internal: Split in to sub-packages

39 files changed, 299 insertions, 290 deletions

diff --git a/compat/json/compat_test.go b/compat/json/compat_test.go
index feb850b..4b167d1 100644
--- a/compat/json/compat_test.go
+++ b/compat/json/compat_test.go
@@ -9,10 +9,12 @@ import (
 	"io"
 
 	"git.lukeshu.com/go/lowmemjson"
-	"git.lukeshu.com/go/lowmemjson/internal"
+	"git.lukeshu.com/go/lowmemjson/internal/jsonparse"
+	"git.lukeshu.com/go/lowmemjson/internal/jsontags"
+	"git.lukeshu.com/go/lowmemjson/internal/jsontest"
 )
 
-var parseTag = internal.ParseTag
+var parseTag = jsontags.ParseTag
 
 type scanner = lowmemjson.ReEncoderConfig
 
@@ -21,13 +23,13 @@ func checkValid(in []byte, scan *lowmemjson.ReEncoderConfig) error {
 }
 
 func isValidNumber(s string) bool {
-	var parser internal.Parser
+	var parser jsonparse.Parser
 	for _, r := range s {
 		if t, _ := parser.HandleRune(r); !t.IsNumber() {
 			return false
 		}
 	}
-	if t, _ := parser.HandleEOF(); t == internal.RuneTypeError {
+	if t, _ := parser.HandleEOF(); t == jsonparse.RuneTypeError {
 		return false
 	}
 	return true
@@ -51,9 +53,9 @@ type encodeState struct {
 }
 
 func (es *encodeState) string(str string, _ bool) {
-	internal.EncodeStringFromString(&es.Buffer, str)
+	jsontest.EncodeStringFromString(&es.Buffer, str)
 }
 
 func (es *encodeState) stringBytes(str []byte, _ bool) {
-	internal.EncodeStringFromBytes(&es.Buffer, str)
+	jsontest.EncodeStringFromBytes(&es.Buffer, str)
 }
diff --git a/decode.go b/decode.go
index 8638148..3a9a4b1 100644
--- a/decode.go
+++ b/decode.go
@@ -23,7 +23,9 @@ import (
 	"unicode/utf16"
 	"unicode/utf8"
 
-	"git.lukeshu.com/go/lowmemjson/internal"
+	"git.lukeshu.com/go/lowmemjson/internal/base64dec"
+	"git.lukeshu.com/go/lowmemjson/internal/fastio"
+	"git.lukeshu.com/go/lowmemjson/internal/jsonparse"
 )
 
 // Decodable is the interface implemented by types that can decode a
@@ -105,7 +107,7 @@ func NewDecoder(r io.RuneScanner) *Decoder {
 	return &Decoder{
 		io: runeTypeScanner{
 			inner: r,
-			parser: internal.Parser{
+			parser: jsonparse.Parser{
 				MaxDepth: maxNestingDepth,
 			},
 		},
@@ -145,7 +147,7 @@ func (dec *Decoder) More() bool {
 	dec.io.Reset()
 	_, _, t, e := dec.io.ReadRuneType()
 	_ = dec.io.UnreadRune() // best effort
-	return e == nil && t != internal.RuneTypeEOF
+	return e == nil && t != jsonparse.RuneTypeEOF
 }
 
 func (dec *Decoder) posStackPush() {
@@ -206,7 +208,7 @@ func (dec *Decoder) DecodeThenEOF(ptr any) (err error) {
 		return err
 	}
 	c, s, t, _ := dec.io.ReadRuneType()
-	if t != internal.RuneTypeEOF {
+	if t != jsonparse.RuneTypeEOF {
 		panic("should not happen")
 	}
 	if s > 0 {
@@ -274,7 +276,7 @@ func (dec *Decoder) panicType(jTyp string, gTyp reflect.Type, err error) {
 	})
 }
 
-func (dec *Decoder) readRune() (rune, internal.RuneType) {
+func (dec *Decoder) readRune() (rune, jsonparse.RuneType) {
 	c, _, t, e := dec.io.ReadRuneType()
 	if e != nil {
 		panic(decodeError{
@@ -295,20 +297,20 @@ func (dec *Decoder) unreadRune() {
 	}
 }
 
-func (dec *Decoder) peekRuneType() internal.RuneType {
+func (dec *Decoder) peekRuneType() jsonparse.RuneType {
 	_, t := dec.readRune()
 	dec.unreadRune()
 	return t
 }
 
-func (dec *Decoder) expectRune(ec rune, et internal.RuneType) {
+func (dec *Decoder) expectRune(ec rune, et jsonparse.RuneType) {
 	ac, at := dec.readRune()
 	if ac != ec || at != et {
 		panic("should not happen")
 	}
 }
 
-func (dec *Decoder) expectRuneType(ec rune, et internal.RuneType, gt reflect.Type) {
+func (dec *Decoder) expectRuneType(ec rune, et jsonparse.RuneType, gt reflect.Type) {
 	ac, at := dec.readRune()
 	if ac != ec || at != et {
 		dec.panicType(at.JSONType(), gt, nil)
@@ -325,7 +327,7 @@ func (sc *decRuneScanner) ReadRune() (rune, int, error) {
 		return 0, 0, io.EOF
 	}
 	c, s, t, e := sc.dec.io.ReadRuneType()
-	if t == internal.RuneTypeEOF {
+	if t == jsonparse.RuneTypeEOF {
 		sc.eof = true
 		sc.dec.io.PopReadBarrier()
 		return 0, 0, io.EOF
@@ -412,7 +414,7 @@ func (dec *Decoder) decode(val reflect.Value, nullOK bool) {
 			dec.panicType(t.JSONType(), reflect.PointerTo(typ), err)
 		}
 	case val.CanAddr() && reflect.PointerTo(typ).Implements(textUnmarshalerType):
-		if nullOK && dec.peekRuneType() == internal.RuneTypeNullN {
+		if nullOK && dec.peekRuneType() == jsonparse.RuneTypeNullN {
 			dec.decodeNull()
 			return
 		}
@@ -425,13 +427,13 @@ func (dec *Decoder) decode(val reflect.Value, nullOK bool) {
 	default:
 		switch kind := typ.Kind(); kind {
 		case reflect.Bool:
-			if nullOK && dec.peekRuneType() == internal.RuneTypeNullN {
+			if nullOK && dec.peekRuneType() == jsonparse.RuneTypeNullN {
 				dec.decodeNull()
 				return
 			}
 			val.SetBool(dec.decodeBool(typ))
 		case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
-			if nullOK && dec.peekRuneType() == internal.RuneTypeNullN {
+			if nullOK && dec.peekRuneType() == jsonparse.RuneTypeNullN {
 				dec.decodeNull()
 				return
 			}
@@ -443,7 +445,7 @@ func (dec *Decoder) decode(val reflect.Value, nullOK bool) {
 			}
 			val.SetInt(n)
 		case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
-			if nullOK && dec.peekRuneType() == internal.RuneTypeNullN {
+			if nullOK && dec.peekRuneType() == jsonparse.RuneTypeNullN {
 				dec.decodeNull()
 				return
 			}
@@ -455,7 +457,7 @@ func (dec *Decoder) decode(val reflect.Value, nullOK bool) {
 			}
 			val.SetUint(n)
 		case reflect.Float32, reflect.Float64:
-			if nullOK && dec.peekRuneType() == internal.RuneTypeNullN {
+			if nullOK && dec.peekRuneType() == jsonparse.RuneTypeNullN {
 				dec.decodeNull()
 				return
 			}
@@ -467,7 +469,7 @@ func (dec *Decoder) decode(val reflect.Value, nullOK bool) {
 			}
 			val.SetFloat(n)
 		case reflect.String:
-			if nullOK && dec.peekRuneType() == internal.RuneTypeNullN {
+			if nullOK && dec.peekRuneType() == jsonparse.RuneTypeNullN {
 				dec.decodeNull()
 				return
 			}
@@ -508,25 +510,25 @@ func (dec *Decoder) decode(val reflect.Value, nullOK bool) {
 				//   in the loop) because the only way it's possible is if there's
 				//   an interface in there, which'd break from the loop on its own.
 				//
-				// ptr.CanSet() || dec.peekRuneType() != internal.RuneTypeNullN
+				// ptr.CanSet() || dec.peekRuneType() != jsonparse.RuneTypeNullN
 				//
 				//   We only need the pointer itself to be settable if we're
 				//   decoding null.
-				if ptr.Elem() != val && (ptr.CanSet() || dec.peekRuneType() != internal.RuneTypeNullN) {
+				if ptr.Elem() != val && (ptr.CanSet() || dec.peekRuneType() != jsonparse.RuneTypeNullN) {
 					dec.decode(ptr, false)
 					break
 				}
 			}
 			// Couldn't get type information from a pointer; fall back to untyped mode.
 			switch dec.peekRuneType() {
-			case internal.RuneTypeNullN:
+			case jsonparse.RuneTypeNullN:
 				dec.decodeNull()
 				val.Set(reflect.Zero(typ))
 			default:
 				val.Set(reflect.ValueOf(dec.decodeAny()))
 			}
 		case reflect.Struct:
-			if nullOK && dec.peekRuneType() == internal.RuneTypeNullN {
+			if nullOK && dec.peekRuneType() == jsonparse.RuneTypeNullN {
 				dec.decodeNull()
 				return
 			}
@@ -557,7 +559,7 @@ func (dec *Decoder) decode(val reflect.Value, nullOK bool) {
 					if dec.disallowUnknownFields {
 						dec.panicType("", typ, fmt.Errorf("json: unknown field %q", name))
 					}
-					dec.scan(internal.Discard)
+					dec.scan(fastio.Discard)
 					return
 				}
 				field := index.byPos[idx]
@@ -569,7 +571,7 @@ func (dec *Decoder) decode(val reflect.Value, nullOK bool) {
 								fmt.Errorf("json: cannot set embedded pointer to unexported struct: %v",
 									fVal.Type().Elem()))
 						}
-						if dec.peekRuneType() != internal.RuneTypeNullN {
+						if dec.peekRuneType() != jsonparse.RuneTypeNullN {
 							if fVal.IsNil() {
 								fVal.Set(reflect.New(fVal.Type().Elem()))
 							}
@@ -580,7 +582,7 @@ func (dec *Decoder) decode(val reflect.Value, nullOK bool) {
 				}
 				if field.Quote {
 					switch t := dec.peekRuneType(); t {
-					case internal.RuneTypeNullN:
+					case jsonparse.RuneTypeNullN:
 						dec.decodeNull()
 						switch fVal.Kind() {
 						// XXX: I can't justify this list, other than "it's what encoding/json
@@ -590,7 +592,7 @@ func (dec *Decoder) decode(val reflect.Value, nullOK bool) {
 						default:
 							// do nothing???
 						}
-					case internal.RuneTypeStringBeg:
+					case jsonparse.RuneTypeStringBeg:
 						// TODO: Figure out how to do this without buffering, have correct offsets.
 						var buf bytes.Buffer
 						dec.decodeString(nil, &buf)
@@ -612,10 +614,10 @@ func (dec *Decoder) decode(val reflect.Value, nullOK bool) {
 			})
 		case reflect.Map:
 			switch t := dec.peekRuneType(); t {
-			case internal.RuneTypeNullN:
+			case jsonparse.RuneTypeNullN:
 				dec.decodeNull()
 				val.Set(reflect.Zero(typ))
-			case internal.RuneTypeObjectBeg:
+			case jsonparse.RuneTypeObjectBeg:
 				if val.IsNil() {
 					val.Set(reflect.MakeMap(typ))
 				}
@@ -670,24 +672,24 @@ func (dec *Decoder) decode(val reflect.Value, nullOK bool) {
 			}
 		case reflect.Slice:
 			switch {
-			case typ.Elem().Kind() == reflect.Uint8 && !(dec.peekRuneType() == internal.RuneTypeArrayBeg && (false ||
+			case typ.Elem().Kind() == reflect.Uint8 && !(dec.peekRuneType() == jsonparse.RuneTypeArrayBeg && (false ||
 				reflect.PointerTo(typ.Elem()).Implements(decodableType) ||
 				reflect.PointerTo(typ.Elem()).Implements(jsonUnmarshalerType) ||
 				reflect.PointerTo(typ.Elem()).Implements(textUnmarshalerType))):
 				switch t := dec.peekRuneType(); t {
-				case internal.RuneTypeNullN:
+				case jsonparse.RuneTypeNullN:
 					dec.decodeNull()
 					val.Set(reflect.Zero(typ))
-				case internal.RuneTypeStringBeg:
+				case jsonparse.RuneTypeStringBeg:
 					if typ.Elem() == byteType {
 						var buf bytes.Buffer
-						dec.decodeString(typ, internal.NewBase64Decoder(&buf))
+						dec.decodeString(typ, base64dec.NewBase64Decoder(&buf))
 						val.Set(reflect.ValueOf(buf.Bytes()))
 					} else {
 						// TODO: Surely there's a better way.  At the very least, we should
 						// avoid buffering.
 						var buf bytes.Buffer
-						dec.decodeString(typ, internal.NewBase64Decoder(&buf))
+						dec.decodeString(typ, base64dec.NewBase64Decoder(&buf))
 						bs := buf.Bytes()
 						val.Set(reflect.MakeSlice(typ, len(bs), len(bs)))
 						for i := 0; i < len(bs); i++ {
@@ -699,10 +701,10 @@ func (dec *Decoder) decode(val reflect.Value, nullOK bool) {
 				}
 			default:
 				switch t := dec.peekRuneType(); t {
-				case internal.RuneTypeNullN:
+				case jsonparse.RuneTypeNullN:
 					dec.decodeNull()
 					val.Set(reflect.Zero(typ))
-				case internal.RuneTypeArrayBeg:
+				case jsonparse.RuneTypeArrayBeg:
 					if val.IsNil() {
 						val.Set(reflect.MakeSlice(typ, 0, 0))
 					}
@@ -725,7 +727,7 @@ func (dec *Decoder) decode(val reflect.Value, nullOK bool) {
 				}
 			}
 		case reflect.Array:
-			if nullOK && dec.peekRuneType() == internal.RuneTypeNullN {
+			if nullOK && dec.peekRuneType() == jsonparse.RuneTypeNullN {
 				dec.decodeNull()
 				return
 			}
@@ -741,7 +743,7 @@ func (dec *Decoder) decode(val reflect.Value, nullOK bool) {
 					dec.decode(mValPtr.Elem(), false)
 					val.Index(i).Set(mValPtr.Elem())
 				} else {
-					dec.scan(internal.Discard)
+					dec.scan(fastio.Discard)
 				}
 				i++
 			})
@@ -750,7 +752,7 @@ func (dec *Decoder) decode(val reflect.Value, nullOK bool) {
 			}
 		case reflect.Pointer:
 			switch dec.peekRuneType() {
-			case internal.RuneTypeNullN:
+			case jsonparse.RuneTypeNullN:
 				dec.decodeNull()
 				val.Set(reflect.Zero(typ))
 			default:
@@ -765,7 +767,7 @@ func (dec *Decoder) decode(val reflect.Value, nullOK bool) {
 	}
 }
 
