package gen
import (
"fmt"
"regexp"
"sort"
"strings"
"google.golang.org/protobuf/compiler/protogen"
"google.golang.org/protobuf/reflect/protoreflect"
)
// decodeFnSuffix returns "_n" when 5y9's int64_as_number option is set
// and `st` is one of the cdata-returning 64-bit scalar kinds, "" otherwise.
// Used to swap wire.decode_int64 -> wire.decode_int64_n at codegen sites
// where the value type is statically known. (5y9)
func decodeFnSuffix(w *writer, st string) string {
if !w.int64AsNumber {
return ""
}
switch st {
case "int64", "uint64", "sint64", "fixed64", "sfixed64":
return "_n"
}
return ""
}
// encodeCallExpr returns the Lua expression that encodes a single value
// of the given scalar type `st`. For types where mode=full can elide
// wire.to_int64 / wire.to_uint64's runtime type dispatch (sint64, fixed64,
// sfixed64), the expression pre-casts the value to int64_t / uint64_t at
// the call site and routes through the typed fast variant (encode_sint64_i
// / encode_fixed64_u / encode_sfixed64_u). For everything else it emits
// the generic wire.encode_<st> call. INT64 and UINT64 are localized in
// the file header (see emitHeader). (a7l)
func encodeCallExpr(st, valExpr string) string {
switch st {
case "sint64":
return fmt.Sprintf("wire.encode_sint64_i(INT64(%s))", valExpr)
case "fixed64":
return fmt.Sprintf("wire.encode_fixed64_u(UINT64(%s))", valExpr)
case "sfixed64":
return fmt.Sprintf("wire.encode_sfixed64_u(UINT64(%s))", valExpr)
}
return fmt.Sprintf("wire.encode_%s(%s)", st, valExpr)
}
// wireRefRe matches `wire.<name>` references inside generated function
// bodies. Generated code never embeds `wire.` inside a string literal, so a
// straight textual sweep is safe here. (Verified: error messages mention
// "wire type" with a space, no dot.)
var wireRefRe = regexp.MustCompile(`\bwire\.([A-Za-z_][A-Za-z0-9_]*)`)
// localizeWireRefs scans `body` for `wire.<name>` references and, for any
// name that appears at least `minUses` times, returns it (sorted) and
// rewrites those occurrences in `body` to the bare name. Caller is
// responsible for emitting `local <name> = wire.<name>` lines for the
// returned refs before flushing the body. Names that occur fewer than
// `minUses` times are left as `wire.<name>` so we don't pay a prelude
// TGETS on every call to save a single in-body lookup.
//
// Why: each `wire.X` access is a hash lookup on the `wire` upvalue.
// LuaJIT hoists it when traces stay hot, but every nested-message
// boundary breaks the trace and re-pays the lookup in the side trace /
// interpreter. Localizing turns each in-body call into a bare local read
// with no table indirection — `kot` in bd. Measured 35-50% improvements
// on scalar-heavy / packed_int32 workloads where wire.* dominates the
// inner loop; the single-use guard prevents a regression on sparse
// small-message decode where the prelude cost outweighs the in-body
// savings.
func localizeWireRefs(body []string, minUses int) (refs []string, rewritten []string) {
count := map[string]int{}
for _, ln := range body {
for _, m := range wireRefRe.FindAllStringSubmatch(ln, -1) {
count[m[1]]++
}
}
keep := map[string]struct{}{}
for n, c := range count {
if c >= minUses {
keep[n] = struct{}{}
}
}
if len(keep) == 0 {
return nil, body
}
refs = make([]string, 0, len(keep))
for n := range keep {
refs = append(refs, n)
}
sort.Strings(refs)
// Only rewrite the kept names; one-shot refs stay as `wire.X` so we
// don't end up referring to a local that was never declared.
keepRe := regexp.MustCompile(`\bwire\.(` + strings.Join(refs, "|") + `)\b`)
rewritten = make([]string, len(body))
for i, ln := range body {
rewritten[i] = keepRe.ReplaceAllString(ln, "$1")
}
return refs, rewritten
}
// emitLocalizedFunction emits the function header, the captured body with
// frequently-used wire.* references rewritten to bare locals (and the
// corresponding `local <name> = wire.<name>` preamble), and the closing
// `end` line. The `minUses` threshold of 2 means a wire ref needs at
// least one repeat use to be worth the prelude allocation.
func emitLocalizedFunction(w *writer, header string, bodyFn func()) {
body := w.captureLines(bodyFn)
refs, body := localizeWireRefs(body, 2)
w.line("%s", header)
for _, name := range refs {
w.line(" local %s = wire.%s", name, name)
}
for _, ln := range body {
w.P(ln)
}
w.line("end")
w.line("")
}
// emitInlineMessage emits per-message _new / _encode / _decode functions with
// no descriptor dispatch. Tag bytes are precomputed as Lua string literals;
// each scalar field's encode/decode call resolves to one wire.<typed> call.
// `exts` is the list of statically-known extensions targeting this message
// (collected via collectExtsByExtendee across all input files). They are
// inlined into the emitted encode/decode bodies so the hot path skips the
// pb.codec.encode_field / decode_extension dispatch.
func emitInlineMessage(w *writer, file *protogen.File, m *protogen.Message, imports map[string]string, prefix string, exts []*protogen.Extension) {
name := luaTypeName(m.Desc.FullName(), file.Desc.Package())
full := emmyMessageFullName(m)
selfPath := luaPackagePath(file.Desc, prefix)
emitEmmyWrapperAnnotations(w, name, full, wrapperNew)
w.line("function M.%s_new(t) return t or {} end", name)
w.line("")
emitInlineEncode(w, name, m, file, selfPath, imports, prefix, exts)
emitInlineDecode(w, name, m, file, selfPath, imports, prefix, exts, true)
emitInlineDecode(w, name, m, file, selfPath, imports, prefix, exts, false)
emitEmmyWrapperAnnotations(w, name, full, wrapperDecodeLazy)
w.line("function M.%s_decode_lazy(b) return pb.decode_lazy(M.%s_descriptor, b) end", name, name)
emitEmmyWrapperAnnotations(w, name, full, wrapperText)
w.line("function M.%s_text(t, opts) return pb.text.encode(M.%s_descriptor, t, opts) end", name, name)
emitOptionalAccessors(w, name, m, full)
w.line("")
}
func emitInlineEncode(w *writer, name string, m *protogen.Message, file *protogen.File, selfPath string, imports map[string]string, prefix string, exts []*protogen.Extension) {
emitEmmyWrapperAnnotations(w, name, emmyMessageFullName(m), wrapperEncode)
emitLocalizedFunction(w, fmt.Sprintf("function M.%s_encode(t)", name), func() {
// C-acceleration: when PB_ENABLE_C=1 was set at module load, dispatch
// into pb.c_runtime.encode. Plan compilation is lazy on first call —
// eager compile would chase sub-message refs that aren't filled in
// yet when finalize_message runs at module load (see init.lua). On
// the default pure-Lua build pb.c_runtime is nil and the branch is a
// single nil-compare.
w.line(" local _d = M.%s_descriptor", name)
w.line(" if pb.c_runtime ~= nil then")
w.line(" local _p = _d.c_plan or pb.c_runtime.compile_plan(_d)")
w.line(" return pb.c_runtime.encode(_p, t)")
w.line(" end")
w.line(" if type(t) ~= 'table' then")
w.line(" error(\"expected table for %s, got \" .. type(t), 0)", m.Desc.FullName())
w.line(" end")
w.line(" local out, n = {}, 0")
w.line(" local v")
// Oneof pre-pass: pick the active branch per oneof (last-set wins).
for _, oo := range realOneofs(m) {
w.line(" local %s", oneofVar(string(oo.Desc.Name())))
for _, f := range oo.Fields {
w.line(" if %s ~= nil then %s = %q end",
luaFieldAccess("t", string(f.Desc.Name())),
oneofVar(string(oo.Desc.Name())),
string(f.Desc.Name()))
}
}
for _, f := range m.Fields {
emitInlineEncodeField(w, f, file, selfPath, imports, prefix)
}
// Proto2 extensions. Static extensions (those visible at codegen
// time) are inlined as dedicated writers — same hot-path quality
// as a regular field. The dynamic walk over extensions_list[N+1..]
// catches anything registered via pb.register_extension after
// module load; `#extensions_list > N` short-circuits when no
// runtime extension was added, which is the common case (every
// known caller defines extensions in the .proto, not at runtime).
// Skip entirely when no extension targets this message — most
// proto3 messages and proto2 messages without `extensions` ranges.
if len(exts) > 0 {
w.line(" local _exts = t._extensions")
w.line(" if _exts ~= nil then")
// Single re-used local for each extension's value, matching the
// pattern in emitInlineEncode for regular fields (`local v` at
// the top).
w.line(" local _ev")
for _, ext := range exts {
emitInlineEncodeExtension(w, ext, file, selfPath, imports, prefix)
}
w.line(" end")
w.line(" local _elist = M.%s_descriptor.extensions_list", name)
w.line(" if _elist ~= nil and #_elist > %d then", len(exts))
w.line(" local _exts2 = t._extensions")
w.line(" if _exts2 ~= nil then")
w.line(" for _i = %d, #_elist do", len(exts)+1)
w.line(" local _ext = _elist[_i]")
w.line(" local _ev = _exts2[_ext.full_name]")
w.line(" if _ev ~= nil then")
w.line(" pb.codec.encode_field(_ext, _ev, out, true)")
w.line(" end")
w.line(" end")
// encode_field uses out[#out + 1] = … and doesn't know
// about our local `n` cursor — resync so the unknown-fields
// append below lands after the extension bytes, not on top.
w.line(" n = #out")
w.line(" end")
w.line(" end")
}
// Preserve unknown fields captured at decode time.
w.line(" local _uf = t._unknown_fields")
w.line(" if _uf ~= nil and _uf ~= '' then n = n + 1; out[n] = _uf end")
w.line(" return table.concat(out)")
})
}
// emitInlineLenPrefix emits the length-prefix append for a length-delimited
// field (LEN wire type: string, bytes, message body, packed scalars).
