Add a data length method to mojo::ScopedSharedBufferHandle.

BUG=788243

Change-Id: Icd243edd24295125599f09adbebcadec62487e89
Reviewed-on: https://chromium-review.googlesource.com/976689
Commit-Queue: Lei Zhang <thestig@chromium.org>
Reviewed-by: Ken Rockot <rockot@chromium.org>
Cr-Commit-Position: refs/heads/master@{#545656}

CrOS-Libchrome-Original-Commit: 7b818885624401be6df25eff4cb6f3e16e43296d

15 files changed, 134 insertions, 7 deletions

diff --git a/mojo/edk/embedder/entrypoints.cc b/mojo/edk/embedder/entrypoints.cc
index ca8675c602..2a96ef64ab 100644
--- a/mojo/edk/embedder/entrypoints.cc
+++ b/mojo/edk/embedder/entrypoints.cc
@@ -193,7 +193,7 @@ MojoResult MojoEndReadDataImpl(MojoHandle data_pipe_consumer_handle,
 }
 
 MojoResult MojoCreateSharedBufferImpl(
-    const struct MojoCreateSharedBufferOptions* options,
+    const MojoCreateSharedBufferOptions* options,
     uint64_t num_bytes,
     MojoHandle* shared_buffer_handle) {
   return g_core->CreateSharedBuffer(options, num_bytes, shared_buffer_handle);
@@ -201,7 +201,7 @@ MojoResult MojoCreateSharedBufferImpl(
 
 MojoResult MojoDuplicateBufferHandleImpl(
     MojoHandle buffer_handle,
-    const struct MojoDuplicateBufferHandleOptions* options,
+    const MojoDuplicateBufferHandleOptions* options,
     MojoHandle* new_buffer_handle) {
   return g_core->DuplicateBufferHandle(buffer_handle, options,
                                        new_buffer_handle);
@@ -219,6 +219,12 @@ MojoResult MojoUnmapBufferImpl(void* buffer) {
   return g_core->UnmapBuffer(buffer);
 }
 
+MojoResult MojoGetBufferInfoImpl(MojoHandle buffer_handle,
+                                 const MojoSharedBufferOptions* options,
+                                 MojoSharedBufferInfo* info) {
+  return g_core->GetBufferInfo(buffer_handle, options, info);
+}
+
 MojoResult MojoWrapPlatformHandleImpl(const MojoPlatformHandle* platform_handle,
                                       MojoHandle* mojo_handle) {
   return g_core->WrapPlatformHandle(platform_handle, mojo_handle);
@@ -279,6 +285,7 @@ MojoSystemThunks g_thunks = {sizeof(MojoSystemThunks),
                              MojoDuplicateBufferHandleImpl,
                              MojoMapBufferImpl,
                              MojoUnmapBufferImpl,
+                             MojoGetBufferInfoImpl,
                              MojoCreateTrapImpl,
                              MojoAddTriggerImpl,
                              MojoRemoveTriggerImpl,
diff --git a/mojo/edk/system/core.cc b/mojo/edk/system/core.cc
index d6477ad3dc..bf2f95c06b 100644
--- a/mojo/edk/system/core.cc
+++ b/mojo/edk/system/core.cc
@@ -1008,6 +1008,21 @@ MojoResult Core::UnmapBuffer(void* buffer) {
   return result;
 }
 