-func (dec *Decoder) scan(out internal.RuneWriter) {
+func (dec *Decoder) scan(out fastio.RuneWriter) {
 	limiter := dec.limitingScanner()
 	for {
 		c, _, err := limiter.ReadRune()
@@ -776,7 +778,7 @@ func (dec *Decoder) scan(out internal.RuneWriter) {
 	}
 }
 
-func (dec *Decoder) scanNumber(gTyp reflect.Type, out internal.RuneWriter) {
+func (dec *Decoder) scanNumber(gTyp reflect.Type, out fastio.RuneWriter) {
 	if t := dec.peekRuneType(); !t.IsNumber() {
 		dec.panicType(t.JSONType(), gTyp, nil)
 	}
@@ -901,23 +903,23 @@ func DecodeObject(r io.RuneScanner, decodeKey, decodeVal func(io.RuneScanner) er
 }
 
 func (dec *Decoder) decodeObject(gTyp reflect.Type, decodeKey, decodeVal func()) {
-	dec.expectRuneType('{', internal.RuneTypeObjectBeg, gTyp)
+	dec.expectRuneType('{', jsonparse.RuneTypeObjectBeg, gTyp)
 	_, t := dec.readRune()
 	switch t {
-	case internal.RuneTypeObjectEnd:
+	case jsonparse.RuneTypeObjectEnd:
 		return
-	case internal.RuneTypeStringBeg:
+	case jsonparse.RuneTypeStringBeg:
 	decodeMember:
 		dec.unreadRune()
 		decodeKey()
-		dec.expectRune(':', internal.RuneTypeObjectColon)
+		dec.expectRune(':', jsonparse.RuneTypeObjectColon)
 		decodeVal()
 		_, t := dec.readRune()
 		switch t {
-		case internal.RuneTypeObjectComma:
-			dec.expectRune('"', internal.RuneTypeStringBeg)
+		case jsonparse.RuneTypeObjectComma:
+			dec.expectRune('"', jsonparse.RuneTypeStringBeg)
 			goto decodeMember
-		case internal.RuneTypeObjectEnd:
+		case jsonparse.RuneTypeObjectEnd:
 			return
 		default:
 			panic("should not happen")
@@ -972,10 +974,10 @@ func DecodeArray(r io.RuneScanner, decodeMember func(r io.RuneScanner) error) (e
 }
 
 func (dec *Decoder) decodeArray(gTyp reflect.Type, decodeMember func()) {
-	dec.expectRuneType('[', internal.RuneTypeArrayBeg, gTyp)
+	dec.expectRuneType('[', jsonparse.RuneTypeArrayBeg, gTyp)
 	_, t := dec.readRune()
 	switch t {
-	case internal.RuneTypeArrayEnd:
+	case jsonparse.RuneTypeArrayEnd:
 		return
 	default:
 		dec.unreadRune()
@@ -983,9 +985,9 @@ func (dec *Decoder) decodeArray(gTyp reflect.Type, decodeMember func()) {
 		decodeMember()
 		_, t := dec.readRune()
 		switch t {
-		case internal.RuneTypeArrayComma:
+		case jsonparse.RuneTypeArrayComma:
 			goto decodeNextMember
-		case internal.RuneTypeArrayEnd:
+		case jsonparse.RuneTypeArrayEnd:
 			return
 		default:
 			panic("should not happen")
@@ -993,17 +995,17 @@ func (dec *Decoder) decodeArray(gTyp reflect.Type, decodeMember func()) {
 	}
 }
 
-func (dec *Decoder) decodeString(gTyp reflect.Type, out internal.RuneWriter) {
-	dec.expectRuneType('"', internal.RuneTypeStringBeg, gTyp)
+func (dec *Decoder) decodeString(gTyp reflect.Type, out fastio.RuneWriter) {
+	dec.expectRuneType('"', jsonparse.RuneTypeStringBeg, gTyp)
 	var uhex [4]byte
 	for {
 		c, t := dec.readRune()
 		switch t {
-		case internal.RuneTypeStringChar:
+		case jsonparse.RuneTypeStringChar:
 			_, _ = out.WriteRune(c)
-		case internal.RuneTypeStringEsc, internal.RuneTypeStringEscU:
+		case jsonparse.RuneTypeStringEsc, jsonparse.RuneTypeStringEscU:
 			// do nothing
-		case internal.RuneTypeStringEsc1:
+		case jsonparse.RuneTypeStringEsc1:
 			switch c {
 			case '"':
 				_, _ = out.WriteRune('"')
@@ -1024,14 +1026,14 @@ func (dec *Decoder) decodeString(gTyp reflect.Type, out internal.RuneWriter) {
 			default:
 				panic("should not happen")
 			}
-		case internal.RuneTypeStringEscUA:
-			uhex[0], _ = internal.HexToInt(c)
-		case internal.RuneTypeStringEscUB:
-			uhex[1], _ = internal.HexToInt(c)
-		case internal.RuneTypeStringEscUC:
-			uhex[2], _ = internal.HexToInt(c)
-		case internal.RuneTypeStringEscUD:
-			uhex[3], _ = internal.HexToInt(c)
+		case jsonparse.RuneTypeStringEscUA:
+			uhex[0], _ = jsonparse.HexToInt(c)
+		case jsonparse.RuneTypeStringEscUB:
+			uhex[1], _ = jsonparse.HexToInt(c)
+		case jsonparse.RuneTypeStringEscUC:
+			uhex[2], _ = jsonparse.HexToInt(c)
+		case jsonparse.RuneTypeStringEscUD:
+			uhex[3], _ = jsonparse.HexToInt(c)
 			c = 0 |
 				rune(uhex[0])<<12 |
 				rune(uhex[1])<<8 |
@@ -1039,25 +1041,25 @@ func (dec *Decoder) decodeString(gTyp reflect.Type, out internal.RuneWriter) {
 				rune(uhex[3])<<0
 		handleUnicode:
 			if utf16.IsSurrogate(c) {
-				if dec.peekRuneType() != internal.RuneTypeStringEsc {
+				if dec.peekRuneType() != jsonparse.RuneTypeStringEsc {
 					_, _ = out.WriteRune(utf8.RuneError)
 					break
 				}
-				dec.expectRune('\\', internal.RuneTypeStringEsc)
-				if dec.peekRuneType() != internal.RuneTypeStringEscU {
+				dec.expectRune('\\', jsonparse.RuneTypeStringEsc)
+				if dec.peekRuneType() != jsonparse.RuneTypeStringEscU {
 					_, _ = out.WriteRune(utf8.RuneError)
 					break
 				}
-				dec.expectRune('u', internal.RuneTypeStringEscU)
+				dec.expectRune('u', jsonparse.RuneTypeStringEscU)
 
