInfo* addInfo = static_cast<AddInfo*>(data);
+    for (int i = 0; i < addInfo->timesToAdd; i++) {
+        sk_atomic_add(&base, addInfo->valueToAdd);
+    }
+}
+
+static void test_atomicAddTests(skiatest::Reporter* reporter) {
+    int32_t total = base;
+    SkThread* threads[SK_ARRAY_COUNT(gAdds)];
+    for (size_t i = 0; i < SK_ARRAY_COUNT(gAdds); i++) {
+        total += gAdds[i].valueToAdd * gAdds[i].timesToAdd;
+    }
+    // Start the threads
+    for (size_t i = 0; i < SK_ARRAY_COUNT(gAdds); i++) {
+        threads[i] = new SkThread(addABunchOfTimes, &gAdds[i]);
+        threads[i]->setProcessorAffinity(gAdds[i].processorAffinity);
+        threads[i]->start();
+    }
+
+    // Now end the threads
+    for (size_t i = 0; i < SK_ARRAY_COUNT(gAdds); i++) {
+        threads[i]->join();
+        delete threads[i];
+    }
+    REPORTER_ASSERT(reporter, total == base);
+    // Ensure that the returned value from sk_atomic_add is correct.
+    int32_t valueToModify = 3;
+    const int32_t originalValue = valueToModify;
+    REPORTER_ASSERT(reporter, originalValue == sk_atomic_add(&valueToModify, 7));
+}
+
+#include "TestClassDef.h"
+DEFINE_TESTCLASS("AtomicAdd", AtomicAddTestClass, test_atomicAddTests)