//
// Lifts the 1-byte varint fast path out of wire.encode_varint and inlines it
// at the call site. Eliminates the function call + dispatch on the dominant
// short-payload case (length < 128). encode_varint dispatch alone was ~17%
// of encode time on the hello.Person 1KB benchmark before this; the
// surrounding `out[n] = wire.encode_varint(#_b)` was another ~33%.
//
// `indent` is the Lua indentation string (e.g. " " or " ") that
// each emitted line starts with. `bodyExpr` is the Lua expression for the
// payload local (typically "v" or "_b"); its length is read once into a
// local so `#bodyExpr` doesn't re-evaluate. Caller is responsible for
// emitting the tag and the body itself around this call.
func emitInlineLenPrefix(w *writer, indent, bodyExpr string) {
w.line("%slocal _len = #%s", indent, bodyExpr)
w.line("%sif _len < 128 then", indent)
w.line("%s n = n + 1; out[n] = CHARS[_len]", indent)
w.line("%selse", indent)
w.line("%s n = n + 1; out[n] = wire.encode_varint(_len)", indent)
w.line("%send", indent)
}
// emitPackedVarintElemDecode emits the per-element decode inside a packed
// varint loop, with 1-byte and 2-byte fast paths inlined for the common
// Lua-number-returning scalar types (int32/uint32/enum/bool). The 2-byte
// branch covers values 128..16383 — the range that drives the residual
// side-trace bridges from the packed-int32 inner loop (see ozn). For
// other types (int64/uint64/sint*/cdata returns) the helper just emits
// the existing wire.decode_<st> call so the call frame stays.
//
// `valExpr` is the lvalue Lua expression for the decoded value (e.g.
// `val`, `list[cnt]`). `indent` is the Lua indentation prefix.
//
// For `enum`, the value is an int32 and bypasses wire.varint_to_int32
// in the inlined branches since 2-byte values 128..16383 fit int32
// directly; the fallback call still wraps with varint_to_int32.
func emitPackedVarintElemDecode(w *writer, indent, st, valExpr string) {
switch st {
case "int32", "uint32":
w.line("%slocal _b = string_byte(payload, p2)", indent)
w.line("%sif _b ~= nil and _b < 0x80 then", indent)
w.line("%s %s = _b", indent, valExpr)
w.line("%s p2 = p2 + 1", indent)
w.line("%selseif _b ~= nil and p2 < lim then", indent)
w.line("%s local _b2 = string_byte(payload, p2 + 1)", indent)
w.line("%s if _b2 ~= nil and _b2 < 0x80 then", indent)
w.line("%s if _b2 == 0 then error(\"overlong varint at offset \" .. p2, 0) end", indent)
w.line("%s %s = _b - 128 + _b2 * 128", indent, valExpr)
w.line("%s p2 = p2 + 2", indent)
w.line("%s else", indent)
w.line("%s %s, p2 = wire.decode_%s%s(payload, p2)", indent, valExpr, st, decodeFnSuffix(w, st))
w.line("%s end", indent)
w.line("%selse", indent)
w.line("%s %s, p2 = wire.decode_%s%s(payload, p2)", indent, valExpr, st, decodeFnSuffix(w, st))
w.line("%send", indent)
case "bool":
// Bool values are spec-valid only as 0 or 1, always 1-byte on the wire.
// A 2-byte form would be either overlong-0 or out-of-range. Keep just
// the 1-byte fast path and let any anomaly fall through to wire.decode_bool.
w.line("%slocal _b = string_byte(payload, p2)", indent)
w.line("%sif _b ~= nil and _b < 0x80 then", indent)
w.line("%s %s = _b ~= 0", indent, valExpr)
w.line("%s p2 = p2 + 1", indent)
w.line("%selse", indent)
w.line("%s %s, p2 = wire.decode_bool(payload, p2)", indent, valExpr)
w.line("%send", indent)
default:
w.line("%s%s, p2 = wire.decode_%s%s(payload, p2)", indent, valExpr, st, decodeFnSuffix(w, st))
}
}
// emitPackedEnumElemDecode is the enum counterpart to
// emitPackedVarintElemDecode. Enum payload is a varint reinterpreted as
// int32; for values 0..16383 the 1-byte and 2-byte fast paths bypass
// wire.varint_to_int32 since the result already fits the int32 range.
func emitPackedEnumElemDecode(w *writer, indent, valExpr string) {
w.line("%slocal _b = string_byte(payload, p2)", indent)
w.line("%sif _b ~= nil and _b < 0x80 then", indent)
w.line("%s %s = _b", indent, valExpr)
w.line("%s p2 = p2 + 1", indent)
w.line("%selseif _b ~= nil and p2 < lim then", indent)
w.line("%s local _b2 = string_byte(payload, p2 + 1)", indent)
w.line("%s if _b2 ~= nil and _b2 < 0x80 then", indent)
w.line("%s if _b2 == 0 then error(\"overlong varint at offset \" .. p2, 0) end", indent)
w.line("%s %s = _b - 128 + _b2 * 128", indent, valExpr)
w.line("%s p2 = p2 + 2", indent)
w.line("%s else", indent)
w.line("%s local _u; _u, p2 = wire.decode_varint(payload, p2)", indent)
w.line("%s %s = wire.varint_to_int32(_u)", indent, valExpr)
w.line("%s end", indent)
w.line("%selse", indent)
w.line("%s local _u; _u, p2 = wire.decode_varint(payload, p2)", indent)
w.line("%s %s = wire.varint_to_int32(_u)", indent, valExpr)
w.line("%send", indent)
}
// emitPackedVarintElem emits the per-element write inside a packed-varint
// loop with an inlined 1-byte CHARS-lookup fast path matching
// wire.encode_varint's hot case. Falls through to wire.encode_<st> for
// negatives, large values, and cdata. For fixed-width scalars (no varint
// fast path) it just emits a straight wire.encode_<st> call.
//
// - indent is the Lua indentation prefix (e.g. " ").
// - list/idx are the parts-table and counter variable names.
// - valExpr is the source expression for the element (e.g. "v[_i]"
// or "nv" after enum-string resolve).
// - st is the scalar name from scalarName().
//
// For sint32/sint64 the 7-bit zigzag range is -64..63 and is encoded
// inline with bit ops. For bool the emit is always 1 byte. For
// int32/int64/uint32/uint64 the fast path triggers when v is a Lua
// number in [0, 128) — covers the dominant small-positive case that
// pure-Lua wire.encode_varint already optimizes for.
func emitPackedVarintElem(w *writer, indent, list, idx, valExpr, st string) {
switch st {
case "bool":
w.line("%s%s = %s + 1; %s[%s] = CHARS[(%s) and 1 or 0]",
indent, idx, idx, list, idx, valExpr)
case "sint32", "sint64":
w.line("%slocal _e = %s", indent, valExpr)
w.line("%sif type(_e) == 'number' and _e >= -64 and _e <= 63 then", indent)
w.line("%s %s = %s + 1; %s[%s] = CHARS[bit.bxor(bit.lshift(_e, 1), bit.arshift(_e, 31))]",
indent, idx, idx, list, idx)
w.line("%selse", indent)
w.line("%s %s = %s + 1; %s[%s] = %s",
indent, idx, idx, list, idx, encodeCallExpr(st, "_e"))
w.line("%send", indent)
case "int32", "int64", "uint32", "uint64":
w.line("%slocal _e = %s", indent, valExpr)
w.line("%sif type(_e) == 'number' and _e >= 0 and _e < 128 then", indent)
w.line("%s %s = %s + 1; %s[%s] = CHARS[_e]",
indent, idx, idx, list, idx)
w.line("%selse", indent)
w.line("%s %s = %s + 1; %s[%s] = %s",
indent, idx, idx, list, idx, encodeCallExpr(st, "_e"))
w.line("%send", indent)
default:
w.line("%s%s = %s + 1; %s[%s] = %s",
indent, idx, idx, list, idx, encodeCallExpr(st, valExpr))
}
}
// realOneofs returns the message's non-synthetic oneofs (skips the ones
// proto3 expands explicit `optional` into).
func realOneofs(m *protogen.Message) []*protogen.Oneof {
var out []*protogen.Oneof
for _, oo := range m.Oneofs {
if oo.Fields[0].Desc.HasOptionalKeyword() {
continue
}
out = append(out, oo)
}
return out
}
func oneofVar(name string) string { return "_of_" + name }
// fieldRealOneof returns the oneof name a field belongs to, or "" if the
// field is not in a real oneof (i.e. either standalone or in a synthetic
// proto3 explicit-optional oneof).
func fieldRealOneof(f *protogen.Field) string {
if f.Oneof == nil || f.Desc.HasOptionalKeyword() {
return ""
}
return string(f.Oneof.Desc.Name())
}
func emitInlineEncodeField(w *writer, f *protogen.Field, file *protogen.File, selfPath string, imports map[string]string, prefix string) {
id := int32(f.Desc.Number())
tag := tagBytesLit(id, wireTypeForField(f))
fname := string(f.Desc.Name())
w.line(" -- field %d: %s", id, fname)
w.line(" v = %s", luaFieldAccess("t", fname))
// Proto2 `required`: error on encode if missing, never elide. Mutually
// exclusive with oneof and repeated, so the rest of the branching below
// stays unchanged for non-required fields.