 				b, _ := dec.readRune()
-				uhex[0], _ = internal.HexToInt(b)
+				uhex[0], _ = jsonparse.HexToInt(b)
 				b, _ = dec.readRune()
-				uhex[1], _ = internal.HexToInt(b)
+				uhex[1], _ = jsonparse.HexToInt(b)
 				b, _ = dec.readRune()
-				uhex[2], _ = internal.HexToInt(b)
+				uhex[2], _ = jsonparse.HexToInt(b)
 				b, _ = dec.readRune()
-				uhex[3], _ = internal.HexToInt(b)
+				uhex[3], _ = jsonparse.HexToInt(b)
 				c2 := 0 |
 					rune(uhex[0])<<12 |
 					rune(uhex[1])<<8 |
@@ -1073,7 +1075,7 @@ func (dec *Decoder) decodeString(gTyp reflect.Type, out internal.RuneWriter) {
 			} else {
 				_, _ = out.WriteRune(c)
 			}
-		case internal.RuneTypeStringEnd:
+		case jsonparse.RuneTypeStringEnd:
 			return
 		default:
 			panic("should not happen")
@@ -1085,15 +1087,15 @@ func (dec *Decoder) decodeBool(gTyp reflect.Type) bool {
 	c, t := dec.readRune()
 	switch c {
 	case 't':
-		dec.expectRune('r', internal.RuneTypeTrueR)
-		dec.expectRune('u', internal.RuneTypeTrueU)
-		dec.expectRune('e', internal.RuneTypeTrueE)
+		dec.expectRune('r', jsonparse.RuneTypeTrueR)
+		dec.expectRune('u', jsonparse.RuneTypeTrueU)
+		dec.expectRune('e', jsonparse.RuneTypeTrueE)
 		return true
 	case 'f':
-		dec.expectRune('a', internal.RuneTypeFalseA)
-		dec.expectRune('l', internal.RuneTypeFalseL)
-		dec.expectRune('s', internal.RuneTypeFalseS)
-		dec.expectRune('e', internal.RuneTypeFalseE)
+		dec.expectRune('a', jsonparse.RuneTypeFalseA)
+		dec.expectRune('l', jsonparse.RuneTypeFalseL)
+		dec.expectRune('s', jsonparse.RuneTypeFalseS)
+		dec.expectRune('e', jsonparse.RuneTypeFalseE)
 		return false
 	default:
 		dec.panicType(t.JSONType(), gTyp, nil)
@@ -1102,8 +1104,8 @@ func (dec *Decoder) decodeBool(gTyp reflect.Type) bool {
 }
 
 func (dec *Decoder) decodeNull() {
-	dec.expectRune('n', internal.RuneTypeNullN)
-	dec.expectRune('u', internal.RuneTypeNullU)
-	dec.expectRune('l', internal.RuneTypeNullL1)
-	dec.expectRune('l', internal.RuneTypeNullL2)
+	dec.expectRune('n', jsonparse.RuneTypeNullN)
+	dec.expectRune('u', jsonparse.RuneTypeNullU)
+	dec.expectRune('l', jsonparse.RuneTypeNullL1)
+	dec.expectRune('l', jsonparse.RuneTypeNullL2)
 }
diff --git a/decode_scan.go b/decode_scan.go
index 521c5c4..7a52975 100644
--- a/decode_scan.go
+++ b/decode_scan.go
@@ -7,7 +7,7 @@ package lowmemjson
 import (
 	"io"
 
-	"git.lukeshu.com/go/lowmemjson/internal"
+	"git.lukeshu.com/go/lowmemjson/internal/jsonparse"
 )
 
 type runeTypeScanner struct {
@@ -16,7 +16,7 @@ type runeTypeScanner struct {
 
 	inner io.RuneScanner // initialized by constructor
 
-	parser internal.Parser // initialized by constructor
+	parser jsonparse.Parser // initialized by constructor
 	offset int64
 
 	initialized bool
@@ -24,13 +24,13 @@ type runeTypeScanner struct {
 
 	rRune rune
 	rSize int
-	rType internal.RuneType
+	rType jsonparse.RuneType
 	rErr  error
 }
 
 func (sc *runeTypeScanner) Reset() {
 	sc.parser.Reset()
-	if sc.repeat || (sc.rType == internal.RuneTypeEOF && sc.rSize > 0) {
+	if sc.repeat || (sc.rType == jsonparse.RuneTypeEOF && sc.rSize > 0) {
 		sc.repeat = false
 		// re-figure the rType and rErr
 		var err error
@@ -57,9 +57,9 @@ func (sc *runeTypeScanner) Reset() {
 //	end of both value and file:     (_, 0, RuneTypeEOF, nil)
 //	end of file in middle of value: (_, 0, RuneTypeError, &DecodeSyntaxError{Offset: offset: Err: io.ErrUnexepctedEOF})
 //	end of file at start of value:  (_, 0, RuneTypeError, &DecodeSyntaxError{Offset: offset: Err: io.EOF})
-func (sc *runeTypeScanner) ReadRuneType() (rune, int, internal.RuneType, error) {
+func (sc *runeTypeScanner) ReadRuneType() (rune, int, jsonparse.RuneType, error) {
 	switch {
-	case sc.initialized && (sc.rType == internal.RuneTypeError || sc.rType == internal.RuneTypeEOF):
+	case sc.initialized && (sc.rType == jsonparse.RuneTypeError || sc.rType == jsonparse.RuneTypeEOF):
 		// do nothing
 	case sc.repeat:
 		_, _, _ = sc.inner.ReadRune()
@@ -80,7 +80,7 @@ func (sc *runeTypeScanner) ReadRuneType() (rune, int, internal.RuneType, error)
 			} else {
 				sc.rErr = nil
 			}
-			if sc.rType == internal.RuneTypeSpace {
+			if sc.rType == jsonparse.RuneTypeSpace {
 				goto again
 			}
 		case io.EOF:
@@ -133,7 +133,7 @@ func (sc *runeTypeScanner) PushReadBarrier() {
 
 func (sc *runeTypeScanner) PopReadBarrier() {
 	sc.parser.PopBarrier()
-	if sc.repeat || (sc.rType == internal.RuneTypeEOF && sc.rSize > 0) {
+	if sc.repeat || (sc.rType == jsonparse.RuneTypeEOF && sc.rSize > 0) {
 		// re-figure the rType and rErr
 		var err error
 		sc.rType, err = sc.parser.HandleRune(sc.rRune)
@@ -147,7 +147,7 @@ func (sc *runeTypeScanner) PopReadBarrier() {
 		}
 		// tell it to use that rType and rErr
 		_ = sc.UnreadRune() // we set it up to always succeed
-	} else if sc.rType == internal.RuneTypeEOF {
+	} else if sc.rType == jsonparse.RuneTypeEOF {
 		// re-figure the rType and rErr
 		var err error
 		sc.rType, err = sc.parser.HandleEOF()
diff --git a/decode_scan_test.go b/decode_scan_test.go
index d0725e5..1d61157 100644
--- a/decode_scan_test.go
+++ b/decode_scan_test.go
@@ -12,13 +12,13 @@ import (
 
 	"github.com/stretchr/testify/assert"
 
-	"git.lukeshu.com/go/lowmemjson/internal"
+	"git.lukeshu.com/go/lowmemjson/internal/jsonparse"
 )
 
 type ReadRuneTypeResult struct {
 	r rune
 	s int
-	t internal.RuneType
+	t jsonparse.RuneType
 	e error
 }
 
