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IOMbufBigMemoryCursor

Overview

An IOMbufMemoryCursor subclass that outputs a vector of IOPhysicalSegments in the big endian byte order.

Discussion

The IOMbufBigMemoryCursor would be used when the DMA hardware requires a big endian address and length pair. This cursor outputs an array of IOPhysicalSegments that are encoded in big-endian format.

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Functions

getPhysicalSegments

Generates a big endian physical scatter/gather list from a given mbuf.

getPhysicalSegmentsWithCoalesce

Generates a big endian physical scatter/gather list from a given mbuf.

withSpecification

Factory function that creates and initializes an IOMbufBigMemoryCursor in one operation.

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getPhysicalSegments

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Generates a big endian physical scatter/gather list from a given mbuf.

public

UInt32 getPhysicalSegments(
    mbuf_t packet, 
    struct IOMemoryCursor::PhysicalSegment *vector, 
    UInt32 numVectorSegments = 0); 

Parameters

packet

The mbuf packet.

vector

Pointer to an array of IOPhysicalSegments for the output physical scatter/gather list.

numVectorSegments

Maximum number of IOPhysicalSegments accepted.

Return Value

Returns the number of segments that were filled in, or 0 if an error occurred.

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getPhysicalSegmentsWithCoalesce

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Generates a big endian physical scatter/gather list from a given mbuf.

public

UInt32 getPhysicalSegmentsWithCoalesce(
    mbuf_t packet, 
    struct IOMemoryCursor::PhysicalSegment *vector, 
    UInt32 numVectorSegments = 0); 

Parameters

packet

The mbuf packet.

vector

Pointer to an array of IOPhysicalSegments for the output physical scatter/gather list.

numVectorSegments

Maximum number of IOPhysicalSegments accepted.

Return Value

Returns the number of segments that were filled in, or 0 if an error occurred.

Discussion

Generate a big endian physical scatter/gather list from a given mbuf. Coalesce mbuf chain when the number of segments in the scatter/gather list exceeds numVectorSegments.

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withSpecification

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Factory function that creates and initializes an IOMbufBigMemoryCursor in one operation.

public

static IOMbufBigMemoryCursor * withSpecification(
    UInt32 maxSegmentSize, 
    UInt32 maxNumSegments); 

Parameters

maxSegmentSize

Maximum allowable size for one segment.

maxNumSegments

Maximum number of segments.

Return Value

Returns a new mbuf cursor if successfully created and initialized, 0 otherwise.

Discussion

See also IOMbufMemoryCursor::initWithSpecification.

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Last Updated: 2008-12-19