if f.Desc.Cardinality() == protoreflect.Required {
emitInlineEncodeRequiredField(w, f, tag, file, selfPath, imports, prefix)
return
}
oneof := fieldRealOneof(f)
// Default presence gate: a regular nil check. For message fields we
// also need to accept box.NULL (which == nil via Tarantool's cdata
// metamethod) because google.protobuf.Value uses it as the canonical
// null_value sentinel.
gate := "v ~= nil"
if oneof != "" {
gate = fmt.Sprintf("%s == %q", oneofVar(oneof), fname)
} else if f.Message != nil {
gate = "v ~= nil or type(v) == 'cdata'"
}
// Presence semantics: oneof branches, proto3 explicit `optional`, and
// every proto2 singular field (`optional` keyword). No default elision.
hasPresence := oneof != "" || f.Desc.HasOptionalKeyword()
switch {
case f.Desc.IsMap():
emitInlineEncodeMap(w, f, tag, file, selfPath, imports, prefix)
case f.Desc.IsList():
emitInlineEncodeRepeated(w, f, tag, fname, file, selfPath, imports, prefix)
case f.Message != nil:
ref := typeRef(file, f.Message.Desc, selfPath, imports, "_encode", prefix)
if f.Desc.Kind() == protoreflect.GroupKind {
// Proto2 group: SGROUP tag + body + EGROUP tag. No length
// prefix — the receiver reads until the matching EGROUP id.
endTag := tagBytesLit(int32(f.Desc.Number()), 4 /* EGROUP */)
w.line(" if %s then", gate)
w.line(" n = n + 1; out[n] = %s", tag)
w.line(" n = n + 1; out[n] = %s(v)", ref)
w.line(" n = n + 1; out[n] = %s", endTag)
w.line(" end")
} else {
// Split the length-delimited payload into separate `out`
// slots: emit tag, varint(#body), body. Avoids the per-field
// concat that wire.encode_len would do.
w.line(" if %s then", gate)
w.line(" local _b = %s(v)", ref)
w.line(" n = n + 1; out[n] = %s", tag)
emitInlineLenPrefix(w, " ", "_b")
w.line(" n = n + 1; out[n] = _b")
w.line(" end")
}
case f.Enum != nil:
enumLocal := typeRef(file, f.Enum.Desc, selfPath, imports, "", prefix)
fullName := string(f.Enum.Desc.FullName())
// Presence (oneof or optional): emit even when value is the enum default.
w.line(" if %s then", gate)
w.line(" local nv = v")
w.line(" if type(v) == 'string' then")
w.line(" nv = %s[v]", enumLocal)
w.line(" if nv == nil then error(\"unknown enum value '\" .. v .. \"' for %s\", 0) end", fullName)
w.line(" end")
if !hasPresence {
w.line(" if nv ~= 0 then")
w.line(" n = n + 1; out[n] = %s", tag)
w.line(" n = n + 1; out[n] = wire.encode_int32(nv)")
w.line(" end")
} else {
w.line(" n = n + 1; out[n] = %s", tag)
w.line(" n = n + 1; out[n] = wire.encode_int32(nv)")
}
w.line(" end")
default:
st := scalarName(f.Desc.Kind())
if st == "" {
panic("unhandled scalar kind: " + f.Desc.Kind().String())
}
if !hasPresence {
w.line(" if v ~= nil and %s then", scalarNotDefaultExpr(st, "v"))
} else {
w.line(" if %s then", gate)
}
if st == "string" || st == "bytes" {
// Length-delimited scalar: same split rationale as nested
// messages above. `encode_string` / `encode_bytes` would
// concatenate the length prefix and body — emit them as
// separate `out` slots instead and let table.concat join.
w.line(" n = n + 1; out[n] = %s", tag)
emitInlineLenPrefix(w, " ", "v")
w.line(" n = n + 1; out[n] = v")
} else {
w.line(" n = n + 1; out[n] = %s", tag)
w.line(" n = n + 1; out[n] = %s", encodeCallExpr(st, "v"))
}
w.line(" end")
}
}
// emitInlineEncodeRequiredField generates the encode body for a proto2
// `required` field: error if missing, always emit (no default elision).
func emitInlineEncodeRequiredField(w *writer, f *protogen.Field, tag string, file *protogen.File, selfPath string, imports map[string]string, prefix string) {
fullName := string(f.Desc.FullName())
w.line(" if v == nil then")
w.line(" error(%q, 0)", "required field missing on encode: "+fullName)
w.line(" end")
switch {
case f.Message != nil:
ref := typeRef(file, f.Message.Desc, selfPath, imports, "_encode", prefix)
w.line(" local _b = %s(v)", ref)
w.line(" n = n + 1; out[n] = %s", tag)
emitInlineLenPrefix(w, " ", "_b")
w.line(" n = n + 1; out[n] = _b")
case f.Enum != nil:
enumLocal := typeRef(file, f.Enum.Desc, selfPath, imports, "", prefix)
enumFull := string(f.Enum.Desc.FullName())
w.line(" do")
w.line(" local nv = v")
w.line(" if type(v) == 'string' then")
w.line(" nv = %s[v]", enumLocal)
w.line(" if nv == nil then error(\"unknown enum value '\" .. v .. \"' for %s\", 0) end", enumFull)
w.line(" end")
w.line(" n = n + 1; out[n] = %s", tag)
w.line(" n = n + 1; out[n] = wire.encode_int32(nv)")
w.line(" end")
default:
st := scalarName(f.Desc.Kind())
if st == "" {
panic("unhandled scalar kind: " + f.Desc.Kind().String())
}
if st == "string" || st == "bytes" {
w.line(" n = n + 1; out[n] = %s", tag)
emitInlineLenPrefix(w, " ", "v")
w.line(" n = n + 1; out[n] = v")
} else {
w.line(" n = n + 1; out[n] = %s", tag)
w.line(" n = n + 1; out[n] = %s", encodeCallExpr(st, "v"))
}
}
}
func emitInlineEncodeRepeated(w *writer, f *protogen.Field, tag, fname string, file *protogen.File, selfPath string, imports map[string]string, prefix string) {
switch {
case f.Message != nil:
ref := typeRef(file, f.Message.Desc, selfPath, imports, "_encode", prefix)
if f.Desc.Kind() == protoreflect.GroupKind {
endTag := tagBytesLit(int32(f.Desc.Number()), 4 /* EGROUP */)
w.line(" if v ~= nil and #v > 0 then")
w.line(" local _stag = %s", tag)
w.line(" local _etag = %s", endTag)
w.line(" for _i = 1, #v do")
w.line(" n = n + 1; out[n] = _stag")
w.line(" n = n + 1; out[n] = %s(v[_i])", ref)
w.line(" n = n + 1; out[n] = _etag")
w.line(" end")
w.line(" end")
} else {
w.line(" if v ~= nil and #v > 0 then")
w.line(" local _tag = %s", tag)
w.line(" for _i = 1, #v do")
w.line(" local _b = %s(v[_i])", ref)
w.line(" n = n + 1; out[n] = _tag")
emitInlineLenPrefix(w, " ", "_b")
w.line(" n = n + 1; out[n] = _b")
w.line(" end")
w.line(" end")
}
case f.Enum != nil:
enumLocal := typeRef(file, f.Enum.Desc, selfPath, imports, "", prefix)
fullName := string(f.Enum.Desc.FullName())
w.line(" if v ~= nil and #v > 0 then")
w.line(" local _n = #v")
w.line(" local parts, m = table_new(_n, 0), 0")
w.line(" for _i = 1, _n do")
w.line(" local elem = v[_i]")
w.line(" local nv = elem")
w.line(" if type(elem) == 'string' then")
w.line(" nv = %s[elem]", enumLocal)
w.line(" if nv == nil then error(\"unknown enum value '\" .. elem .. \"' for %s\", 0) end", fullName)
w.line(" end")
emitPackedVarintElem(w, " ", "parts", "m", "nv", "int32")
w.line(" end")
w.line(" local _b = table.concat(parts)")
w.line(" n = n + 1; out[n] = %s", tag)
emitInlineLenPrefix(w, " ", "_b")
w.line(" n = n + 1; out[n] = _b")
w.line(" end")
default:
st := scalarName(f.Desc.Kind())
packable := st != "string" && st != "bytes"
if packable && f.Desc.IsPacked() {
w.line(" if v ~= nil and #v > 0 then")
w.line(" local _n = #v")
w.line(" local parts, m = table_new(_n, 0), 0")
w.line(" for _i = 1, _n do")
emitPackedVarintElem(w, " ", "parts", "m", "v[_i]", st)
w.line(" end")
w.line(" local _b = table.concat(parts)")
w.line(" n = n + 1; out[n] = %s", tag)
emitInlineLenPrefix(w, " ", "_b")
w.line(" n = n + 1; out[n] = _b")
w.line(" end")
} else if st == "string" || st == "bytes" {
w.line(" if v ~= nil and #v > 0 then")
w.line(" local _tag = %s", tag)
w.line(" for _i = 1, #v do")
w.line(" local _b = v[_i]")
w.line(" n = n + 1; out[n] = _tag")
emitInlineLenPrefix(w, " ", "_b")
w.line(" n = n + 1; out[n] = _b")
w.line(" end")
w.line(" end")
} else {
w.line(" if v ~= nil and #v > 0 then")
w.line(" local _tag = %s", tag)
w.line(" for _i = 1, #v do")
w.line(" n = n + 1; out[n] = _tag")
w.line(" n = n + 1; out[n] = %s", encodeCallExpr(st, "v[_i]"))
w.line(" end")
w.line(" end")
}
}
}
// emitInlineEncodeExtension emits an inline writer for a single statically
// known proto2 extension targeting the current message. Lives inside the
// `if _exts ~= nil then` block of the encode body, so the access pattern
// is `_exts[<full_name>]` rather than `t.<fname>`. Extensions are always
// presence-tracked (never proto3 implicit zero), never required, never in
// oneofs, never maps — the dispatch is correspondingly simpler than
// emitInlineEncodeField.