@@ -54,149 +54,149 @@ func TestRuneTypeScanner(t *testing.T) {
 	t.Parallel()
 	testcases := map[string]runeTypeScannerTestcase{
 		"basic": {`{"foo": 12.0}`, ``, []ReadRuneTypeResult{
-			{'{', 1, internal.RuneTypeObjectBeg, nil},
-			{'"', 1, internal.RuneTypeStringBeg, nil},
-			{'f', 1, internal.RuneTypeStringChar, nil},
-			{'o', 1, internal.RuneTypeStringChar, nil},
-			{'o', 1, internal.RuneTypeStringChar, nil},
-			{'"', 1, internal.RuneTypeStringEnd, nil},
-			{':', 1, internal.RuneTypeObjectColon, nil},
-			{'1', 1, internal.RuneTypeNumberIntDig, nil},
-			{'2', 1, internal.RuneTypeNumberIntDig, nil},
-			{'.', 1, internal.RuneTypeNumberFracDot, nil},
-			{'0', 1, internal.RuneTypeNumberFracDig, nil},
-			{'}', 1, internal.RuneTypeObjectEnd, nil},
-			{0, 0, internal.RuneTypeEOF, nil},
-			{0, 0, internal.RuneTypeEOF, nil},
+			{'{', 1, jsonparse.RuneTypeObjectBeg, nil},
+			{'"', 1, jsonparse.RuneTypeStringBeg, nil},
+			{'f', 1, jsonparse.RuneTypeStringChar, nil},
+			{'o', 1, jsonparse.RuneTypeStringChar, nil},
+			{'o', 1, jsonparse.RuneTypeStringChar, nil},
+			{'"', 1, jsonparse.RuneTypeStringEnd, nil},
+			{':', 1, jsonparse.RuneTypeObjectColon, nil},
+			{'1', 1, jsonparse.RuneTypeNumberIntDig, nil},
+			{'2', 1, jsonparse.RuneTypeNumberIntDig, nil},
+			{'.', 1, jsonparse.RuneTypeNumberFracDot, nil},
+			{'0', 1, jsonparse.RuneTypeNumberFracDig, nil},
+			{'}', 1, jsonparse.RuneTypeObjectEnd, nil},
+			{0, 0, jsonparse.RuneTypeEOF, nil},
+			{0, 0, jsonparse.RuneTypeEOF, nil},
 		}},
 		"unread": {`{"foo": 12.0}`, ``, []ReadRuneTypeResult{
-			{'{', 1, internal.RuneTypeObjectBeg, nil},
-			{'"', 1, internal.RuneTypeStringBeg, nil},
-			{'f', 1, internal.RuneTypeStringChar, nil},
-			{'o', 1, internal.RuneTypeStringChar, nil},
-			{'o', 1, internal.RuneTypeStringChar, nil},
-			{'"', 1, internal.RuneTypeStringEnd, nil},
-			{':', 1, internal.RuneTypeObjectColon, nil},
-			{'1', 1, internal.RuneTypeNumberIntDig, nil},
+			{'{', 1, jsonparse.RuneTypeObjectBeg, nil},
+			{'"', 1, jsonparse.RuneTypeStringBeg, nil},
+			{'f', 1, jsonparse.RuneTypeStringChar, nil},
+			{'o', 1, jsonparse.RuneTypeStringChar, nil},
+			{'o', 1, jsonparse.RuneTypeStringChar, nil},
+			{'"', 1, jsonparse.RuneTypeStringEnd, nil},
+			{':', 1, jsonparse.RuneTypeObjectColon, nil},
+			{'1', 1, jsonparse.RuneTypeNumberIntDig, nil},
 			{0, unreadRune, 0, nil},
-			{'1', 1, internal.RuneTypeNumberIntDig, nil},
-			{'2', 1, internal.RuneTypeNumberIntDig, nil},
-			{'.', 1, internal.RuneTypeNumberFracDot, nil},
-			{'0', 1, internal.RuneTypeNumberFracDig, nil},
-			{'}', 1, internal.RuneTypeObjectEnd, nil},
-			{0, 0, internal.RuneTypeEOF, nil},
-			{0, 0, internal.RuneTypeEOF, nil},
+			{'1', 1, jsonparse.RuneTypeNumberIntDig, nil},
+			{'2', 1, jsonparse.RuneTypeNumberIntDig, nil},
+			{'.', 1, jsonparse.RuneTypeNumberFracDot, nil},
+			{'0', 1, jsonparse.RuneTypeNumberFracDig, nil},
+			{'}', 1, jsonparse.RuneTypeObjectEnd, nil},
+			{0, 0, jsonparse.RuneTypeEOF, nil},
+			{0, 0, jsonparse.RuneTypeEOF, nil},
 		}},
 		"unread2": {`{"foo": 12.0}`, ``, []ReadRuneTypeResult{
-			{'{', 1, internal.RuneTypeObjectBeg, nil},
-			{'"', 1, internal.RuneTypeStringBeg, nil},
-			{'f', 1, internal.RuneTypeStringChar, nil},
-			{'o', 1, internal.RuneTypeStringChar, nil},
-			{'o', 1, internal.RuneTypeStringChar, nil},
-			{'"', 1, internal.RuneTypeStringEnd, nil},
-			{':', 1, internal.RuneTypeObjectColon, nil},
-			{'1', 1, internal.RuneTypeNumberIntDig, nil},
+			{'{', 1, jsonparse.RuneTypeObjectBeg, nil},
+			{'"', 1, jsonparse.RuneTypeStringBeg, nil},
+			{'f', 1, jsonparse.RuneTypeStringChar, nil},
+			{'o', 1, jsonparse.RuneTypeStringChar, nil},
+			{'o', 1, jsonparse.RuneTypeStringChar, nil},
+			{'"', 1, jsonparse.RuneTypeStringEnd, nil},
+			{':', 1, jsonparse.RuneTypeObjectColon, nil},
+			{'1', 1, jsonparse.RuneTypeNumberIntDig, nil},
 			{0, unreadRune, 0, nil},
 			{0, unreadRune, 0, ErrInvalidUnreadRune},
-			{'1', 1, internal.RuneTypeNumberIntDig, nil},
-			{'2', 1, internal.RuneTypeNumberIntDig, nil},
-			{'.', 1, internal.RuneTypeNumberFracDot, nil},
-			{'0', 1, internal.RuneTypeNumberFracDig, nil},
-			{'}', 1, internal.RuneTypeObjectEnd, nil},
-			{0, 0, internal.RuneTypeEOF, nil},
-			{0, 0, internal.RuneTypeEOF, nil},
+			{'1', 1, jsonparse.RuneTypeNumberIntDig, nil},
+			{'2', 1, jsonparse.RuneTypeNumberIntDig, nil},
+			{'.', 1, jsonparse.RuneTypeNumberFracDot, nil},
+			{'0', 1, jsonparse.RuneTypeNumberFracDig, nil},
+			{'}', 1, jsonparse.RuneTypeObjectEnd, nil},
+			{0, 0, jsonparse.RuneTypeEOF, nil},
+			{0, 0, jsonparse.RuneTypeEOF, nil},
 		}},
 		"unread-eof": {`{"foo": 12.0}`, ``, []ReadRuneTypeResult{
-			{'{', 1, internal.RuneTypeObjectBeg, nil},
-			{'"', 1, internal.RuneTypeStringBeg, nil},
-			{'f', 1, internal.RuneTypeStringChar, nil},
-			{'o', 1, internal.RuneTypeStringChar, nil},
-			{'o', 1, internal.RuneTypeStringChar, nil},
-			{'"', 1, internal.RuneTypeStringEnd, nil},
-			{':', 1, internal.RuneTypeObjectColon, nil},
-			{'1', 1, internal.RuneTypeNumberIntDig, nil},
-			{'2', 1, internal.RuneTypeNumberIntDig, nil},
-			{'.', 1, internal.RuneTypeNumberFracDot, nil},
-			{'0', 1, internal.RuneTypeNumberFracDig, nil},
-			{'}', 1, internal.RuneTypeObjectEnd, nil},
-			{0, 0, internal.RuneTypeEOF, nil},
+			{'{', 1, jsonparse.RuneTypeObjectBeg, nil},
+			{'"', 1, jsonparse.RuneTypeStringBeg, nil},
+			{'f', 1, jsonparse.RuneTypeStringChar, nil},
+			{'o', 1, jsonparse.RuneTypeStringChar, nil},
+			{'o', 1, jsonparse.RuneTypeStringChar, nil},
+			{'"', 1, jsonparse.RuneTypeStringEnd, nil},
+			{':', 1, jsonparse.RuneTypeObjectColon, nil},
+			{'1', 1, jsonparse.RuneTypeNumberIntDig, nil},
+			{'2', 1, jsonparse.RuneTypeNumberIntDig, nil},
+			{'.', 1, jsonparse.RuneTypeNumberFracDot, nil},
+			{'0', 1, jsonparse.RuneTypeNumberFracDig, nil},
+			{'}', 1, jsonparse.RuneTypeObjectEnd, nil},
+			{0, 0, jsonparse.RuneTypeEOF, nil},
 			{0, unreadRune, 0, ErrInvalidUnreadRune},
-			{0, 0, internal.RuneTypeEOF, nil},
-			{0, 0, internal.RuneTypeEOF, nil},
+			{0, 0, jsonparse.RuneTypeEOF, nil},
+			{0, 0, jsonparse.RuneTypeEOF, nil},
 		}},
 		"tail-ws": {`{"foo": 12.0}  `, ``, []ReadRuneTypeResult{
-			{'{', 1, internal.RuneTypeObjectBeg, nil},
-			{'"', 1, internal.RuneTypeStringBeg, nil},
-			{'f', 1, internal.RuneTypeStringChar, nil},
-			{'o', 1, internal.RuneTypeStringChar, nil},
-			{'o', 1, internal.RuneTypeStringChar, nil},
-			{'"', 1, internal.RuneTypeStringEnd, nil},
-			{':', 1, internal.RuneTypeObjectColon, nil},
-			{'1', 1, internal.RuneTypeNumberIntDig, nil},
-			{'2', 1, internal.RuneTypeNumberIntDig, nil},
-			{'.', 1, internal.RuneTypeNumberFracDot, nil},
-			{'0', 1, internal.RuneTypeNumberFracDig, nil},
-			{'}', 1, internal.RuneTypeObjectEnd, nil},
-			{0, 0, internal.RuneTypeEOF, nil},
-			{0, 0, internal.RuneTypeEOF, nil},
+			{'{', 1, jsonparse.RuneTypeObjectBeg, nil},
+			{'"', 1, jsonparse.RuneTypeStringBeg, nil},
+			{'f', 1, jsonparse.RuneTypeStringChar, nil},
+			{'o', 1, jsonparse.RuneTypeStringChar, nil},
+			{'o', 1, jsonparse.RuneTypeStringChar, nil},
+			{'"', 1, jsonparse.RuneTypeStringEnd, nil},
+			{':', 1, jsonparse.RuneTypeObjectColon, nil},
+			{'1', 1, jsonparse.RuneTypeNumberIntDig, nil},
+			{'2', 1, jsonparse.RuneTypeNumberIntDig, nil},
+			{'.', 1, jsonparse.RuneTypeNumberFracDot, nil},
+			{'0', 1, jsonparse.RuneTypeNumberFracDig, nil},
+			{'}', 1, jsonparse.RuneTypeObjectEnd, nil},
+			{0, 0, jsonparse.RuneTypeEOF, nil},
+			{0, 0, jsonparse.RuneTypeEOF, nil},
 		}},
 		"syntax-error": {`[[0,]`, ``, []ReadRuneTypeResult{
-			{'[', 1, internal.RuneTypeArrayBeg, nil},
-			{'[', 1, internal.RuneTypeArrayBeg, nil},
-			{'0', 1, internal.RuneTypeNumberIntZero, nil},
-			{',', 1, internal.RuneTypeArrayComma, nil},
-			{']', 1, internal.RuneTypeError, &DecodeSyntaxError{Offset: 4, Err: fmt.Errorf("invalid character %q looking for beginning of value", ']')}},
-			{']', 1, internal.RuneTypeError, &DecodeSyntaxError{Offset: 4, Err: fmt.Errorf("invalid character %q looking for beginning of value", ']')}},
-			{']', 1, internal.RuneTypeError, &DecodeSyntaxError{Offset: 4, Err: fmt.Errorf("invalid character %q looking for beginning of value", ']')}},
+			{'[', 1, jsonparse.RuneTypeArrayBeg, nil},
+			{'[', 1, jsonparse.RuneTypeArrayBeg, nil},
+			{'0', 1, jsonparse.RuneTypeNumberIntZero, nil},
+			{',', 1, jsonparse.RuneTypeArrayComma, nil},
+			{']', 1, jsonparse.RuneTypeError, &DecodeSyntaxError{Offset: 4, Err: fmt.Errorf("invalid character %q looking for beginning of value", ']')}},
+			{']', 1, jsonparse.RuneTypeError, &DecodeSyntaxError{Offset: 4, Err: fmt.Errorf("invalid character %q looking for beginning of value", ']')}},
+			{']', 1, jsonparse.RuneTypeError, &DecodeSyntaxError{Offset: 4, Err: fmt.Errorf("invalid character %q looking for beginning of value", ']')}},
 		}},
 		"multi-value": {`1{}`, `}`, []ReadRuneTypeResult{
-			{'1', 1, internal.RuneTypeNumberIntDig, nil},
-			{'{', 1, internal.RuneTypeEOF, nil},
-			{'{', 1, internal.RuneTypeEOF, nil},
-			{'{', 1, internal.RuneTypeEOF, nil},
+			{'1', 1, jsonparse.RuneTypeNumberIntDig, nil},
+			{'{', 1, jsonparse.RuneTypeEOF, nil},
+			{'{', 1, jsonparse.RuneTypeEOF, nil},
+			{'{', 1, jsonparse.RuneTypeEOF, nil},
 		}},
 		"early-eof": {` {`, ``, []ReadRuneTypeResult{
-			{'{', 1, internal.RuneTypeObjectBeg, nil},
-			{0, 0, internal.RuneTypeError, &DecodeSyntaxError{Offset: 2, Err: io.ErrUnexpectedEOF}},
-			{0, 0, internal.RuneTypeError, &DecodeSyntaxError{Offset: 2, Err: io.ErrUnexpectedEOF}},
-			{0, 0, internal.RuneTypeError, &DecodeSyntaxError{Offset: 2, Err: io.ErrUnexpectedEOF}},
+			{'{', 1, jsonparse.RuneTypeObjectBeg, nil},
+			{0, 0, jsonparse.RuneTypeError, &DecodeSyntaxError{Offset: 2, Err: io.ErrUnexpectedEOF}},
+			{0, 0, jsonparse.RuneTypeError, &DecodeSyntaxError{Offset: 2, Err: io.ErrUnexpectedEOF}},
+			{0, 0, jsonparse.RuneTypeError, &DecodeSyntaxError{Offset: 2, Err: io.ErrUnexpectedEOF}},
 		}},
 		"empty": {``, ``, []ReadRuneTypeResult{
-			{0, 0, internal.RuneTypeError, &DecodeSyntaxError{Offset: 0, Err: io.EOF}},
-			{0, 0, internal.RuneTypeError, &DecodeSyntaxError{Offset: 0, Err: io.EOF}},
-			{0, 0, internal.RuneTypeError, &DecodeSyntaxError{Offset: 0, Err: io.EOF}},
+			{0, 0, jsonparse.RuneTypeError, &DecodeSyntaxError{Offset: 0, Err: io.EOF}},
+			{0, 0, jsonparse.RuneTypeError, &DecodeSyntaxError{Offset: 0, Err: io.EOF}},
+			{0, 0, jsonparse.RuneTypeError, &DecodeSyntaxError{Offset: 0, Err: io.EOF}},
 		}},
 		"basic2": {`1`, ``, []ReadRuneTypeResult{
-			{'1', 1, internal.RuneTypeNumberIntDig, nil},
-			{0, 0, internal.RuneTypeEOF, nil},
-			{0, 0, internal.RuneTypeEOF, nil},
-			{0, 0, internal.RuneTypeEOF, nil},
+			{'1', 1, jsonparse.RuneTypeNumberIntDig, nil},
+			{0, 0, jsonparse.RuneTypeEOF, nil},
+			{0, 0, jsonparse.RuneTypeEOF, nil},
+			{0, 0, jsonparse.RuneTypeEOF, nil},
 		}},
 		"fragment": {`1,`, ``, []ReadRuneTypeResult{
-			{'1', 1, internal.RuneTypeNumberIntDig, nil},
-			{',', 1, internal.RuneTypeEOF, nil},
-			{',', 1, internal.RuneTypeEOF, nil},
-			{',', 1, internal.RuneTypeEOF, nil},
+			{'1', 1, jsonparse.RuneTypeNumberIntDig, nil},
+			{',', 1, jsonparse.RuneTypeEOF, nil},
+			{',', 1, jsonparse.RuneTypeEOF, nil},
+			{',', 1, jsonparse.RuneTypeEOF, nil},
 		}},
 		"elem": {` { "foo" : 12.0 } `, ``, []ReadRuneTypeResult{
-			{'{', 1, internal.RuneTypeObjectBeg, nil},
-			{'"', 1, internal.RuneTypeStringBeg, nil},
-			{'f', 1, internal.RuneTypeStringChar, nil},
-			{'o', 1, internal.RuneTypeStringChar, nil},
-			{'o', 1, internal.RuneTypeStringChar, nil},
-			{'"', 1, internal.RuneTypeStringEnd, nil},
-			{':', 1, internal.RuneTypeObjectColon, nil},
+			{'{', 1, jsonparse.RuneTypeObjectBeg, nil},
+			{'"', 1, jsonparse.RuneTypeStringBeg, nil},
+			{'f', 1, jsonparse.RuneTypeStringChar, nil},
+			{'o', 1, jsonparse.RuneTypeStringChar, nil},
+			{'o', 1, jsonparse.RuneTypeStringChar, nil},
+			{'"', 1, jsonparse.RuneTypeStringEnd, nil},
+			{':', 1, jsonparse.RuneTypeObjectColon, nil},
 			{0, pushReadBarrier, 0, nil},
-			{'1', 1, internal.RuneTypeNumberIntDig, nil},
-			{'2', 1, internal.RuneTypeNumberIntDig, nil},
-			{'.', 1, internal.RuneTypeNumberFracDot, nil},
-			{'0', 1, internal.RuneTypeNumberFracDig, nil},
-			{'}', 1, internal.RuneTypeEOF, nil},
-			{'}', 1, internal.RuneTypeEOF, nil},
+			{'1', 1, jsonparse.RuneTypeNumberIntDig, nil},
+			{'2', 1, jsonparse.RuneTypeNumberIntDig, nil},
+			{'.', 1, jsonparse.RuneTypeNumberFracDot, nil},
+			{'0', 1, jsonparse.RuneTypeNumberFracDig, nil},
+			{'}', 1, jsonparse.RuneTypeEOF, nil},
+			{'}', 1, jsonparse.RuneTypeEOF, nil},
 			{0, popReadBarrier, 0, nil},
-			{'}', 1, internal.RuneTypeObjectEnd, nil},
-			{0, 0, internal.RuneTypeEOF, nil},
-			{0, 0, internal.RuneTypeEOF, nil},
+			{'}', 1, jsonparse.RuneTypeObjectEnd, nil},
+			{0, 0, jsonparse.RuneTypeEOF, nil},
+			{0, 0, jsonparse.RuneTypeEOF, nil},
 		}},
 	}
 	func() {
@@ -214,9 +214,9 @@ func TestRuneTypeScanner(t *testing.T) {
 			}
 			tc.Input = `[1,` + tc.Input
 			tc.Exp = append([]ReadRuneTypeResult{
-				{'[', 1, internal.RuneTypeArrayBeg, nil},
-				{'1', 1, internal.RuneTypeNumberIntDig, nil},
-				{',', 1, internal.RuneTypeArrayComma, nil},
+				{'[', 1, jsonparse.RuneTypeArrayBeg, nil},
+				{'1', 1, jsonparse.RuneTypeNumberIntDig, nil},
+				{',', 1, jsonparse.RuneTypeArrayComma, nil},
 				{0, pushReadBarrier, 0, nil},
 			}, tc.Exp...)
 			for i := 2; i < len(tc.Exp); i++ {
diff --git a/encode_string.go b/encode_string.go
index 12f934e..a5d6633 100644
--- a/encode_string.go
+++ b/encode_string.go
@@ -8,17 +8,19 @@ import (
 	"io"
 	"unicode/utf8"
 
