Switch to lazy init() in decoder and encoder

This will prevent go-json from consuming heap unless it is used.

internal/decoder/compile.go

@@ -5,6 +5,7 @@ import (
 	"fmt"
 	"reflect"
 	"strings"
+	"sync"
 	"sync/atomic"
 	"unicode"
 	"unsafe"
@@ -17,22 +18,27 @@ var (
 	typeAddr         *runtime.TypeAddr
 	cachedDecoderMap unsafe.Pointer // map[uintptr]decoder
 	cachedDecoder    []Decoder
+	initOnce         sync.Once
 )
 
-func init() {
-	typeAddr = runtime.AnalyzeTypeAddr()
-	if typeAddr == nil {
-		typeAddr = &runtime.TypeAddr{}
-	}
-	cachedDecoder = make([]Decoder, typeAddr.AddrRange>>typeAddr.AddrShift+1)
+func initDecoder() {
+	initOnce.Do(func() {
+		typeAddr = runtime.AnalyzeTypeAddr()
+		if typeAddr == nil {
+			typeAddr = &runtime.TypeAddr{}
+		}
+		cachedDecoder = make([]Decoder, typeAddr.AddrRange>>typeAddr.AddrShift+1)
+	})
 }
 
 func loadDecoderMap() map[uintptr]Decoder {
+	initDecoder()
 	p := atomic.LoadPointer(&cachedDecoderMap)
 	return *(*map[uintptr]Decoder)(unsafe.Pointer(&p))
 }
 
 func storeDecoder(typ uintptr, dec Decoder, m map[uintptr]Decoder) {
+	initDecoder()
 	newDecoderMap := make(map[uintptr]Decoder, len(m)+1)
 	newDecoderMap[typ] = dec
 

internal/decoder/compile_norace.go

@@ -10,6 +10,7 @@ import (
 )
 
 func CompileToGetDecoder(typ *runtime.Type) (Decoder, error) {
+	initDecoder()
 	typeptr := uintptr(unsafe.Pointer(typ))
 	if typeptr > typeAddr.MaxTypeAddr {
 		return compileToGetDecoderSlowPath(typeptr, typ)

internal/decoder/compile_race.go

@@ -13,6 +13,7 @@ import (
 var decMu sync.RWMutex
 
 func CompileToGetDecoder(typ *runtime.Type) (Decoder, error) {
+	initDecoder()
 	typeptr := uintptr(unsafe.Pointer(typ))
 	if typeptr > typeAddr.MaxTypeAddr {
 		return compileToGetDecoderSlowPath(typeptr, typ)

internal/encoder/compiler.go

@@ -5,6 +5,7 @@ import (
 	"encoding"
 	"encoding/json"
 	"reflect"
+	"sync"
 	"sync/atomic"
 	"unsafe"
 
@@ -24,14 +25,17 @@ var (
 	cachedOpcodeSets       []*OpcodeSet
 	cachedOpcodeMap        unsafe.Pointer // map[uintptr]*OpcodeSet
 	typeAddr               *runtime.TypeAddr
+	initEncoderOnce        sync.Once
 )
 
-func init() {
-	typeAddr = runtime.AnalyzeTypeAddr()
-	if typeAddr == nil {
-		typeAddr = &runtime.TypeAddr{}
-	}
-	cachedOpcodeSets = make([]*OpcodeSet, typeAddr.AddrRange>>typeAddr.AddrShift+1)
+func initEncoder() {
+	initEncoderOnce.Do(func() {
+		typeAddr = runtime.AnalyzeTypeAddr()
+		if typeAddr == nil {
+			typeAddr = &runtime.TypeAddr{}
+		}
+		cachedOpcodeSets = make([]*OpcodeSet, typeAddr.AddrRange>>typeAddr.AddrShift+1)
+	})
 }
 
 func loadOpcodeMap() map[uintptr]*OpcodeSet {

internal/encoder/compiler_norace.go

@@ -4,6 +4,7 @@
 package encoder
 
 func CompileToGetCodeSet(ctx *RuntimeContext, typeptr uintptr) (*OpcodeSet, error) {
+	initEncoder()
 	if typeptr > typeAddr.MaxTypeAddr || typeptr < typeAddr.BaseTypeAddr {
 		codeSet, err := compileToGetCodeSetSlowPath(typeptr)
 		if err != nil {

internal/encoder/compiler_race.go

@@ -10,6 +10,7 @@ import (
 var setsMu sync.RWMutex
 
 func CompileToGetCodeSet(ctx *RuntimeContext, typeptr uintptr) (*OpcodeSet, error) {
+	initEncoder()
 	if typeptr > typeAddr.MaxTypeAddr || typeptr < typeAddr.BaseTypeAddr {
 		codeSet, err := compileToGetCodeSetSlowPath(typeptr)
 		if err != nil {

internal/encoder/int.go

@@ -25,59 +25,70 @@
 package encoder
 
 import (
+	"sync"
 	"unsafe"
 )
 