func emitInlineEncodeExtension(w *writer, ext *protogen.Extension, file *protogen.File, selfPath string, imports map[string]string, prefix string) {
id := int32(ext.Desc.Number())
full := string(ext.Desc.FullName())
tag := tagBytesLit(id, wireTypeForField(ext))
w.line(" -- extension %d: %s", id, full)
w.line(" _ev = _exts[%q]", full)
if ext.Desc.IsList() {
emitInlineEncodeExtensionRepeated(w, ext, tag, full, file, selfPath, imports, prefix)
return
}
switch {
case ext.Message != nil:
ref := typeRef(file, ext.Message.Desc, selfPath, imports, "_encode", prefix)
if ext.Desc.Kind() == protoreflect.GroupKind {
endTag := tagBytesLit(id, 4 /* EGROUP */)
w.line(" if _ev ~= nil then")
w.line(" n = n + 1; out[n] = %s", tag)
w.line(" n = n + 1; out[n] = %s(_ev)", ref)
w.line(" n = n + 1; out[n] = %s", endTag)
w.line(" end")
} else {
w.line(" if _ev ~= nil then")
w.line(" local _b = %s(_ev)", ref)
w.line(" n = n + 1; out[n] = %s", tag)
emitInlineLenPrefix(w, " ", "_b")
w.line(" n = n + 1; out[n] = _b")
w.line(" end")
}
case ext.Enum != nil:
enumLocal := typeRef(file, ext.Enum.Desc, selfPath, imports, "", prefix)
enumFull := string(ext.Enum.Desc.FullName())
w.line(" if _ev ~= nil then")
w.line(" local _nv = _ev")
w.line(" if type(_ev) == 'string' then")
w.line(" _nv = %s[_ev]", enumLocal)
w.line(" if _nv == nil then error(\"unknown enum value '\" .. _ev .. \"' for %s\", 0) end", enumFull)
w.line(" end")
w.line(" n = n + 1; out[n] = %s", tag)
w.line(" n = n + 1; out[n] = wire.encode_int32(_nv)")
w.line(" end")
default:
st := scalarName(ext.Desc.Kind())
if st == "" {
panic("unhandled extension scalar kind: " + ext.Desc.Kind().String())
}
w.line(" if _ev ~= nil then")
if st == "string" || st == "bytes" {
w.line(" n = n + 1; out[n] = %s", tag)
emitInlineLenPrefix(w, " ", "_ev")
w.line(" n = n + 1; out[n] = _ev")
} else {
w.line(" n = n + 1; out[n] = %s", tag)
w.line(" n = n + 1; out[n] = %s", encodeCallExpr(st, "_ev"))
}
w.line(" end")
}
}
// emitInlineEncodeExtensionRepeated mirrors emitInlineEncodeRepeated but
// uses `_ev` (the extension value table read from `_exts[full_name]`) as
// the source instead of a field access on `t`. Same packing rules:
// packable scalars under [packed=true] pack into a single LEN payload,
// string/bytes and messages emit one wire entry per element, groups use
// SGROUP/EGROUP framing.
func emitInlineEncodeExtensionRepeated(w *writer, ext *protogen.Extension, tag, full string, file *protogen.File, selfPath string, imports map[string]string, prefix string) {
switch {
case ext.Message != nil:
ref := typeRef(file, ext.Message.Desc, selfPath, imports, "_encode", prefix)
if ext.Desc.Kind() == protoreflect.GroupKind {
endTag := tagBytesLit(int32(ext.Desc.Number()), 4 /* EGROUP */)
w.line(" if _ev ~= nil and #_ev > 0 then")
w.line(" local _stag, _etag = %s, %s", tag, endTag)
w.line(" for _i = 1, #_ev do")
w.line(" n = n + 1; out[n] = _stag")
w.line(" n = n + 1; out[n] = %s(_ev[_i])", ref)
w.line(" n = n + 1; out[n] = _etag")
w.line(" end")
w.line(" end")
} else {
w.line(" if _ev ~= nil and #_ev > 0 then")
w.line(" local _tag = %s", tag)
w.line(" for _i = 1, #_ev do")
w.line(" local _b = %s(_ev[_i])", ref)
w.line(" n = n + 1; out[n] = _tag")
emitInlineLenPrefix(w, " ", "_b")
w.line(" n = n + 1; out[n] = _b")
w.line(" end")
w.line(" end")
}
case ext.Enum != nil:
enumLocal := typeRef(file, ext.Enum.Desc, selfPath, imports, "", prefix)
enumFull := string(ext.Enum.Desc.FullName())
w.line(" if _ev ~= nil and #_ev > 0 then")
if ext.Desc.IsPacked() {
w.line(" local _n = #_ev")
w.line(" local parts, m = table_new(_n, 0), 0")
w.line(" for _i = 1, _n do")
w.line(" local elem = _ev[_i]")
w.line(" local nv = elem")
w.line(" if type(elem) == 'string' then")
w.line(" nv = %s[elem]", enumLocal)
w.line(" if nv == nil then error(\"unknown enum value '\" .. elem .. \"' for %s\", 0) end", enumFull)
w.line(" end")
emitPackedVarintElem(w, " ", "parts", "m", "nv", "int32")
w.line(" end")
w.line(" local _b = table.concat(parts)")
w.line(" n = n + 1; out[n] = %s", tag)
emitInlineLenPrefix(w, " ", "_b")
w.line(" n = n + 1; out[n] = _b")
} else {
w.line(" local _tag = %s", tag)
w.line(" for _i = 1, #_ev do")
w.line(" local elem = _ev[_i]")
w.line(" local nv = elem")
w.line(" if type(elem) == 'string' then")
w.line(" nv = %s[elem]", enumLocal)
w.line(" if nv == nil then error(\"unknown enum value '\" .. elem .. \"' for %s\", 0) end", enumFull)
w.line(" end")
w.line(" n = n + 1; out[n] = _tag")
w.line(" n = n + 1; out[n] = wire.encode_int32(nv)")
w.line(" end")
}
w.line(" end")
default:
st := scalarName(ext.Desc.Kind())
packable := st != "string" && st != "bytes"
if packable && ext.Desc.IsPacked() {
w.line(" if _ev ~= nil and #_ev > 0 then")
w.line(" local _n = #_ev")
w.line(" local parts, m = table_new(_n, 0), 0")
w.line(" for _i = 1, _n do")
emitPackedVarintElem(w, " ", "parts", "m", "_ev[_i]", st)
w.line(" end")
w.line(" local _b = table.concat(parts)")
w.line(" n = n + 1; out[n] = %s", tag)
emitInlineLenPrefix(w, " ", "_b")
w.line(" n = n + 1; out[n] = _b")
w.line(" end")
} else if st == "string" || st == "bytes" {
w.line(" if _ev ~= nil and #_ev > 0 then")
w.line(" local _tag = %s", tag)
w.line(" for _i = 1, #_ev do")
w.line(" local _b = _ev[_i]")
w.line(" n = n + 1; out[n] = _tag")
emitInlineLenPrefix(w, " ", "_b")
w.line(" n = n + 1; out[n] = _b")
w.line(" end")
w.line(" end")
} else {
w.line(" if _ev ~= nil and #_ev > 0 then")
w.line(" local _tag = %s", tag)
w.line(" for _i = 1, #_ev do")
w.line(" n = n + 1; out[n] = _tag")
w.line(" n = n + 1; out[n] = %s", encodeCallExpr(st, "_ev[_i]"))
w.line(" end")
w.line(" end")
}
}
}
// emitInlineDecodeExtension emits an elseif-body that decodes one wire
// entry for a statically known extension and stores it under
// result._extensions[full_name]. For repeated extensions, appends to the
// existing list (creating it on first encounter). Mirrors
// pb.codec.decode_extension but inlines the dispatch and skips the
// per-call function frame.
func emitInlineDecodeExtension(w *writer, ext *protogen.Extension, file *protogen.File, selfPath string, imports map[string]string, prefix string, validateUTF8 bool) {
full := string(ext.Desc.FullName())
// Common preamble: ensure result._extensions exists.