+MojoResult Core::GetBufferInfo(MojoHandle buffer_handle,
+                               const MojoSharedBufferOptions* options,
+                               MojoSharedBufferInfo* info) {
+  if (options && options->struct_size != sizeof(MojoSharedBufferOptions))
+    return MOJO_RESULT_INVALID_ARGUMENT;
+  if (!info || info->struct_size != sizeof(MojoSharedBufferInfo))
+    return MOJO_RESULT_INVALID_ARGUMENT;
+
+  scoped_refptr<Dispatcher> dispatcher(GetDispatcher(buffer_handle));
+  if (!dispatcher)
+    return MOJO_RESULT_INVALID_ARGUMENT;
+
+  return dispatcher->GetBufferInfo(info);
+}
+
 MojoResult Core::WrapPlatformHandle(const MojoPlatformHandle* platform_handle,
                                     MojoHandle* mojo_handle) {
   ScopedPlatformHandle handle;
diff --git a/mojo/edk/system/core.h b/mojo/edk/system/core.h
index 542a448e65..478971e2dc 100644
--- a/mojo/edk/system/core.h
+++ b/mojo/edk/system/core.h
@@ -282,6 +282,9 @@ class MOJO_SYSTEM_IMPL_EXPORT Core {
                        void** buffer,
                        MojoMapBufferFlags flags);
   MojoResult UnmapBuffer(void* buffer);
+  MojoResult GetBufferInfo(MojoHandle buffer_handle,
+                           const MojoSharedBufferOptions* options,
+                           MojoSharedBufferInfo* info);
 
   // These methods correspond to the API functions defined in
   // "mojo/public/c/system/platform_handle.h".
diff --git a/mojo/edk/system/dispatcher.cc b/mojo/edk/system/dispatcher.cc
index 43959288a8..e736276dfd 100644
--- a/mojo/edk/system/dispatcher.cc
+++ b/mojo/edk/system/dispatcher.cc
@@ -66,6 +66,10 @@ MojoResult Dispatcher::MapBuffer(
   return MOJO_RESULT_INVALID_ARGUMENT;
 }
 
+MojoResult Dispatcher::GetBufferInfo(MojoSharedBufferInfo* info) {
+  return MOJO_RESULT_INVALID_ARGUMENT;
+}
+
 MojoResult Dispatcher::ReadData(void* elements,
                                 uint32_t* num_bytes,
                                 MojoReadDataFlags flags) {
diff --git a/mojo/edk/system/dispatcher.h b/mojo/edk/system/dispatcher.h
index ec3d0193e0..3e13c1bd14 100644
--- a/mojo/edk/system/dispatcher.h
+++ b/mojo/edk/system/dispatcher.h
@@ -106,6 +106,8 @@ class MOJO_SYSTEM_IMPL_EXPORT Dispatcher
       MojoMapBufferFlags flags,
       std::unique_ptr<PlatformSharedBufferMapping>* mapping);
 
+  virtual MojoResult GetBufferInfo(MojoSharedBufferInfo* info);
+
   ///////////// Data pipe consumer API /////////////
 
   virtual MojoResult ReadData(void* elements,
diff --git a/mojo/edk/system/multiprocess_message_pipe_unittest.cc b/mojo/edk/system/multiprocess_message_pipe_unittest.cc
index 8a6a3c3f74..c9a00de91d 100644
--- a/mojo/edk/system/multiprocess_message_pipe_unittest.cc
+++ b/mojo/edk/system/multiprocess_message_pipe_unittest.cc
@@ -338,6 +338,11 @@ TEST_F(MultiprocessMessagePipeTest, SharedBufferPassing) {
     MojoHandle shared_buffer;
     ASSERT_EQ(MOJO_RESULT_OK,
               MojoCreateSharedBuffer(&options, 100, &shared_buffer));
+    MojoSharedBufferInfo buffer_info;
+    buffer_info.struct_size = sizeof(buffer_info);
+    ASSERT_EQ(MOJO_RESULT_OK,
+              MojoGetBufferInfo(shared_buffer, nullptr, &buffer_info));
+    EXPECT_EQ(100U, buffer_info.size);
 
     // Send the shared buffer.
     const std::string go1("go 1");
@@ -346,6 +351,10 @@ TEST_F(MultiprocessMessagePipeTest, SharedBufferPassing) {
     ASSERT_EQ(MOJO_RESULT_OK,
               MojoDuplicateBufferHandle(shared_buffer, nullptr,
                                         &duplicated_shared_buffer));
+    buffer_info.size = 0;
+    ASSERT_EQ(MOJO_RESULT_OK,
+              MojoGetBufferInfo(shared_buffer, nullptr, &buffer_info));
+    EXPECT_EQ(100U, buffer_info.size);
     MojoHandle handles[1];
     handles[0] = duplicated_shared_buffer;
     ASSERT_EQ(MOJO_RESULT_OK,
diff --git a/mojo/edk/system/shared_buffer_dispatcher.cc b/mojo/edk/system/shared_buffer_dispatcher.cc
index a72ebecfd1..ca9a1a8435 100644
--- a/mojo/edk/system/shared_buffer_dispatcher.cc
+++ b/mojo/edk/system/shared_buffer_dispatcher.cc
@@ -239,6 +239,15 @@ MojoResult SharedBufferDispatcher::MapBuffer(
   return MOJO_RESULT_OK;
 }
 