-var endianness int
+var (
+	endianness  int
+	initIntOnce sync.Once
+	intLELookup *[100]uint16
+	intBELookup *[100]uint16
+	intLookup   [2]*[100]uint16
+)
 
-func init() {
-	var b [2]byte
-	*(*uint16)(unsafe.Pointer(&b)) = uint16(0xABCD)
+func initInt() {
+	initIntOnce.Do(func() {
+		var b [2]byte
+		*(*uint16)(unsafe.Pointer(&b)) = uint16(0xABCD)
+
+		switch b[0] {
+		case 0xCD:
+			endianness = 0 // LE
+		case 0xAB:
+			endianness = 1 // BE
+		default:
+			panic("could not determine endianness")
+		}
 
-	switch b[0] {
-	case 0xCD:
-		endianness = 0 // LE
-	case 0xAB:
-		endianness = 1 // BE
-	default:
-		panic("could not determine endianness")
-	}
-}
+		// "00010203...96979899" cast to []uint16
+		intLELookup = &[100]uint16{
+			0x3030, 0x3130, 0x3230, 0x3330, 0x3430, 0x3530, 0x3630, 0x3730, 0x3830, 0x3930,
+			0x3031, 0x3131, 0x3231, 0x3331, 0x3431, 0x3531, 0x3631, 0x3731, 0x3831, 0x3931,
+			0x3032, 0x3132, 0x3232, 0x3332, 0x3432, 0x3532, 0x3632, 0x3732, 0x3832, 0x3932,
+			0x3033, 0x3133, 0x3233, 0x3333, 0x3433, 0x3533, 0x3633, 0x3733, 0x3833, 0x3933,
+			0x3034, 0x3134, 0x3234, 0x3334, 0x3434, 0x3534, 0x3634, 0x3734, 0x3834, 0x3934,
+			0x3035, 0x3135, 0x3235, 0x3335, 0x3435, 0x3535, 0x3635, 0x3735, 0x3835, 0x3935,
+			0x3036, 0x3136, 0x3236, 0x3336, 0x3436, 0x3536, 0x3636, 0x3736, 0x3836, 0x3936,
+			0x3037, 0x3137, 0x3237, 0x3337, 0x3437, 0x3537, 0x3637, 0x3737, 0x3837, 0x3937,
+			0x3038, 0x3138, 0x3238, 0x3338, 0x3438, 0x3538, 0x3638, 0x3738, 0x3838, 0x3938,
+			0x3039, 0x3139, 0x3239, 0x3339, 0x3439, 0x3539, 0x3639, 0x3739, 0x3839, 0x3939,
+		}
 
