feat: add jsonparser

jsonparser/bytes.go

@@ -0,0 +1,51 @@
+package jsonparser
+
+const absMinInt64 = 1 << 63
+const maxInt64 = 1<<63 - 1
+const maxUint64 = 1<<64 - 1
+
+// About 2x faster then strconv.ParseInt because it only supports base 10, which is enough for JSON
+func parseInt(bytes []byte) (v int64, ok bool, overflow bool) {
+	if len(bytes) == 0 {
+		return 0, false, false
+	}
+
+	var neg bool = false
+	if bytes[0] == '-' {
+		neg = true
+		bytes = bytes[1:]
+	}
+
+	var n uint64 = 0
+	for idx, c := range bytes {
+		if c < '0' || c > '9' {
+			return 0, false, false
+		}
+		// Deal with invalid data such as "00"
+		if n == 0 && idx != 0 {
+			return 0, false, false
+		}
+		if n > maxUint64/10 {
+			return 0, false, true
+		}
+		n *= 10
+		n1 := n + uint64(c-'0')
+		if n1 < n {
+			return 0, false, true
+		}
+		n = n1
+	}
+
+	if n > maxInt64 {
+		if neg && n == absMinInt64 {
+			return -absMinInt64, true, false
+		}
+		return 0, false, true
+	}
+
+	if neg {
+		return -int64(n), true, false
+	} else {
+		return int64(n), true, false
+	}
+}