nsIStreamBufferAccess

IID:ac923b72-ac87-4892-ac7a-ca385d429435
Inherits From:nsISupports

An interface for access to a buffering stream implementation's underlying memory buffer.

Stream implementations that QueryInterface to nsIStreamBufferAccess must ensure that all buffers are aligned on the most restrictive type size for the current architecture (e.g., sizeof(double) for RISCy CPUs). malloc(3) satisfies this requirement.


Properties

readonly nsISupports unbufferedStream

The underlying, unbuffered input or output stream.


Methods

void disableBuffering ( ) void enableBuffering ( ) [notxpcom] charPtr* getBuffer ( PRUint32 length , PRUint32 alignMask ) [notxpcom] void putBuffer ( charPtr* buffer , PRUint32 length )

void disableBuffering ( )

Disable and enable buffering on the stream implementing this interface. DisableBuffering flushes an output stream's buffer, and invalidates an input stream's buffer.


void enableBuffering ( )


[notxpcom] charPtr* getBuffer ( PRUint32 length , PRUint32 alignMask )

Get access to a contiguous, aligned run of bytes in the stream's buffer. Exactly one successful getBuffer call must occur before a putBuffer call taking the non-null pointer returned by the successful getBuffer.

The run of bytes are the next bytes (modulo alignment padding) to read for an input stream, and the next bytes (modulo alignment padding) to store before (eventually) writing buffered data to an output stream. There can be space beyond this run of bytes in the buffer for further accesses before the fill or flush point is reached.

Arguments:
length: Count of contiguous bytes requested at the address A that satisfies (A & alignMask) == 0 in the buffer, starting from the current stream position, mapped to a buffer address B. The stream implementation must pad from B to A by skipping bytes (if input stream) or storing zero bytes (if output stream).
alignMask: Bit-mask computed by subtracting 1 from the power-of-two alignment modulus (e.g., 3 or sizeof(PRUint32)-1 for PRUint32 alignment).
Returns:
The aligned pointer to aLength bytes in the buffer, or null if the buffer has no room for aLength bytes starting at the next address A after the current position that satisfies (A aAlignMask) == 0.

[notxpcom] void putBuffer ( charPtr* buffer , PRUint32 length )

Relinquish access to the stream's buffer, filling if at end of an input buffer, flushing if completing an output buffer. After a getBuffer call that returns non-null, putBuffer must be called.

Arguments:
buffer: A non-null pointer returned by getBuffer on the same stream buffer access object.
length: The same count of contiguous bytes passed to the getBuffer call that returned buffer.

Reference documentation is generated from Mozilla's source.

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