gecko/xpcom/io/nsIStreamBufferAccess.idl

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/* -*- 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/. */
#include "nsISupports.idl"
#include "nsrootidl.idl"
/**
* 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.
*/
[scriptable, uuid(ac923b72-ac87-4892-ac7a-ca385d429435)]
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).
*
* @return
* 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.
*/
void disableBuffering();
void enableBuffering();
/**
* The underlying, unbuffered input or output stream.
*/
readonly attribute nsISupports unbufferedStream;
};
%{C++
// Swap macros, used to convert to/from canonical (big-endian) format
#if defined IS_LITTLE_ENDIAN
# define NS_SWAP16(x) ((((x) & 0xff) << 8) | (((x) >> 8) & 0xff))
# define NS_SWAP32(x) ((NS_SWAP16((x) & 0xffff) << 16) | (NS_SWAP16((x) >> 16)))
// We want to avoid casting to 32-bit types if possible, since that violates
// aliasing rules (a standard compiler may assume that pointers of two types
// do not address overlapping storage).
//
// XXX What if we have a compiler that follows aliasing rules strictly but
// doesn't have a 64-bit int type?
//
// XXXbe shouldn't NSPR's LL_INIT work for non-constant arguments in all cases?
# if defined HAVE_LONG_LONG
# if PR_BYTES_PER_LONG == 8
# define ULL_(x) x ## UL
# elif defined WIN32 && defined _MSC_VER
# define ULL_(x) x ## ui64
# else
# define ULL_(x) x ## ULL
# endif
# define NS_SWAP64(x) ((((x) & ULL_(0xff00000000000000)) >> 56) | \
(((x) & ULL_(0x00ff000000000000)) >> 40) | \
(((x) & ULL_(0x0000ff0000000000)) >> 24) | \
(((x) & ULL_(0x000000ff00000000)) >> 8) | \
(((x) & ULL_(0x00000000ff000000)) << 8) | \
(((x) & ULL_(0x0000000000ff0000)) << 24) | \
(((x) & ULL_(0x000000000000ff00)) << 40) | \
(((x) /* & ULL_(0x00000000000000ff) */) << 56))
# else
# define NS_SWAP64(x) LL_INIT((((x).lo /* & 0xff000000ul */) >> 24) | \
(((x).lo & 0x00ff0000ul) >> 8) | \
(((x).lo & 0x0000ff00ul) << 8) | \
(((x).lo /* & 0x000000fful */) << 24), \
(((x).hi /* & 0xff000000ul */) >> 24) | \
(((x).hi & 0x00ff0000ul) >> 8) | \
(((x).hi & 0x0000ff00ul) << 8) | \
(((x).hi /* & 0x000000fful */) << 24))
# endif
#elif defined IS_BIG_ENDIAN
# define NS_SWAP16(x) (x)
# define NS_SWAP32(x) (x)
# define NS_SWAP64(x) (x)
#else
# error "Unknown byte order"
#endif
/**
* 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))
#define NS_GET8(p) (*(uint8_t*)(p))
#define NS_GET16(p) NS_SWAP16(*(uint16_t*)(p))
#define NS_GET32(p) NS_SWAP32(*(uint32_t*)(p))
#define NS_GET64(p) NS_SWAP64(*(uint64_t*)(p))
#define NS_PUT8(p,x) (*(uint8_t*)(p) = (x))
#define NS_PUT16(p,x) (*(uint16_t*)(p) = NS_SWAP16(x))
#define NS_PUT32(p,x) (*(uint32_t*)(p) = NS_SWAP32(x))
#define NS_PUT64(p,x) (*(uint64_t*)(p) = NS_SWAP64(x))
%}