if ext.Desc.IsList() {
emitInlineDecodeExtensionRepeated(w, ext, full, file, selfPath, imports, prefix, validateUTF8)
return
}
switch {
case ext.Message != nil:
decodeSuffix := "_decode"
if !validateUTF8 && !isWellKnownTypeFile(ext.Message.Desc.ParentFile()) {
decodeSuffix = "_decode_unsafe"
}
ref := typeRef(file, ext.Message.Desc, selfPath, imports, decodeSuffix, prefix)
if ext.Desc.Kind() == protoreflect.GroupKind {
descRef := typeRef(file, ext.Message.Desc, selfPath, imports, "_descriptor", prefix)
w.line(" local _payload")
w.line(" _payload, pos = pb.codec.decode_group(%s, buf, pos, %d)",
descRef, ext.Desc.Number())
w.line(" local _e = result._extensions")
w.line(" if _e == nil then _e = {}; result._extensions = _e end")
w.line(" _e[%q] = _payload", full)
} else {
w.line(" local _payload")
w.line(" _payload, pos = wire.decode_len(buf, pos)")
w.line(" local _e = result._extensions")
w.line(" if _e == nil then _e = {}; result._extensions = _e end")
w.line(" _e[%q] = %s(_payload)", full, ref)
}
case ext.Enum != nil:
w.line(" local _u")
w.line(" _u, pos = wire.decode_varint(buf, pos)")
w.line(" local _e = result._extensions")
w.line(" if _e == nil then _e = {}; result._extensions = _e end")
w.line(" _e[%q] = wire.varint_to_int32(_u)", full)
default:
st := scalarName(ext.Desc.Kind())
if st == "" {
panic("unhandled extension scalar kind: " + ext.Desc.Kind().String())
}
if st == "string" && !validateUTF8 {
st = "bytes"
}
w.line(" local _val")
w.line(" _val, pos = wire.decode_%s%s(buf, pos)", st, decodeFnSuffix(w, st))
w.line(" local _e = result._extensions")
w.line(" if _e == nil then _e = {}; result._extensions = _e end")
w.line(" _e[%q] = _val", full)
}
}
// emitInlineDecodeExtensionRepeated handles the repeated branch. Uses
// `#list + 1` rather than a hoisted counter — repeated extensions are
// uncommon enough that adding per-extension counters at function scope
// isn't worth the prelude noise.
func emitInlineDecodeExtensionRepeated(w *writer, ext *protogen.Extension, full string, file *protogen.File, selfPath string, imports map[string]string, prefix string, validateUTF8 bool) {
w.line(" local _e = result._extensions")
w.line(" if _e == nil then _e = {}; result._extensions = _e end")
w.line(" local _list = _e[%q]", full)
w.line(" if _list == nil then _list = {}; _e[%q] = _list end", full)
switch {
case ext.Message != nil:
decodeSuffix := "_decode"
if !validateUTF8 && !isWellKnownTypeFile(ext.Message.Desc.ParentFile()) {
decodeSuffix = "_decode_unsafe"
}
ref := typeRef(file, ext.Message.Desc, selfPath, imports, decodeSuffix, prefix)
if ext.Desc.Kind() == protoreflect.GroupKind {
descRef := typeRef(file, ext.Message.Desc, selfPath, imports, "_descriptor", prefix)
w.line(" local _payload")
w.line(" _payload, pos = pb.codec.decode_group(%s, buf, pos, %d)",
descRef, ext.Desc.Number())
w.line(" _list[#_list + 1] = _payload")
} else {
w.line(" local _payload")
w.line(" _payload, pos = wire.decode_len(buf, pos)")
w.line(" _list[#_list + 1] = %s(_payload)", ref)
}
case ext.Enum != nil:
w.line(" if wt == 2 then")
w.line(" local _payload")
w.line(" _payload, pos = wire.decode_len(buf, pos)")
w.line(" local p2, lim = 1, #_payload")
w.line(" while p2 <= lim do")
w.line(" local _u")
w.line(" _u, p2 = wire.decode_varint(_payload, p2)")
w.line(" _list[#_list + 1] = wire.varint_to_int32(_u)")
w.line(" end")
w.line(" else")
w.line(" local _u")
w.line(" _u, pos = wire.decode_varint(buf, pos)")
w.line(" _list[#_list + 1] = wire.varint_to_int32(_u)")
w.line(" end")
default:
st := scalarName(ext.Desc.Kind())
packable := st != "string" && st != "bytes"
if st == "string" && !validateUTF8 {
st = "bytes"
}
if packable {
w.line(" if wt == 2 then")
w.line(" local _payload")
w.line(" _payload, pos = wire.decode_len(buf, pos)")
w.line(" local p2, lim = 1, #_payload")
w.line(" while p2 <= lim do")
w.line(" local _val")
w.line(" _val, p2 = wire.decode_%s%s(_payload, p2)", st, decodeFnSuffix(w, st))
w.line(" _list[#_list + 1] = _val")
w.line(" end")
w.line(" else")
w.line(" local _val")
w.line(" _val, pos = wire.decode_%s%s(buf, pos)", st, decodeFnSuffix(w, st))
w.line(" _list[#_list + 1] = _val")
w.line(" end")
} else {
w.line(" local _val")
w.line(" _val, pos = wire.decode_%s%s(buf, pos)", st, decodeFnSuffix(w, st))
w.line(" _list[#_list + 1] = _val")
}
}
}
// emitInlineDecode emits a per-message decoder. When validateUTF8 is true the
// emitted function is `<Name>_decode` (proto3-conformant — every decoded string
// field is checked with utf8_len). When false the function is
// `<Name>_decode_unsafe`, intended for re-decoding bytes produced by a trusted
// peer (typed RPC against our own encoder, JSON/text round-trips, in-process
// pipelines). The unsafe variant drops the utf8_len check at every string site
// and routes the >=128-byte fallback through wire.decode_bytes instead of
// wire.decode_string. Both variants dispatch to the C runtime when available;
// the unsafe path calls c_runtime.decode_unsafe which gates is_valid_utf8 on
// a per-call flag (kyt). (6bb)
func emitInlineDecode(w *writer, name string, m *protogen.Message, file *protogen.File, selfPath string, imports map[string]string, prefix string, exts []*protogen.Extension, validateUTF8 bool) {
suffix := "_decode"
cEntry := "decode"
if !validateUTF8 {
suffix = "_decode_unsafe"
cEntry = "decode_unsafe"
}
emitEmmyWrapperAnnotations(w, name, emmyMessageFullName(m), wrapperDecode)
emitLocalizedFunction(w, fmt.Sprintf("function M.%s%s(buf)", name, suffix), func() {
w.line(" local _d = M.%s_descriptor", name)
// C-acceleration: see emitInlineEncode for rationale and lazy-compile.
w.line(" if pb.c_runtime ~= nil then")
w.line(" local _p = _d.c_plan or pb.c_runtime.compile_plan(_d)")
w.line(" return pb.c_runtime.%s(_p, buf)", cEntry)
w.line(" end")
w.line(" if type(buf) ~= 'string' then")
w.line(" error(\"expected string for %s decode, got \" .. type(buf), 0)", m.Desc.FullName())
w.line(" end")
w.line(" local result = {}")
w.line(" local pos, len = 1, #buf")
w.line(" local _uf")
// Per-repeated-field counters. Replace `#list + 1` (re-traverses
// the list every append) with `_n_<fname> = _n_<fname> + 1`. The
// counter survives across loop iterations, so out-of-order wire
// entries for the same field continue counting from the existing
// position without re-scanning. Map fields don't need a counter
// (hash keys, not array indices).
for _, f := range m.Fields {
if f.Desc.IsList() && !f.Desc.IsMap() {
w.line(" local _n_%s = 0", string(f.Desc.Name()))
}
}
w.line(" while pos <= len do")
w.line(" local _tag_start = pos")
w.line(" local id, wt")
// Inline the 1-byte tag fast path (field numbers 1..15) and the
// 2-byte tag fast path (field numbers 16..4095) directly. Together
// these cover almost every real RPC payload — the >=3-byte fallback
// only fires for field numbers >= 4096. Inlining literally at the
// dispatch site keeps the side trace inside the parent's own frame
// when the 1-byte guard fails, instead of bridging to interpreter
// through wire.decode_tag's frame return (auj). (kot, aah, auj)
w.line(" local _b = string_byte(buf, pos)")
w.line(" if _b ~= nil and _b < 0x80 then")
w.line(" wt = band(_b, 7)")
w.line(" if wt >= 6 then error(\"illegal wire type \" .. wt, 0) end")
w.line(" id = rshift(_b, 3)")
w.line(" if id == 0 then error(\"illegal field number 0\", 0) end")
w.line(" pos = pos + 1")
w.line(" elseif _b ~= nil and pos < len then")
w.line(" local _b2 = string_byte(buf, pos + 1)")
w.line(" if _b2 < 0x80 then")
w.line(" if _b2 == 0 then error(\"overlong tag varint at offset \" .. pos, 0) end")
w.line(" local _v = _b - 128 + _b2 * 128")
w.line(" wt = band(_v, 7)")
w.line(" if wt >= 6 then error(\"illegal wire type \" .. wt, 0) end")
w.line(" id = rshift(_v, 3)")
w.line(" pos = pos + 2")
w.line(" else")
w.line(" id, wt, pos = wire.decode_tag(buf, pos)")
w.line(" end")
w.line(" else")
w.line(" id, wt, pos = wire.decode_tag(buf, pos)")
w.line(" end")
first := true
for _, f := range m.Fields {
op := "elseif"
if first {
op = "if"
first = false
}
w.line(" %s id == %d then", op, f.Desc.Number())
emitInlineDecodeFieldBody(w, f, file, selfPath, imports, prefix, validateUTF8)
}
// Static extension dispatch arms: route known extension ids
// straight into inline decoders that store into
// result._extensions[full_name]. Skips the
// pb.codec.decode_extension dispatch for the common case.
for _, ext := range exts {
op := "elseif"
if first {
op = "if"
first = false
}
w.line(" %s id == %d then", op, ext.Desc.Number())
emitInlineDecodeExtension(w, ext, file, selfPath, imports, prefix, validateUTF8)
}
if first {
// No fields — every wire byte is unknown.
