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Go → Rust mapping (lib/encoding port)

Source of truth: VictoriaMetrics/lib/encoding (local clone at ./VictoriaMetrics). Port: crates/encoding. One Go file → one Rust module; function order preserved.

Go file Rust module
int.go src/int.rs
encoding.go src/encoding.rs
nearest_delta.go src/nearest_delta.rs
nearest_delta2.go src/nearest_delta2.rs
compress.go + lib/encoding/zstd src/compress.rs
float.go + pools in int.go src/pool.rs
util.go src/util.rs
lib/fastnum (subset) src/fastnum.rs
— (optimization kernels, no Go counterpart) src/simd.rs, simd_decode.rs, simd_encode.rs, simd_scan.rs

Naming: Go MarshalVarInt64s → marshal_var_int64s, etc. Unexported Go functions keep their names (marshalInt64Array → marshal_int64_array, public in Rust for in-package-style tests).

API shape conventions

  • Go append-style func F(dst []byte, ...) []byte → fn f(dst: &mut Vec<u8>, ...).
  • Go (value, size int) where size <= 0 signals failure → (T, isize) same contract.
  • Go (result, error) → Result<T, encoding::Error> (Error wraps the fmt.Errorf string).
  • Go silent integer wraparound → explicit wrapping_*.
  • sync.Pool → thread-local pools in pool.rs (same cost model: hit = length reset, miss = zeroed alloc).
  • logger.Panicf("BUG: ...") → panic!("BUG: ...").

Deliberate divergences

  • zstd: real libzstd via the zstd/zstd-safe crates with thread-local reused CCtx/DCtx (equivalent of gozstd's context pooling). Go cgo builds use the same libzstd; pure-Go builds use klauspost/compress, which produces different (but interoperable) frames and slightly different compressed sizes — this can flip the marshal-type compress-or-plain decision near the 0.9 threshold, so golden parity fixtures are generated with CGO_ENABLED=1.
  • vm_zstd_* metrics counters (compress.go): not ported.
  • Optimization pass rewrote hot loop internals (SIMD kernels, spare-capacity writes, bulk fills); wire format, results, and error conditions are unchanged and enforced by tests/parity_test.rs golden vectors generated from upstream Go.

Tests

Go test file Rust
int_test.go tests/int_test.rs
util_test.go tests/util_test.rs
compress_test.go tests/compress_test.rs
encoding_test.go tests/encoding_test.rs
nearest_delta_test.go tests/nearest_delta_test.rs
nearest_delta2_test.go tests/nearest_delta2_test.rs
— tests/parity_test.rs (golden vectors vs real Go output; see bench/go/gen)

encoding_pure_test.go / encoding_cgo_test.go (zstd-impl-specific size goldens) were not ported.