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platform/FileHandle.h
- Committer:
- thedo
- Date:
- 2017-06-29
- Revision:
- 166:3a9487d57a5c
File content as of revision 166:3a9487d57a5c:
/* mbed Microcontroller Library * Copyright (c) 2017 ARM Limited * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ #ifndef MBED_FILEHANDLE_H #define MBED_FILEHANDLE_H typedef int FILEHANDLE; #include <cstdio> #include "Callback.h" #include "platform/mbed_poll.h" #include "platform/platform.h" namespace mbed { /** \addtogroup platform */ /** Class FileHandle * * An abstract interface that represents operations on a file-like * object. The core functions are read, write, and seek, but only * a subset of these operations can be provided. * * @note to create a file, @see File * @note Synchronization level: Set by subclass * @ingroup platform */ class FileHandle { public: virtual ~FileHandle() {} /** Read the contents of a file into a buffer * * Devices acting as FileHandles should follow POSIX semantics: * * * if no data is available, and non-blocking set return -EAGAIN * * if no data is available, and blocking set, wait until data is available * * If any data is available, call returns immediately * * @param buffer The buffer to read in to * @param size The number of bytes to read * @return The number of bytes read, 0 at end of file, negative error on failure */ virtual ssize_t read(void *buffer, size_t size) = 0; /** Write the contents of a buffer to a file * * @param buffer The buffer to write from * @param size The number of bytes to write * @return The number of bytes written, negative error on failure */ virtual ssize_t write(const void *buffer, size_t size) = 0; /** Move the file position to a given offset from from a given location * * @param offset The offset from whence to move to * @param whence The start of where to seek * SEEK_SET to start from beginning of file, * SEEK_CUR to start from current position in file, * SEEK_END to start from end of file * @return The new offset of the file, negative error code on failure */ virtual off_t seek(off_t offset, int whence = SEEK_SET) = 0; /** Close a file * * @return 0 on success, negative error code on failure */ virtual int close() = 0; /** Flush any buffers associated with the file * * @return 0 on success, negative error code on failure */ virtual int sync() { return 0; } /** Check if the file in an interactive terminal device * * @return True if the file is a terminal * @return False if the file is not a terminal * @return Negative error code on failure */ virtual int isatty() { return false; } /** Get the file position of the file * * @note This is equivalent to seek(0, SEEK_CUR) * * @return The current offset in the file, negative error code on failure */ virtual off_t tell() { return seek(0, SEEK_CUR); } /** Rewind the file position to the beginning of the file * * @note This is equivalent to seek(0, SEEK_SET) */ virtual void rewind() { seek(0, SEEK_SET); } /** Get the size of the file * * @return Size of the file in bytes */ virtual off_t size(); /** Move the file position to a given offset from a given location. * * @param offset The offset from whence to move to * @param whence SEEK_SET for the start of the file, SEEK_CUR for the * current file position, or SEEK_END for the end of the file. * * @returns * new file position on success, * -1 on failure or unsupported */ MBED_DEPRECATED_SINCE("mbed-os-5.4", "Replaced by FileHandle::seek") virtual off_t lseek(off_t offset, int whence) { return seek(offset, whence); } /** Flush any buffers associated with the FileHandle, ensuring it * is up to date on disk * * @returns * 0 on success or un-needed, * -1 on error */ MBED_DEPRECATED_SINCE("mbed-os-5.4", "Replaced by FileHandle::sync") virtual int fsync() { return sync(); } /** Find the length of the file * * @returns * Length of the file */ MBED_DEPRECATED_SINCE("mbed-os-5.4", "Replaced by FileHandle::size") virtual off_t flen() { return size(); } /** Set blocking or non-blocking mode of the file operation like read/write. * Definition depends upon the subclass implementing FileHandle. * The default is blocking. * * @param blocking true for blocking mode, false for non-blocking mode. */ virtual int set_blocking(bool blocking) { return -1; } /** Check for poll event flags * The input parameter can be used or ignored - the could always return all events, * or could check just the events listed in events. * Call is non-blocking - returns instantaneous state of events. * Whenever an event occurs, the derived class should call the sigio() callback). * * @param events bitmask of poll events we're interested in - POLLIN/POLLOUT etc. * * @returns * bitmask of poll events that have occurred. */ virtual short poll(short events) const { // Possible default for real files return POLLIN | POLLOUT; } /** Returns true if the FileHandle is writable. * Definition depends upon the subclass implementing FileHandle. * For example, if the FileHandle is of type Stream, writable() could return * true when there is ample buffer space available for write() calls. */ bool writable() const { return poll(POLLOUT) & POLLOUT; } /** Returns true if the FileHandle is readable. * Definition depends upon the subclass implementing FileHandle. * For example, if the FileHandle is of type Stream, readable() could return * true when there is something available to read. */ bool readable() const { return poll(POLLIN) & POLLIN; } /** Register a callback on state change of the file. * * The specified callback will be called on state changes such as when * the file can be written to or read from. * * The callback may be called in an interrupt context and should not * perform expensive operations. * * Note! This is not intended as an attach-like asynchronous api, but rather * as a building block for constructing such functionality. * * The exact timing of when the registered function * is called is not guaranteed and susceptible to change. It should be used * as a cue to make read/write/poll calls to find the current state. * * @param func Function to call on state change */ virtual void sigio(Callback<void()> func) { //Default for real files. Do nothing for real files. } }; /** Not a member function * This call is equivalent to posix fdopen(). * Returns a pointer to std::FILE. * It associates a Stream to an already opened file descriptor (FileHandle) * * @param fh a pointer to an opened file descriptor * @param mode operation upon the file descriptor, e.g., 'wb+'*/ std::FILE *fdopen(FileHandle *fh, const char *mode); } // namespace mbed #endif