w.line(" if true then")
}
w.line(" else")
// Proto2 extensions registered at runtime (past the static set):
// fall back to pb.codec.decode_extension. Unknown ids land in
// the unknown-fields buffer.
w.line(" local _ebid = M.%s_descriptor.extensions_by_id", name)
w.line(" local _ext = _ebid and _ebid[id] or nil")
w.line(" if _ext ~= nil then")
w.line(" pos = pb.codec.decode_extension(_ext, buf, pos, wt, result)")
w.line(" else")
w.line(" pos = wire.skip_field(buf, pos, wt, id)")
w.line(" if _uf == nil then _uf = {} end")
w.line(" _uf[#_uf + 1] = buf:sub(_tag_start, pos - 1)")
w.line(" end")
w.line(" end")
w.line(" end")
w.line(" if _uf ~= nil then result._unknown_fields = table.concat(_uf) end")
w.line(" return result")
})
}
func emitInlineDecodeFieldBody(w *writer, f *protogen.Field, file *protogen.File, selfPath string, imports map[string]string, prefix string, validateUTF8 bool) {
fname := string(f.Desc.Name())
switch {
case f.Desc.IsMap():
emitInlineDecodeMap(w, f, fname, file, selfPath, imports, prefix, validateUTF8)
case f.Desc.IsList():
emitInlineDecodeRepeated(w, f, fname, file, selfPath, imports, prefix, validateUTF8)
case f.Message != nil:
// Recurse into the sub-message's matching unsafe variant when the
// caller is itself an _decode_unsafe — otherwise nested string
// fields would still be validated. WKT decoders (Timestamp,
// Duration, Any, …) live in pb.wkt and don't have an _unsafe
// twin; they're cheap (no string-validation hot path) so route
// through the normal _decode unconditionally.
decodeSuffix := "_decode"
if !validateUTF8 && !isWellKnownTypeFile(f.Message.Desc.ParentFile()) {
decodeSuffix = "_decode_unsafe"
}
ref := typeRef(file, f.Message.Desc, selfPath, imports, decodeSuffix, prefix)
dst := luaFieldAccess("result", fname)
descRef := typeRef(file, f.Message.Desc, selfPath, imports, "_descriptor", prefix)
if f.Desc.Kind() == protoreflect.GroupKind {
// Group: no length prefix. The codec reads body fields until
// it hits an EGROUP tag matching this field's id; returns the
// decoded table and the new position.
w.line(" local payload")
w.line(" payload, pos = pb.codec.decode_group(%s, buf, pos, %d)",
descRef, f.Desc.Number())
w.line(" local prev = %s", dst)
w.line(" if prev == nil then")
w.line(" %s = payload", dst)
w.line(" else")
w.line(" pb.codec.merge_message(%s, prev, payload)", descRef)
w.line(" end")
} else {
w.line(" local payload")
w.line(" payload, pos = wire.decode_len(buf, pos)")
if isWellKnownTypeFile(f.Message.Desc.ParentFile()) {
// WKT decoders return unwrapped values (datetime, number, string),
// not Lua tables — there is nothing to merge into. Replace.
w.line(" %s = %s(payload)", dst, ref)
} else {
// Per proto3 spec, repeated occurrences of a singular message
// field merge recursively. This holds for oneof branches too;
// sibling clearing below enforces oneof exclusivity.
w.line(" local prev = %s", dst)
w.line(" if prev == nil then")
w.line(" %s = %s(payload)", dst, ref)
w.line(" else")
w.line(" pb.codec.merge_message(%s, prev, %s(payload))",
descRef, ref)
w.line(" end")
}
}
case f.Enum != nil:
w.line(" local u")
w.line(" u, pos = wire.decode_varint(buf, pos)")
w.line(" %s = wire.varint_to_int32(u)", luaFieldAccess("result", fname))
default:
st := scalarName(f.Desc.Kind())
if st == "string" || st == "bytes" {
// Inline the 1-byte LEN fast path (length < 128). Skips the
// `wire.decode_string` / `wire.decode_bytes` function call
// frame for the typical short-string case; the resulting
// straight-line code stays inside the parent JIT trace
// instead of stitching through a child trace. (a6n)
dst := luaFieldAccess("result", fname)
emitInlineStringBytesScalar(w, st, dst, validateUTF8)
} else {
w.line(" local val")
w.line(" val, pos = wire.decode_%s%s(buf, pos)", st, decodeFnSuffix(w, st))
w.line(" %s = val", luaFieldAccess("result", fname))
}
}
// Oneof: clear sibling branches so callers see exactly one set field.
if oneof := fieldRealOneof(f); oneof != "" {
for _, sib := range f.Oneof.Fields {
if sib == f {
continue
}
w.line(" %s = nil",
luaFieldAccess("result", string(sib.Desc.Name())))
}
}
}
func emitInlineDecodeRepeated(w *writer, f *protogen.Field, fname string, file *protogen.File, selfPath string, imports map[string]string, prefix string, validateUTF8 bool) {
dst := luaFieldAccess("result", fname)
cnt := "_n_" + string(f.Desc.Name())
// For packable scalar/enum fields, defer the list allocation into the
// wt==2 branch so the element count estimate (derived from the packed
// payload length) can drive table.new(N, 0) and avoid the rehash
// cascade. For non-packable types (message/string/bytes) and for the
// per-element wt!=2 fallback, fall back to a bare `{}` — the size
// hint would require a per-tag scan that costs more than it saves. (2sn)
packable := false
estExpr := ""
switch {
case f.Message != nil:
// fallthrough to default alloc + standard emit
case f.Enum != nil:
packable = true
estExpr = "lim" // upper-bound (each varint ≥ 1 byte)
default:
st := scalarName(f.Desc.Kind())
if st != "string" && st != "bytes" {
packable = true
if sz := fixedScalarBytes(f.Desc.Kind()); sz > 0 {
estExpr = fmt.Sprintf("rshift(lim, %d)", sz) // /4 or /8 via bit shift
} else {
estExpr = "lim"
}
}
}
if !packable {
// Default-allocation prelude for non-packable fields.
w.line(" local list = %s", dst)
w.line(" if list == nil then list = {}; %s = list end", dst)
}
switch {
case f.Message != nil:
decodeSuffix := "_decode"
if !validateUTF8 && !isWellKnownTypeFile(f.Message.Desc.ParentFile()) {
decodeSuffix = "_decode_unsafe"
}
ref := typeRef(file, f.Message.Desc, selfPath, imports, decodeSuffix, prefix)
if f.Desc.Kind() == protoreflect.GroupKind {
descRef := typeRef(file, f.Message.Desc, selfPath, imports, "_descriptor", prefix)
w.line(" local payload")
w.line(" payload, pos = pb.codec.decode_group(%s, buf, pos, %d)",
descRef, f.Desc.Number())
w.line(" %s = %s + 1; list[%s] = payload", cnt, cnt, cnt)
} else {
w.line(" local payload")
w.line(" payload, pos = wire.decode_len(buf, pos)")
w.line(" %s = %s + 1; list[%s] = %s(payload)", cnt, cnt, cnt, ref)
}
case f.Enum != nil:
// Enums are packable (proto3 default). Accept both packed and per-element.
// The packed inner loop uses the enum-aware inline varint decoder so
// 1-byte and 2-byte values bypass the wire.decode_varint + varint_to_int32
// frames (ozn).
w.line(" if wt == 2 then")
w.line(" local payload")
w.line(" payload, pos = wire.decode_len(buf, pos)")
w.line(" local p2, lim = 1, #payload")
w.line(" local list = %s", dst)
w.line(" if list == nil then list = table_new(%s, 0); %s = list end", estExpr, dst)
w.line(" while p2 <= lim do")
w.line(" local val")
emitPackedEnumElemDecode(w, " ", "val")
w.line(" %s = %s + 1; list[%s] = val", cnt, cnt, cnt)
w.line(" end")
w.line(" else")
w.line(" local list = %s", dst)
w.line(" if list == nil then list = {}; %s = list end", dst)
w.line(" local u")
w.line(" u, pos = wire.decode_varint(buf, pos)")
w.line(" %s = %s + 1; list[%s] = wire.varint_to_int32(u)", cnt, cnt, cnt)
w.line(" end")
default:
st := scalarName(f.Desc.Kind())
if packable {
w.line(" if wt == 2 then")
w.line(" local payload")
w.line(" payload, pos = wire.decode_len(buf, pos)")
w.line(" local p2, lim = 1, #payload")
w.line(" local list = %s", dst)
w.line(" if list == nil then list = table_new(%s, 0); %s = list end", estExpr, dst)
w.line(" while p2 <= lim do")
w.line(" local val")
// Inline 1-byte and 2-byte varint fast paths for int32/uint32/bool
// (Lua-number returns). Other types fall through to wire.decode_<st>
// per the helper. (ozn)
emitPackedVarintElemDecode(w, " ", st, "val")
w.line(" %s = %s + 1; list[%s] = val", cnt, cnt, cnt)
w.line(" end")
w.line(" else")
w.line(" local list = %s", dst)
w.line(" if list == nil then list = {}; %s = list end", dst)
w.line(" local val")
w.line(" val, pos = wire.decode_%s%s(buf, pos)", st, decodeFnSuffix(w, st))
w.line(" %s = %s + 1; list[%s] = val", cnt, cnt, cnt)
w.line(" end")
} else {
// Repeated string/bytes — inline 1-byte LEN fast path. (a6n)
emitInlineStringBytesRepeated(w, st, cnt, validateUTF8)
}
}
}
// fixedScalarBytes returns the log2 of element size in bytes for
// fixed-width scalar kinds, or 0 for varint-based kinds. Used by 2sn
// to derive an exact count from the packed payload length via bit
// shift (count = lim >> log2_sz).
func fixedScalarBytes(k protoreflect.Kind) int {
switch k {
case protoreflect.Fixed32Kind, protoreflect.Sfixed32Kind, protoreflect.FloatKind:
return 2 // 4 bytes -> shift right by 2
case protoreflect.Fixed64Kind, protoreflect.Sfixed64Kind, protoreflect.DoubleKind:
return 3 // 8 bytes -> shift right by 3
}
return 0
}
// emitInlineStringBytesScalar emits the singular string/bytes decode with the
// 1-byte LEN fast path (lengths 0..127) and the 2-byte LEN fast path (lengths
// 128..16383) inlined directly. Falls back to `wire.decode_<st>` only for
// lengths >= 16384. UTF-8 validation runs only for `string`, not `bytes`. When
// validateUTF8 is false the inline check is dropped and the fallback for
// strings is routed through wire.decode_bytes (same shape, no utf8_len call).
