BufferedBlockDevice.h

/* mbed Microcontroller Library
 * Copyright (c) 2018-2020 ARM Limited
 * SPDX-License-Identifier: Apache-2.0
 *
 * 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_BUFFERED_BLOCK_DEVICE_H
#define MBED_BUFFERED_BLOCK_DEVICE_H
 
#include "BlockDevice.h"
 
namespace mbed {
 
/** \addtogroup storage-blockdevice */
/** @{*/
 
/**
 * Block device which allows minimal read and program sizes (of 1) for the underlying BD
 * using a buffer on the heap.  This essentially "simulates" a byte-programmable device
 * like a NOR flash or an EEPROM, using a non-byte-programmable device like an SD card or
 * NAND flash.
 *
 * @note While the read and write size of the buffered block device will always be 1,
 *     the erase size is the same as the underlying block device. In other words, you
 *     still must erase in the hardware erase sector size.
 */
class BufferedBlockDevice : public BlockDevice {
public:
    /** Lifetime of a memory-buffered block device wrapping an underlying block device
     *
     *  @param bd        Block device to back the BufferedBlockDevice
     */
    BufferedBlockDevice(BlockDevice *bd);
 
    /** Lifetime of the memory-buffered block device
     */
    virtual ~BufferedBlockDevice();
 
    /** Initialize a buffered-memory block device and its underlying block device
     *
     *  @return         0 on success or a negative error code on failure
     */
    virtual int init();
 
    /** Deinitialize the buffered-memory block device and its underlying block device
     *
     *  @return         0 on success or a negative error code on failure
     */
    virtual int deinit();
 
    /** Ensure that data on the underlying storage block device is in sync with the
     *  memory-buffered block device
     *
     *  @return         0 on success or a negative error code on failure
     */
    virtual int sync();
 
    /** Read blocks from the memory-buffered block device
     *
     *  @param buffer   Buffer to read blocks into
     *  @param addr     Address of block to begin reading from
     *  @param size     Size to read in bytes, must be a multiple of read block size
     *  @return         0 on success, negative error code on failure
     */
    virtual int read(void *buffer, bd_addr_t addr, bd_size_t size);
 
    /** Program data to the memory-buffered block device
     *
     *  The write address blocks must be erased prior to being programmed.
     *
     *  @param buffer   Buffer of data to write to blocks
     *  @param addr     Address of block to begin writing to
     *  @param size     Size to write in bytes, must be a multiple of program block size
     *  @return         0 on success, negative error code on failure
     */
    virtual int program(const void *buffer, bd_addr_t addr, bd_size_t size);
 
    /** Erase blocks from the memory-buffered block device
     *
     *  The state of an erased block is undefined until it has been programmed,
     *  unless get_erase_value returns a non-negative byte value.
     *
     *  @param addr     Address of block to begin erasing
     *  @param size     Size to erase in bytes, must be a multiple of erase block size
     *  @return         0 on success, negative error code on failure
     */
    virtual int erase(bd_addr_t addr, bd_size_t size);
 
    /** Mark blocks as no longer in use
     *
     *  This function provides a hint to the underlying block device that a region of blocks
     *  is no longer in use and may be erased without side effects. Erase must still be called
     *  before programming, but trimming allows flash-translation-layers to schedule erases when
     *  the device is not busy.
     *
     *  @param addr     Address of block to mark as unused
     *  @param size     Size to mark as unused in bytes, must be a multiple of erase block size
     *  @return         0 on success, negative error code on failure
     */
    virtual int trim(bd_addr_t addr, bd_size_t size);
 
    /** Get the size of a readable block
     *
     *  @return         Size of a readable block in bytes
     */
    virtual bd_size_t get_read_size() const;
 
    /** Get the size of a programmable block
     *
     *  @return         Size of a programmable block in bytes
     *  @note Must be a multiple of the read size
     */
    virtual bd_size_t get_program_size() const;
 
    /** Get the size of an erasable block
     *
     *  @return         Size of an erasable block in bytes
     *  @note Must be a multiple of the program size
     */
    virtual bd_size_t get_erase_size() const;
 
    /** Get the size of an erasable block of a given address
     *
     *  @param addr     Address within the erasable block
     *  @return         Size of an erasable block in bytes
     *  @note Must be a multiple of the program size
     */
    virtual bd_size_t get_erase_size(bd_addr_t addr) const;
 
    /** Get the value of storage data after being erased
     *
     *  If get_erase_value returns a non-negative byte value, the underlying
     *  storage is set to that value when erased, and storage containing
     *  that value can be programmed without another erase.
     *
     *  @return         The value of storage when erased, or -1 if you can't
     *                  rely on the value of erased storage
     */
    virtual int get_erase_value() const;
 
    /** Get the total size of the underlying device
     *
     *  @return         Size of the underlying device in bytes
     */
    virtual bd_size_t size() const;
 
    /** Get the underlying BlockDevice class type
     *
     *  @return         A string representing the underlying BlockDevice class type
     */
    virtual const char *get_type() const;
 
protected:
    BlockDevice *_bd;
    bd_size_t _bd_program_size;
    bd_size_t _bd_read_size;
    bd_size_t _bd_size;
    bd_size_t _write_cache_addr;
    bool _write_cache_valid;
    uint8_t *_write_cache;
    uint8_t *_read_buf;
    uint32_t _init_ref_count;
    bool _is_initialized;
 
#if !(DOXYGEN_ONLY)
    /** Flush data in cache
     *
     *  @return         0 on success or a negative error code on failure
     */
    int flush();
 
    /** Invalidate write cache
     *
     *  @return         none
     */
    void invalidate_write_cache();
#endif //#if !(DOXYGEN_ONLY)
};
 
/** @}*/
 
} // namespace mbed
 
// Added "using" for backwards compatibility
#ifndef MBED_NO_GLOBAL_USING_DIRECTIVE
using mbed::BufferedBlockDevice;
#endif
 
#endif