Added filesystem implementations of truncate

- File::truncate
- FileSystem::file_truncate
- FATFileSystem::file_truncate
- LittleFileSystem::file_truncate

Author: geky

features/storage/filesystem/File.cpp

@@ -110,4 +110,10 @@ off_t File::size()
     return _fs->file_size(_file);
 }
 
+int File::truncate(off_t length)
+{
+    MBED_ASSERT(_fs);
+    return _fs->file_truncate(_file, length);
+}
+
 } // namespace mbed

features/storage/filesystem/File.h

@@ -126,6 +126,18 @@ class File : public FileHandle {
      */
     virtual off_t size();
 
+    /** Truncate or extend a file.
+     *
+     * The file's length is set to the specified value. The seek pointer is
+     * not changed. If the file is extended, the extended area appears as if
+     * it were zero-filled.
+     *
+     *  @param length   The requested new length for the file
+     *
+     *  @return         Zero on success, negative error code on failure
+     */
+    virtual int truncate(off_t length);
+
 private:
     FileSystem *_fs;
     fs_file_t _file;

features/storage/filesystem/FileSystem.cpp

@@ -84,6 +84,11 @@ off_t FileSystem::file_size(fs_file_t file)
     return size;
 }
 
+int FileSystem::file_truncate(fs_file_t file, off_t length)
+{
+    return -ENOSYS;
+}
+
 int FileSystem::dir_open(fs_dir_t *dir, const char *path)
 {
     return -ENOSYS;

features/storage/filesystem/FileSystem.h

@@ -220,6 +220,19 @@ class FileSystem : public FileSystemLike {
      */
     virtual off_t file_size(fs_file_t file);
 
+    /** Truncate or extend a file.
+     *
+     * The file's length is set to the specified value. The seek pointer is
+     * not changed. If the file is extended, the extended area appears as if
+     * it were zero-filled.
+     *
+     *  @param file     File handle
+     *  @param length   The requested new length for the file
+     *
+     *  @return         Zero on success, negative error code on failure
+     */
+    virtual int file_truncate(fs_file_t file, off_t length);
+
     /** Open a directory on the filesystem
      *
      *  @param dir      Destination for the handle to the directory

features/storage/filesystem/fat/FATFileSystem.cpp

@@ -721,6 +721,37 @@ off_t FATFileSystem::file_size(fs_file_t file)
     return res;
 }
 
+int FATFileSystem::file_truncate(fs_file_t file, off_t length)
+{
+    FIL *fh = static_cast<FIL *>(file);
+
+    lock();
+    // save current position
+    FSIZE_t oldoff = f_tell(fh);
+
+    // seek to new file size and truncate
+    FRESULT res = f_lseek(fh, length);
+    if (res) {
+        unlock();
+        return fat_error_remap(res);
+    }
+
+    res = f_truncate(fh);
+    if (res) {
+        unlock();
+        return fat_error_remap(res);
+    }
+
+    // restore old position
+    res = f_lseek(fh, oldoff);
+    if (res) {
+        unlock();
+        return fat_error_remap(res);
+    }
+
+    return 0;
+}
+
 
 ////// Dir operations //////
 int FATFileSystem::dir_open(fs_dir_t *dir, const char *path)

features/storage/filesystem/fat/FATFileSystem.h

@@ -222,6 +222,19 @@ class FATFileSystem : public FileSystem {
      */
     virtual off_t file_size(fs_file_t file);
 
+    /** Truncate or extend a file.
+     *
+     * The file's length is set to the specified value. The seek pointer is
+     * not changed. If the file is extended, the extended area appears as if
+     * it were zero-filled.
+     *
+     *  @param file     File handle
+     *  @param length   The requested new length for the file
+     *
+     *  @return         Zero on success, negative error code on failure
+     */
+    virtual int file_truncate(mbed::fs_file_t file, off_t length);
+
     /** Open a directory on the filesystem
      *
      *  @param dir      Destination for the handle to the directory

features/storage/filesystem/littlefs/LittleFileSystem.cpp

@@ -500,6 +500,17 @@ off_t LittleFileSystem::file_size(fs_file_t file)
     return lfs_toerror(res);
 }
 
+int LittleFileSystem::file_truncate(fs_file_t file, off_t length)
+{
+    lfs_file_t *f = (lfs_file_t *)file;
+    _mutex.lock();
+    LFS_INFO("file_truncate(%p)", file);
+    int err = lfs_file_truncate(&_lfs, f, length);
+    LFS_INFO("file_truncate -> %d", lfs_toerror(err));
+    _mutex.unlock();
+    return lfs_toerror(err);
+}
+
 
 ////// Dir operations //////
 int LittleFileSystem::dir_open(fs_dir_t *dir, const char *path)

features/storage/filesystem/littlefs/LittleFileSystem.h

@@ -227,6 +227,19 @@ class LittleFileSystem : public mbed::FileSystem {
      */
     virtual off_t file_size(mbed::fs_file_t file);
 
+    /** Truncate or extend a file.
+     *
+     * The file's length is set to the specified value. The seek pointer is
+     * not changed. If the file is extended, the extended area appears as if
+     * it were zero-filled.
+     *
+     *  @param file     File handle
+     *  @param length   The requested new length for the file
+     *
+     *  @return         Zero on success, negative error code on failure
+     */
+    virtual int file_truncate(mbed::fs_file_t file, off_t length);
+
     /** Open a directory on the filesystem
      *
      *  @param dir      Destination for the handle to the directory