Added Path and Paths for getting the original path of a Result

This commit adds a two new functions of the Result type:

- Result.Path:  Returns the original path of a `Result` that was
                returned from a simple `Get` operation.
- Result.Paths: Returns the original paths of a `Result` that was
                returned from a `Get` operation with a query.

See issue #206 for more details

gjson.go

@@ -249,6 +249,7 @@ func (t Result) ForEach(iterator func(key, value Result) bool) {
 	var str string
 	var vesc bool
 	var ok bool
+	var idx int
 	for ; i < len(json); i++ {
 		if keys {
 			if json[i] != '"' {
@@ -265,7 +266,7 @@ func (t Result) ForEach(iterator func(key, value Result) bool) {
 				key.Str = str[1 : len(str)-1]
 			}
 			key.Raw = str
-			key.Index = s
+			key.Index = s + t.Index
 		}
 		for ; i < len(json); i++ {
 			if json[i] <= ' ' || json[i] == ',' || json[i] == ':' {
@@ -278,10 +279,17 @@ func (t Result) ForEach(iterator func(key, value Result) bool) {
 		if !ok {
 			return
 		}
-		value.Index = s
+		if t.Indexes != nil {
+			if idx < len(t.Indexes) {
+				value.Index = t.Indexes[idx]
+			}
+		} else {
+			value.Index = s + t.Index
+		}
 		if !iterator(key, value) {
 			return
 		}
+		idx++
 	}
 }
 
@@ -298,7 +306,15 @@ func (t Result) Map() map[string]Result {
 // Get searches result for the specified path.
 // The result should be a JSON array or object.
 func (t Result) Get(path string) Result {
-	return Get(t.Raw, path)
+	r := Get(t.Raw, path)
+	if r.Indexes != nil {
+		for i := 0; i < len(r.Indexes); i++ {
+			r.Indexes[i] += t.Index
+		}
+	} else {
+		r.Index += t.Index
+	}
+	return r
 }
 
 type arrayOrMapResult struct {
@@ -389,6 +405,8 @@ func (t Result) arrayOrMap(vc byte, valueize bool) (r arrayOrMapResult) {
 			value.Raw, value.Str = tostr(json[i:])
 			value.Num = 0
 		}
+		value.Index = i + t.Index
+
 		i += len(value.Raw) - 1
 
 		if r.vc == '{' {
@@ -415,6 +433,17 @@ func (t Result) arrayOrMap(vc byte, valueize bool) (r arrayOrMapResult) {
 		}
 	}
 end:
+	if t.Indexes != nil {
+		if len(t.Indexes) != len(r.a) {
+			for i := 0; i < len(r.a); i++ {
+				r.a[i].Index = 0
+			}
+		} else {
+			for i := 0; i < len(r.a); i++ {
+				r.a[i].Index = t.Indexes[i]
+			}
+		}
+	}
 	return
 }
 
@@ -1515,7 +1544,6 @@ func parseArray(c *parseContext, i int, path string) (int, bool) {
 							}
 							if idx < len(c.json) && c.json[idx] != ']' {
 								_, res, ok := parseAny(c.json, idx, true)
-								parentIndex := res.Index
 								if ok {
 									res := res.Get(rp.alogkey)
 									if res.Exists() {
@@ -1527,8 +1555,7 @@ func parseArray(c *parseContext, i int, path string) (int, bool) {
 											raw = res.String()
 										}
 										jsons = append(jsons, []byte(raw)...)
-										indexes = append(indexes,
+										indexes = append(indexes, res.Index)
-											res.Index+parentIndex)
 										k++
 									}
 								}
@@ -2974,30 +3001,175 @@ func bytesString(b []byte) string {
 	return *(*string)(unsafe.Pointer(&b))
 }
 
