Buffer Manipulation and Query APIs

The buffer manipulation and query APIs are used to create, query, and manipulate input and command buffers that interact with the screen.

The two buffer types used by the low-level interfaces are command and input. A command buffer can be used to accumulate a sequence of low-level commands without performing an I/O operation. The entire buffer can be written out at once in a single I/O operation. See Direct and Indirect Operations for further discussion of command buffers. When an input operation is performed, you can specify an input buffer as the target of the operation. The input results are placed in this buffer, which can then be queried through several interfaces. You may query for individual pieces of information, such as the AID byte from the input operation using the Retrieve AID Code on Read (QsnRtvReadAID) API or for multiple pieces of information using the Retrieve Read Information (QsnRtvReadInf) API.

Command and input buffers can be used across activation groups if the activation group in which the buffer was created still exists.

The buffer manipulation and query interfaces are:

• Clear Buffer (QsnClrBuf) clears all commands or data in a buffer resets its state.
• Copy Buffer (QsnCpyBuf) copies the contents of one buffer to another.
• Create Command Buffer (QsnCrtCmdBuf) creates a command buffer to accumulate low-level commands.
• Create Input Buffer (QsnCrtInpBuf) creates an input buffer to receive input results.
• Delete Buffer (QsnDltBuf) deletes a buffer.
• Put Command Buffer (QsnPutBuf) sends the commands in a command buffer to the screen.
• Put Command Buffer and Perform Get (QsnPutGetBuf) sends the commands in a command buffer to the screen and performs a read operation.
• Retrieve AID Code on Read (QsnRtvReadAID) determines the Aid code for a given input operation.
• Retrieve Available Data (QsnRtvAvailData) copies the user's data into an input buffer.
• Retrieve Buffer Data Length (QsnRtvBufLen) returns the length of data in a buffer.
• Retrieve Buffer Size (QsnRtvBufSiz) returns the size of a buffer.
• Retrieve Cursor Address on Read (QsnRtvReadAdr) retrieves the cursor position at the completion of an input operation.
• Retrieve Field Information (QsnRtvFldInf) returns information about a particular field in an input buffer.
• Retrieve Length of Data in Input Buffer (QsnRtvDtaLen) retrieves the number of data bytes in an input buffer after an input operation.
• Retrieve Length of Field Data in Buffer (QsnRtvFldDtaLen) retrieves the number of bytes of field data after an input operation.
• Retrieve Number of Bytes Read from Screen (QsnRtvReadLen) retrieves the number of data bytes read from the screen after an input operation.
• Retrieve Number of Fields Read (QsnRtvFldCnt) retrieves the number of fields in an input buffer.
• Retrieve Pointer to Data in Input Buffer (QsnRtvDta) returns a pointer to the first byte of input data in an input buffer.
• Retrieve Pointer to Field Data (QsnRtvFldDta) returns a pointer to the first byte of field data in an input buffer.
• Retrieve Read Information (QsnRtvReadInf) returns information about the input operation.