CMD_READ

Read from a clip on the clipboard.

The read function serves two purposes.

When io_Offset is within the clip, this acts as a normal read request, and io_Data is filled with data from the clipboard. The first read request should have a zero io_ClipID, which will be filled with the ID assigned for this read. Normal sequential access from the beginning of the clip is achieved by setting io_Offset to zero for the first read, then leaving it untouched for subsequent reads. If io_Data is null, then io_Offset is incremented by io_Actual as if io_Length bytes had been read: this is useful to skip to the end of file by using a huge io_Length.

When io_Offset is beyond the end of the clip, this acts as a signal to the clipboard device that the application is through reading this clip. Realize that while an application is in the middle of reading a clip, any attempts to write new data to the clipboard are held off. This read past the end of file indicates that those operations may now be initiated.

io_Message

mn_ReplyPort set up

io_Device

Preset by OpenDevice

io_Unit

Preset by OpenDevice

io_Command

CMD_READ

io_Length

Number of bytes to put in data buffer

io_Data

Pointer to buffer of data to fill, or null to skip over data

io_Offset

Byte offset of data to read

io_ClipID

Zero if this is the initial read

io_Error

Non-zero if an error occurred

io_Actual

Filled with the actual number of bytes read

io_Data

The buffer now has io_Actual bytes of data

io_Offset

Updated to next read position, which is beyond EOF if io_Actual != io_Length

io_ClipID

The clip ID assigned to this read: do not alter for subsequent reads