gecko-dev/xpcom/io/nsIPipe.idl

/* -*- 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"

interface nsIAsyncInputStream;
interface nsIAsyncOutputStream;

/**
 * nsIPipe represents an in-process buffer that can be read using nsIInputStream
 * and written using nsIOutputStream.  The reader and writer of a pipe do not
 * have to be on the same thread.  As a result, the pipe is an ideal mechanism
 * to bridge data exchange between two threads.  For example, a worker thread
 * might write data to a pipe from which the main thread will read.
 *
 * Each end of the pipe can be either blocking or non-blocking.  Recall that a
 * non-blocking stream will return NS_BASE_STREAM_WOULD_BLOCK if it cannot be
 * read or written to without blocking the calling thread.  For example, if you
 * try to read from an empty pipe that has not yet been closed, then if that
 * pipe's input end is non-blocking, then the read call will fail immediately
 * with NS_BASE_STREAM_WOULD_BLOCK as the error condition.  However, if that
 * pipe's input end is blocking, then the read call will not return until the
 * pipe has data or until the pipe is closed.  This example presumes that the
 * pipe is being filled asynchronously on some background thread.
 *
 * The pipe supports nsIAsyncInputStream and nsIAsyncOutputStream, which give
 * the user of a non-blocking pipe the ability to wait for the pipe to become
 * ready again.  For example, in the case of an empty non-blocking pipe, the
 * user can call AsyncWait on the input end of the pipe to be notified when
 * the pipe has data to read (or when the pipe becomes closed).
 *
 * NS_NewPipe2 and NS_NewPipe provide convenient pipe constructors.  In most
 * cases nsIPipe is not actually used.  It is usually enough to just get
 * references to the pipe's input and output end.  In which case, the pipe is
 * automatically closed when the respective pipe ends are released.
 */
[scriptable, uuid(25d0de93-685e-4ea4-95d3-d884e31df63c)]
interface nsIPipe : nsISupports
{
    /**
     * initialize this pipe
     *
     * @param nonBlockingInput
     *        true specifies non-blocking input stream behavior
     * @param nonBlockingOutput
     *        true specifies non-blocking output stream behavior
     * @param segmentSize
     *        specifies the segment size in bytes (pass 0 to use default value)
     * @param segmentCount
     *        specifies the max number of segments (pass 0 to use default
     *        value).   Passing UINT32_MAX here causes the pipe to have
     *        "infinite" space.  This mode can be useful in some cases, but
     *        should always be used with caution.  The default value for this
     *        parameter is a finite value.
     */
    [must_use] void init(in boolean nonBlockingInput,
                         in boolean nonBlockingOutput,
                         in unsigned long segmentSize,
                         in unsigned long segmentCount);

    /**
     * The pipe's input end, which also implements nsISearchableInputStream.
     * Getting fails if the pipe hasn't been initialized.
     */
    [must_use] readonly attribute nsIAsyncInputStream inputStream;

    /**
     * The pipe's output end. Getting fails if the pipe hasn't been
     * initialized.
     */
    [must_use] readonly attribute nsIAsyncOutputStream outputStream;
};

/**
 * XXX this interface doesn't really belong in here.  It is here because
 * currently nsPipeInputStream is the only implementation of this interface.
 */
[scriptable, uuid(8C39EF62-F7C9-11d4-98F5-001083010E9B)]
interface nsISearchableInputStream : nsISupports
{
    /**
     * Searches for a string in the input stream. Since the stream has a notion
     * of EOF, it is possible that the string may at some time be in the
     * buffer, but is is not currently found up to some offset. Consequently,
     * both the found and not found cases return an offset:
     *    if found, return offset where it was found
     *    if not found, return offset of the first byte not searched
     * In the case the stream is at EOF and the string is not found, the first
     * byte not searched will correspond to the length of the buffer.
     */
    void search(in string forString,
                in boolean ignoreCase,
                out boolean found,
                out unsigned long offsetSearchedTo);
};

%{C++

class nsIInputStream;
class nsIOutputStream;

/**
 * NS_NewPipe2
 *
 * This function supersedes NS_NewPipe.  It differs from NS_NewPipe in two
 * major ways:
 *  (1) returns nsIAsyncInputStream and nsIAsyncOutputStream, so it is
 *      not necessary to QI in order to access these interfaces.
 *  (2) the size of the pipe is determined by the number of segments
 *      times the size of each segment.
 *
 * @param pipeIn
 *        resulting input end of the pipe
 * @param pipeOut
 *        resulting output end of the pipe
 * @param nonBlockingInput
 *        true specifies non-blocking input stream behavior
 * @param nonBlockingOutput
 *        true specifies non-blocking output stream behavior
 * @param segmentSize
 *        specifies the segment size in bytes (pass 0 to use default value)
 * @param segmentCount
 *        specifies the max number of segments (pass 0 to use default value)
 *        passing UINT32_MAX here causes the pipe to have "infinite" space.
 *        this mode can be useful in some cases, but should always be used with
 *        caution.  the default value for this parameter is a finite value.
 */
[[nodiscard]] extern nsresult
NS_NewPipe2(nsIAsyncInputStream **pipeIn,
            nsIAsyncOutputStream **pipeOut,
            bool nonBlockingInput = false,
            bool nonBlockingOutput = false,
            uint32_t segmentSize = 0,
            uint32_t segmentCount = 0);

/**
 * NS_NewPipe
 *
 * Preserved for backwards compatibility.  Plus, this interface is more
 * amiable in certain contexts (e.g., when you don't need the pipe's async
 * capabilities).
 *
 * @param pipeIn
 *        resulting input end of the pipe
 * @param pipeOut
 *        resulting output end of the pipe
 * @param segmentSize
 *        specifies the segment size in bytes (pass 0 to use default value)
 * @param maxSize
 *        specifies the max size of the pipe (pass 0 to use default value)
 *        number of segments is maxSize / segmentSize, and maxSize must be a
 *        multiple of segmentSize.  passing UINT32_MAX here causes the
 *        pipe to have "infinite" space.  this mode can be useful in some
 *        cases, but should always be used with caution.  the default value
 *        for this parameter is a finite value.
 * @param nonBlockingInput
 *        true specifies non-blocking input stream behavior
 * @param nonBlockingOutput
 *        true specifies non-blocking output stream behavior
 */
[[nodiscard]] extern nsresult
NS_NewPipe(nsIInputStream **pipeIn,
           nsIOutputStream **pipeOut,
           uint32_t segmentSize = 0,
           uint32_t maxSize = 0,
           bool nonBlockingInput = false,
           bool nonBlockingOutput = false);

%}