-	"git.lukeshu.com/go/lowmemjson/internal"
+	"git.lukeshu.com/go/lowmemjson/internal/fastio"
+	"git.lukeshu.com/go/lowmemjson/internal/jsonparse"
+	"git.lukeshu.com/go/lowmemjson/internal/jsontest"
 )
 
 func writeStringUnicodeEscape(w io.Writer, c rune) (int, error) {
 	buf := [6]byte{
 		'\\',
 		'u',
-		internal.Hex[(c>>12)&0xf],
-		internal.Hex[(c>>8)&0xf],
-		internal.Hex[(c>>4)&0xf],
-		internal.Hex[(c>>0)&0xf],
+		jsonparse.Hex[(c>>12)&0xf],
+		jsonparse.Hex[(c>>8)&0xf],
+		jsonparse.Hex[(c>>4)&0xf],
+		jsonparse.Hex[(c>>0)&0xf],
 	}
 	return w.Write(buf[:])
 }
@@ -45,7 +47,7 @@ func writeStringShortEscape(w io.Writer, c rune) (int, error) {
 	return w.Write(buf[:])
 }
 
-func writeStringChar(w internal.AllWriter, c rune, wasEscaped BackslashEscapeMode, escaper BackslashEscaper) (int, error) {
+func writeStringChar(w fastio.AllWriter, c rune, wasEscaped BackslashEscapeMode, escaper BackslashEscaper) (int, error) {
 	if escaper == nil {
 		escaper = EscapeDefault
 	}
@@ -83,7 +85,7 @@ func writeStringChar(w internal.AllWriter, c rune, wasEscaped BackslashEscapeMod
 	}
 }
 
-func encodeStringFromString(w internal.AllWriter, escaper BackslashEscaper, str string) error {
+func encodeStringFromString(w fastio.AllWriter, escaper BackslashEscaper, str string) error {
 	if err := w.WriteByte('"'); err != nil {
 		return err
 	}
@@ -98,7 +100,7 @@ func encodeStringFromString(w internal.AllWriter, escaper BackslashEscaper, str
 	return nil
 }
 
-func encodeStringFromBytes(w internal.AllWriter, escaper BackslashEscaper, str []byte) error {
+func encodeStringFromBytes(w fastio.AllWriter, escaper BackslashEscaper, str []byte) error {
 	if err := w.WriteByte('"'); err != nil {
 		return err
 	}
@@ -116,13 +118,13 @@ func encodeStringFromBytes(w internal.AllWriter, escaper BackslashEscaper, str [
 }
 
 func init() {
-	internal.EncodeStringFromString = func(w io.Writer, s string) {
-		if err := encodeStringFromString(internal.NewAllWriter(w), nil, s); err != nil {
+	jsontest.EncodeStringFromString = func(w io.Writer, s string) {
+		if err := encodeStringFromString(fastio.NewAllWriter(w), nil, s); err != nil {
 			panic(err)
 		}
 	}
-	internal.EncodeStringFromBytes = func(w io.Writer, s []byte) {
-		if err := encodeStringFromBytes(internal.NewAllWriter(w), nil, s); err != nil {
+	jsontest.EncodeStringFromBytes = func(w io.Writer, s []byte) {
+		if err := encodeStringFromBytes(fastio.NewAllWriter(w), nil, s); err != nil {
 			panic(err)
 		}
 	}
diff --git a/errors.go b/errors.go
index fe48723..0a47db4 100644
--- a/errors.go
+++ b/errors.go
@@ -11,7 +11,7 @@ import (
 	"reflect"
 	"strings"
 
-	"git.lukeshu.com/go/lowmemjson/internal"
+	"git.lukeshu.com/go/lowmemjson/internal/jsonparse"
 )
 
 // ErrInvalidUnreadRune is returned to Decodable.DecodeJSON(scanner)
@@ -24,7 +24,7 @@ var ErrInvalidUnreadRune = errors.New("lowmemjson: invalid use of UnreadRune")
 // ErrParserExceededMaxDepth is the base error that a
 // *DecodeSyntaxError wraps when the depth of the JSON document
 // exceeds 10000.
-var ErrParserExceededMaxDepth = internal.ErrParserExceededMaxDepth
+var ErrParserExceededMaxDepth = jsonparse.ErrParserExceededMaxDepth
 
 // low-level decode errors /////////////////////////////////////////////////////////////////////////
 // These will be wrapped in a *DecodeError.
diff --git a/internal/base64.go b/internal/base64dec/base64.go
index 291a229..dcb4b1c 100644
--- a/internal/base64.go
+++ b/internal/base64dec/base64.go
@@ -2,12 +2,14 @@
 //
 // SPDX-License-Identifier: GPL-2.0-or-later
 
-package internal
+package base64dec
 
 import (
 	"encoding/base64"
 	"io"
 	"strings"
+
+	"git.lukeshu.com/go/lowmemjson/internal/fastio"
 )
 
 type base64Decoder struct {
@@ -21,7 +23,7 @@ type base64Decoder struct {
 
 func NewBase64Decoder(w io.Writer) interface {
 	io.WriteCloser
-	RuneWriter
+	fastio.RuneWriter
 } {
 	return &base64Decoder{
 		dst: w,
@@ -116,7 +118,7 @@ func (dec *base64Decoder) Write(dat []byte) (int, error) {
 }
 
 func (dec *base64Decoder) WriteRune(r rune) (int, error) {
-	return WriteRune(dec, r)
+	return fastio.WriteRune(dec, r)
 }
 
 func (dec *base64Decoder) Close() error {
diff --git a/internal/base64_test.go b/internal/base64dec/base64_test.go
index f18bcd7..cb3063d 100644
--- a/internal/base64_test.go
+++ b/internal/base64dec/base64_test.go
@@ -2,7 +2,7 @@
 //
 // SPDX-License-Identifier: GPL-2.0-or-later
 
