Implement a proxy for Pepper FileIO.

ppapi/api/ppb_file_io.idl

Index: ppapi/api/ppb_file_io.idl
diff --git a/ppapi/api/ppb_file_io.idl b/ppapi/api/ppb_file_io.idl
index 0d2c845bfd2a10c8c91784782f2d8ef32ba88099..2d78b943db2b56f5efa032aa1de3ae447c2f1a62 100644
--- a/ppapi/api/ppb_file_io.idl
+++ b/ppapi/api/ppb_file_io.idl
@@ -99,8 +99,9 @@ interface PPB_FileIO {
                [in] PP_CompletionCallback callback);
 
   /**
-   * Query() queries info about the file opened by this FileIO object. This
-   * function will fail if the FileIO object has not been opened.
+   * Query() queries info about the file opened by this FileIO object. The
+   * FileIO object must be opened, and there must be no other operations

[viettrungluu, 2011/11/30 23:44:42]

We should have tests for restrictions like this.

+   * pending.
    *
    * @param[in] file_io A <code>PP_Resource</code> corresponding to a
    * FileIO.
@@ -110,6 +111,8 @@ interface PPB_FileIO {
    * completion of Query().
    *
    * @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
+   * PP_ERROR_INPROGRESS will be returned if there is another operation pending.
    */
   int32_t Query([in] PP_Resource file_io,
                 [out] PP_FileInfo info,
@@ -150,7 +153,8 @@ interface PPB_FileIO {
    * @return An The number of bytes read an error code from
    * <code>pp_errors.h</code>. If the return value is 0, then end-of-file was
    * reached. It is valid to call Read() multiple times with a completion
-   * callback to queue up parallel reads from the file at different offsets.
+   * callback to queue up parallel reads from the file at different offsets,
+   * but pending reads can not be interleaved with other operations.

[viettrungluu, 2011/11/30 23:44:42]

s/can not/cannot/

    */
   int32_t Read([in] PP_Resource file_io,
                [in] int64_t offset,
@@ -174,7 +178,8 @@ interface PPB_FileIO {
    * @return An The number of bytes written or an error code from
    * <code>pp_errors.h</code>. If the return value is 0, then end-of-file was
    * reached. It is valid to call Write() multiple times with a completion
-   * callback to queue up parallel writes to the file at different offsets.
+   * callback to queue up parallel writes to the file at different offsets, but
+   * pending writes can not be interleaved with other operations.

[viettrungluu, 2011/11/30 23:44:42]

s/can not/cannot/

Also, does "different offsets" mean just the offsets or do we really mean
"disjoint ranges"?

    */
   int32_t Write([in] PP_Resource file_io,
                 [in] int64_t offset,