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CDROM_PERFORMANCE_HEADER structure (ntddcdrm.h)

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The CDROM_PERFORMANCE_HEADER structure is used by the IOCTL_CDROM_GET_PERFORMANCE IOCTL to return data. When the request type is CdromPerformanceRequest, the IOCTL returns this header followed by optional descriptors.

Syntax

typedef struct _CDROM_PERFORMANCE_HEADER {
  UCHAR DataLength[4];
  UCHAR Except : 1;
  UCHAR Write : 1;
  UCHAR Reserved1 : 6;
  UCHAR Reserved2[3];
  UCHAR Data[0];
} CDROM_PERFORMANCE_HEADER, *PCDROM_PERFORMANCE_HEADER;

Members

DataLength[4]

The size of the available data (not just the size of returned data). The size does not include this Datalength field.

Except

The format of the descriptors that follow the header depend on the value in this field. If false (0), the CDROM_NOMINAL_PERFORMANCE_DESCRIPTOR follows the CDROM_PERFORMANCE_HEADER in the returned data. If true (1), the CDROM_EXCEPTION_PERFORMANCE_DESCRIPTOR follows the CDROM_PERFORMANCE_HEADER in the returned data.

Write

Indicates whether the result data is for read or write performance. If false (0), it indicates that the result data is for read performance. If true (1), it indicates that the result data is for write performance.

Reserved1

Reserved.

Reserved2[3]

Reserved.

Data[0]

Contains a list of the following records, depending upon the type of request: CDROM_NOMINAL_PERFORMANCE_DESCRIPTOR,
CDROM_EXCEPTION_PERFORMANCE_DESCRIPTOR,
CDROM_WRITE_SPEED_DESCRIPTOR.

Requirements

Requirement Value
Header ntddcdrm.h (include Ntddcdrm.h)

See also

CDROM_EXCEPTION_PERFORMANCE_DESCRIPTOR

CDROM_NOMINAL_PERFORMANCE_DESCRIPTOR

CDROM_WRITE_SPEED_DESCRIPTOR

IOCTL_CDROM_GET_PERFORMANCE