-package internal
+package base64dec
 
 import (
 	"bytes"
diff --git a/internal/testdata/fuzz/FuzzBase64Decoder/06e2c9db80a08b67fad7f1a4606dc7419750995a57828aa25ea57fe7099d5c03 b/internal/base64dec/testdata/fuzz/FuzzBase64Decoder/06e2c9db80a08b67fad7f1a4606dc7419750995a57828aa25ea57fe7099d5c03
index c3774e7..c3774e7 100644
--- a/internal/testdata/fuzz/FuzzBase64Decoder/06e2c9db80a08b67fad7f1a4606dc7419750995a57828aa25ea57fe7099d5c03
+++ b/internal/base64dec/testdata/fuzz/FuzzBase64Decoder/06e2c9db80a08b67fad7f1a4606dc7419750995a57828aa25ea57fe7099d5c03
diff --git a/internal/testdata/fuzz/FuzzBase64Decoder/24f53a36f8832fec65cac0aa0f3b43ec1c904414fa6d38f6fc288b0bbd69588a b/internal/base64dec/testdata/fuzz/FuzzBase64Decoder/24f53a36f8832fec65cac0aa0f3b43ec1c904414fa6d38f6fc288b0bbd69588a
index 4c861db..4c861db 100644
--- a/internal/testdata/fuzz/FuzzBase64Decoder/24f53a36f8832fec65cac0aa0f3b43ec1c904414fa6d38f6fc288b0bbd69588a
+++ b/internal/base64dec/testdata/fuzz/FuzzBase64Decoder/24f53a36f8832fec65cac0aa0f3b43ec1c904414fa6d38f6fc288b0bbd69588a
diff --git a/internal/testdata/fuzz/FuzzBase64Decoder/2d49311ef22319f70a3590a86b406b9f2565987a4a3b6d7660ddc308b5b2fae2 b/internal/base64dec/testdata/fuzz/FuzzBase64Decoder/2d49311ef22319f70a3590a86b406b9f2565987a4a3b6d7660ddc308b5b2fae2
index 3d32e14..3d32e14 100644
--- a/internal/testdata/fuzz/FuzzBase64Decoder/2d49311ef22319f70a3590a86b406b9f2565987a4a3b6d7660ddc308b5b2fae2
+++ b/internal/base64dec/testdata/fuzz/FuzzBase64Decoder/2d49311ef22319f70a3590a86b406b9f2565987a4a3b6d7660ddc308b5b2fae2
diff --git a/internal/testdata/fuzz/FuzzBase64Decoder/356e28f5914a0f16f3cef81330f1d92060be4d694a93dedd654bf48743a7d2bd b/internal/base64dec/testdata/fuzz/FuzzBase64Decoder/356e28f5914a0f16f3cef81330f1d92060be4d694a93dedd654bf48743a7d2bd
index d08ef92..d08ef92 100644
--- a/internal/testdata/fuzz/FuzzBase64Decoder/356e28f5914a0f16f3cef81330f1d92060be4d694a93dedd654bf48743a7d2bd
+++ b/internal/base64dec/testdata/fuzz/FuzzBase64Decoder/356e28f5914a0f16f3cef81330f1d92060be4d694a93dedd654bf48743a7d2bd
diff --git a/internal/testdata/fuzz/FuzzBase64Decoder/582528ddfad69eb57775199a43e0f9fd5c94bba343ce7bb6724d4ebafe311ed4 b/internal/base64dec/testdata/fuzz/FuzzBase64Decoder/582528ddfad69eb57775199a43e0f9fd5c94bba343ce7bb6724d4ebafe311ed4
index a96f559..a96f559 100644
--- a/internal/testdata/fuzz/FuzzBase64Decoder/582528ddfad69eb57775199a43e0f9fd5c94bba343ce7bb6724d4ebafe311ed4
+++ b/internal/base64dec/testdata/fuzz/FuzzBase64Decoder/582528ddfad69eb57775199a43e0f9fd5c94bba343ce7bb6724d4ebafe311ed4
diff --git a/internal/testdata/fuzz/FuzzBase64Decoder/60c81ee499a7f1e151b66b08f0a4ff81edd7cb53d00dce8ee0eaf31683996026 b/internal/base64dec/testdata/fuzz/FuzzBase64Decoder/60c81ee499a7f1e151b66b08f0a4ff81edd7cb53d00dce8ee0eaf31683996026
index 87c024d..87c024d 100644
--- a/internal/testdata/fuzz/FuzzBase64Decoder/60c81ee499a7f1e151b66b08f0a4ff81edd7cb53d00dce8ee0eaf31683996026
+++ b/internal/base64dec/testdata/fuzz/FuzzBase64Decoder/60c81ee499a7f1e151b66b08f0a4ff81edd7cb53d00dce8ee0eaf31683996026
diff --git a/internal/testdata/fuzz/FuzzBase64Decoder/66498f377f38b53eebe1ceaa4a53e4de01a04efc02ac9cfda60f9815f80e9b9d b/internal/base64dec/testdata/fuzz/FuzzBase64Decoder/66498f377f38b53eebe1ceaa4a53e4de01a04efc02ac9cfda60f9815f80e9b9d
index 959401e..959401e 100644
--- a/internal/testdata/fuzz/FuzzBase64Decoder/66498f377f38b53eebe1ceaa4a53e4de01a04efc02ac9cfda60f9815f80e9b9d
+++ b/internal/base64dec/testdata/fuzz/FuzzBase64Decoder/66498f377f38b53eebe1ceaa4a53e4de01a04efc02ac9cfda60f9815f80e9b9d
diff --git a/internal/testdata/fuzz/FuzzBase64Decoder/731951fe84fa6f3a7f6ee8adaa585d4f6a01f359a04737e51ffc70f16f480b9b b/internal/base64dec/testdata/fuzz/FuzzBase64Decoder/731951fe84fa6f3a7f6ee8adaa585d4f6a01f359a04737e51ffc70f16f480b9b
index bd1ae59..bd1ae59 100644
--- a/internal/testdata/fuzz/FuzzBase64Decoder/731951fe84fa6f3a7f6ee8adaa585d4f6a01f359a04737e51ffc70f16f480b9b
+++ b/internal/base64dec/testdata/fuzz/FuzzBase64Decoder/731951fe84fa6f3a7f6ee8adaa585d4f6a01f359a04737e51ffc70f16f480b9b
diff --git a/internal/testdata/fuzz/FuzzBase64Decoder/7d6367ba84cd18550920b5202cd1269174416ce32769c7f59376e76b7dd3129c b/internal/base64dec/testdata/fuzz/FuzzBase64Decoder/7d6367ba84cd18550920b5202cd1269174416ce32769c7f59376e76b7dd3129c
index 09e0ad2..09e0ad2 100644
--- a/internal/testdata/fuzz/FuzzBase64Decoder/7d6367ba84cd18550920b5202cd1269174416ce32769c7f59376e76b7dd3129c
+++ b/internal/base64dec/testdata/fuzz/FuzzBase64Decoder/7d6367ba84cd18550920b5202cd1269174416ce32769c7f59376e76b7dd3129c
diff --git a/internal/testdata/fuzz/FuzzBase64Decoder/8727b16d337d7b8187433233f3a90099024e580a6ba319ea2bf539880c50bd7c b/internal/base64dec/testdata/fuzz/FuzzBase64Decoder/8727b16d337d7b8187433233f3a90099024e580a6ba319ea2bf539880c50bd7c
index e8000f3..e8000f3 100644
--- a/internal/testdata/fuzz/FuzzBase64Decoder/8727b16d337d7b8187433233f3a90099024e580a6ba319ea2bf539880c50bd7c
+++ b/internal/base64dec/testdata/fuzz/FuzzBase64Decoder/8727b16d337d7b8187433233f3a90099024e580a6ba319ea2bf539880c50bd7c
diff --git a/internal/testdata/fuzz/FuzzBase64Decoder/9201a772731543760326638b8915f80863feab0ba0108183b3093934bdc0420c b/internal/base64dec/testdata/fuzz/FuzzBase64Decoder/9201a772731543760326638b8915f80863feab0ba0108183b3093934bdc0420c
index aac6b7d..aac6b7d 100644
--- a/internal/testdata/fuzz/FuzzBase64Decoder/9201a772731543760326638b8915f80863feab0ba0108183b3093934bdc0420c
+++ b/internal/base64dec/testdata/fuzz/FuzzBase64Decoder/9201a772731543760326638b8915f80863feab0ba0108183b3093934bdc0420c
diff --git a/internal/testdata/fuzz/FuzzBase64Decoder/92f75f690317ace34aeaae3fe39f5f2ff9830777253ff371c5ef6f403a0f8f0f b/internal/base64dec/testdata/fuzz/FuzzBase64Decoder/92f75f690317ace34aeaae3fe39f5f2ff9830777253ff371c5ef6f403a0f8f0f
index f3bf6d9..f3bf6d9 100644
--- a/internal/testdata/fuzz/FuzzBase64Decoder/92f75f690317ace34aeaae3fe39f5f2ff9830777253ff371c5ef6f403a0f8f0f
+++ b/internal/base64dec/testdata/fuzz/FuzzBase64Decoder/92f75f690317ace34aeaae3fe39f5f2ff9830777253ff371c5ef6f403a0f8f0f
diff --git a/internal/testdata/fuzz/FuzzBase64Decoder/93d6f7bc0d93f998c7b7fe654ff46010d6fa76f0a142c3523c42454f8ad10b07 b/internal/base64dec/testdata/fuzz/FuzzBase64Decoder/93d6f7bc0d93f998c7b7fe654ff46010d6fa76f0a142c3523c42454f8ad10b07
index 2e7f462..2e7f462 100644
--- a/internal/testdata/fuzz/FuzzBase64Decoder/93d6f7bc0d93f998c7b7fe654ff46010d6fa76f0a142c3523c42454f8ad10b07
+++ b/internal/base64dec/testdata/fuzz/FuzzBase64Decoder/93d6f7bc0d93f998c7b7fe654ff46010d6fa76f0a142c3523c42454f8ad10b07
diff --git a/internal/testdata/fuzz/FuzzBase64Decoder/a7450fd77fc7c53cc5bd136874415dddfff5c586e662f21420caa7a94131a56a b/internal/base64dec/testdata/fuzz/FuzzBase64Decoder/a7450fd77fc7c53cc5bd136874415dddfff5c586e662f21420caa7a94131a56a
index c541f52..c541f52 100644
--- a/internal/testdata/fuzz/FuzzBase64Decoder/a7450fd77fc7c53cc5bd136874415dddfff5c586e662f21420caa7a94131a56a
+++ b/internal/base64dec/testdata/fuzz/FuzzBase64Decoder/a7450fd77fc7c53cc5bd136874415dddfff5c586e662f21420caa7a94131a56a
diff --git a/internal/testdata/fuzz/FuzzBase64Decoder/a95d2a0f87501a643d54218d2ad8112204672cc1fb30be297853616788208a5c b/internal/base64dec/testdata/fuzz/FuzzBase64Decoder/a95d2a0f87501a643d54218d2ad8112204672cc1fb30be297853616788208a5c
index 5d56f29..5d56f29 100644
--- a/internal/testdata/fuzz/FuzzBase64Decoder/a95d2a0f87501a643d54218d2ad8112204672cc1fb30be297853616788208a5c
+++ b/internal/base64dec/testdata/fuzz/FuzzBase64Decoder/a95d2a0f87501a643d54218d2ad8112204672cc1fb30be297853616788208a5c
diff --git a/internal/testdata/fuzz/FuzzBase64Decoder/beed435aa2fee4819eab217543561dfd8001d4a44f53ceb664aaba86cebfaf21 b/internal/base64dec/testdata/fuzz/FuzzBase64Decoder/beed435aa2fee4819eab217543561dfd8001d4a44f53ceb664aaba86cebfaf21
index 4b4d59f..4b4d59f 100644
--- a/internal/testdata/fuzz/FuzzBase64Decoder/beed435aa2fee4819eab217543561dfd8001d4a44f53ceb664aaba86cebfaf21
+++ b/internal/base64dec/testdata/fuzz/FuzzBase64Decoder/beed435aa2fee4819eab217543561dfd8001d4a44f53ceb664aaba86cebfaf21
diff --git a/internal/testdata/fuzz/FuzzBase64Decoder/c2501043394e49f2477408be5ef9389790e33ed1886073dec445d4cf05bcd4b4 b/internal/base64dec/testdata/fuzz/FuzzBase64Decoder/c2501043394e49f2477408be5ef9389790e33ed1886073dec445d4cf05bcd4b4
index ef9f9d4..ef9f9d4 100644
--- a/internal/testdata/fuzz/FuzzBase64Decoder/c2501043394e49f2477408be5ef9389790e33ed1886073dec445d4cf05bcd4b4
+++ b/internal/base64dec/testdata/fuzz/FuzzBase64Decoder/c2501043394e49f2477408be5ef9389790e33ed1886073dec445d4cf05bcd4b4
diff --git a/internal/testdata/fuzz/FuzzBase64Decoder/caf81e9797b19c76c1fc4dbf537d4d81f389524539f402d13aa01f93a65ac7e9 b/internal/base64dec/testdata/fuzz/FuzzBase64Decoder/caf81e9797b19c76c1fc4dbf537d4d81f389524539f402d13aa01f93a65ac7e9
index 67322c7..67322c7 100644
--- a/internal/testdata/fuzz/FuzzBase64Decoder/caf81e9797b19c76c1fc4dbf537d4d81f389524539f402d13aa01f93a65ac7e9
+++ b/internal/base64dec/testdata/fuzz/FuzzBase64Decoder/caf81e9797b19c76c1fc4dbf537d4d81f389524539f402d13aa01f93a65ac7e9
diff --git a/internal/testdata/fuzz/FuzzBase64Decoder/cc90a4a40ae9b3beac70baf6d7821a5a6f3a90cabb033575790be91723593680 b/internal/base64dec/testdata/fuzz/FuzzBase64Decoder/cc90a4a40ae9b3beac70baf6d7821a5a6f3a90cabb033575790be91723593680
index f195330..f195330 100644
--- a/internal/testdata/fuzz/FuzzBase64Decoder/cc90a4a40ae9b3beac70baf6d7821a5a6f3a90cabb033575790be91723593680
+++ b/internal/base64dec/testdata/fuzz/FuzzBase64Decoder/cc90a4a40ae9b3beac70baf6d7821a5a6f3a90cabb033575790be91723593680
diff --git a/internal/testdata/fuzz/FuzzBase64Decoder/ec72f669d648d8d9b9f75a3b303897c59b11e4bfb7622f25ff251a92f182bc2a b/internal/base64dec/testdata/fuzz/FuzzBase64Decoder/ec72f669d648d8d9b9f75a3b303897c59b11e4bfb7622f25ff251a92f182bc2a
index 5b0d392..5b0d392 100644
--- a/internal/testdata/fuzz/FuzzBase64Decoder/ec72f669d648d8d9b9f75a3b303897c59b11e4bfb7622f25ff251a92f182bc2a
+++ b/internal/base64dec/testdata/fuzz/FuzzBase64Decoder/ec72f669d648d8d9b9f75a3b303897c59b11e4bfb7622f25ff251a92f182bc2a
diff --git a/internal/testdata/fuzz/FuzzBase64Decoder/f34630c44c11bb13d27531927c5c1e65d159b70f39cd161da0dba348c1221ab3 b/internal/base64dec/testdata/fuzz/FuzzBase64Decoder/f34630c44c11bb13d27531927c5c1e65d159b70f39cd161da0dba348c1221ab3
index a389d3c..a389d3c 100644
--- a/internal/testdata/fuzz/FuzzBase64Decoder/f34630c44c11bb13d27531927c5c1e65d159b70f39cd161da0dba348c1221ab3
+++ b/internal/base64dec/testdata/fuzz/FuzzBase64Decoder/f34630c44c11bb13d27531927c5c1e65d159b70f39cd161da0dba348c1221ab3
diff --git a/internal/testdata/fuzz/FuzzBase64Decoder/fd67efb09d433a1351a201281dbf6568628b4135c35c811dd9bce97620a75d43 b/internal/base64dec/testdata/fuzz/FuzzBase64Decoder/fd67efb09d433a1351a201281dbf6568628b4135c35c811dd9bce97620a75d43
index 17d10b2..17d10b2 100644
--- a/internal/testdata/fuzz/FuzzBase64Decoder/fd67efb09d433a1351a201281dbf6568628b4135c35c811dd9bce97620a75d43
+++ b/internal/base64dec/testdata/fuzz/FuzzBase64Decoder/fd67efb09d433a1351a201281dbf6568628b4135c35c811dd9bce97620a75d43
diff --git a/internal/allwriter.go b/internal/fastio/allwriter.go
index 187aa8e..9de8fdc 100644
--- a/internal/allwriter.go
+++ b/internal/fastio/allwriter.go
@@ -2,7 +2,7 @@
 //
 // SPDX-License-Identifier: GPL-2.0-or-later
 