-// "00010203...96979899" cast to []uint16
-var intLELookup = [100]uint16{
-	0x3030, 0x3130, 0x3230, 0x3330, 0x3430, 0x3530, 0x3630, 0x3730, 0x3830, 0x3930,
-	0x3031, 0x3131, 0x3231, 0x3331, 0x3431, 0x3531, 0x3631, 0x3731, 0x3831, 0x3931,
-	0x3032, 0x3132, 0x3232, 0x3332, 0x3432, 0x3532, 0x3632, 0x3732, 0x3832, 0x3932,
-	0x3033, 0x3133, 0x3233, 0x3333, 0x3433, 0x3533, 0x3633, 0x3733, 0x3833, 0x3933,
-	0x3034, 0x3134, 0x3234, 0x3334, 0x3434, 0x3534, 0x3634, 0x3734, 0x3834, 0x3934,
-	0x3035, 0x3135, 0x3235, 0x3335, 0x3435, 0x3535, 0x3635, 0x3735, 0x3835, 0x3935,
-	0x3036, 0x3136, 0x3236, 0x3336, 0x3436, 0x3536, 0x3636, 0x3736, 0x3836, 0x3936,
-	0x3037, 0x3137, 0x3237, 0x3337, 0x3437, 0x3537, 0x3637, 0x3737, 0x3837, 0x3937,
-	0x3038, 0x3138, 0x3238, 0x3338, 0x3438, 0x3538, 0x3638, 0x3738, 0x3838, 0x3938,
-	0x3039, 0x3139, 0x3239, 0x3339, 0x3439, 0x3539, 0x3639, 0x3739, 0x3839, 0x3939,
-}
+		intBELookup = &[100]uint16{
+			0x3030, 0x3031, 0x3032, 0x3033, 0x3034, 0x3035, 0x3036, 0x3037, 0x3038, 0x3039,
+			0x3130, 0x3131, 0x3132, 0x3133, 0x3134, 0x3135, 0x3136, 0x3137, 0x3138, 0x3139,
+			0x3230, 0x3231, 0x3232, 0x3233, 0x3234, 0x3235, 0x3236, 0x3237, 0x3238, 0x3239,
+			0x3330, 0x3331, 0x3332, 0x3333, 0x3334, 0x3335, 0x3336, 0x3337, 0x3338, 0x3339,
+			0x3430, 0x3431, 0x3432, 0x3433, 0x3434, 0x3435, 0x3436, 0x3437, 0x3438, 0x3439,
+			0x3530, 0x3531, 0x3532, 0x3533, 0x3534, 0x3535, 0x3536, 0x3537, 0x3538, 0x3539,
+			0x3630, 0x3631, 0x3632, 0x3633, 0x3634, 0x3635, 0x3636, 0x3637, 0x3638, 0x3639,
+			0x3730, 0x3731, 0x3732, 0x3733, 0x3734, 0x3735, 0x3736, 0x3737, 0x3738, 0x3739,
+			0x3830, 0x3831, 0x3832, 0x3833, 0x3834, 0x3835, 0x3836, 0x3837, 0x3838, 0x3839,
+			0x3930, 0x3931, 0x3932, 0x3933, 0x3934, 0x3935, 0x3936, 0x3937, 0x3938, 0x3939,
+		}
 
-var intBELookup = [100]uint16{
-	0x3030, 0x3031, 0x3032, 0x3033, 0x3034, 0x3035, 0x3036, 0x3037, 0x3038, 0x3039,
-	0x3130, 0x3131, 0x3132, 0x3133, 0x3134, 0x3135, 0x3136, 0x3137, 0x3138, 0x3139,
-	0x3230, 0x3231, 0x3232, 0x3233, 0x3234, 0x3235, 0x3236, 0x3237, 0x3238, 0x3239,
-	0x3330, 0x3331, 0x3332, 0x3333, 0x3334, 0x3335, 0x3336, 0x3337, 0x3338, 0x3339,
-	0x3430, 0x3431, 0x3432, 0x3433, 0x3434, 0x3435, 0x3436, 0x3437, 0x3438, 0x3439,
-	0x3530, 0x3531, 0x3532, 0x3533, 0x3534, 0x3535, 0x3536, 0x3537, 0x3538, 0x3539,
-	0x3630, 0x3631, 0x3632, 0x3633, 0x3634, 0x3635, 0x3636, 0x3637, 0x3638, 0x3639,
-	0x3730, 0x3731, 0x3732, 0x3733, 0x3734, 0x3735, 0x3736, 0x3737, 0x3738, 0x3739,
-	0x3830, 0x3831, 0x3832, 0x3833, 0x3834, 0x3835, 0x3836, 0x3837, 0x3838, 0x3839,
-	0x3930, 0x3931, 0x3932, 0x3933, 0x3934, 0x3935, 0x3936, 0x3937, 0x3938, 0x3939,
+		intLookup = [2]*[100]uint16{intLELookup, intBELookup}
+	})
 }
 
-var intLookup = [2]*[100]uint16{&intLELookup, &intBELookup}
-
 func numMask(numBitSize uint8) uint64 {
 	return 1<<numBitSize - 1
 }
 
 func AppendInt(_ *RuntimeContext, out []byte, p uintptr, code *Opcode) []byte {
+	initInt() // lazy init
+
 	var u64 uint64
 	switch code.NumBitSize {
 	case 8:
@@ -132,6 +143,8 @@ func AppendInt(_ *RuntimeContext, out []byte, p uintptr, code *Opcode) []byte {
 }
 
 func AppendUint(_ *RuntimeContext, out []byte, p uintptr, code *Opcode) []byte {
+	initInt() // lazy init
+
 	var u64 uint64
 	switch code.NumBitSize {
 	case 8: