Generally faster parsing

This commit includes an optimization that increases overall
performance.

The gains are roughly between 20% to 300% depending on the size
of the JSON document. Larger documents will see the greates gains,
particularly when searching for keys that are deeply embedded, or
near the end of the document.

Author: tidwall

README.md

@@ -438,7 +438,7 @@ Benchmarks of GJSON alongside [encoding/json](https://golang.org/pkg/encoding/js
 and [json-iterator](https://github.com/json-iterator/go)
 
 ```
-BenchmarkGJSONGet-10             14919366    240.9 ns/op      0 B/op     0 allocs/op
+BenchmarkGJSONGet-10             17893731    202.1 ns/op      0 B/op     0 allocs/op
 BenchmarkGJSONUnmarshalMap-10     1663548   2157 ns/op     1920 B/op    26 allocs/op
 BenchmarkJSONUnmarshalMap-10       832236   4279 ns/op     2920 B/op    68 allocs/op
 BenchmarkJSONUnmarshalStruct-10   1076475   3219 ns/op      920 B/op    12 allocs/op
@@ -489,6 +489,4 @@ widget.text.onMouseUp
 
 **
 
-Last run: Oct 1, 2024
-
 *These benchmarks were run on a MacBook Pro M1 Max using Go 1.22 and can be found [here](https://github.com/tidwall/gjson-benchmarks).*

gjson.go

@@ -1040,50 +1040,148 @@ func parseObjectPath(path string) (r objectPathResult) {
 	return
 }
 
+var vchars = [256]byte{
+	'"': 2, '{': 3, '(': 3, '[': 3, '}': 1, ')': 1, ']': 1,
+}
+
 func parseSquash(json string, i int) (int, string) {
 	// expects that the lead character is a '[' or '{' or '('
 	// squash the value, ignoring all nested arrays and objects.
 	// the first '[' or '{' or '(' has already been read
 	s := i
 	i++
 	depth := 1
-	for ; i < len(json); i++ {
-		if json[i] >= '"' && json[i] <= '}' {
-			switch json[i] {
-			case '"':
+	var c byte
+	for i < len(json) {
+		for i < len(json)-8 {
+			jslice := json[i : i+8]
+			c = vchars[jslice[0]]
+			if c != 0 {
+				i += 0
+				goto token
+			}
+			c = vchars[jslice[1]]
+			if c != 0 {
+				i += 1
+				goto token
+			}
+			c = vchars[jslice[2]]
+			if c != 0 {
+				i += 2
+				goto token
+			}
+			c = vchars[jslice[3]]
+			if c != 0 {
+				i += 3
+				goto token
+			}
+			c = vchars[jslice[4]]
+			if c != 0 {
+				i += 4
+				goto token
+			}
+			c = vchars[jslice[5]]
+			if c != 0 {
+				i += 5
+				goto token
+			}
+			c = vchars[jslice[6]]
+			if c != 0 {
+				i += 6
+				goto token
+			}
+			c = vchars[jslice[7]]
+			if c != 0 {
+				i += 7
+				goto token
+			}
+			i += 8
+		}
+		c = vchars[json[i]]
+		if c == 0 {
+			i++
+			continue
+		}
+	token:
+		if c == 2 {
+			// '"' string
+			i++
+			s2 := i
+		nextquote:
+			for i < len(json)-8 {
+				jslice := json[i : i+8]
+				if jslice[0] == '"' {
+					i += 0
+					goto strchkesc
+				}
+				if jslice[1] == '"' {
+					i += 1
+					goto strchkesc
+				}
+				if jslice[2] == '"' {
+					i += 2
+					goto strchkesc
+				}
+				if jslice[3] == '"' {
+					i += 3
+					goto strchkesc
+				}
+				if jslice[4] == '"' {
+					i += 4
+					goto strchkesc
+				}
+				if jslice[5] == '"' {
+					i += 5
+					goto strchkesc
+				}
+				if jslice[6] == '"' {
+					i += 6
+					goto strchkesc
+				}
+				if jslice[7] == '"' {
+					i += 7
+					goto strchkesc
+				}
+				i += 8
+			}
+			goto strchkstd
+		strchkesc:
+			if json[i-1] != '\\' {
 				i++
-				s2 := i
-				for ; i < len(json); i++ {
-					if json[i] > '\\' {
-						continue
-					}
-					if json[i] == '"' {
-						// look for an escaped slash
-						if json[i-1] == '\\' {
-							n := 0
-							for j := i - 2; j > s2-1; j-- {
-								if json[j] != '\\' {
-									break
-								}
-								n++
-							}
-							if n%2 == 0 {
-								continue
-							}
+				continue
+			}
+		strchkstd:
+			for i < len(json) {
+				if json[i] > '\\' || json[i] != '"' {
+					i++
+					continue
+				}
+				// look for an escaped slash
+				if json[i-1] == '\\' {
+					n := 0
+					for j := i - 2; j > s2-1; j-- {
+						if json[j] != '\\' {
+							break
 						}
-						break
+						n++
+					}
+					if n%2 == 0 {
+						i++
+						goto nextquote
 					}
 				}
-			case '{', '[', '(':
-				depth++
-			case '}', ']', ')':
-				depth--
-				if depth == 0 {
-					i++
-					return i, json[s:i]
-				}
+				break
+			}
+		} else {
+			// '{', '[', '(', '}', ']', ')'
+			// open close tokens
+			depth += int(c) - 2
+			if depth == 0 {
+				i++
+				return i, json[s:i]
 			}
 		}
+		i++
 	}
 	return i, json[s:]
 }