-func GetPath(r Result, json string) (string, bool) {
+func revSquash(json string) string {
-	if len(r.Raw) == 0 || len(json) == 0 {
+	// reverse squash
-		return "", false
+	// expects that the tail character is a ']' or '}' or ')' or '"'
+	// squash the value, ignoring all nested arrays and objects.
+	i := len(json) - 1
+	var depth int
+	if json[i] != '"' {
+		depth++
 	}
-	p := uintptr((*(*stringHeader)(unsafe.Pointer(&(r.Raw)))).data)
+	if json[i] == '}' || json[i] == ']' || json[i] == ')' {
-	s := uintptr((*(*stringHeader)(unsafe.Pointer(&(json)))).data)
+		i--
-	e := s + uintptr(len(json))
-	if p < s || p >= e {
-		return "", false
 	}
-	i := int(p - s)
+	for ; i >= 0; i-- {
-	_ = i
+		switch json[i] {
-	// for ; i >= 0; i-- {
+		case '"':
-	// 	if json[i] <= ' ' {
+			i--
-	// 	} else if json[i] == ':' {
+			for ; i >= 0; i-- {
-	// 		// inside of an object, read the key string
+				if json[i] == '"' {
-	// 	} else if json[i] == ',' {
+					esc := 0
-	// 		// array-value
+					for i > 0 && json[i-1] == '\\' {
-	// 	} else if json[i] == '[' {
+						i--
-	// 		// array-value (end or array)
+						esc++
-	// 	} else {
+					}
-
+					if esc%2 == 1 {
-	// 	}
+						continue
-	// }
+					}
-	// return "", false
+					i += esc
-	return "", false
+					break
+				}
+			}
+			if depth == 0 {
+				if i < 0 {
+					i = 0
+				}
+				return json[i:]
+			}
+		case '}', ']', ')':
+			depth++
+		case '{', '[', '(':
+			depth--
+			if depth == 0 {
+				return json[i:]
+			}
+		}
+	}
+	return json
+}
+
+func (t Result) Paths(json string) []string {
+	if t.Indexes == nil {
+		return nil
+	}
+	paths := make([]string, 0, len(t.Indexes))
+	t.ForEach(func(_, value Result) bool {
+		paths = append(paths, value.Path(json))
+		return true
+	})
+	if len(paths) != len(t.Indexes) {
+		return nil
+	}
+	return paths
+}
+
+// Path returns the original GJSON path for Result.
+// The json param must be the original JSON used when calling Get.
+func (t Result) Path(json string) string {
+	var path []byte
+	var comps []string // raw components
+	i := t.Index - 1
+	if t.Index+len(t.Raw) > len(json) {
+		// JSON cannot safely contain Result.
+		goto fail
+	}
+	if !strings.HasPrefix(json[t.Index:], t.Raw) {
+		// Result is not at the JSON index as exepcted.
+		goto fail
+	}
+	for ; i >= 0; i-- {
+		if json[i] <= ' ' {
+			continue
+		}
+		if json[i] == ':' {
+			// inside of object, get the key
+			for ; i >= 0; i-- {
+				if json[i] != '"' {
+					continue
+				}
+				break
+			}
+			raw := revSquash(json[:i+1])
+			i = i - len(raw)
+			comps = append(comps, raw)
+			// key gotten, now squash the rest
+			raw = revSquash(json[:i+1])
+			i = i - len(raw)
+			i++ // increment the index for next loop step
+		} else if json[i] == '{' {
+			// Encountered an open object. The original result was probably an
+			// object key.
+			goto fail
+		} else if json[i] == ',' || json[i] == '[' {
+			// inside of an array, count the position
+			var arrIdx int
+			if json[i] == ',' {
+				arrIdx++
+				i--
+			}
+			for ; i >= 0; i-- {
+				if json[i] == ':' {
+					// Encountered an unexpected colon. The original result was
+					// probably an object key.
+					goto fail
+				} else if json[i] == ',' {
+					arrIdx++
+				} else if json[i] == '[' {
+					comps = append(comps, strconv.Itoa(arrIdx))
+					break
+				} else if json[i] == ']' || json[i] == '}' || json[i] == '"' {
+					raw := revSquash(json[:i+1])
+					i = i - len(raw) + 1
+				}
+			}
+		}
+	}
+	if len(comps) == 0 {
+		if DisableModifiers {
+			goto fail
+		}
+		return "@this"
+	}
+	for i := len(comps) - 1; i >= 0; i-- {
+		rcomp := Parse(comps[i])
+		if !rcomp.Exists() {
+			goto fail
+		}
+		comp := escapeComp(rcomp.String())
+		path = append(path, '.')
+		path = append(path, comp...)
+	}
+	if len(path) > 0 {
+		path = path[1:]
+	}
+	return string(path)
+fail:
+	return ""
+}
+
+// isSafePathKeyChar returns true if the input character is safe for not
+// needing escaping.
+func isSafePathKeyChar(c byte) bool {
+	return c <= ' ' || c > '~' || c == '_' || c == '-' || c == ':' ||
+		(c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z') ||
+		(c >= '0' && c <= '9')
+}
+
+// escapeComp escaped a path compontent, making it safe for generating a
+// path for later use.
+func escapeComp(comp string) string {
+	for i := 0; i < len(comp); i++ {
+		if !isSafePathKeyChar(comp[i]) {
+			ncomp := []byte(comp[:i])
+			for ; i < len(comp); i++ {
+				if !isSafePathKeyChar(comp[i]) {
+					ncomp = append(ncomp, '\\')
+				}
+				ncomp = append(ncomp, comp[i])
+			}
+			return string(ncomp)
+		}
+	}
+	return comp
 }

