/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
* 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.
interface nsIStreamBufferAccess : nsISupports
* 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.
* @param aLength
* Count of contiguous bytes requested at the address A that satisfies
* (A & aAlignMask) == 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).
* @param aAlignMask
* Bit-mask computed by subtracting 1 from the power-of-two alignment
* modulus (e.g., 3 or sizeof(uint32_t)-1 for uint32_t alignment).
* 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,noscript] charPtr getBuffer(in uint32_t aLength, in uint32_t aAlignMask);
* 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.
* @param aBuffer
* A non-null pointer returned by getBuffer on the same stream buffer
* access object.
* @param aLength
* The same count of contiguous bytes passed to the getBuffer call that
* returned aBuffer.
[notxpcom,noscript] void putBuffer(in charPtr aBuffer, in uint32_t aLength);
* Disable and enable buffering on the stream implementing this interface.
* DisableBuffering flushes an output stream's buffer, and invalidates an
* input stream's buffer.
* The underlying, unbuffered input or output stream.
readonly attribute nsISupports unbufferedStream;
* These macros get and put a buffer given either an sba parameter that may
* point to an object implementing nsIStreamBufferAccess, nsIObjectInputStream,
* or nsIObjectOutputStream.
#define NS_GET_BUFFER(sba,n,a) ((sba)->GetBuffer(n, a))
#define NS_PUT_BUFFER(sba,p,n) ((sba)->PutBuffer(p, n))