FileHandle.h

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