The Buffering and Input/Output Preferences Structure(IM:XP)

Inside Macintosh: QuickDraw GX Printing Extensions and Drivers /

Chapter 6 - Printing Resources / Printing Resources Reference

The Buffering and Input/Output Preferences Structure
The buffering and input/output preferences structure, of data type gxIOPrefsRec, is used to specify the contents of the buffering and input/output preferences ('iobm') resource.
struct gxIOPrefsRec {
   unsigned long  communicationsOptions;
   unsigned long  numBuffers;
   unsigned long  bufferSize;
   unsigned long  numReqBlocks;
   unsigned long  openCloseTimeout;
   unsigned long  readWriteTimeout
};

typedef struct gxIOPrefsRec gxIOPrefsRec, *gxIOPrefsPtr, 
**gxIOPrefsHdl;
Field Description

communicationsOptions
The options for how a driver handles input and output communications. The value of this field is 0 for standard I/O mechanisms and gxUseCustomIO (1) for nonstandard mechanisms, including SCSI.
numBuffers
The number of buffers created for the driver.
bufferSize
The number of bytes in each buffer.
numReqBlocks
The maximum number of input or output requests that can be pending at any time.
openCloseTimeout

The number of clock ticks that constitute a timeout when trying to open or close the device.
readWriteTimeout
The number of clock ticks that constitute a timeout when trying to read from or write to the device.