-package internal
+package fastio
 
 import (
 	"io"
diff --git a/internal/hex.go b/internal/jsonparse/hex.go
index 62a818f..3ed5f01 100644
--- a/internal/hex.go
+++ b/internal/jsonparse/hex.go
@@ -2,7 +2,7 @@
 //
 // SPDX-License-Identifier: GPL-2.0-or-later
 
-package internal
+package jsonparse
 
 const Hex = "0123456789abcdef"
 
diff --git a/internal/parse.go b/internal/jsonparse/parse.go
index 36db4a9..7d97be0 100644
--- a/internal/parse.go
+++ b/internal/jsonparse/parse.go
@@ -2,7 +2,7 @@
 //
 // SPDX-License-Identifier: GPL-2.0-or-later
 
-package internal
+package jsonparse
 
 import (
 	"errors"
diff --git a/internal/parse_test.go b/internal/jsonparse/parse_test.go
index 34977fb..e531daf 100644
--- a/internal/parse_test.go
+++ b/internal/jsonparse/parse_test.go
@@ -2,7 +2,7 @@
 //
 // SPDX-License-Identifier: GPL-2.0-or-later
 
-package internal
+package jsonparse
 
 import (
 	"testing"
diff --git a/internal/borrowed_tags.go b/internal/jsontags/borrowed_tags.go
index 6eaf5da..aa94b9b 100644
--- a/internal/borrowed_tags.go
+++ b/internal/jsontags/borrowed_tags.go
@@ -4,7 +4,7 @@
 //
 // SPDX-License-Identifier: BSD-3-Clause
 
-package internal // MODIFIED: changed package name
+package jsontags // MODIFIED: changed package name
 
 import (
 	"strings"
diff --git a/internal/tags.go b/internal/jsontags/tags.go
index bdf1f72..386824d 100644
--- a/internal/tags.go
+++ b/internal/jsontags/tags.go
@@ -2,6 +2,6 @@
 //
 // SPDX-License-Identifier: GPL-2.0-or-later
 
-package internal
+package jsontags
 
 var ParseTag = parseTag
diff --git a/internal/encode.go b/internal/jsontest/jsontest.go
index 8aae673..fbc775d 100644
--- a/internal/encode.go
+++ b/internal/jsontest/jsontest.go
@@ -2,7 +2,7 @@
 //
 // SPDX-License-Identifier: GPL-2.0-or-later
 
-package internal
+package jsontest
 
 import (
 	"io"
diff --git a/reencode.go b/reencode.go
index 3e9cf37..232d91d 100644
--- a/reencode.go
+++ b/reencode.go
@@ -10,7 +10,8 @@ import (
 	"io"
 	"unicode/utf8"
 
-	"git.lukeshu.com/go/lowmemjson/internal"
+	"git.lukeshu.com/go/lowmemjson/internal/fastio"
+	"git.lukeshu.com/go/lowmemjson/internal/jsonparse"
 )
 
 // A ReEncoderConfig controls how a ReEncoder should behave.
@@ -71,7 +72,7 @@ type ReEncoderConfig struct {
 func NewReEncoder(out io.Writer, cfg ReEncoderConfig) *ReEncoder {
 	return &ReEncoder{
 		ReEncoderConfig: cfg,
-		out:             internal.NewAllWriter(out),
+		out:             fastio.NewAllWriter(out),
 		specu:           new(speculation),
 	}
 }
@@ -86,7 +87,7 @@ func NewReEncoder(out io.Writer, cfg ReEncoderConfig) *ReEncoder {
 // The memory use of a ReEncoder is O(CompactIfUnder+depth).
 type ReEncoder struct {
 	ReEncoderConfig
-	out internal.AllWriter
+	out fastio.AllWriter
 
 	// state: .Write's and .WriteString's utf8-decoding buffer
 	buf    [utf8.UTFMax]byte
@@ -94,13 +95,13 @@ type ReEncoder struct {
 
 	// state: .WriteRune
 	err      error
-	par      internal.Parser
+	par      jsonparse.Parser
 	written  int
 	inputPos int64
 
 	// state: .handleRune
-	lastNonSpace       internal.RuneType
-	lastNonSpaceNonEOF internal.RuneType
+	lastNonSpace       jsonparse.RuneType
+	lastNonSpaceNonEOF jsonparse.RuneType
 	wasNumber          bool
 	curIndent          int
 	uhex               [4]byte // "\uABCD"-encoded characters in strings
@@ -135,15 +136,15 @@ func (specu *speculation) Reset() {
 
 type inputTuple struct {
 	c         rune
-	t         internal.RuneType
+	t         jsonparse.RuneType
 	stackSize int
 }
 
 // public API //////////////////////////////////////////////////////////////////
 
 var (
-	_ internal.AllWriter = (*ReEncoder)(nil)
-	_ io.Closer          = (*ReEncoder)(nil)
+	_ fastio.AllWriter = (*ReEncoder)(nil)
+	_ io.Closer        = (*ReEncoder)(nil)
 )
 
 // Write implements io.Writer; it does what you'd expect.
@@ -208,7 +209,7 @@ func (enc *ReEncoder) WriteString(p string) (int, error) {
 
 // WriteByte implements io.ByteWriter; it does what you'd expect.
 func (enc *ReEncoder) WriteByte(b byte) error {
-	return internal.WriteByte(enc, b)
+	return fastio.WriteByte(enc, b)
 }
 
