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 /** Class FileHandle
00032  *
00033  *  An abstract interface that represents operations on a file-like
00034  *  object. The core functions are read, write, and seek, but only
00035  *  a subset of these operations can be provided.
00036  *
00037  *  @note to create a file, @see File
00038  *  @note Synchronization level: Set by subclass
00039  *  @ingroup platform
00040  */
00041 class FileHandle : private NonCopyable<FileHandle> {
00042 public:
00043     virtual ~FileHandle() {}
00044 
00045     /** Read the contents of a file into a buffer
00046      *
00047      *  Devices acting as FileHandles should follow POSIX semantics:
00048      *
00049      *  * if no data is available, and non-blocking set return -EAGAIN
00050      *  * if no data is available, and blocking set, wait until data is available
00051      *  * If any data is available, call returns immediately
00052      *
00053      *  @param buffer   The buffer to read in to
00054      *  @param size     The number of bytes to read
00055      *  @return         The number of bytes read, 0 at end of file, negative error on failure
00056      */
00057     virtual ssize_t read(void *buffer, size_t size) = 0;
00058 
00059     /** Write the contents of a buffer to a file
00060      *
00061      *  @param buffer   The buffer to write from
00062      *  @param size     The number of bytes to write 
00063      *  @return         The number of bytes written, negative error on failure
00064      */
00065     virtual ssize_t write(const void *buffer, size_t size) = 0;
00066 
00067     /** Move the file position to a given offset from from a given location
00068      *
00069      *  @param offset   The offset from whence to move to
00070      *  @param whence   The start of where to seek
00071      *      SEEK_SET to start from beginning of file,
00072      *      SEEK_CUR to start from current position in file,
00073      *      SEEK_END to start from end of file
00074      *  @return         The new offset of the file, negative error code on failure
00075      */
00076     virtual off_t seek(off_t offset, int whence = SEEK_SET) = 0;
00077 
00078     /** Close a file
00079      *
00080      *  @return         0 on success, negative error code on failure
00081      */
00082     virtual int close() = 0;
00083 
00084     /** Flush any buffers associated with the file
00085      *
00086      *  @return         0 on success, negative error code on failure
00087      */
00088     virtual int sync()
00089     {
00090         return 0;
00091     }
00092 
00093     /** Check if the file in an interactive terminal device
00094      *
00095      *  @return         True if the file is a terminal
00096      *  @return         False if the file is not a terminal
00097      *  @return         Negative error code on failure
00098      */
00099     virtual int isatty()
00100     {
00101         return false;
00102     }
00103 
00104     /** Get the file position of the file
00105      *
00106      *  @note This is equivalent to seek(0, SEEK_CUR)
00107      *
00108      *  @return         The current offset in the file, negative error code on failure
00109      */
00110     virtual off_t tell()
00111     {
00112         return seek(0, SEEK_CUR);
00113     }
00114 
00115     /** Rewind the file position to the beginning of the file
00116      *
00117      *  @note This is equivalent to seek(0, SEEK_SET)
00118      */
00119     virtual void rewind()
00120     {
00121         seek(0, SEEK_SET);
00122     }
00123 
00124     /** Get the size of the file
00125      *
00126      *  @return         Size of the file in bytes
00127      */
00128     virtual off_t size();
00129 
00130     /** Move the file position to a given offset from a given location.
00131      *
00132      *  @param offset The offset from whence to move to
00133      *  @param whence SEEK_SET for the start of the file, SEEK_CUR for the
00134      *   current file position, or SEEK_END for the end of the file.
