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 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      *  @param buffer   The buffer to write from
00066      *  @param size     The number of bytes to write 
00067      *  @return         The number of bytes written, negative error on failure
00068      */
00069     virtual ssize_t write(const void *buffer, size_t size) = 0;
00070 
00071     /** Move the file position to a given offset from from a given location
00072      *
00073      *  @param offset   The offset from whence to move to
00074      *  @param whence   The start of where to seek
00075      *      SEEK_SET to start from beginning of file,
00076      *      SEEK_CUR to start from current position in file,
00077      *      SEEK_END to start from end of file
00078      *  @return         The new offset of the file, negative error code on failure
00079      */
00080     virtual off_t seek(off_t offset, int whence = SEEK_SET) = 0;
00081 
00082     /** Close a file
00083      *
00084      *  @return         0 on success, negative error code on failure
00085      */
00086     virtual int close() = 0;
00087 
00088     /** Flush any buffers associated with the file
00089      *
00090      *  @return         0 on success, negative error code on failure
00091      */
00092     virtual int sync()
00093     {
00094         return 0;
00095     }
00096 
00097     /** Check if the file in an interactive terminal device
00098      *
00099      *  @return         True if the file is a terminal
00100      *  @return         False if the file is not a terminal
00101      *  @return         Negative error code on failure
00102      */
00103     virtual int isatty()
00104     {
00105         return false;
00106     }
00107 
00108     /** Get the file position of the file
00109      *
00110      *  @note This is equivalent to seek(0, SEEK_CUR)
00111      *
00112      *  @return         The current offset in the file, negative error code on failure
00113      */
00114     virtual off_t tell()
00115     {
00116         return seek(0, SEEK_CUR);
00117     }
00118 
00119     /** Rewind the file position to the beginning of the file
00120      *
00121      *  @note This is equivalent to seek(0, SEEK_SET)
00122      */
00123     virtual void rewind()
00124     {
00125         seek(0, SEEK_SET);
00126     }
00127 
00128     /** Get the size of the file
00129      *
00130      *  @return         Size of the file in bytes
00131      */
00132     virtual off_t size();
00133 
00134     /** Move the file position to a given offset from a given location.
00135      *
00136      *  @param offset The offset from whence to move to
00137      *  @param whence SEEK_SET for the start of the file, SEEK_CUR for the
00138      *   current file position, or SEEK_END for the end of the file.
00139      *
00140      *  @returns
00141      *    new file position on success,
00142      *    -1 on failure or unsupported
00143      */
00144     MBED_DEPRECATED_SINCE("mbed-os-5.4", "Replaced by FileHandle::seek")
00145     virtual off_t lseek(off_t offset, int whence)
00146     {
00147         return seek(offset, whence);
00148     }
00149 
00150     /** Flush any buffers associated with the FileHandle, ensuring it
00151      *  is up to date on disk
00152      *
00153      *  @returns
00154      *    0 on success or un-needed,
00155      *   -1 on error
00156      */
00157     MBED_DEPRECATED_SINCE("mbed-os-5.4", "Replaced by FileHandle::sync")
00158     virtual int fsync()
00159     {
00160         return sync();
00161     }
00162 
00163     /** Find the length of the file
00164      *
00165      *  @returns
00166      *   Length of the file
00167      */
00168     MBED_DEPRECATED_SINCE("mbed-os-5.4", "Replaced by FileHandle::size")
00169     virtual off_t flen()
00170     {
00171         return size();
00172     }
00173 
00174     /** Set blocking or non-blocking mode of the file operation like read/write.
00175      *  Definition depends upon the subclass implementing FileHandle.
00176      *  The default is blocking.
00177      *
00178      *  @param blocking     true for blocking mode, false for non-blocking mode.
00179      *
00180      *  @return             0 on success
00181      *  @return             Negative error code on failure
00182      */
00183     virtual int set_blocking(bool blocking)
00184     {
00185         return -1;
00186     }
00187 
00188     /** Check for poll event flags
00189      * The input parameter can be used or ignored - the could always return all events,
00190      * or could check just the events listed in events.
00191      * Call is non-blocking - returns instantaneous state of events.
00192      * Whenever an event occurs, the derived class should call the sigio() callback).
00193      *
00194      * @param events        bitmask of poll events we're interested in - POLLIN/POLLOUT etc.
00195      *
00196      * @returns             bitmask of poll events that have occurred.
00197      */
00198     virtual short poll(short events) const
00199     {
00200         // Possible default for real files
00201         return POLLIN | POLLOUT;
00202     }
00203 
00204     /** Definition depends upon the subclass implementing FileHandle.
00205      *  For example, if the FileHandle is of type Stream, writable() could return
00206      *  true when there is ample buffer space available for write() calls.
00207      *
00208      * @returns             true if the FileHandle is writable.
00209      */
00210     bool writable() const
00211     {
00212         return poll(POLLOUT) & POLLOUT;
00213     }
00214 
00215     /** Definition depends upon the subclass implementing FileHandle.
00216      *  For example, if the FileHandle is of type Stream, readable() could return
00217      *  true when there is something available to read.
00218      *
00219      *  @returns            true when there is something available to read.
00220      */
00221     bool readable() const
00222     {
00223         return poll(POLLIN) & POLLIN;
00224     }
00225 
00226     /** Register a callback on state change of the file.
00227      *
00228      *  The specified callback will be called on state changes such as when
00229      *  the file can be written to or read from.
00230      *
00231      *  The callback may be called in an interrupt context and should not
00232      *  perform expensive operations.
00233      *
00234      *  Note! This is not intended as an attach-like asynchronous api, but rather
00235      *  as a building block for constructing  such functionality.
00236      *
00237      *  The exact timing of when the registered function
00238      *  is called is not guaranteed and susceptible to change. It should be used
00239      *  as a cue to make read/write/poll calls to find the current state.
00240      *
00241      *  @param func     Function to call on state change
00242      */
00243     virtual void sigio(Callback<void()> func)
00244     {
00245         //Default for real files. Do nothing for real files.
00246     }
00247 };
00248 
00249 /** Not a member function
00250  *  This call is equivalent to posix fdopen().
00251  *  It associates a Stream to an already opened file descriptor (FileHandle)
00252  *
00253  *  @param fh       a pointer to an opened file descriptor
00254  *  @param mode     operation upon the file descriptor, e.g., 'wb+'
00255  *
00256  *  @returns        a pointer to std::FILE
00257 */
00258 
00259 std::FILE *fdopen(FileHandle *fh, const char *mode);
00260 
00261 /**@}*/
00262 
00263 /**@}*/
00264 
00265 
00266 } // namespace mbed
00267 
00268 #endif