michael@0: /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
michael@0: /* This Source Code Form is subject to the terms of the Mozilla Public
michael@0:  * License, v. 2.0. If a copy of the MPL was not distributed with this
michael@0:  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
michael@0: 
michael@0: #include "nsISupports.idl"
michael@0: 
michael@0: /**
michael@0:  * An interface for access to a buffering stream implementation's underlying
michael@0:  * memory buffer.
michael@0:  *
michael@0:  * Stream implementations that QueryInterface to nsIStreamBufferAccess must
michael@0:  * ensure that all buffers are aligned on the most restrictive type size for
michael@0:  * the current architecture (e.g., sizeof(double) for RISCy CPUs).  malloc(3)
michael@0:  * satisfies this requirement.
michael@0:  */
michael@0: [scriptable, uuid(ac923b72-ac87-4892-ac7a-ca385d429435)]
michael@0: interface nsIStreamBufferAccess : nsISupports
michael@0: {
michael@0:     /**
michael@0:      * Get access to a contiguous, aligned run of bytes in the stream's buffer.
michael@0:      * Exactly one successful getBuffer call must occur before a putBuffer call
michael@0:      * taking the non-null pointer returned by the successful getBuffer.
michael@0:      *
michael@0:      * The run of bytes are the next bytes (modulo alignment padding) to read
michael@0:      * for an input stream, and the next bytes (modulo alignment padding) to
michael@0:      * store before (eventually) writing buffered data to an output stream.
michael@0:      * There can be space beyond this run of bytes in the buffer for further
michael@0:      * accesses before the fill or flush point is reached.
michael@0:      *
michael@0:      * @param aLength
michael@0:      *    Count of contiguous bytes requested at the address A that satisfies
michael@0:      *    (A & aAlignMask) == 0 in the buffer, starting from the current stream
michael@0:      *    position, mapped to a buffer address B.  The stream implementation
michael@0:      *    must pad from B to A by skipping bytes (if input stream) or storing
michael@0:      *    zero bytes (if output stream).
michael@0:      *
michael@0:      * @param aAlignMask
michael@0:      *    Bit-mask computed by subtracting 1 from the power-of-two alignment
michael@0:      *    modulus (e.g., 3 or sizeof(uint32_t)-1 for uint32_t alignment).
michael@0:      *
michael@0:      * @return
michael@0:      *    The aligned pointer to aLength bytes in the buffer, or null if the
michael@0:      *    buffer has no room for aLength bytes starting at the next address A
michael@0:      *    after the current position that satisfies (A & aAlignMask) == 0.
michael@0:      */
michael@0:     [notxpcom,noscript] charPtr getBuffer(in uint32_t aLength, in uint32_t aAlignMask);
michael@0: 
michael@0:     /**
michael@0:      * Relinquish access to the stream's buffer, filling if at end of an input
michael@0:      * buffer, flushing if completing an output buffer.  After a getBuffer call
michael@0:      * that returns non-null, putBuffer must be called.
michael@0:      *
michael@0:      * @param aBuffer
michael@0:      *    A non-null pointer returned by getBuffer on the same stream buffer
michael@0:      *    access object.
michael@0:      *
michael@0:      * @param aLength
michael@0:      *    The same count of contiguous bytes passed to the getBuffer call that
michael@0:      *    returned aBuffer.
michael@0:      */
michael@0:     [notxpcom,noscript] void putBuffer(in charPtr aBuffer, in uint32_t aLength);
michael@0: 
michael@0:     /**
michael@0:      * Disable and enable buffering on the stream implementing this interface.
michael@0:      * DisableBuffering flushes an output stream's buffer, and invalidates an
michael@0:      * input stream's buffer.
michael@0:      */
michael@0:     void disableBuffering();
michael@0:     void enableBuffering();
michael@0: 
michael@0:     /**
michael@0:      * The underlying, unbuffered input or output stream.
michael@0:      */
michael@0:     readonly attribute nsISupports unbufferedStream;
michael@0: };
michael@0: 
michael@0: %{C++
michael@0: 
michael@0: /**
michael@0:  * These macros get and put a buffer given either an sba parameter that may
michael@0:  * point to an object implementing nsIStreamBufferAccess, nsIObjectInputStream,
michael@0:  * or nsIObjectOutputStream.
michael@0:  */
michael@0: #define NS_GET_BUFFER(sba,n,a)  ((sba)->GetBuffer(n, a))
michael@0: #define NS_PUT_BUFFER(sba,p,n)  ((sba)->PutBuffer(p, n))
michael@0: 
michael@0: %}