Avoid memory allocation for PPB_FileIO Read when callback is blocking.

Performs file read directly into caller's buffer.

BUG=194304

Review URL: https://codereview.chromium.org/27730003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@230282 0039d316-1c4b-4281-b951-d872f2087c98

2 files changed, 15 insertions, 6 deletions

diff --git a/ppapi/api/pp_array_output.idl b/ppapi/api/pp_array_output.idl
index be1aca7..8e04a4c 100644
--- a/ppapi/api/pp_array_output.idl
+++ b/ppapi/api/pp_array_output.idl
@@ -9,7 +9,7 @@
  *
  * This function will be called reentrantly. This means that if you call a
  * function PPB_Foo.GetData(&array_output), GetData will call your
- * GetDataBuffer function before it returns. 
+ * GetDataBuffer function before it returns.
  *
  * This function will be called even when returning 0-length arrays, so be sure
  * your implementation can support that. You can return NULL for 0 length
@@ -34,7 +34,10 @@
  * @param element_size The size of each element in bytes.
  *
  * @return Returns a pointer to the allocated memory. On failure, returns null.
- * You can also return null if the element_count is 0.
+ * You can also return null if the element_count is 0. When a non-null value is
+ * returned, the buffer must remain valid until after the callback runs. If used
+ * with a blocking callback, the buffer must remain valid until after the
+ * function returns. The plugin can then free any memory that it allocated.
  */
 typedef mem_t PP_ArrayOutput_GetDataBuffer([inout] mem_t user_data,
                                            [in] uint32_t element_count,
@@ -78,7 +81,7 @@ typedef mem_t PP_ArrayOutput_GetDataBuffer([inout] mem_t user_data,
 [passByValue]
 struct PP_ArrayOutput {
   /**
-   * A pointer to the allocation function that the browser implements.
+   * A pointer to the allocation function that the browser will call.
    */
   PP_ArrayOutput_GetDataBuffer GetDataBuffer;
 
diff --git a/ppapi/api/ppb_file_io.idl b/ppapi/api/ppb_file_io.idl
index 2e43ec5..9b8c9e2 100644
--- a/ppapi/api/ppb_file_io.idl
+++ b/ppapi/api/ppb_file_io.idl
@@ -121,7 +121,9 @@ interface PPB_FileIO {
    * @param[out] info The <code>PP_FileInfo</code> structure representing all
    * information about the file.
    * @param[in] callback A <code>PP_CompletionCallback</code> to be called upon
-   * completion of Query().
+   * completion of Query(). <code>info</code> must remain valid until after the
+   * callback runs. If you pass a blocking callback, <code>info</code> must
+   * remain valid until after Query() returns.
    *
    * @return An int32_t containing an error code from <code>pp_errors.h</code>.
    * PP_ERROR_FAILED will be returned if the file isn't opened, and
@@ -158,6 +160,7 @@ interface PPB_FileIO {
    * large enough to hold the specified number of bytes to read.  This function
    * might perform a partial read, meaning all the requested bytes
    * might not be returned, even if the end of the file has not been reached.
+   * The FileIO object must have been opened with read access.
    *
    * ReadToArray() is preferred to Read() when doing asynchronous operations.
    *
@@ -168,7 +171,9 @@ interface PPB_FileIO {
    * @param[in] bytes_to_read The number of bytes to read from
    * <code>offset</code>.
    * @param[in] callback A <code>PP_CompletionCallback</code> to be called upon
-   * completion of Read().
+   * completion of Read(). <code>buffer</code> must remain valid until after
+   * the callback runs. If you pass a blocking callback, <code>buffer</code>
+   * must remain valid until after Read() returns.
    *
    * @return The number of bytes read or an error code from
    * <code>pp_errors.h</code>. If the return value is 0, then end-of-file was
@@ -260,7 +265,8 @@ interface PPB_FileIO {
   /**
    * ReadToArray() reads from an offset in the file.  A PP_ArrayOutput must be
    * provided so that output will be stored in its allocated buffer.  This
-   * function might perform a partial read.
+   * function might perform a partial read. The FileIO object must have been
+   * opened with read access.
    *
    * @param[in] file_io A <code>PP_Resource</code> corresponding to a file
    * FileIO.