+MojoResult SharedBufferDispatcher::GetBufferInfo(MojoSharedBufferInfo* info) {
+  if (!info)
+    return MOJO_RESULT_INVALID_ARGUMENT;
+
+  base::AutoLock lock(lock_);
+  info->size = shared_buffer_->GetNumBytes();
+  return MOJO_RESULT_OK;
+}
+
 void SharedBufferDispatcher::StartSerialize(uint32_t* num_bytes,
                                             uint32_t* num_ports,
                                             uint32_t* num_platform_handles) {
diff --git a/mojo/edk/system/shared_buffer_dispatcher.h b/mojo/edk/system/shared_buffer_dispatcher.h
index 351a7d19d3..fcaf5c1913 100644
--- a/mojo/edk/system/shared_buffer_dispatcher.h
+++ b/mojo/edk/system/shared_buffer_dispatcher.h
@@ -76,6 +76,7 @@ class MOJO_SYSTEM_IMPL_EXPORT SharedBufferDispatcher final : public Dispatcher {
       uint64_t num_bytes,
       MojoMapBufferFlags flags,
       std::unique_ptr<PlatformSharedBufferMapping>* mapping) override;
+  MojoResult GetBufferInfo(MojoSharedBufferInfo* info) override;
   void StartSerialize(uint32_t* num_bytes,
                       uint32_t* num_ports,
                       uint32_t* num_platform_handles) override;
diff --git a/mojo/public/c/system/buffer.h b/mojo/public/c/system/buffer.h
index 09f6d285f3..0e086fc3a2 100644
--- a/mojo/public/c/system/buffer.h
+++ b/mojo/public/c/system/buffer.h
@@ -43,6 +43,35 @@ struct MOJO_ALIGNAS(8) MojoCreateSharedBufferOptions {
 MOJO_STATIC_ASSERT(sizeof(MojoCreateSharedBufferOptions) == 8,
                    "MojoCreateSharedBufferOptions has wrong size");
 
+// Flags passed to |MojoGetBufferInfo()| via |MojoSharedBufferOptions|.
+typedef uint32_t MojoSharedBufferOptionsFlags;
+
+#ifdef __cplusplus
+const MojoSharedBufferOptionsFlags MOJO_SHARED_BUFFER_OPTIONS_FLAG_NONE = 0;
+#else
+#define MOJO_SHARED_BUFFER_OPTIONS_FLAG_NONE ((MojoSharedBufferOptionsFlags)0)
+#endif
+
+struct MOJO_ALIGNAS(8) MojoSharedBufferOptions {
+  // The size of this structure, used for versioning.
+  uint32_t struct_size;
+
+  // See |MojoSharedBufferOptionsFlags|.
+  MojoSharedBufferOptionsFlags flags;
+};
+MOJO_STATIC_ASSERT(sizeof(MojoSharedBufferOptions) == 8,
+                   "MojoSharedBufferOptions has wrong size");
+
+struct MOJO_ALIGNAS(8) MojoSharedBufferInfo {
+  // The size of this structure, used for versioning.
+  uint32_t struct_size;
+
+  // The size of the shared buffer.
+  uint64_t size;
+};
+MOJO_STATIC_ASSERT(sizeof(MojoSharedBufferInfo) == 16,
+                   "MojoSharedBufferInfo has wrong size");
+
 // |MojoDuplicateBufferHandleOptions|: Used to specify parameters in duplicating
 // access to a shared buffer to |MojoDuplicateBufferHandle()|.
 //
@@ -181,6 +210,21 @@ MOJO_SYSTEM_EXPORT MojoResult MojoMapBuffer(MojoHandle buffer_handle,
 //       result of |MojoMapBuffer()| or has already been unmapped).
 MOJO_SYSTEM_EXPORT MojoResult MojoUnmapBuffer(void* buffer);  // In.
 
