gecko-dev/netwerk/base/nsIFileStreams.idl

/* -*- 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 "nsIInputStream.idl"
#include "nsIOutputStream.idl"

interface nsIEventTarget;
interface nsIFile;
interface nsIFileMetadataCallback;

%{C++
struct PRFileDesc;
%}

[ptr] native PRFileDescPtr(PRFileDesc);

/**
 * An input stream that allows you to read from a file.
 */
[scriptable, uuid(e3d56a20-c7ec-11d3-8cda-0060b0fc14a3)]
interface nsIFileInputStream : nsIInputStream
{
    /**
     * @param file          file to read from
     * @param ioFlags       file open flags listed in prio.h (see
     *                      PR_Open documentation) or -1 to open the
     *                      file in default mode (PR_RDONLY).
     * @param perm          file mode bits listed in prio.h or -1 to
     *                      use the default value (0)
     * @param behaviorFlags flags specifying various behaviors of the class
     *        (see enumerations in the class)
     */
    void init(in nsIFile file, in long ioFlags, in long perm,
              in long behaviorFlags);

    /**
     * If this is set, the file will close automatically when the end of the
     * file is reached.
     */
    const long CLOSE_ON_EOF = 1<<2;

    /**
     * If this is set, the file will be reopened whenever we reach the start of
     * the file, either by doing a Seek(0, NS_SEEK_CUR), or by doing a relative
     * seek that happen to reach the beginning of the file. If the file is
     * already open and the seek occurs, it will happen naturally.  (The file
     * will only be reopened if it is closed for some reason.)
     */
    const long REOPEN_ON_REWIND = 1<<3;

    /**
     * If this is set, the file will be opened (i.e., a call to
     * PR_Open done) only when we do an actual operation on the stream,
     * or more specifically, when one of the following is called:
     *   - Seek
     *   - Tell
     *   - SetEOF
     *   - Available
     *   - Read
     *   - ReadLine
     *
     * DEFER_OPEN is useful if we use the stream on a background
     * thread, so that the opening and possible |stat|ing of the file
     * happens there as well.
     *
     * @note Using this flag results in the file not being opened
     *       during the call to Init.  This means that any errors that might
     *       happen when this flag is not set would happen during the
     *       first read.  Also, the file is not locked when Init is called,
     *       so it might be deleted before we try to read from it.
     */
    const long DEFER_OPEN = 1<<4;

    /**
     * This flag has no effect and is totally ignored on any platform except
     * Windows since this is the default behavior on POSIX systems. On Windows
     * if this flag is set then the stream is opened in a special mode that
     * allows the OS to delete the file from disk just like POSIX.
     */
    const long SHARE_DELETE = 1<<5;
};

/**
 * An output stream that lets you stream to a file.
 */
[scriptable, uuid(e734cac9-1295-4e6f-9684-3ac4e1f91063)]
interface nsIFileOutputStream : nsIOutputStream
{
    /**
     * @param file          file to write to
     * @param ioFlags       file open flags listed in prio.h (see
     *                      PR_Open documentation) or -1 to open the
     *                      file in default mode (PR_WRONLY |
     *                      PR_CREATE_FILE | PR_TRUNCATE)
     * @param perm          file mode bits listed in prio.h or -1 to
     *                      use the default permissions (0664)
     * @param behaviorFlags flags specifying various behaviors of the class
     *        (currently none supported)
     */
    void init(in nsIFile file, in long ioFlags, in long perm,
              in long behaviorFlags);

    /**
     * @param length        asks the operating system to allocate storage for
     *                      this file of at least |length| bytes long, and
     *                      set the file length to the corresponding size.
     * @throws NS_ERROR_FAILURE if the preallocation fails.
     * @throws NS_ERROR_NOT_INITIALIZED if the file is not opened.
     */
    [noscript] void preallocate(in long long length);

    /**
     * See the same constant in nsIFileInputStream. The deferred open will
     * be performed when one of the following is called:
     *   - Seek
     *   - Tell
     *   - SetEOF
     *   - Write
     *   - Flush
     *
     * @note Using this flag results in the file not being opened
     *       during the call to Init.  This means that any errors that might
     *       happen when this flag is not set would happen during the
     *       first write, and if the file is to be created, then it will not
     *       appear on the disk until the first write.
     */
    const long DEFER_OPEN = 1<<0;
};

