leb128.nx

leb128.nx -- LEB128 (Little-Endian Base 128) integer encoding. Used by WASM (every length, every offset, every section header is LEB128), DWARF debug info, Android dex files. Distinct from varint.nx (protobuf): - Same 7-bit-per-byte continuation pattern - LEB128 has a SIGNED variant (sleb128) that uses 2's complement sign-extension across the final byte's high bit -- different from protobuf's ZigZag mapping - sleb128's 1-byte encoding covers -64..63; ZigZag's covers -1..1. Choose by ecosystem interop need. Invariants: LB1 Encoders write at most 10 bytes (covers full i64 range). LB2 Decoders bound-check; sequences > 10 bytes return overflow. LB3 ULEB128 round-trips any unsigned i64 exactly. LB4 SLEB128 round-trips any signed i64 exactly via sign extension on the final byte.