 // Close implements io.Closer; it does what you'd expect, mostly.
@@ -230,7 +231,7 @@ func (enc *ReEncoder) Close() error {
 		return enc.err
 	}
 	if len(enc.barriers) == 0 {
-		if err := enc.handleRune(0, internal.RuneTypeError, enc.stackSize()); err != nil {
+		if err := enc.handleRune(0, jsonparse.RuneTypeError, enc.stackSize()); err != nil {
 			enc.err = &ReEncodeSyntaxError{
 				Err:    err,
 				Offset: enc.inputPos,
@@ -274,7 +275,7 @@ rehandle:
 		return enc.written, enc.err
 	}
 	enc.err = enc.handleRune(c, t, enc.stackSize())
-	if enc.err == nil && t == internal.RuneTypeEOF {
+	if enc.err == nil && t == jsonparse.RuneTypeEOF {
 		if enc.AllowMultipleValues && len(enc.barriers) == 0 {
 			enc.par.Reset()
 			goto rehandle
@@ -319,7 +320,7 @@ func (enc *ReEncoder) stackSize() int {
 	return sz
 }
 
-func (enc *ReEncoder) handleRune(c rune, t internal.RuneType, stackSize int) error {
+func (enc *ReEncoder) handleRune(c rune, t jsonparse.RuneType, stackSize int) error {
 	if enc.CompactIfUnder == 0 || enc.Compact || enc.Indent == "" {
 		return enc.handleRuneNoSpeculation(c, t)
 	}
@@ -327,7 +328,7 @@ func (enc *ReEncoder) handleRune(c rune, t internal.RuneType, stackSize int) err
 	// main
 	if !enc.specu.speculating { // not speculating
 		switch t {
-		case internal.RuneTypeObjectBeg, internal.RuneTypeArrayBeg: // start speculating
+		case jsonparse.RuneTypeObjectBeg, jsonparse.RuneTypeArrayBeg: // start speculating
 			if err, _ := enc.handleRunePre(c, t); err != nil {
 				return err
 			}
@@ -385,7 +386,7 @@ func (enc *ReEncoder) handleRune(c rune, t internal.RuneType, stackSize int) err
 	return nil
 }
 
-func (enc *ReEncoder) handleRuneNoSpeculation(c rune, t internal.RuneType) error {
+func (enc *ReEncoder) handleRuneNoSpeculation(c rune, t jsonparse.RuneType) error {
 	err, shouldHandle := enc.handleRunePre(c, t)
 	if err != nil {
 		return err
@@ -398,9 +399,9 @@ func (enc *ReEncoder) handleRuneNoSpeculation(c rune, t internal.RuneType) error
 
 // handleRunePre handles buffered things that need to happen before
 // the new rune itself is handled.
-func (enc *ReEncoder) handleRunePre(c rune, t internal.RuneType) (error, bool) {
+func (enc *ReEncoder) handleRunePre(c rune, t jsonparse.RuneType) (error, bool) {
 	// emit newlines between top-level values
-	if enc.lastNonSpace == internal.RuneTypeEOF {
+	if enc.lastNonSpace == jsonparse.RuneTypeEOF {
 		switch {
 		case enc.wasNumber && t.IsNumber():
 			if err := enc.emitByte('\n'); err != nil {
@@ -415,10 +416,10 @@ func (enc *ReEncoder) handleRunePre(c rune, t internal.RuneType) (error, bool) {
 
 	// shorten numbers
 	switch t { // trim trailing '0's from the fraction-part, but don't remove all digits
-	case internal.RuneTypeNumberFracDot:
+	case jsonparse.RuneTypeNumberFracDot:
 		enc.fracZeros = 0
-	case internal.RuneTypeNumberFracDig:
-		if c == '0' && enc.lastNonSpace == internal.RuneTypeNumberFracDig {
+	case jsonparse.RuneTypeNumberFracDig:
+		if c == '0' && enc.lastNonSpace == jsonparse.RuneTypeNumberFracDig {
 			enc.fracZeros++
 			return nil, false
 		}
@@ -432,9 +433,9 @@ func (enc *ReEncoder) handleRunePre(c rune, t internal.RuneType) (error, bool) {
 		}
 	}
 	switch t { // trim leading '0's from the exponent-part, but don't remove all digits
-	case internal.RuneTypeNumberExpE, internal.RuneTypeNumberExpSign:
+	case jsonparse.RuneTypeNumberExpE, jsonparse.RuneTypeNumberExpSign:
 		enc.expZero = true
-	case internal.RuneTypeNumberExpDig:
+	case jsonparse.RuneTypeNumberExpDig:
 		if c == '0' && enc.expZero {
 			return nil, false
 		}
@@ -451,18 +452,18 @@ func (enc *ReEncoder) handleRunePre(c rune, t internal.RuneType) (error, bool) {
 	// whitespace
 	switch {
 	case enc.Compact:
-		if t == internal.RuneTypeSpace {
+		if t == jsonparse.RuneTypeSpace {
 			return nil, false
 		}
 	case enc.Indent != "":
 		switch t {
-		case internal.RuneTypeSpace:
+		case jsonparse.RuneTypeSpace:
 			// let us manage whitespace, don't pass it through
 			return nil, false
-		case internal.RuneTypeObjectEnd, internal.RuneTypeArrayEnd:
+		case jsonparse.RuneTypeObjectEnd, jsonparse.RuneTypeArrayEnd:
 			enc.curIndent--
 			switch enc.lastNonSpace {
-			case internal.RuneTypeObjectBeg, internal.RuneTypeArrayBeg:
+			case jsonparse.RuneTypeObjectBeg, jsonparse.RuneTypeArrayBeg:
 				// collapse
 			default:
 				if err := enc.emitNlIndent(); err != nil {
@@ -471,17 +472,17 @@ func (enc *ReEncoder) handleRunePre(c rune, t internal.RuneType) (error, bool) {
 			}
 		default:
 			switch enc.lastNonSpace {
-			case internal.RuneTypeObjectBeg, internal.RuneTypeObjectComma, internal.RuneTypeArrayBeg, internal.RuneTypeArrayComma:
+			case jsonparse.RuneTypeObjectBeg, jsonparse.RuneTypeObjectComma, jsonparse.RuneTypeArrayBeg, jsonparse.RuneTypeArrayComma:
 				if err := enc.emitNlIndent(); err != nil {
 					return err, false
 				}
-			case internal.RuneTypeObjectColon:
+			case jsonparse.RuneTypeObjectColon:
 				if err := enc.emitByte(' '); err != nil {
 					return err, false
 				}
 			}
 			switch t {
-			case internal.RuneTypeObjectBeg, internal.RuneTypeArrayBeg:
+			case jsonparse.RuneTypeObjectBeg, jsonparse.RuneTypeArrayBeg:
 				enc.curIndent++
 			}
 		}
@@ -491,15 +492,15 @@ func (enc *ReEncoder) handleRunePre(c rune, t internal.RuneType) (error, bool) {
 }
 
 // handleRuneMain handles the new rune itself, not buffered things.
-func (enc *ReEncoder) handleRuneMain(c rune, t internal.RuneType) error {
+func (enc *ReEncoder) handleRuneMain(c rune, t jsonparse.RuneType) error {
 	var err error
 	switch t {
 
-	case internal.RuneTypeStringChar:
+	case jsonparse.RuneTypeStringChar:
 		err = enc.emit(writeStringChar(enc.out, c, BackslashEscapeNone, enc.BackslashEscape))
-	case internal.RuneTypeStringEsc, internal.RuneTypeStringEscU:
+	case jsonparse.RuneTypeStringEsc, jsonparse.RuneTypeStringEscU:
 		// do nothing
-	case internal.RuneTypeStringEsc1:
+	case jsonparse.RuneTypeStringEsc1:
 		switch c {
 		case '"':
 			err = enc.emit(writeStringChar(enc.out, '"', BackslashEscapeShort, enc.BackslashEscape))
@@ -520,14 +521,14 @@ func (enc *ReEncoder) handleRuneMain(c rune, t internal.RuneType) error {
 		default:
 			panic("should not happen")
 		}
-	case internal.RuneTypeStringEscUA:
-		enc.uhex[0], _ = internal.HexToInt(c)
-	case internal.RuneTypeStringEscUB:
-		enc.uhex[1], _ = internal.HexToInt(c)
-	case internal.RuneTypeStringEscUC:
-		enc.uhex[2], _ = internal.HexToInt(c)
-	case internal.RuneTypeStringEscUD:
-		enc.uhex[3], _ = internal.HexToInt(c)
+	case jsonparse.RuneTypeStringEscUA:
+		enc.uhex[0], _ = jsonparse.HexToInt(c)
+	case jsonparse.RuneTypeStringEscUB:
+		enc.uhex[1], _ = jsonparse.HexToInt(c)
+	case jsonparse.RuneTypeStringEscUC:
+		enc.uhex[2], _ = jsonparse.HexToInt(c)
+	case jsonparse.RuneTypeStringEscUD:
+		enc.uhex[3], _ = jsonparse.HexToInt(c)
 		c := 0 |
 			rune(enc.uhex[0])<<12 |
 			rune(enc.uhex[1])<<8 |
@@ -535,24 +536,24 @@ func (enc *ReEncoder) handleRuneMain(c rune, t internal.RuneType) error {
 			rune(enc.uhex[3])<<0
 		err = enc.emit(writeStringChar(enc.out, c, BackslashEscapeUnicode, enc.BackslashEscape))
 
-	case internal.RuneTypeError: // EOF explicitly stated by .Close()
+	case jsonparse.RuneTypeError: // EOF explicitly stated by .Close()
 		fallthrough
-	case internal.RuneTypeEOF: // EOF implied by the start of the next top-level value
+	case jsonparse.RuneTypeEOF: // EOF implied by the start of the next top-level value
 		enc.wasNumber = enc.lastNonSpace.IsNumber()
 		switch {
 		case enc.ForceTrailingNewlines && len(enc.barriers) == 0:
-			t = internal.RuneTypeError // enc.lastNonSpace : an NL isn't needed (we already printed one)
+			t = jsonparse.RuneTypeError // enc.lastNonSpace : an NL isn't needed (we already printed one)
 			err = enc.emitByte('\n')
 		default:
-			t = internal.RuneTypeEOF // enc.lastNonSpace : an NL *might* be needed
+			t = jsonparse.RuneTypeEOF // enc.lastNonSpace : an NL *might* be needed
 		}
 	default:
 		err = enc.emitByte(byte(c))
 	}
 
-	if t != internal.RuneTypeSpace {
+	if t != jsonparse.RuneTypeSpace {
 		enc.lastNonSpace = t
-		if t != internal.RuneTypeEOF {
+		if t != jsonparse.RuneTypeEOF {
 			enc.lastNonSpaceNonEOF = t
 		}
 	}
diff --git a/struct.go b/struct.go
index 81bc22d..5ccb62f 100644
--- a/struct.go
+++ b/struct.go
@@ -9,7 +9,7 @@ import (
 
 	"git.lukeshu.com/go/typedsync"
 
-	"git.lukeshu.com/go/lowmemjson/internal"
+	"git.lukeshu.com/go/lowmemjson/internal/jsontags"
 )
 
 type structField struct {
@@ -157,7 +157,7 @@ func indexStructInner(typ reflect.Type, byPos *[]structField, byName map[string]
 		if tag == "-" {
 			continue
 		}
-		tagName, opts := internal.ParseTag(tag)
+		tagName, opts := jsontags.ParseTag(tag)
 		name := tagName
 		if !isValidTag(name) {
 			name = ""