/* -*- Mode: C++; tab-width: 2; 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" interface nsIInputStream; %{C++ /** * The signature of the writer function passed to ReadSegments. This * is the "consumer" of data that gets read from the stream's buffer. * * @param aInStream stream being read * @param aClosure opaque parameter passed to ReadSegments * @param aFromSegment pointer to memory owned by the input stream. This is * where the writer function should start consuming data. * @param aToOffset amount of data already consumed by this writer during this * ReadSegments call. This is also the sum of the aWriteCount * returns from this writer over the previous invocations of * the writer by this ReadSegments call. * @param aCount Number of bytes available to be read starting at aFromSegment * @param [out] aWriteCount number of bytes read by this writer function call * * Implementers should return the following: * * @return NS_OK and (*aWriteCount > 0) if consumed some data * @return if not interested in consuming any data * * Errors are never passed to the caller of ReadSegments. * * NOTE: returning NS_OK and (*aWriteCount = 0) has undefined behavior. */ typedef nsresult (*nsWriteSegmentFun)(nsIInputStream *aInStream, void *aClosure, const char *aFromSegment, uint32_t aToOffset, uint32_t aCount, uint32_t *aWriteCount); %} native nsWriteSegmentFun(nsWriteSegmentFun); /** * nsIInputStream * * An interface describing a readable stream of data. An input stream may be * "blocking" or "non-blocking" (see the IsNonBlocking method). A blocking * input stream may suspend the calling thread in order to satisfy a call to * Close, Available, Read, or ReadSegments. A non-blocking input stream, on * the other hand, must not block the calling thread of execution. * * NOTE: blocking input streams are often read on a background thread to avoid * locking up the main application thread. For this reason, it is generally * the case that a blocking input stream should be implemented using thread- * safe AddRef and Release. */ [scriptable, builtinclass, uuid(53cdbc97-c2d7-4e30-b2c3-45b2ee79db18)] interface nsIInputStream : nsISupports { /** * Close the stream. This method causes subsequent calls to Read and * ReadSegments to return 0 bytes read to indicate end-of-file. Any * subsequent calls to Available or StreamStatus should throw * NS_BASE_STREAM_CLOSED. * * Succeeds (without side effects) if already closed. */ void close(); /** * Determine number of bytes available in the stream. A non-blocking * stream that does not yet have any data to read should return 0 bytes * from this method (i.e., it must not throw the NS_BASE_STREAM_WOULD_BLOCK * exception). * * In addition to the number of bytes available in the stream, this method * also informs the caller of the current status of the stream. A stream * that is closed will throw an exception when this method is called. That * enables the caller to know the condition of the stream before attempting * to read from it. If a stream is at end-of-file, but not closed, then * this method returns 0 bytes available. (Note: some nsIInputStream * implementations automatically close when eof is reached; some do not). * * NOTE: Streams implementing nsIAsyncInputStream must automatically close * when eof is reached, as otherwise it is impossible to distinguish between * a stream waiting for more data and a stream at EOF using Available(). * * @return number of bytes currently available in the stream. * * @throws NS_BASE_STREAM_CLOSED if the stream is closed normally. * @throws if the stream is closed due to some error * condition */ unsigned long long available(); /** * Check the current status of the stream. A stream that is closed will * throw an exception when this method is called. That enables the caller * to know the condition of the stream before attempting to read from it. * * This method will not throw NS_BASE_STREAM_WOULD_BLOCK, even if the stream * is an non-blocking stream with no data. A non-blocking stream that does * not yet have any data to read should return NS_OK. * * NOTE: Unlike available, his method should not block the calling thread * (e.g. to query the state of a file descriptor), even when called on a * blocking stream. * * @throws NS_BASE_STREAM_CLOSED if the stream closed normally * @throws if the stream closed with a different status */ void streamStatus(); /** * Read data from the stream. * * @param aBuf the buffer into which the data is to be read * @param aCount the maximum number of bytes to be read * * @return number of bytes read (may be less than aCount). * @return 0 if reached end-of-file * * @throws NS_BASE_STREAM_WOULD_BLOCK if reading from the input stream would * block the calling thread (non-blocking mode only) * @throws on failure * * NOTE: this method should not throw NS_BASE_STREAM_CLOSED. */ [noscript] unsigned long read(in charPtr aBuf, in unsigned long aCount); /** * Low-level read method that provides access to the stream's underlying * buffer. The writer function may be called multiple times for segmented * buffers. ReadSegments is expected to keep calling the writer until * either there is nothing left to read or the writer returns an error. * ReadSegments should not call the writer with zero bytes to consume. * * @param aWriter the "consumer" of the data to be read * @param aClosure opaque parameter passed to writer * @param aCount the maximum number of bytes to be read * * @return number of bytes read (may be less than aCount) * @return 0 if reached end-of-file (or if aWriter refused to consume data) * * @throws NS_BASE_STREAM_WOULD_BLOCK if reading from the input stream would * block the calling thread (non-blocking mode only) * @throws NS_ERROR_NOT_IMPLEMENTED if the stream has no underlying buffer * @throws on failure * * NOTE: this function may be unimplemented if a stream has no underlying * buffer (e.g., socket input stream). * * NOTE: this method should not throw NS_BASE_STREAM_CLOSED. */ [noscript] unsigned long readSegments(in nsWriteSegmentFun aWriter, in voidPtr aClosure, in unsigned long aCount); /** * @return true if stream is non-blocking * * NOTE: reading from a blocking input stream will block the calling thread * until at least one byte of data can be extracted from the stream. * * NOTE: a non-blocking input stream may implement nsIAsyncInputStream to * provide consumers with a way to wait for the stream to have more data * once its read method is unable to return any data without blocking. */ boolean isNonBlocking(); };