Added SharedMemory::MapFrom.

base/shared_memory_unittest.cc

Index: base/shared_memory_unittest.cc
diff --git a/base/shared_memory_unittest.cc b/base/shared_memory_unittest.cc
index bd537692f4880febe1ce12dc9a18e91991296ca4..205a9c408174736872205a1816693ab99e994430 100644
--- a/base/shared_memory_unittest.cc
+++ b/base/shared_memory_unittest.cc
@@ -8,6 +8,7 @@
 #endif
 #include "base/memory/scoped_ptr.h"
 #include "base/shared_memory.h"
+#include "base/sys_info.h"
 #include "base/test/multiprocess_test.h"
 #include "base/threading/platform_thread.h"
 #include "base/time.h"
@@ -343,6 +344,36 @@ TEST(SharedMemoryTest, AnonymousPrivate) {
   }
 }
 
+TEST(SharedMemoryTest, MapFrom) {
+  ASSERT_TRUE(SysInfo::VMAllocationGranularity() >= sizeof(uint32));
+  const size_t kCount = SysInfo::VMAllocationGranularity();
+  const size_t kDataSize = kCount * sizeof(uint32);
+  static const char kTestName[] = "SharedMemoryMapFrom";
+
+  SharedMemory memory1;
+  memory1.Delete(kTestName);
+  ASSERT_TRUE(memory1.CreateNamed(kTestName, false, kDataSize));
+  ASSERT_TRUE(memory1.Map(kDataSize));
+  uint32* ptr1 = static_cast<uint32*>(memory1.memory());
+  ASSERT_NE(ptr1, static_cast<void*>(NULL));
+
+  for (size_t i = 0; i < kCount; ++i) {
+    ptr1[i] = i;
+  }
+
+  SharedMemory memory2;
+  ASSERT_TRUE(memory2.CreateNamed(kTestName, true, kDataSize));
+  off_t offset = SysInfo::VMAllocationGranularity();
+  ASSERT_TRUE(memory2.MapFrom(offset, kDataSize - offset));
+  offset /= sizeof(uint32);
+  uint32* ptr2 = static_cast<uint32*>(memory2.memory());
+  ASSERT_NE(ptr2, static_cast<void*>(NULL));
+  for (size_t i = offset; i < kCount; ++i) {
+    ASSERT_EQ(ptr2[i - offset], i);
+  }
+  memory1.Delete(kTestName);
+}
+
 #if defined(OS_POSIX)
 // Create a shared memory object, mmap it, and mprotect it to PROT_EXEC.
 TEST(SharedMemoryTest, AnonymousExecutable) {