Add a size parameter to SharedMemoryHandle.

base/memory/shared_memory_handle.h

Index: base/memory/shared_memory_handle.h
diff --git a/base/memory/shared_memory_handle.h b/base/memory/shared_memory_handle.h
index 469eba227d5e71ca93f129da491438cc5752b76b..099723e896fbf98576bffc9a8cd50e76d8903990 100644
--- a/base/memory/shared_memory_handle.h
+++ b/base/memory/shared_memory_handle.h
@@ -71,6 +71,10 @@ class BASE_EXPORT SharedMemoryHandle {
   // memory region will have the same GUID. Preserved across IPC.
   base::UnguessableToken GetGUID() const;
 
+  // Returns false on a failure to determine the size. On success, populates the
+  // output variable |size|.

[Nico, 2017/05/15 22:13:36]

What?

[erikchen, 2017/05/15 22:57:18]

Updated comment.

+  size_t GetSize() const;
+
 #if defined(OS_MACOSX) && !defined(OS_IOS)
   enum Type {
     // The SharedMemoryHandle is backed by a POSIX fd.
@@ -92,6 +96,7 @@ class BASE_EXPORT SharedMemoryHandle {
   // SharedMemoryHandle. Otherwise, the caller should generate a new
   // UnguessableToken.

[Nico, 2017/05/15 22:13:36]

Document size and what happens if the passed-in size doesn't match the "real"
size of the thing backed by the fd (also other ctors)

[erikchen, 2017/05/15 22:57:18]

Done.

   SharedMemoryHandle(const base::FileDescriptor& file_descriptor,
+                     size_t size,
                      const base::UnguessableToken& guid);
 
   // Makes a Mach-based SharedMemoryHandle of the given size. On error,
@@ -108,10 +113,6 @@ class BASE_EXPORT SharedMemoryHandle {
   // processes.
   mach_port_t GetMemoryObject() const;
 
-  // Returns false on a failure to determine the size. On success, populates the
-  // output variable |size|.
-  bool GetSize(size_t* size) const;
-
   // The SharedMemoryHandle must be valid.
   // Returns whether the SharedMemoryHandle was successfully mapped into memory.
   // On success, |memory| is an output variable that contains the start of the
@@ -124,7 +125,7 @@ class BASE_EXPORT SharedMemoryHandle {
   // SharedMemoryHandle, the caller must pass the |guid| of that
   // SharedMemoryHandle. Otherwise, the caller should generate a new
   // UnguessableToken.
-  SharedMemoryHandle(HANDLE h, const base::UnguessableToken& guid);
+  SharedMemoryHandle(HANDLE h, size_t size, const base::UnguessableToken& guid);
   HANDLE GetHandle() const;
 #else
   // |guid| uniquely identifies the shared memory region pointed to by the
@@ -133,18 +134,16 @@ class BASE_EXPORT SharedMemoryHandle {
   // SharedMemoryHandle. Otherwise, the caller should generate a new
   // UnguessableToken.
   SharedMemoryHandle(const base::FileDescriptor& file_descriptor,
+                     size_t size,
                      const base::UnguessableToken& guid);
 
   // Creates a SharedMemoryHandle from an |fd| supplied from an external
   // service.
-  static SharedMemoryHandle ImportHandle(int fd);
+  static SharedMemoryHandle ImportHandle(int fd, size_t size);
 
   // Returns the underlying OS resource.
   int GetHandle() const;
 
-  // Takes ownership of the OS resource.
-  void SetHandle(int fd);
-
   // Invalidates [but doesn't close] the underlying OS resource. This will leak
   // unless the caller is careful.
   int Release();
@@ -164,10 +163,6 @@ class BASE_EXPORT SharedMemoryHandle {
     struct {
       mach_port_t memory_object_;
 
-      // The size of the shared memory region when |type_| is MACH. Only
-      // relevant if |memory_object_| is not |MACH_PORT_NULL|.
-      mach_vm_size_t size_;
-
       // Whether passing this object as a parameter to an IPC message passes
       // ownership of |memory_object_| to the IPC stack. This is meant to mimic
       // the behavior of the |auto_close| parameter of FileDescriptor.
@@ -189,6 +184,9 @@ class BASE_EXPORT SharedMemoryHandle {
 #endif
 
   base::UnguessableToken guid_;
+
+  // The size of the region referenced by the SharedMemoryHandle.
+  size_t size_ = 0;

[Nico, 2017/05/15 22:13:36]

Either use in-class initialization for all fields or for none of them.

[erikchen, 2017/05/15 22:57:18]

all of them, it is.

 };
 
 }  // namespace base