// (a6n, 6bb, auj)
func emitInlineStringBytesScalar(w *writer, st, dst string, validateUTF8 bool) {
wireCall := st
if st == "string" && !validateUTF8 {
wireCall = "bytes"
}
w.line(" local _lb = string_byte(buf, pos)")
w.line(" if _lb ~= nil and _lb < 0x80 then")
w.line(" local _np = pos + 1")
w.line(" local _epos = _np + _lb")
w.line(" if _epos - 1 > len then error(\"truncated LEN at offset \" .. pos, 0) end")
w.line(" local _s = buf:sub(_np, _epos - 1)")
if st == "string" && validateUTF8 {
w.line(" if utf8_len(_s) == nil then error(\"invalid UTF-8 in string field at offset \" .. pos, 0) end")
}
w.line(" %s = _s", dst)
w.line(" pos = _epos")
w.line(" elseif _lb ~= nil and pos < len then")
w.line(" local _lb2 = string_byte(buf, pos + 1)")
w.line(" if _lb2 ~= nil and _lb2 < 0x80 then")
w.line(" if _lb2 == 0 then error(\"overlong LEN varint at offset \" .. pos, 0) end")
w.line(" local _ln = _lb - 128 + _lb2 * 128")
w.line(" local _np = pos + 2")
w.line(" local _epos = _np + _ln")
w.line(" if _epos - 1 > len then error(\"truncated LEN at offset \" .. pos, 0) end")
w.line(" local _s = buf:sub(_np, _epos - 1)")
if st == "string" && validateUTF8 {
w.line(" if utf8_len(_s) == nil then error(\"invalid UTF-8 in string field at offset \" .. pos, 0) end")
}
w.line(" %s = _s", dst)
w.line(" pos = _epos")
w.line(" else")
w.line(" local val")
w.line(" val, pos = wire.decode_%s(buf, pos)", wireCall)
w.line(" %s = val", dst)
w.line(" end")
w.line(" else")
w.line(" local val")
w.line(" val, pos = wire.decode_%s(buf, pos)", wireCall)
w.line(" %s = val", dst)
w.line(" end")
}
// emitInlineStringBytesRepeated mirrors emitInlineStringBytesScalar but
// appends to the per-field list via the `_n_<f>` counter. Both 1-byte and
// 2-byte LEN fast paths are inlined; falls back only for lengths >= 16384.
// (a6n, 6bb, auj)
func emitInlineStringBytesRepeated(w *writer, st, cnt string, validateUTF8 bool) {
wireCall := st
if st == "string" && !validateUTF8 {
wireCall = "bytes"
}
w.line(" local _lb = string_byte(buf, pos)")
w.line(" if _lb ~= nil and _lb < 0x80 then")
w.line(" local _np = pos + 1")
w.line(" local _epos = _np + _lb")
w.line(" if _epos - 1 > len then error(\"truncated LEN at offset \" .. pos, 0) end")
w.line(" local _s = buf:sub(_np, _epos - 1)")
if st == "string" && validateUTF8 {
w.line(" if utf8_len(_s) == nil then error(\"invalid UTF-8 in string field at offset \" .. pos, 0) end")
}
w.line(" %s = %s + 1; list[%s] = _s", cnt, cnt, cnt)
w.line(" pos = _epos")
w.line(" elseif _lb ~= nil and pos < len then")
w.line(" local _lb2 = string_byte(buf, pos + 1)")
w.line(" if _lb2 ~= nil and _lb2 < 0x80 then")
w.line(" if _lb2 == 0 then error(\"overlong LEN varint at offset \" .. pos, 0) end")
w.line(" local _ln = _lb - 128 + _lb2 * 128")
w.line(" local _np = pos + 2")
w.line(" local _epos = _np + _ln")
w.line(" if _epos - 1 > len then error(\"truncated LEN at offset \" .. pos, 0) end")
w.line(" local _s = buf:sub(_np, _epos - 1)")
if st == "string" && validateUTF8 {
w.line(" if utf8_len(_s) == nil then error(\"invalid UTF-8 in string field at offset \" .. pos, 0) end")
}
w.line(" %s = %s + 1; list[%s] = _s", cnt, cnt, cnt)
w.line(" pos = _epos")
w.line(" else")
w.line(" local val")
w.line(" val, pos = wire.decode_%s(buf, pos)", wireCall)
w.line(" %s = %s + 1; list[%s] = val", cnt, cnt, cnt)
w.line(" end")
w.line(" else")
w.line(" local val")
w.line(" val, pos = wire.decode_%s(buf, pos)", wireCall)
w.line(" %s = %s + 1; list[%s] = val", cnt, cnt, cnt)
w.line(" end")
}
// ----------------------------------------------------------------------------
// Map field codegen
// ----------------------------------------------------------------------------
// emitInlineEncodeMap emits the encode block for a map<K,V> field. Map fields
// are wire-equivalent to `repeated <Field>Entry`, where the synthetic Entry
// message has key=field 1 and value=field 2.
func emitInlineEncodeMap(w *writer, f *protogen.Field, tag string, file *protogen.File, selfPath string, imports map[string]string, prefix string) {
keyF, valF := f.Message.Fields[0], f.Message.Fields[1]
keyTag := tagBytesLit(1, mapSubFieldWireType(keyF))
valTag := tagBytesLit(2, mapSubFieldWireType(valF))
w.line(" if v ~= nil and next(v) ~= nil then")
w.line(" local _tag, _ktag, _vtag = %s, %s, %s", tag, keyTag, valTag)
w.line(" for _k, _val in pairs(v) do")
w.line(" local entry, _m = {}, 0")
// Key emit
keyDef := mapKeyDefaultExpr(keyF)
w.line(" if _k ~= %s then", keyDef)
emitMapPiece(w, "entry", "_m", "_ktag", "_k", keyF, file, selfPath, imports, prefix)
w.line(" end")
// Value emit
emitMapValueGuard(w, valF, "_val")
emitMapPiece(w, "entry", "_m", "_vtag", "_val", valF, file, selfPath, imports, prefix)
w.line(" end")
w.line(" n = n + 1; out[n] = _tag")
w.line(" local _b = table.concat(entry)")
emitInlineLenPrefix(w, " ", "_b")
w.line(" n = n + 1; out[n] = _b")
w.line(" end")
w.line(" end")
}
// emitMapPiece emits the two-line append:
//
// <list>[<idx> + 1] = <tag>; <list>[<idx> + 2] = wire.encode_<typed>(<expr>)
//
// (or the message form). Increments <idx> by 2 in two separate statements.
func emitMapPiece(w *writer, list, idx, tag, valExpr string, f *protogen.Field, file *protogen.File, selfPath string, imports map[string]string, prefix string) {
switch {
case f.Message != nil:
ref := typeRef(file, f.Message.Desc, selfPath, imports, "_encode", prefix)
w.line(" %s = %s + 1; %s[%s] = %s",
idx, idx, list, idx, tag)
w.line(" %s = %s + 1; %s[%s] = wire.encode_len(%s(%s))",
idx, idx, list, idx, ref, valExpr)
case f.Enum != nil:
// For enum value: input may be string name; resolve.
enumLocal := typeRef(file, f.Enum.Desc, selfPath, imports, "", prefix)
fullName := string(f.Enum.Desc.FullName())
w.line(" local _nv = %s", valExpr)
w.line(" if type(%s) == 'string' then", valExpr)
w.line(" _nv = %s[%s]", enumLocal, valExpr)
w.line(" if _nv == nil then error(\"unknown enum value '\" .. %s .. \"' for %s\", 0) end",
valExpr, fullName)
w.line(" end")
w.line(" %s = %s + 1; %s[%s] = %s", idx, idx, list, idx, tag)
w.line(" %s = %s + 1; %s[%s] = wire.encode_int32(_nv)", idx, idx, list, idx)
default:
st := scalarName(f.Desc.Kind())
w.line(" %s = %s + 1; %s[%s] = %s", idx, idx, list, idx, tag)
w.line(" %s = %s + 1; %s[%s] = %s",
idx, idx, list, idx, encodeCallExpr(st, valExpr))
}
}
// emitMapValueGuard emits an `if <not-default> then` guarding the value emit
// for default-elision in map entries. Closing `end` is the caller's job.
func emitMapValueGuard(w *writer, f *protogen.Field, valExpr string) {
switch {
case f.Message != nil:
// Messages have no notion of "default value" elision in this position;
// emit unconditionally (nil is excluded by the outer iteration anyway).
w.line(" if %s ~= nil then", valExpr)
case f.Enum != nil:
// Need to resolve string -> int first, but we delay that. The cheap
// guard here is only for default elision, so check `~= 0` once it's
// been resolved. To keep things simple, always emit and let the proto
// receiver re-resolve to default. (Defaults round-trip correctly.)
w.line(" do")
default:
st := scalarName(f.Desc.Kind())
w.line(" if %s then", scalarNotDefaultExpr(st, valExpr))
}
}
// mapKeyDefaultExpr returns the Lua literal for the proto3 default of a map key.