00135      *
00136      *  @returns
00137      *    new file position on success,
00138      *    -1 on failure or unsupported
00139      */
00140     MBED_DEPRECATED_SINCE("mbed-os-5.4", "Replaced by FileHandle::seek")
00141     virtual off_t lseek(off_t offset, int whence)
00142     {
00143         return seek(offset, whence);
00144     }
00145 
00146     /** Flush any buffers associated with the FileHandle, ensuring it
00147      *  is up to date on disk
00148      *
00149      *  @returns
00150      *    0 on success or un-needed,
00151      *   -1 on error
00152      */
00153     MBED_DEPRECATED_SINCE("mbed-os-5.4", "Replaced by FileHandle::sync")
00154     virtual int fsync()
00155     {
00156         return sync();
00157     }
00158 
00159     /** Find the length of the file
00160      *
00161      *  @returns
00162      *   Length of the file
00163      */
00164     MBED_DEPRECATED_SINCE("mbed-os-5.4", "Replaced by FileHandle::size")
00165     virtual off_t flen()
00166     {
00167         return size();
00168     }
00169 
00170     /** Set blocking or non-blocking mode of the file operation like read/write.
00171      *  Definition depends upon the subclass implementing FileHandle.
00172      *  The default is blocking.
00173      *
00174      *  @param blocking     true for blocking mode, false for non-blocking mode.
00175      *
00176      *  @return             0 on success
00177      *  @return             Negative error code on failure
00178      */
00179     virtual int set_blocking(bool blocking)
00180     {
00181         return -1;
00182     }
00183 
00184     /** Check for poll event flags
00185      * The input parameter can be used or ignored - the could always return all events,
00186      * or could check just the events listed in events.
00187      * Call is non-blocking - returns instantaneous state of events.
00188      * Whenever an event occurs, the derived class should call the sigio() callback).
00189      *
00190      * @param events        bitmask of poll events we're interested in - POLLIN/POLLOUT etc.
00191      *
00192      * @returns             bitmask of poll events that have occurred.
00193      */
00194     virtual short poll(short events) const
00195     {
00196         // Possible default for real files
00197         return POLLIN | POLLOUT;
00198     }
00199 
00200     /** Definition depends upon the subclass implementing FileHandle.
00201      *  For example, if the FileHandle is of type Stream, writable() could return
00202      *  true when there is ample buffer space available for write() calls.
00203      *
00204      * @returns             true if the FileHandle is writable.
00205      */
00206     bool writable() const
00207     {
00208         return poll(POLLOUT) & POLLOUT;
00209     }
00210 
00211     /** Definition depends upon the subclass implementing FileHandle.
00212      *  For example, if the FileHandle is of type Stream, readable() could return
00213      *  true when there is something available to read.
00214      *
00215      *  @returns            true when there is something available to read.
00216      */
00217     bool readable() const
00218     {
00219         return poll(POLLIN) & POLLIN;
00220     }
00221 
00222     /** Register a callback on state change of the file.
00223      *
00224      *  The specified callback will be called on state changes such as when
00225      *  the file can be written to or read from.
00226      *
00227      *  The callback may be called in an interrupt context and should not
00228      *  perform expensive operations.
00229      *
00230      *  Note! This is not intended as an attach-like asynchronous api, but rather
00231      *  as a building block for constructing  such functionality.
00232      *
00233      *  The exact timing of when the registered function
00234      *  is called is not guaranteed and susceptible to change. It should be used
00235      *  as a cue to make read/write/poll calls to find the current state.
00236      *
00237      *  @param func     Function to call on state change
00238      */
00239     virtual void sigio(Callback<void()> func)
00240     {
00241         //Default for real files. Do nothing for real files.
00242     }
00243 };
00244 
00245 /** Not a member function
00246  *  This call is equivalent to posix fdopen().
00247  *  It associates a Stream to an already opened file descriptor (FileHandle)
00248  *
00249  *  @param fh       a pointer to an opened file descriptor
00250  *  @param mode     operation upon the file descriptor, e.g., 'wb+'
00251  *
00252  *  @returns        a pointer to std::FILE
00253 */
00254 
00255 std::FILE *fdopen(FileHandle *fh, const char *mode);
00256 
00257 } // namespace mbed
00258 
00259 #endif