Diff: platform/FileHandle.h

Revision:

167:e84263d55307

Child:

168:9672193075cf

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/platform/FileHandle.h	Wed Jun 21 17:46:44 2017 +0100
@@ -0,0 +1,258 @@
+/* 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.
+     *
+     *  @return             0 on success
+     *  @return             Negative error code on failure
+     */
+    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;
+    }
+
+    /** 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.
+     *
+     * @returns             true if the FileHandle is writable.
+     */
+    bool writable() const
+    {
+        return poll(POLLOUT) & POLLOUT;
+    }
+
+    /** 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.
+     *
+     *  @returns            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().
+ *  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+'
+ *
+ *  @returns        a pointer to std::FILE
+*/
+
+std::FILE *fdopen(FileHandle *fh, const char *mode);
+
+} // namespace mbed
+
+#endif