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

1 files changed, 44 insertions, 0 deletions

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