File content as of revision 3:d86a4ddc1867:

/*
The MIT License (MIT)

Copyright (c) 2016 British Broadcasting Corporation.
This software is provided by Lancaster University by arrangement with the BBC.

Permission is hereby granted, free of charge, to any person obtaining a
copy of this software and associated documentation files (the "Software"),
to deal in the Software without restriction, including without limitation
the rights to use, copy, modify, merge, publish, distribute, sublicense,
and/or sell copies of the Software, and to permit persons to whom the
Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
DEALINGS IN THE SOFTWARE.
*/

#ifndef MICROBIT_STORAGE_H
#define MICROBIT_STORAGE_H

#include "mbed.h"
#include "MicroBitConfig.h"
#include "ManagedString.h"
#include "ErrorNo.h"

#define MICROBIT_STORAGE_MAGIC       0xCAFE

#define MICROBIT_STORAGE_BLOCK_SIZE             48
#define MICROBIT_STORAGE_KEY_SIZE               16
#define MICROBIT_STORAGE_VALUE_SIZE             MICROBIT_STORAGE_BLOCK_SIZE - MICROBIT_STORAGE_KEY_SIZE

#define MICROBIT_STORAGE_STORE_PAGE_OFFSET      17      //Use the page just above the BLE Bond Data.
#define MICROBIT_STORAGE_SCRATCH_PAGE_OFFSET    19      //Use the page just below the BLE Bond Data.

struct KeyValuePair
{
    uint8_t key[MICROBIT_STORAGE_KEY_SIZE];
    uint8_t value[MICROBIT_STORAGE_VALUE_SIZE];
};

struct KeyValueStore
{
    uint32_t magic;
    uint32_t size;

    KeyValueStore(uint32_t magic, uint32_t size)
    {
        this->magic = magic;
        this->size = size;
    }

    KeyValueStore()
    {
        this->magic = 0;
        this->size = 0;
    }
};


/**
  * Class definition for the MicroBitStorage class.
  * This allows reading and writing of small blocks of data to FLASH memory.
  *
  * This class operates as a key value store, it allows the retrieval, addition
  * and deletion of KeyValuePairs.
  *
  * The first 8 bytes are reserved for the KeyValueStore struct which gives core
  * information such as the number of KeyValuePairs in the store, and whether the
  * store has been initialised.
  *
  * After the KeyValueStore struct, KeyValuePairs are arranged contiguously until
  * the end of the block used as persistent storage.
  *
  * |-------8-------|--------48-------|-----|---------48--------|
  * | KeyValueStore | KeyValuePair[0] | ... | KeyValuePair[N-1] |
  * |---------------|-----------------|-----|-------------------|
  */
class MicroBitStorage
{
    /**
      * Function for copying words from one location to another.
      *
      * @param from the address to copy data from.
      *
      * @param to the address to copy the data to.
      *
      * @param sizeInWords the number of words to copy
      */
    void flashCopy(uint32_t* from, uint32_t* to, int sizeInWords);

    /**
      * Function for populating the scratch page with a KeyValueStore.
      *
      * @param store the KeyValueStore struct to write to the scratch page.
      */
    void scratchKeyValueStore(KeyValueStore store);

    /**
      * Function for populating the scratch page with a KeyValuePair.
      *
      * @param pair the KeyValuePair struct to write to the scratch page.
      *
      * @param flashPointer the pointer in flash where this KeyValuePair resides. This pointer
      * is used to determine the offset into the scratch page, where the KeyValuePair should
      * be written.
      */
    void scratchKeyValuePair(KeyValuePair pair, uint32_t* flashPointer);

    public:

    /**
      * Default constructor.
      *
      * Creates an instance of MicroBitStorage which acts like a KeyValueStore
      * that allows the retrieval, addition and deletion of KeyValuePairs.
      */
    MicroBitStorage();

    /**
      * Writes the given number of bytes to the address specified.
      *
      * @param buffer the data to write.
      *
      * @param address the location in memory to write to.
      *
      * @param length the number of bytes to write.
      *
      * @note currently not implemented.
      */
    int writeBytes(uint8_t *buffer, uint32_t address, int length);

    /**
      * Method for erasing a page in flash.
      *
      * @param page_address Address of the first word in the page to be erased.
      */
    void flashPageErase(uint32_t * page_address);

    /**
      * Method for writing a word of data in flash with a value.
      *
      * @param address Address of the word to change.
      *
      * @param value Value to be written to flash.
      */
    void flashWordWrite(uint32_t * address, uint32_t value);

    /**
      * Places a given key, and it's corresponding value into flash at the earliest
      * available point.
      *
      * @param key the unique name that should be used as an identifier for the given data.
      *            The key is presumed to be null terminated.
      *
      * @param data a pointer to the beginning of the data to be persisted.
      *
      * @return MICROBIT_OK on success, or MICROBIT_NO_RESOURCES if the storage page is full
      */
    int put(const char* key, uint8_t* data);

    /**
      * Places a given key, and it's corresponding value into flash at the earliest
      * available point.
      *
      * @param key the unique name that should be used as an identifier for the given data.
      *
      * @param data a pointer to the beginning of the data to be persisted.
      *
      * @return MICROBIT_OK on success, or MICROBIT_NO_RESOURCES if the storage page is full
      */
    int put(ManagedString key, uint8_t* data);

    /**
      * Retreives a KeyValuePair identified by a given key.
      *
      * @param key the unique name used to identify a KeyValuePair in flash.
      *
      * @return a pointer to a heap allocated KeyValuePair struct, this pointer will be
      *         NULL if the key was not found in storage.
      *
      * @note it is up to the user to free memory after use.
      */
    KeyValuePair* get(const char* key);

    /**
      * Retreives a KeyValuePair identified by a given key.
      *
      * @param key the unique name used to identify a KeyValuePair in flash.
      *
      * @return a pointer to a heap allocated KeyValuePair struct, this pointer will be
      *         NULL if the key was not found in storage.
      *
      * @note it is up to the user to free memory after use.
      */
    KeyValuePair* get(ManagedString key);

    /**
      * Removes a KeyValuePair identified by a given key.
      *
      * @param key the unique name used to identify a KeyValuePair in flash.
      *
      * @return MICROBIT_OK on success, or MICROBIT_NO_DATA if the given key
      *         was not found in flash.
      */
    int remove(const char* key);

    /**
      * Removes a KeyValuePair identified by a given key.
      *
      * @param key the unique name used to identify a KeyValuePair in flash.
      *
      * @return MICROBIT_OK on success, or MICROBIT_NO_DATA if the given key
      *         was not found in flash.
      */
    int remove(ManagedString key);

    /**
      * The size of the flash based KeyValueStore.
      *
      * @return the number of entries in the key value store
      */
    int size();
};

#endif