Codec Variants

svb provides five codec variants spanning three element widths. Each is a zero-sized type implementing the same encode/decode surface.

Variant	Element	Tag bits	Byte widths	Wire-compatible with
`Svb16`	`u16`	1	1/2	ONT `vbz_hdf_plugin`
`U32Classic`	`u32`	2	1/2/3/4	Lemire C library, `stream-vbyte` crate
`U32Variant0124`	`u32`	2	0/1/2/4	Lemire "0124" variant
`U64Coder1234`	`u64`	2	1/2/3/4	`streamvbyte64::Coder1234` (u32 values)
`U64Coder1248`	`u64`	2	1/2/4/8	`streamvbyte64::Coder1248`

Tag encoding

All u32 and u64 codecs pack four 2-bit tags into each control byte, LSB-first:

control byte n
bits 1:0  → tag for value 4n+0
bits 3:2  → tag for value 4n+1
bits 5:4  → tag for value 4n+2
bits 7:6  → tag for value 4n+3

Svb16 uses 1-bit tags and packs eight tags per control byte.

Buffer layout

All codecs use the same flat layout: control bytes first, data bytes immediately after.

[ ctrl[0] ctrl[1] ... ctrl[ceil(n/4)-1] | data bytes ... ]

The control stream length is always ceil(n / 4) bytes for 2-bit codecs, ceil(n / 8) for Svb16. No length prefix is stored; the caller supplies the element count to decode.