gjson_test.go

@@ -108,7 +108,7 @@ func TestEscapePath(t *testing.T) {
 }
 
 // this json block is poorly formed on purpose.
-var basicJSON = `{"age":100, "name":{"here":"B\\\"R"},
+var basicJSON = `  {"age":100, "name":{"here":"B\\\"R"},
 	"noop":{"what is a wren?":"a bird"},
 	"happy":true,"immortal":false,
 	"items":[1,2,3,{"tags":[1,2,3],"points":[[1,2],[3,4]]},4,5,6,7],
@@ -141,9 +141,67 @@ var basicJSON = `{"age":100, "name":{"here":"B\\\"R"},
 			}
     	]
 	},
-	"lastly":{"yay":"final"}
+	"lastly":{"end...ing":"soon","yay":"final"}
 }`
 
+func TestPath(t *testing.T) {
+	json := basicJSON
+	r := Get(json, "@this")
+	path := r.Path(json)
+	if path != "@this" {
+		t.FailNow()
+	}
+
+	r = Parse(json)
+	path = r.Path(json)
+	if path != "@this" {
+		t.FailNow()
+	}
+
+	obj := Parse(json)
+	obj.ForEach(func(key, val Result) bool {
+		kp := key.Path(json)
+		assert(t, kp == "")
+		vp := val.Path(json)
+		if vp == "name" {
+			// there are two "name" keys
+			return true
+		}
+		val2 := obj.Get(vp)
+		assert(t, val2.Raw == val.Raw)
+		return true
+	})
+	arr := obj.Get("loggy.programmers")
+	arr.ForEach(func(_, val Result) bool {
+		vp := val.Path(json)
+		val2 := Get(json, vp)
+		assert(t, val2.Raw == val.Raw)
+		return true
+	})
+	get := func(path string) {
+		r1 := Get(json, path)
+		path2 := r1.Path(json)
+		r2 := Get(json, path2)
+		assert(t, r1.Raw == r2.Raw)
+	}
+	get("age")
+	get("name")
+	get("name.here")
+	get("noop")
+	get("noop.what is a wren?")
+	get("arr.0")
+	get("arr.1")
+	get("arr.2")
+	get("arr.3")
+	get("arr.3.hello")
+	get("arr.4")
+	get("arr.5")
+	get("loggy.programmers.2.email")
+	get("lastly.end\\.\\.\\.ing")
+	get("lastly.yay")
+
+}
+
 func TestTimeResult(t *testing.T) {
 	assert(t, Get(basicJSON, "created").String() ==
 		Get(basicJSON, "created").Time().Format(time.RFC3339Nano))
@@ -1288,10 +1346,10 @@ func TestArrayValues(t *testing.T) {
 	}
 	expect := strings.Join([]string{
 		`gjson.Result{Type:3, Raw:"\"PERSON1\"", Str:"PERSON1", Num:0, ` +
-			`Index:0, Indexes:[]int(nil)}`,
+			`Index:11, Indexes:[]int(nil)}`,
 		`gjson.Result{Type:3, Raw:"\"PERSON2\"", Str:"PERSON2", Num:0, ` +
-			`Index:0, Indexes:[]int(nil)}`,
+			`Index:21, Indexes:[]int(nil)}`,
-		`gjson.Result{Type:2, Raw:"0", Str:"", Num:0, Index:0, Indexes:[]int(nil)}`,
+		`gjson.Result{Type:2, Raw:"0", Str:"", Num:0, Index:31, Indexes:[]int(nil)}`,
 	}, "\n")
 	if output != expect {
 		t.Fatalf("expected '%v', got '%v'", expect, output)
@@ -2292,3 +2350,63 @@ func TestParseIndex(t *testing.T) {
 	assert(t, Parse(` +inf`).Index == 1)