+// Retrieve information about |buffer_handle| into |info|. |options| is optional
+// and reserved for future use.
+//
+// Returns:
+//   |MOJO_RESULT_OK| on success.
+//   |MOJO_RESULT_INVALID_ARGUMENT| if |buffer_handle| is invalid or if |info|
+//       is NULL.
+//
+// On success, |info->size| will be set to the size of the buffer. On failure it
+// is not modified.
+MOJO_SYSTEM_EXPORT MojoResult
+MojoGetBufferInfo(MojoHandle buffer_handle,
+                  const struct MojoSharedBufferOptions* options,  // Optional.
+                  struct MojoSharedBufferInfo* info);             // Out.
+
 #ifdef __cplusplus
 }  // extern "C"
 #endif
diff --git a/mojo/public/c/system/tests/core_api_unittest.cc b/mojo/public/c/system/tests/core_api_unittest.cc
index ff24b5d7c0..10c049d443 100644
--- a/mojo/public/c/system/tests/core_api_unittest.cc
+++ b/mojo/public/c/system/tests/core_api_unittest.cc
@@ -264,23 +264,30 @@ TEST(CoreAPITest, BasicDataPipe) {
 }
 
 TEST(CoreAPITest, BasicSharedBuffer) {
-  MojoHandle h0, h1;
-  void* pointer;
+  MojoSharedBufferInfo buffer_info;
+  buffer_info.struct_size = sizeof(buffer_info);
+  MojoHandle h0 = MOJO_HANDLE_INVALID;
+  EXPECT_EQ(MOJO_RESULT_INVALID_ARGUMENT,
+            MojoGetBufferInfo(h0, nullptr, &buffer_info));
 
   // Create a shared buffer (|h0|).
-  h0 = MOJO_HANDLE_INVALID;
   EXPECT_EQ(MOJO_RESULT_OK, MojoCreateSharedBuffer(nullptr, 100, &h0));
   EXPECT_NE(h0, MOJO_HANDLE_INVALID);
 
+  EXPECT_EQ(MOJO_RESULT_INVALID_ARGUMENT,
+            MojoGetBufferInfo(h0, nullptr, nullptr));
+  ASSERT_EQ(MOJO_RESULT_OK, MojoGetBufferInfo(h0, nullptr, &buffer_info));
+  EXPECT_EQ(100U, buffer_info.size);
+
   // Map everything.
-  pointer = nullptr;
+  void* pointer = nullptr;
   EXPECT_EQ(MOJO_RESULT_OK,
             MojoMapBuffer(h0, 0, 100, &pointer, MOJO_MAP_BUFFER_FLAG_NONE));
   ASSERT_TRUE(pointer);
   static_cast<char*>(pointer)[50] = 'x';
 
   // Duplicate |h0| to |h1|.
-  h1 = MOJO_HANDLE_INVALID;
+  MojoHandle h1 = MOJO_HANDLE_INVALID;
   EXPECT_EQ(MOJO_RESULT_OK, MojoDuplicateBufferHandle(h0, nullptr, &h1));
   EXPECT_NE(h1, MOJO_HANDLE_INVALID);
 
@@ -306,6 +313,10 @@ TEST(CoreAPITest, BasicSharedBuffer) {
   // Unmap it.
   EXPECT_EQ(MOJO_RESULT_OK, MojoUnmapBuffer(pointer));
 
+  buffer_info.size = 0;
+  ASSERT_EQ(MOJO_RESULT_OK, MojoGetBufferInfo(h1, nullptr, &buffer_info));
+  EXPECT_EQ(100U, buffer_info.size);
+
   EXPECT_EQ(MOJO_RESULT_OK, MojoClose(h1));
 }
 
diff --git a/mojo/public/c/system/thunks.cc b/mojo/public/c/system/thunks.cc
index b3a0564463..cbd9aed62c 100644
--- a/mojo/public/c/system/thunks.cc
+++ b/mojo/public/c/system/thunks.cc
@@ -138,6 +138,13 @@ MojoResult MojoUnmapBuffer(void* buffer) {
   return g_thunks.UnmapBuffer(buffer);
 }
 
