Segmented Durable Key-Value Store

Simulate a durable string key-value store over an ordered batch of commands. The durable store is an append-only log split greedily across numbered segments, each with capacity 1024 bytes.

Commands

• PUT key value: append a record and set key to value using last-write-wins semantics. Return OK. The value is the entire suffix after the second space and may be empty.
• GET key: return VALUE:value for a present key, or NOT_FOUND.
• RELOAD: discard the in-memory map and reconstruct it by replaying every complete record in segment order. Return OK.
• SEGMENTS: return SEGMENTS:s1,s2,..., where each value is the used-byte count of one durable segment in order. With no records, return SEGMENTS:.

Record encoding and segmentation

All keys and values are printable ASCII, so one character occupies one byte. Encode a record as keyLength:keyvalueLength:value, where each length is written in base 10. A record is never split. Before an append that would make the current segment exceed 1024 bytes, start a new segment. Every encoded record is guaranteed to fit in one segment.