optimize read int32

feature_iter_int.go

@@ -0,0 +1,171 @@
+package jsoniter
+
+
+var intDigits []int8
+const maxUint64 = (1<<64 - 1)
+const cutoffUint64 = maxUint64/10 + 1
+const maxUint32 = (1<<32 - 1)
+const cutoffUint32 = maxUint32/10 + 1
+const int32SafeToMultiply10 = uint32(int32(0x7fffffff)/10 - 10)
+const uint32SafeToMultiply10 = uint32(0xffffffff)/10 - 10
+
+func init() {
+	intDigits = make([]int8, 256)
+	for i := 0; i < len(floatDigits); i++ {
+		intDigits[i] = invalidCharForNumber
+	}
+	for i := int8('0'); i <= int8('9'); i++ {
+		intDigits[i] = i - int8('0')
+	}
+}
+
+// ReadUint reads a json object as Uint
+func (iter *Iterator) ReadUint() (ret uint) {
+	val := iter.ReadUint64()
+	converted := uint(val)
+	if uint64(converted) != val {
+		iter.reportError("ReadUint", "int overflow")
+		return
+	}
+	return converted
+}
+
+// ReadUint8 reads a json object as Uint8
+func (iter *Iterator) ReadUint8() (ret uint8) {
+	val := iter.ReadUint64()
+	converted := uint8(val)
+	if uint64(converted) != val {
+		iter.reportError("ReadUint8", "int overflow")
+		return
+	}
+	return converted
+}
+
+// ReadUint16 reads a json object as Uint16
+func (iter *Iterator) ReadUint16() (ret uint16) {
+	val := iter.ReadUint64()
+	converted := uint16(val)
+	if uint64(converted) != val {
+		iter.reportError("ReadUint16", "int overflow")
+		return
+	}
+	return converted
+}
+
+// ReadUint64 reads a json object as Uint64
+func (iter *Iterator) ReadUint64() (ret uint64) {
+	c := iter.nextToken()
+	v := hexDigits[c]
+	if v == 0 {
+		return 0 // single zero
+	}
+	if v == 255 {
+		iter.reportError("ReadUint64", "unexpected character")
+		return
+	}
+	for {
+		if ret >= cutoffUint64 {
+			iter.reportError("ReadUint64", "overflow")
+			return
+		}
+		ret = ret*10 + uint64(v)
+		c = iter.readByte()
+		v = hexDigits[c]
+		if v == 255 {
+			iter.unreadByte()
+			break
+		}
+	}
+	return ret
+}
+
+// ReadInt reads a json object as Int
+func (iter *Iterator) ReadInt() (ret int) {
+	val := iter.ReadInt64()
+	converted := int(val)
+	if int64(converted) != val {
+		iter.reportError("ReadInt", "int overflow")
+		return
+	}
+	return converted
+}
+
+// ReadInt8 reads a json object as Int8
+func (iter *Iterator) ReadInt8() (ret int8) {
+	val := iter.ReadInt64()
+	converted := int8(val)
+	if int64(converted) != val {
+		iter.reportError("ReadInt8", "int overflow")
+		return
+	}
+	return converted
+}
+
+// ReadInt16 reads a json object as Int16
+func (iter *Iterator) ReadInt16() (ret int16) {
+	val := iter.ReadInt64()
+	converted := int16(val)
+	if int64(converted) != val {
+		iter.reportError("ReadInt16", "int overflow")
+		return
+	}
+	return converted
+}
+
+func (iter *Iterator) ReadInt32() int32 {
+	c := iter.nextToken()
+	if c == '-' {
+		return -int32(iter.readUint32(int32SafeToMultiply10, iter.readByte()))
+	} else {
+		return int32(iter.readUint32(int32SafeToMultiply10, c))
+	}
+}
+
+func (iter *Iterator) ReadUint32() uint32 {
+	return iter.readUint32(uint32SafeToMultiply10, iter.nextToken())
+}
+
+func (iter *Iterator) readUint32(safeToMultiply10 uint32, c byte) (ret uint32) {
+	ind := intDigits[c]
+	if ind == 0 {
+		return 0 // single zero
+	}
+	if ind == invalidCharForNumber {
+		iter.reportError("readUint32", "unexpected character: " + string([]byte{byte(ind)}))
+		return
+	}
+	value := uint32(ind)
+	for {
+		for i := iter.head; i < iter.tail; i++ {
+			if value > safeToMultiply10 {
+				iter.reportError("readUint32", "overflow")
+				return
+			}
+			ind = intDigits[iter.buf[i]]
+			if ind == invalidCharForNumber {
+				return value
+			}
+			value =  (value << 3) + (value << 1) + uint32(ind)
+		}
+		if (!iter.loadMore()) {
+			return value
+		}
+	}
+}
+
+// ReadInt64 reads a json object as Int64
+func (iter *Iterator) ReadInt64() (ret int64) {
+	c := iter.nextToken()
+	if iter.Error != nil {
+		return
+	}
+
+	/* optional leading minus */
+	if c == '-' {
+		n := iter.ReadUint64()
+		return -int64(n)
+	}
+	iter.unreadByte()
+	n := iter.ReadUint64()
+	return int64(n)
+}