+MojoResult MojoGetBufferInfo(MojoHandle buffer_handle,
+                             const struct MojoSharedBufferOptions* options,
+                             struct MojoSharedBufferInfo* info) {
+  assert(g_thunks.GetBufferInfo);
+  return g_thunks.GetBufferInfo(buffer_handle, options, info);
+}
+
 MojoResult MojoCreateTrap(MojoTrapEventHandler handler,
                           const MojoCreateTrapOptions* options,
                           MojoHandle* trap_handle) {
diff --git a/mojo/public/c/system/thunks.h b/mojo/public/c/system/thunks.h
index 0564ea6025..b68e71758b 100644
--- a/mojo/public/c/system/thunks.h
+++ b/mojo/public/c/system/thunks.h
@@ -72,6 +72,9 @@ struct MojoSystemThunks {
                           void** buffer,
                           MojoMapBufferFlags flags);
   MojoResult (*UnmapBuffer)(void* buffer);
+  MojoResult (*GetBufferInfo)(MojoHandle buffer_handle,
+                              const struct MojoSharedBufferOptions* options,
+                              struct MojoSharedBufferInfo* info);
   MojoResult (*CreateTrap)(MojoTrapEventHandler handler,
                            const struct MojoCreateTrapOptions* options,
                            MojoHandle* trap_handle);
diff --git a/mojo/public/cpp/system/buffer.cc b/mojo/public/cpp/system/buffer.cc
index 49f45d8498..13f2026316 100644
--- a/mojo/public/cpp/system/buffer.cc
+++ b/mojo/public/cpp/system/buffer.cc
@@ -43,4 +43,12 @@ ScopedSharedBufferMapping SharedBufferHandle::MapAtOffset(
   return ScopedSharedBufferMapping(buffer);
 }
 
+uint64_t SharedBufferHandle::GetSize() const {
+  MojoSharedBufferInfo buffer_info;
+  buffer_info.struct_size = sizeof(buffer_info);
+  return MojoGetBufferInfo(value(), nullptr, &buffer_info) == MOJO_RESULT_OK
+             ? buffer_info.size
+             : 0;
+}
+
 }  // namespace mojo
diff --git a/mojo/public/cpp/system/buffer.h b/mojo/public/cpp/system/buffer.h
index 660b7503a1..d72d197650 100644
--- a/mojo/public/cpp/system/buffer.h
+++ b/mojo/public/cpp/system/buffer.h
@@ -69,6 +69,9 @@ class MOJO_CPP_SYSTEM_EXPORT SharedBufferHandle : public Handle {
   // Maps |size| bytes of this shared buffer, starting |offset| bytes into the
   // buffer. On failure, this will return a null mapping.
   ScopedSharedBufferMapping MapAtOffset(uint64_t size, uint64_t offset) const;
+
+  // Get the size of this shared buffer.
+  uint64_t GetSize() const;
 };
 
 static_assert(sizeof(SharedBufferHandle) == sizeof(Handle),
diff --git a/mojo/public/cpp/system/tests/core_unittest.cc b/mojo/public/cpp/system/tests/core_unittest.cc
index b134e9bf18..d727431fb0 100644
--- a/mojo/public/cpp/system/tests/core_unittest.cc
+++ b/mojo/public/cpp/system/tests/core_unittest.cc
@@ -386,6 +386,7 @@ TEST(CoreCppTest, ScopedHandleMoveCtor) {
 TEST(CoreCppTest, BasicSharedBuffer) {
   ScopedSharedBufferHandle h0 = SharedBufferHandle::Create(100);
   ASSERT_TRUE(h0.is_valid());
+  EXPECT_EQ(100U, h0->GetSize());
 
   // Map everything.
   ScopedSharedBufferMapping mapping = h0->Map(100);