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Speed up integer parsing #112

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merged 1 commit into from
Dec 8, 2021
Merged

Speed up integer parsing #112

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58 changes: 18 additions & 40 deletions json/parse.go
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Original file line number Diff line number Diff line change
Expand Up @@ -131,33 +131,22 @@ func (d decoder) parseInt(b []byte, t reflect.Type) (int64, []byte, error) {

count++
} else {
const max = math.MaxInt64
const lim = max / 10

if len(b) > 1 && b[0] == '0' && '0' <= b[1] && b[1] <= '9' {
return 0, b, syntaxError(b, "invalid leading character '0' in integer")
}

for _, c := range b {
if !(c >= '0' && c <= '9') {
if count == 0 {
b, err := d.inputError(b, t)
return 0, b, err
}
break
}
x := int64(c - '0')

if value > lim {
return 0, b, unmarshalOverflow(b, t)
}

if value *= 10; value > (max - x) {
for ; count < len(b) && b[count] >= '0' && b[count] <= '9'; count++ {
x := int64(b[count] - '0')
next := value*10 + x
if next < value {
return 0, b, unmarshalOverflow(b, t)
}
value = next
}

value += x
count++
if count == 0 {
b, err := d.inputError(b, t)
return 0, b, err
}
}

Expand All @@ -177,9 +166,6 @@ func (d decoder) parseInt(b []byte, t reflect.Type) (int64, []byte, error) {

// parseUint is like parseInt but for unsigned integers.
func (d decoder) parseUint(b []byte, t reflect.Type) (uint64, []byte, error) {
const max = math.MaxUint64
const lim = max / 10

var value uint64
var count int

Expand All @@ -191,26 +177,18 @@ func (d decoder) parseUint(b []byte, t reflect.Type) (uint64, []byte, error) {
return 0, b, syntaxError(b, "invalid leading character '0' in integer")
}

for _, c := range b {
if !(c >= '0' && c <= '9') {
if count == 0 {
b, err := d.inputError(b, t)
return 0, b, err
}
break
}
x := uint64(c - '0')

if value > lim {
return 0, b, unmarshalOverflow(b, t)
}

if value *= 10; value > (max - x) {
for ; count < len(b) && b[count] >= '0' && b[count] <= '9'; count++ {
x := uint64(b[count] - '0')
next := value*10 + x
if next < value {
return 0, b, unmarshalOverflow(b, t)
}
value = next
}

value += x
count++
if count == 0 {
b, err := d.inputError(b, t)
return 0, b, err
}

if count < len(b) {
Expand Down