FileHandle.h

00001 /* mbed Microcontroller Library
00002  * Copyright (c) 2017 ARM Limited
00003  * SPDX-License-Identifier: Apache-2.0
00004  *
00005  * Licensed under the Apache License, Version 2.0 (the "License");
00006  * you may not use this file except in compliance with the License.
00007  * You may obtain a copy of the License at
00008  *
00009  *     http://www.apache.org/licenses/LICENSE-2.0
00010  *
00011  * Unless required by applicable law or agreed to in writing, software
00012  * distributed under the License is distributed on an "AS IS" BASIS,
00013  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
00014  * See the License for the specific language governing permissions and
00015  * limitations under the License.
00016  */
00017 #ifndef MBED_FILEHANDLE_H
00018 #define MBED_FILEHANDLE_H
00019 
00020 typedef int FILEHANDLE;
00021 
00022 #include <cstdio>
00023 #include "Callback.h"
00024 #include "platform/mbed_poll.h"
00025 #include "platform/platform.h"
00026 #include "platform/NonCopyable.h"
00027 
00028 namespace mbed {
00029 /** \addtogroup platform */
00030 /** @{*/
00031 /**
00032  * \defgroup platform_FileHandle FileHandle functions
00033  * @{
00034  */
00035 
00036 
00037 /** Class FileHandle
00038  *
00039  *  An abstract interface that represents operations on a file-like
00040  *  object. The core functions are read, write and seek, but only
00041  *  a subset of these operations can be provided.
00042  *
00043  *  @note to create a file, @see File
00044  *  @note Synchronization level: Set by subclass
00045  */
00046 class FileHandle : private NonCopyable<FileHandle> {
00047 public:
00048     virtual ~FileHandle() {}
00049 
00050     /** Read the contents of a file into a buffer
00051      *
00052      *  Devices acting as FileHandles should follow POSIX semantics:
00053      *
00054      *  * if no data is available, and nonblocking set, return -EAGAIN
00055      *  * if no data is available, and blocking set, wait until some data is available
00056      *  * If any data is available, call returns immediately
00057      *
00058      *  @param buffer   The buffer to read in to
00059      *  @param size     The number of bytes to read
00060      *  @return         The number of bytes read, 0 at end of file, negative error on failure
00061      */
00062     virtual ssize_t read(void *buffer, size_t size) = 0;
00063 
00064     /** Write the contents of a buffer to a file
00065      *
00066      *  Devices acting as FileHandles should follow POSIX semantics:
00067      *
00068      * * if blocking, block until all data is written
00069      * * if no data can be written, and nonblocking set, return -EAGAIN
00070      * * if some data can be written, and nonblocking set, write partial
00071      *
00072      *  @param buffer   The buffer to write from
00073      *  @param size     The number of bytes to write
00074      *  @return         The number of bytes written, negative error on failure
00075      */
00076     virtual ssize_t write(const void *buffer, size_t size) = 0;
00077 
00078     /** Move the file position to a given offset from from a given location
00079      *
00080      *  @param offset   The offset from whence to move to
00081      *  @param whence   The start of where to seek
00082      *      SEEK_SET to start from beginning of file,
00083      *      SEEK_CUR to start from current position in file,
00084      *      SEEK_END to start from end of file
00085      *  @return         The new offset of the file, negative error code on failure
00086      */
00087     virtual off_t seek(off_t offset, int whence = SEEK_SET) = 0;
00088 
00089     /** Close a file
00090      *
00091      *  @return         0 on success, negative error code on failure
00092      */
00093     virtual int close() = 0;
00094 
00095     /** Flush any buffers associated with the file
00096      *
00097      *  @return         0 on success, negative error code on failure
00098      */
00099     virtual int sync()
00100     {
00101         return 0;
00102     }
00103 
00104     /** Check if the file in an interactive terminal device
00105      *
00106      *  @return         True if the file is a terminal
00107      *  @return         False if the file is not a terminal
00108      *  @return         Negative error code on failure
00109      */
00110     virtual int isatty()
00111     {
00112         return false;
00113     }
00114 
00115     /** Get the file position of the file
00116      *
00117      *  @note This is equivalent to seek(0, SEEK_CUR)
00118      *
00119      *  @return         The current offset in the file, negative error code on failure
00120      */
00121     virtual off_t tell()
00122     {
00123         return seek(0, SEEK_CUR);
00124     }
00125 
00126     /** Rewind the file position to the beginning of the file
00127      *
00128      *  @note This is equivalent to seek(0, SEEK_SET)
00129      */
00130     virtual void rewind()
00131     {
00132         seek(0, SEEK_SET);
00133     }
00134 
00135     /** Get the size of the file
00136      *
00137      *  @return         Size of the file in bytes
00138      */
00139     virtual off_t size();
00140 
00141     /** Move the file position to a given offset from a given location.