/**
 * A stream that allows you to read from a file or stream to a file.
 */
[scriptable, uuid(82cf605a-8393-4550-83ab-43cd5578e006)]
interface nsIFileStream : nsISupports
{
    /**
     * @param file          file to read from or stream to
     * @param ioFlags       file open flags listed in prio.h (see
     *                      PR_Open documentation) or -1 to open the
     *                      file in default mode (PR_RDWR).
     * @param perm          file mode bits listed in prio.h or -1 to
     *                      use the default value (0)
     * @param behaviorFlags flags specifying various behaviors of the class
     *        (see enumerations in the class)
     */
    void init(in nsIFile file, in long ioFlags, in long perm,
              in long behaviorFlags);

    /**
     * See the same constant in nsIFileInputStream. The deferred open will
     * be performed when one of the following is called:
     *   - Seek
     *   - Tell
     *   - SetEOF
     *   - Available
     *   - Read
     *   - Flush
     *   - Write
     *   - GetSize
     *   - GetLastModified
     *
     * @note Using this flag results in the file not being opened
     *       during the call to Init.  This means that any errors that might
     *       happen when this flag is not set would happen during the
     *       first read or write. The file is not locked when Init is called,
     *       so it might be deleted before we try to read from it and if the
     *       file is to be created, then it will not appear on the disk until
     *       the first write.
     */
    const long DEFER_OPEN = 1<<0;
};

/**
 * An interface that allows you to get some metadata like file size and
 * file last modified time. These methods and attributes can throw
 * NS_BASE_STREAM_WOULD_BLOCK in case the informations are not available yet.
 * If this happens, consider the use of nsIAsyncFileMetadata.
 *
 * If using nsIAsyncFileMetadata, you should retrieve any data via this
 * interface before taking any action that might consume the underlying stream.
 * For example, once Available(), Read(), or nsIAsyncInputStream::AsyncWait()
 * are invoked, these methods may return NS_BASE_STREAM_CLOSED.  This will
 * happen when using RemoteLazyInputStream with an underlying file stream, for
 * example.
 */
[scriptable, uuid(07f679e4-9601-4bd1-b510-cd3852edb881)]
interface nsIFileMetadata : nsISupports
{
    /**
     * File size in bytes.
     */
    readonly attribute long long size;

    /**
     * File last modified time in milliseconds from midnight (00:00:00),
     * January 1, 1970 Greenwich Mean Time (GMT).
     */
    readonly attribute long long lastModified;

    /**
     * The internal file descriptor. It can be used for memory mapping of the
     * underlying file. Please use carefully! If this returns
     * NS_BASE_STREAM_WOULD_BLOCK, consider the use of nsIAsyncFileMetadata.
     */
    [noscript] PRFileDescPtr getFileDescriptor();
};

[scriptable, uuid(de15b80b-29ba-4b7f-9220-a3d75b17ae8c)]
interface nsIAsyncFileMetadata : nsIFileMetadata
{
    /**
     * Asynchronously wait for the object to be ready.
     *
     * @param aCallback The callback will be used when the stream is ready to
     *                  return File metadata. Use a nullptr to cancel a
     *                  previous operation.
     *
     * @param aEventTarget The event target where aCallback will be executed.
     *                     If aCallback is passed, aEventTarget cannot be null.
     */
    void asyncFileMetadataWait(in nsIFileMetadataCallback aCallback,
                               in nsIEventTarget aEventTarget);
};

/**
 * This is a companion interface for
 * nsIAsyncFileMetadata::asyncFileMetadataWait.
 */
[function, scriptable, uuid(d01c7ead-7ba3-4726-b399-618ec8ec7057)]
interface nsIFileMetadataCallback : nsISupports
{
    /**
     * Called to indicate that the nsIFileMetadata object is ready.
     */
    void onFileMetadataReady(in nsIAsyncFileMetadata aObject);
};