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..d595bdc6a97b81787d9bb1ea4dec7c5b11aade68 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
+   * 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,
@@ -117,7 +120,9 @@ interface PPB_FileIO {
 
   /**
    * Touch() Updates time stamps for the file opened by this FileIO object.
-   * This function will fail if the FileIO object has not been opened.
+   * This function will fail if the FileIO object has not been opened. The
+   * FileIO object must be opened, and there must be no other operations
+   * pending.
    *
    * @param[in] file_io A <code>PP_Resource</code> corresponding to a file
    * FileIO.
@@ -127,6 +132,8 @@ interface PPB_FileIO {
    * completion of Touch().
    *
    * @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 Touch([in] PP_Resource file_io,
                 [in] PP_Time last_access_time,
@@ -150,7 +157,8 @@ 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, but pending reads
+   * cannot be interleaved with other operations.
    */
   int32_t Read([in] PP_Resource file_io,
                [in] int64_t offset,
@@ -174,7 +182,8 @@ 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, but pending writes
+   * cannot be interleaved with other operations.
    */
   int32_t Write([in] PP_Resource file_io,
                 [in] int64_t offset,
@@ -183,8 +192,9 @@ interface PPB_FileIO {
                 [in] PP_CompletionCallback callback);
   /**
    * SetLength() sets the length of the file.  If the file size is extended,
-   * then the extended area of the file is zero-filled.  The FileIO object must
-   * have been opened with write access.
+   * then the extended area of the file is zero-filled. The FileIO object must
+   * have been opened with write access and there must be no other operations
+   * pending.
    *
    * @param[in] file_io A <code>PP_Resource</code> corresponding to a file
    * FileIO.
@@ -193,13 +203,17 @@ interface PPB_FileIO {
    * completion of SetLength().
    *
    * @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 SetLength([in] PP_Resource file_io,
                     [in] int64_t length,
                     [in] PP_CompletionCallback callback);
 
   /**
-   * Flush() flushes changes to disk.  This call can be very expensive!
+   * Flush() flushes changes to disk.  This call can be very expensive! The
+   * FileIO object must have been opened with write access and there must be no
+   * other operations pending.
    *
    * @param[in] file_io A <code>PP_Resource</code> corresponding to a file
    * FileIO.
@@ -207,6 +221,8 @@ interface PPB_FileIO {
    * completion of Flush().
    *
    * @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 Flush([in] PP_Resource file_io,
                 [in] PP_CompletionCallback callback);