Improve performance at decoding

decode_int.go

@@ -2,7 +2,6 @@ package json
 
 import (
 	"errors"
-	"math"
 )
 
 type intDecoder struct {
@@ -13,6 +12,13 @@ func newIntDecoder(op func(uintptr, int64)) *intDecoder {
 	return &intDecoder{op: op}
 }
 
+var (
+	pow10i64 = [...]int64{
+		1e00, 1e01, 1e02, 1e03, 1e04, 1e05, 1e06, 1e07, 1e08, 1e09,
+		1e10, 1e11, 1e12, 1e13, 1e14, 1e15, 1e16, 1e17, 1e18,
+	}
+)
+
 func (d *intDecoder) parseInt(b []byte) int64 {
 	isNegative := false
 	if b[0] == '-' {
@@ -23,7 +29,7 @@ func (d *intDecoder) parseInt(b []byte) int64 {
 	sum := int64(0)
 	for i := 0; i < maxDigit; i++ {
 		c := int64(b[i]) - 48
-		digitValue := int64(math.Pow10(maxDigit - i - 1))
+		digitValue := pow10i64[maxDigit-i-1]
 		sum += c * digitValue
 	}
 	if isNegative {
@@ -33,13 +39,15 @@ func (d *intDecoder) parseInt(b []byte) int64 {
 }
 
 func (d *intDecoder) decodeByte(ctx *context) ([]byte, error) {
-	ctx.skipWhiteSpace()
 	buf := ctx.buf
 	cursor := ctx.cursor
 	buflen := ctx.buflen
+	for ; cursor < buflen; cursor++ {
 		switch buf[cursor] {
+		case ' ', '\n', '\t', '\r':
+			continue
 		case '-', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9':
-		start := ctx.cursor
+			start := cursor
 			cursor++
 			for ; cursor < buflen; cursor++ {
 				tk := int(buf[cursor])
@@ -50,9 +58,9 @@ func (d *intDecoder) decodeByte(ctx *context) ([]byte, error) {
 			}
 			num := ctx.buf[start:cursor]
 			ctx.cursor = cursor
-		//fmt.Printf("number = [%s]\n", string(num))
 			return num, nil
 		}
+	}
 	return nil, errors.New("unexpected error number")
 }
 

decode_string.go

@@ -22,30 +22,31 @@ func (d *stringDecoder) decode(ctx *context, p uintptr) error {
 }
 
 func (d *stringDecoder) decodeByte(ctx *context) ([]byte, error) {
-	ctx.skipWhiteSpace()
 	buf := ctx.buf
-	cursor := ctx.cursor
 	buflen := ctx.buflen
-	if buf[cursor] != '"' {
+	cursor := ctx.cursor
-		return nil, errors.New("unexpected error key delimiter")
+	for ; cursor < buflen; cursor++ {
-	}
+		switch buf[cursor] {
-	start := cursor + 1
+		case ' ', '\n', '\t', '\r':
+			continue
+		case '"':
 			cursor++
+			start := cursor
 			for ; cursor < buflen; cursor++ {
 				tk := buf[cursor]
 				if tk == '\\' {
+					cursor++
 					continue
 				}
 				if tk == '"' {
-			break
-		}
-	}
-	if buf[cursor] != '"' {
-		return nil, errors.New("unexpected error string")
-	}
 					literal := buf[start:cursor]
-	//fmt.Printf("string = [%s]\n", string(literal))
 					cursor++
 					ctx.cursor = cursor
 					return literal, nil
+				}
+			}
+			return nil, errors.New("unexpected error string")
+		}
+	}
+	return nil, errors.New("unexpected error key delimiter")
 }

decode_struct.go

@@ -81,7 +81,6 @@ func (d *structDecoder) decode(ctx *context, p uintptr) error {
 		k := *(*string)(unsafe.Pointer(&key))
 		field, exists := d.fieldMap[k]
 		if exists {
-			//fmt.Printf("k = %s dec = %#v, p = %x\n", k, field.dec, p)
 			if err := field.dec.decode(ctx, p+field.offset); err != nil {
 				return err
 			}

decode_uint.go

@@ -2,8 +2,6 @@ package json
 
 import (
 	"errors"
-	"fmt"
-	"math"
 )
 
 type uintDecoder struct {
@@ -14,23 +12,30 @@ func newUintDecoder(op func(uintptr, uint64)) *uintDecoder {
 	return &uintDecoder{op: op}
 }
 
+var pow10u64 = [...]uint64{
+	1e00, 1e01, 1e02, 1e03, 1e04, 1e05, 1e06, 1e07, 1e08, 1e09,
+	1e10, 1e11, 1e12, 1e13, 1e14, 1e15, 1e16, 1e17, 1e18, 1e19,
+}
+
 func (d *uintDecoder) parseUint(b []byte) uint64 {
 	maxDigit := len(b)
 	sum := uint64(0)
 	for i := 0; i < maxDigit; i++ {
 		c := uint64(b[i]) - 48
-		digitValue := uint64(math.Pow10(maxDigit - i - 1))
+		digitValue := pow10u64[maxDigit-i-1]
 		sum += c * digitValue
 	}
 	return sum
 }
 
 func (d *uintDecoder) decodeByte(ctx *context) ([]byte, error) {
-	ctx.skipWhiteSpace()
 	buf := ctx.buf
 	buflen := ctx.buflen
 	cursor := ctx.cursor
+	for ; cursor < buflen; cursor++ {
 		switch buf[cursor] {
+		case ' ', '\n', '\t', '\r':
+			continue
 		case '0', '1', '2', '3', '4', '5', '6', '7', '8', '9':
 			start := cursor
 			cursor++
@@ -42,10 +47,10 @@ func (d *uintDecoder) decodeByte(ctx *context) ([]byte, error) {
 				break
 			}
 			num := buf[start:cursor]
-		fmt.Printf("number = [%s]\n", string(num))
 			ctx.cursor = cursor
 			return num, nil
 		}
+	}
 	return nil, errors.New("unexpected error number")
 }