mirror of https://github.com/metabarcoding/obitools4.git synced 2026-04-30 12:00:39 +00:00

Files

T

Eric Coissac 8c7017a99d ⬆️ version bump to v4.5

- Update obioptions.Version from "Release 4.4.29" to "/v/ Release v5"
- Update version.txt from 4.29 → .30
(automated by Makefile)

2026-04-13 13:34:53 +02:00

1.7 KiB

Raw Blame History

Varint Encoding and Decoding Module (`obikmer`)

This Go package implements variable-length integer encoding/decoding, commonly used in binary protocols (e.g., Protocol Buffers, SQLite) to efficiently store small integers using fewer bytes.

Core Features

EncodeVarint(w io.Writer, v uint64) (n int, err error)
Encodes a uint64 value into the minimal number of bytes (1–10) using LEB128-style varint, writing the result to a writer. Returns bytes written and any I/O error.
DecodeVarint(r io.Reader) (uint64, error)
Reads and decodes a varint from an io.Reader, reconstructing the original uint64. Fails on malformed or incomplete data.
VarintLen(v uint64) int
Computes the exact number of bytes required to encode v, without performing I/O.

Test Coverage

Round-trip correctness: All test values (including edge cases like 0, powers of two, and max uint64) encode → decode back identically.
Length validation: Encoded length matches VarintLen predictions exactly (e.g., 127 → 1 byte; 16384 → 3 bytes).
Sequence handling: Multiple varints can be concatenated and decoded in order, preserving data integrity.

Efficiency & Design

Uses 7-bit groups per byte, with the MSB as a continuation flag (1 = more bytes follow).
Minimal memory footprint — no allocations beyond buffer I/O.
Designed for streaming use (e.g., network or file serialization).

Edge Cases Verified

Value	Encoded Length
`0`	1 byte
`2⁷−1 = 127`	1 byte
`2⁷ = 128`	2 bytes
`2¹⁴−1 = 16383`	2 bytes
`^uint64(0)`	10 bytes

1.7 KiB Raw Blame History Unescape Escape

Varint Encoding and Decoding Module (obikmer)