// Only string + integer + bool keys are valid in maps.
func mapKeyDefaultExpr(f *protogen.Field) string {
switch f.Desc.Kind() {
case protoreflect.StringKind:
return "''"
case protoreflect.BoolKind:
return "false"
}
return "0"
}
// mapSubFieldWireType returns the wire type for a map entry's key or value
// (both are singular and never packed).
func mapSubFieldWireType(f *protogen.Field) int {
switch {
case f.Message != nil:
return 2 // LEN
case f.Enum != nil:
return 0 // VARINT
}
switch f.Desc.Kind() {
case protoreflect.Int32Kind, protoreflect.Int64Kind,
protoreflect.Uint32Kind, protoreflect.Uint64Kind,
protoreflect.Sint32Kind, protoreflect.Sint64Kind,
protoreflect.BoolKind:
return 0 // VARINT
case protoreflect.Fixed32Kind, protoreflect.Sfixed32Kind, protoreflect.FloatKind:
return 5 // I32
case protoreflect.Fixed64Kind, protoreflect.Sfixed64Kind, protoreflect.DoubleKind:
return 1 // I64
case protoreflect.StringKind, protoreflect.BytesKind:
return 2 // LEN
}
panic("unhandled map sub-field kind: " + f.Desc.Kind().String())
}
// emitInlineDecodeMap emits the decode block for a map<K,V> field.
func emitInlineDecodeMap(w *writer, f *protogen.Field, fname string, file *protogen.File, selfPath string, imports map[string]string, prefix string, validateUTF8 bool) {
keyF, valF := f.Message.Fields[0], f.Message.Fields[1]
dst := luaFieldAccess("result", fname)
w.line(" local map = %s", dst)
w.line(" if map == nil then map = {}; %s = map end", dst)
w.line(" local payload")
w.line(" payload, pos = wire.decode_len(buf, pos)")
w.line(" local _ep, _elim = 1, #payload")
w.line(" local _key, _val = %s, %s",
mapDefaultExpr(keyF), mapDefaultExpr(valF))
w.line(" while _ep <= _elim do")
w.line(" local eid, ewt")
w.line(" eid, ewt, _ep = wire.decode_tag(payload, _ep)")
w.line(" if eid == 1 then")
emitMapDecode(w, "_key", keyF, file, selfPath, imports, prefix, validateUTF8)
w.line(" elseif eid == 2 then")
emitMapDecode(w, "_val", valF, file, selfPath, imports, prefix, validateUTF8)
w.line(" else")
w.line(" _ep = wire.skip_field(payload, _ep, ewt, eid)")
w.line(" end")
w.line(" end")
if mapKeyNeedsCdataDedup(keyF) {
// 64-bit int keys are LuaJIT cdata; LuaJIT hashes cdata by pointer,
// so duplicate-key wire entries land in different hash buckets even
// though __eq matches. Walk once to find a canonical key and
// preserve proto3 "last value wins" semantics. Only emitted for
// cdata-yielding key types so string/int32-keyed maps stay on the
// JIT trace.
w.line(" for _k in pairs(map) do")
w.line(" if _k == _key then _key = _k; break end")
w.line(" end")
}
w.line(" map[_key] = _val")
}
// mapKeyNeedsCdataDedup reports whether a map key type yields LuaJIT
// cdata and therefore needs pointer-vs-value dedup on decode. Mirrors the
// runtime gate set up in pb.finalize_message.
func mapKeyNeedsCdataDedup(keyF *protogen.Field) bool {
switch keyF.Desc.Kind() {
case protoreflect.Int64Kind, protoreflect.Uint64Kind,
protoreflect.Sint64Kind, protoreflect.Fixed64Kind,
protoreflect.Sfixed64Kind:
return true
}
return false
}
// mapDefaultExpr returns the Lua expression for a map sub-field's default.
func mapDefaultExpr(f *protogen.Field) string {
switch {
case f.Message != nil:
return "{}"
case f.Enum != nil:
return "0"
}
switch f.Desc.Kind() {
case protoreflect.StringKind, protoreflect.BytesKind:
return "''"
case protoreflect.BoolKind:
return "false"
}
return "0"
}
// emitMapDecode emits the per-sub-field decode body inside the map entry's
// while-loop. Stores into <dst>; advances _ep.
func emitMapDecode(w *writer, dst string, f *protogen.Field, file *protogen.File, selfPath string, imports map[string]string, prefix string, validateUTF8 bool) {
switch {
case f.Message != nil:
decodeSuffix := "_decode"
if !validateUTF8 && !isWellKnownTypeFile(f.Message.Desc.ParentFile()) {
decodeSuffix = "_decode_unsafe"
}
ref := typeRef(file, f.Message.Desc, selfPath, imports, decodeSuffix, prefix)
w.line(" local _payload")
w.line(" _payload, _ep = wire.decode_len(payload, _ep)")
w.line(" %s = %s(_payload)", dst, ref)
case f.Enum != nil:
w.line(" local _u")
w.line(" _u, _ep = wire.decode_varint(payload, _ep)")
w.line(" %s = wire.varint_to_int32(_u)", dst)
default:
st := scalarName(f.Desc.Kind())
// Map key/value strings on the unsafe path bypass UTF-8 validation
// by calling wire.decode_bytes (identical wire shape, no utf8_len).
if st == "string" && !validateUTF8 {
st = "bytes"
}
w.line(" %s, _ep = wire.decode_%s%s(payload, _ep)", dst, st, decodeFnSuffix(w, st))
}
}
// ----------------------------------------------------------------------------
// Helpers
// ----------------------------------------------------------------------------
// wireTypeForField returns the proto wire type used to encode this field.
//
// For repeated packable fields with packed=true (proto3 default for primitive
// scalars and enums), the *element* tag is LEN — caller still calls this with
// care. We return the singular-element wire type and let the emit logic decide
// when to swap it to LEN for packed encoding.
func wireTypeForField(f *protogen.Field) int {
switch {
case f.Message != nil:
// Proto2 groups: the *opening* tag carries SGROUP (3). The
// closing tag is emitted separately as EGROUP (4) at the end of
// the field body.
if f.Desc.Kind() == protoreflect.GroupKind {
return 3 // SGROUP
}
return 2 // LEN
case f.Enum != nil:
// Repeated packed enums use LEN tag; non-packed elements use VARINT.
if f.Desc.IsList() && f.Desc.IsPacked() {
return 2
}
return 0 // VARINT
}
switch f.Desc.Kind() {
case protoreflect.Int32Kind, protoreflect.Int64Kind,
protoreflect.Uint32Kind, protoreflect.Uint64Kind,
protoreflect.Sint32Kind, protoreflect.Sint64Kind,
protoreflect.BoolKind:
// Repeated packed primitives use LEN tag.
if f.Desc.IsList() && f.Desc.IsPacked() {
return 2
}
return 0 // VARINT
case protoreflect.Fixed32Kind, protoreflect.Sfixed32Kind, protoreflect.FloatKind:
if f.Desc.IsList() && f.Desc.IsPacked() {
return 2
}
return 5 // I32
case protoreflect.Fixed64Kind, protoreflect.Sfixed64Kind, protoreflect.DoubleKind:
if f.Desc.IsList() && f.Desc.IsPacked() {
return 2
}
return 1 // I64
case protoreflect.StringKind, protoreflect.BytesKind:
return 2 // LEN (never packable)
}
panic("unhandled kind: " + f.Desc.Kind().String())
}
// tagBytesLit returns a Lua string literal (e.g. "\"\\x0a\"") encoding the
// varint for tag = (id << 3) | wireType. Tags are 1 byte for ids ≤ 15 with
// VARINT/I32/I64, 1 byte for ids ≤ 31 with LEN, 2 bytes for ids ≤ 2047,
// and so on.
func tagBytesLit(id int32, wireType int) string {
tag := uint64(id)*8 + uint64(wireType)
var b []byte
for tag >= 128 {
b = append(b, byte(tag&0x7f)|0x80)
tag >>= 7
}
b = append(b, byte(tag))
return luaByteString(b)
}
func luaByteString(b []byte) string {
var sb strings.Builder
sb.WriteByte('"')
for _, c := range b {
sb.WriteString(fmt.Sprintf("\\x%02x", c))
}
sb.WriteByte('"')
return sb.String()
}
// scalarNotDefaultExpr returns a Lua expression that evaluates true when
// the value `v` is NOT the proto3 default for the given scalar type.
// Default is elided on encode.
//
// Floats and doubles need a sign-bit guard: -0.0 == 0.0 in IEEE, but
// they aren't the proto3 default (the wire bytes differ, and the
// TextFormatInput conformance corpus pins this). `1/v == -math.huge`
// is the standard sign-bit probe — division by +0 yields +inf, by -0
// yields -inf, and any non-zero value short-circuits via `v ~= 0`.
func scalarNotDefaultExpr(scalar, v string) string {
switch scalar {
case "string", "bytes":
return v + ` ~= ''`
case "bool":
return v + ` ~= false`
case "float", "double":
return "(" + v + ` ~= 0 or 1/` + v + " == -math.huge)"
}
return v + ` ~= 0`
}