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/* -*- 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 <any-error> 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, 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 should throw NS_BASE_STREAM_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).
*
* @return number of bytes currently available in the stream.
*
* @throws NS_BASE_STREAM_CLOSED if the stream is closed normally.
* @throws <other-error> if the stream is closed due to some error
* condition
*/
unsigned long long available();
/**
* 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 <other-error> 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 <other-error> 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();
};