Package io.permazen.kv.array

package io.permazen.kv.array
A simple KVStore implementation based on a sorted array of key/value pairs.

Instances are optimized for relatively few writes and have minimal memory overhead.

Key and value data must not exceed 2GB (each separately). File Format

There are three files: index, keys, and values.

The index file contains zero or more index entries, which are pairs of big endian 32-bit values where the first value in a pair describes the offset of the corresponding key in the keys file, while the second describes the offset of the corresponding value in the values file. Index entries are sorted by key.

For index entries in a slot equal to zero mod 32, the 32-bit value is the absolute offset of the key, and this is called a "base key"; otherwise, the first 8 bits are the length of the key's prefix matching the previous base key (from zero to 255), while the remaining 24 bits are the offset from the beginning of the previous base key to the start of the suffix. In both cases, the end of the key is the starting offset of the next key (or end of file).

For all index entries, the second 32-bit value is the absolute offset of the value in the values file. The end of the value is the starting offset of the next value (or end of file).