00142      *
00143      *  @param offset The offset from whence to move to
00144      *  @param whence SEEK_SET for the start of the file, SEEK_CUR for the
00145      *   current file position, or SEEK_END for the end of the file.
00146      *
00147      *  @returns
00148      *    new file position on success,
00149      *    -1 on failure or unsupported
00150      *  @deprecated Replaced by `off_t FileHandle::seek(off_t offset, int whence = SEEK_SET)'
00151      *
00152      */
00153     MBED_DEPRECATED_SINCE("mbed-os-5.4", "Replaced by FileHandle::seek")
00154     virtual off_t lseek(off_t offset, int whence)
00155     {
00156         return seek(offset, whence);
00157     }
00158 
00159     /** Flush any buffers associated with the FileHandle, ensuring it
00160      *  is up to date on disk
00161      *
00162      *  @returns
00163      *    0 on success or un-needed,
00164      *   -1 on error
00165      *  @deprecated Replaced by `int FileHandle::sync()'
00166      */
00167     MBED_DEPRECATED_SINCE("mbed-os-5.4", "Replaced by FileHandle::sync")
00168     virtual int fsync()
00169     {
00170         return sync();
00171     }
00172 
00173     /** Find the length of the file
00174      *
00175      *  @returns
00176      *   Length of the file
00177      *  @deprecated Replaced by `off_t FileHandle::size()'
00178      */
00179     MBED_DEPRECATED_SINCE("mbed-os-5.4", "Replaced by FileHandle::size")
00180     virtual off_t flen()
00181     {
00182         return size();
00183     }
00184 
00185     /** Set blocking or nonblocking mode of the file operation like read/write.
00186      *  Definition depends on the subclass implementing FileHandle.
00187      *  The default is blocking.
00188      *
00189      *  @param blocking     true for blocking mode, false for nonblocking mode.
00190      *
00191      *  @return             0 on success
00192      *  @return             Negative error code on failure
00193      */
00194     virtual int set_blocking(bool blocking)
00195     {
00196         return blocking ? 0 : -ENOTTY;
00197     }
00198 
00199     /** Check current blocking or nonblocking mode for file operations.
00200      *
00201      *  @return             true for blocking mode, false for nonblocking mode.
00202      */
00203     virtual bool is_blocking() const
00204     {
00205         return true;
00206     }
00207 
00208     /** Check for poll event flags
00209      * You can use or ignore the input parameter. You can return all events
00210      * or check just the events listed in events.
00211      * Call is nonblocking - returns instantaneous state of events.
00212      * Whenever an event occurs, the derived class should call the sigio() callback).
00213      *
00214      * @param events        bitmask of poll events we're interested in - POLLIN/POLLOUT etc.
00215      *
00216      * @returns             bitmask of poll events that have occurred.
00217      */
00218     virtual short poll(short events) const
00219     {
00220         // Possible default for real files
00221         return POLLIN | POLLOUT;
00222     }
00223 
00224     /** Definition depends on the subclass implementing FileHandle.
00225      *  For example, if the FileHandle is of type Stream, writable() could return
00226      *  true when there is ample buffer space available for write() calls.
00227      *
00228      * @returns             true if the FileHandle is writable.
00229      */
00230     bool writable() const
00231     {
00232         return poll(POLLOUT) & POLLOUT;
00233     }
00234 
00235     /** Definition depends on the subclass implementing FileHandle.
00236      *  For example, if the FileHandle is of type Stream, readable() could return
00237      *  true when there is something available to read.
00238      *
00239      *  @returns            true when there is something available to read.
00240      */
00241     bool readable() const
00242     {
00243         return poll(POLLIN) & POLLIN;
00244     }
00245 
00246     /** Register a callback on state change of the file.
00247      *
00248      *  The specified callback will be called on state changes such as when
00249      *  the file can be written to or read from.
00250      *
00251      *  The callback may be called in an interrupt context and should not
00252      *  perform expensive operations.
00253      *
00254      *  Note! This is not intended as an attach-like asynchronous API, but rather
00255      *  as a building block for constructing such functionality.
00256      *
00257      *  The exact timing of when the registered function
00258      *  is called is not guaranteed and is susceptible to change. It should be used
00259      *  as a cue to make read/write/poll calls to find the current state.
00260      *
00261      *  @param func     Function to call on state change
00262      */
00263     virtual void sigio(Callback<void()> func)
00264     {
00265         //Default for real files. Do nothing for real files.
00266     }
00267 };
00268 
00269 /**@}*/
00270 
00271 /**@}*/
00272 
00273 
00274 } // namespace mbed
00275 
00276 #endif