 	assert(t, Parse(` -inf`).Index == 1)
 }
+
+func TestRevSquash(t *testing.T) {
+	assert(t, revSquash(` {}`) == `{}`)
+	assert(t, revSquash(` }`) == ` }`)
+	assert(t, revSquash(` [123]`) == `[123]`)
+	assert(t, revSquash(` ,123,123]`) == ` ,123,123]`)
+	assert(t, revSquash(` hello,[[true,false],[0,1,2,3,5],[123]]`) == `[[true,false],[0,1,2,3,5],[123]]`)
+	assert(t, revSquash(` "hello"`) == `"hello"`)
+	assert(t, revSquash(` "hel\\lo"`) == `"hel\\lo"`)
+	assert(t, revSquash(` "hel\\"lo"`) == `"lo"`)
+	assert(t, revSquash(` "hel\\\"lo"`) == `"hel\\\"lo"`)
+	assert(t, revSquash(`hel\\\"lo"`) == `hel\\\"lo"`)
+	assert(t, revSquash(`\"hel\\\"lo"`) == `\"hel\\\"lo"`)
+	assert(t, revSquash(`\\\"hel\\\"lo"`) == `\\\"hel\\\"lo"`)
+	assert(t, revSquash(`\\\\"hel\\\"lo"`) == `"hel\\\"lo"`)
+	assert(t, revSquash(`hello"`) == `hello"`)
+	json := `true,[0,1,"sadf\"asdf",{"hi":["hello","t\"\"u",{"a":"b"}]},9]`
+	assert(t, revSquash(json) == json[5:])
+	assert(t, revSquash(json[:len(json)-3]) == `{"hi":["hello","t\"\"u",{"a":"b"}]}`)
+	assert(t, revSquash(json[:len(json)-4]) == `["hello","t\"\"u",{"a":"b"}]`)
+	assert(t, revSquash(json[:len(json)-5]) == `{"a":"b"}`)
+	assert(t, revSquash(json[:len(json)-6]) == `"b"`)
+	assert(t, revSquash(json[:len(json)-10]) == `"a"`)
+	assert(t, revSquash(json[:len(json)-15]) == `"t\"\"u"`)
+	assert(t, revSquash(json[:len(json)-24]) == `"hello"`)
+	assert(t, revSquash(json[:len(json)-33]) == `"hi"`)
+	assert(t, revSquash(json[:len(json)-39]) == `"sadf\"asdf"`)
+}
+
+const readmeJSON = `
+{
+  "name": {"first": "Tom", "last": "Anderson"},
+  "age":37,
+  "children": ["Sara","Alex","Jack"],
+  "fav.movie": "Deer Hunter",
+  "friends": [
+    {"first": "Dale", "last": "Murphy", "age": 44, "nets": ["ig", "fb", "tw"]},
+    {"first": "Roger", "last": "Craig", "age": 68, "nets": ["fb", "tw"]},
+    {"first": "Jane", "last": "Murphy", "age": 47, "nets": ["ig", "tw"]}
+  ]
+}
+`
+
+func TestQueryGetPath(t *testing.T) {
+	assert(t, strings.Join(
+		Get(readmeJSON, "friends.#.first").Paths(readmeJSON), " ") ==
+		"friends.0.first friends.1.first friends.2.first")
+	assert(t, strings.Join(
+		Get(readmeJSON, "friends.#(last=Murphy)").Paths(readmeJSON), " ") ==
+		"")
+	assert(t, Get(readmeJSON, "friends.#(last=Murphy)").Path(readmeJSON) ==
+		"friends.0")
+	assert(t, strings.Join(
+		Get(readmeJSON, "friends.#(last=Murphy)#").Paths(readmeJSON), " ") ==
+		"friends.0 friends.2")
+	arr := Get(readmeJSON, "friends.#.first").Array()
+	for i := 0; i < len(arr); i++ {
+		assert(t, arr[i].Path(readmeJSON) == fmt.Sprintf("friends.%d.first", i))
+	}
+}