searchKeys now accepts escaped JSON keys

The keys parameter passed in to searchKeys are interpreted literally, however,
and are not unescaped. If search key may contain escape sequences that should
be unescaped, the calling code must handle this.

Author: daboyuka

parser.go

@@ -116,6 +116,8 @@ func searchKeys(data []byte, keys ...string) int {
 	ln := len(data)
 	lk := len(keys)
 
+	var stackbuf [unescapeStackBufSize]byte // stack-allocated array for allocation-free unescaping of small strings
+
 	for i < ln {
 		switch data[i] {
 		case '"':
@@ -138,14 +140,22 @@ func searchKeys(data []byte, keys ...string) int {
 
 			// if string is a Key, and key level match
 			if data[i] == ':' {
-				key := unsafeBytesToString(data[keyBegin:keyEnd])
-
-				if keyLevel == level-1 && // If key nesting level match current object nested level
-					keys[level-1] == key {
-					keyLevel++
-					// If we found all keys in path
-					if keyLevel == lk {
-						return i + 1
+				key := data[keyBegin:keyEnd]
+
+				// for unescape: if there are no escape sequences, this is cheap; if there are, it is a
+				// bit more expensive, but causes no allocations unless len(key) > unescapeStackBufSize
+				if keyUnesc, err := unescape(key, stackbuf[:]); err != nil {
+					return -1
+				} else {
+					keyUnescStr := unsafeBytesToString(keyUnesc)
+
+					if keyLevel == level-1 && // If key nesting level match current object nested level
+						keys[level-1] == keyUnescStr {
+						keyLevel++
+						// If we found all keys in path
+						if keyLevel == lk {
+							return i + 1
+						}
 					}
 				}
 			} else {

parser_test.go

@@ -158,6 +158,30 @@ var getTests = []Test{
 		isFound: true,
 		data:    `3`,
 	},
+
+	// Escaped key tests
+	Test{
+		desc:    `key with simple escape`,
+		json:    `{"a\\b":1}`,
+		path:    []string{"a\\b"},
+		isFound: true,
+		data:    `1`,
+	},
+	Test{
+		desc:    `key with Unicode escape`,
+		json:    `{"a\u00B0b":1}`,
+		path:    []string{"a\u00B0b"},
+		isFound: true,
+		data:    `1`,
+	},
+	Test{
+		desc:    `key with complex escape`,
+		json:    `{"a\uD83D\uDE03b":1}`,
+		path:    []string{"a\U0001F603b"},
+		isFound: true,
+		data:    `1`,
+	},
+
 	Test{ // This test returns a match instead of a parse error, as checking for the malformed JSON would reduce performance
 		desc:    `malformed with trailing whitespace`,
 		json:    `{"a":1 `,
@@ -268,6 +292,7 @@ var getTests = []Test{
 		path:  []string{"a"},
 		isErr: true,
 	},
+
 	Test{ // This test returns not found instead of a parse error, as checking for the malformed JSON would reduce performance
 		desc:  "malformed key (followed by comma followed by colon)",
 		json:  `{"a",:1}`,