REMARK: This is an old version of KVS, I am going to change the entries storage method to reduce size and simplify the library

KVS - key value store for embedded devices

Generic key value store interface to store and retrieve key-value entries on different kind of memory devices e.g. RAM, FLASH (nor or nand), EEPROM, ...

Introduction

KVS stores Key-value entries as:

  Entry header: the maximum length of the header is 13 bytes.
     byte 0: |. . .. .. ..|
              | | |  |  |-- value length bits 0-3: value length is 1-4 bytes
              | | |  |----- key length bits 0-3: key length is 1-4 bytes
              | | |------ unused
              | |-------- 1: includes wrap/erase counter, 0 no wrap counter
              |---------- odd parity bit (makes byte 0 odd parity)
     key length bytes
     value length bytes
     wrap counter (if included, 4 bytes)
   Entry data:
     key bytes (key length)
     value bytes (value length)
     fill bytes
   Entry footer:
     CRC32 value calculated over entry header and data (excluding fill).

Entries are written sequentially to blocks that have a configurable size. At the beginning of each block a wrap counter is added to the entry. The wrap counter is increased each time the memory wraps around. When a new block is started the key value store verifies whether it needs to move old entries to keep a copy and does so if required.

The configurable block size needs to be a power of 2. The block size limits the maximum size of an entry as it needs to fit within one block. The block size is not limited to an erase block size of the memory device, this allows using memory devices with non constant erase block sizes. However in this last case carefull parameter selection is required to guarantee that there will be no loss of data.

documentation

The API for KVS is documented in the header file kvs.h.