Improve readability of json parser code

json/filter.go

@@ -6,7 +6,6 @@ import (
 )
 
 func Filter(w *bytes.Buffer, b []byte, keys []string) error {
-	s := 0
 	state := expectKey
 	var err error
 
@@ -19,10 +18,29 @@ func Filter(w *bytes.Buffer, b []byte, keys []string) error {
 		}
 	}
 
+	// is an list
 	isList := false
+
+	// list item
 	item := 0
+
+	// field in an object
 	field := 0
+
+	s, e, d := 0, 0, 0
+
+	kf := false
+
 	for i := 0; i < len(b); i++ {
+		if state == expectObjClose || state == expectListClose {
+			switch b[i] {
+			case '{', '[':
+				d++
+			case '}', ']':
+				d--
+			}
+		}
+
 		switch {
 		case state == expectKey:
 			switch b[i] {
@@ -35,7 +53,7 @@ func Filter(w *bytes.Buffer, b []byte, keys []string) error {
 				if item == 0 {
 					err = w.WriteByte('{')
 				} else {
-					_, err = w.WriteString("},{")
+					_, err = w.Write([]byte("},{"))
 				}
 				item++
 				field = 0
@@ -44,36 +62,14 @@ func Filter(w *bytes.Buffer, b []byte, keys []string) error {
 				s = i
 				i++
 			}
+			if err != nil {
+				return err
+			}
 		case state == expectKeyClose && b[i] == '"':
 			state = expectColon
-			i++
+			k := b[(s + 1):i]
-		}
+			_, kf = kmap[sha1.Sum(k)]
 
-		if err != nil {
-			return nil
-		}
-
-		if state != expectColon {
-			continue
-		}
-
-		k := b[(s + 1):(i - 1)]
-		h := sha1.Sum(k)
-		_, kf := kmap[h]
-
-		e := 0
-		d := 0
-		for ; i < len(b); i++ {
-			if state == expectObjClose || state == expectListClose {
-				switch b[i] {
-				case '{', '[':
-					d++
-				case '}', ']':
-					d--
-				}
-			}
-
-			switch {
 		case state == expectColon && b[i] == ':':
 			state = expectValue
 
@@ -115,14 +111,20 @@ func Filter(w *bytes.Buffer, b []byte, keys []string) error {
 		}
 
 		if e != 0 {
-				if kf {
+			state = expectKey
+			cb := b[s:(e + 1)]
+			e = 0
+
+			if !kf {
+				continue
+			}
+
 			if field != 0 {
 				if err := w.WriteByte(','); err != nil {
 					return err
 				}
 			}
 
-					cb := b[s:(e + 1)]
 			sk := 0
 			for i := 0; i < len(cb); i++ {
 				if cb[i] == '\n' || cb[i] == '\t' {
@@ -138,21 +140,20 @@ func Filter(w *bytes.Buffer, b []byte, keys []string) error {
 			} else {
 				_, err = w.Write(cb)
 			}
+
 			if err != nil {
 				return err
 			}
 			field++
 		}
-				state = expectKey
-				break
-			}
-		}
 	}
+
 	if item != 0 {
 		if err := w.WriteByte('}'); err != nil {
 			return err
 		}
 	}
+
 	if isList {
 		if err := w.WriteByte(']'); err != nil {
 			return err

json/get.go

@@ -34,31 +34,15 @@ func Get(b []byte, keys [][]byte) []Field {
 		}
 	}
 
-	l := 10
+	prealloc := 20
-	res := make([]Field, l)
+	res := make([]Field, prealloc)
+
+	s, e, d := 0, 0, 0
+
+	var kf bool
+	var k []byte
 
 	for i := 0; i < len(b); i++ {
-		switch {
-		case state == expectKey && b[i] == '"':
-			state = expectKeyClose
-			s = i + 1
-			continue
-
-		case state == expectKeyClose && b[i] == '"':
-			state = expectColon
-		}
-
-		if state != expectColon {
-			continue
-		}
-
-		k := b[s:i]
-		h := sha1.Sum(k)
-		_, kf := kmap[h]
-
-		e := 0
-		d := 0
-		for ; i < len(b); i++ {
 		if state == expectObjClose || state == expectListClose {
 			switch b[i] {
 			case '{', '[':
@@ -69,6 +53,15 @@ func Get(b []byte, keys [][]byte) []Field {
 		}
 
 		switch {
+		case state == expectKey && b[i] == '"':
+			state = expectKeyClose
+			s = i
+
+		case state == expectKeyClose && b[i] == '"':
+			state = expectColon
+			k = b[(s + 1):i]
+			_, kf = kmap[sha1.Sum(k)]
+
 		case state == expectColon && b[i] == ':':
 			state = expectValue
 
@@ -117,21 +110,17 @@ func Get(b []byte, keys [][]byte) []Field {
 		}
 
 		if e != 0 {
-				e++
-
 			if kf {
 				if len(res) == cap(res) {
-						r := make([]Field, 0, (len(res) + l))
+					r := make([]Field, 0, (len(res) * 2))
 					copy(r, res)
 					res = r
 				}
-
+				res = append(res, Field{k, b[s:(e + 1)]})
-					res = append(res, Field{k, b[s:e]})
 			}
 
 			state = expectKey
-				break
+			e = 0
-			}
 		}
 	}
 

json/replace.go

@@ -11,12 +11,6 @@ func Replace(w *bytes.Buffer, b []byte, from, to []Field) error {
 		return errors.New("'from' and 'to' must be of the same length")
 	}
 
-	state := expectKey
-	ws, we := 0, len(b)
-
-	s := 0
-	fi := -1
-
 	fmap := make(map[[20]byte]int, (len(from) * 2))
 	tmap := make(map[[20]byte]int, (len(from)))
 
@@ -33,36 +27,18 @@ func Replace(w *bytes.Buffer, b []byte, from, to []Field) error {
 		tmap[h2] = i
 	}
 
+	state := expectKey
+	ws, we := 0, len(b)
+
+	s, e, d := 0, 0, 0
+	fi := -1
+
 	for i := 0; i < len(b); i++ {
-		switch {
+		// skip any left padding whitespace
-		case ws == 0 && b[i] == '{' || b[i] == '[':
+		if ws == 0 && (b[i] == '{' || b[i] == '[') {
 			ws = i
-
-		case state == expectKey && b[i] == '"':
-			state = expectKeyClose
-			s = i + 1
-			continue
-
-		case state == expectKeyClose && b[i] == '"':
-			state = expectColon
-
-		default:
-			continue
 		}
 
-		if state != expectColon {
-			continue
-		}
-
-		h1 := sha1.Sum(b[s:i])
-		if n, ok := fmap[h1]; ok {
-			we = s
-			fi = n
-		}
-
-		e := 0
-		d := 0
-		for ; i < len(b); i++ {
 		if state == expectObjClose || state == expectListClose {
 			switch b[i] {
 			case '{', '[':
@@ -73,6 +49,18 @@ func Replace(w *bytes.Buffer, b []byte, from, to []Field) error {
 		}
 
 		switch {
+		case state == expectKey && b[i] == '"':
+			state = expectKeyClose
+			s = i
+
+		case state == expectKeyClose && b[i] == '"':
+			state = expectColon
+			h1 := sha1.Sum(b[(s + 1):i])
+			if n, ok := fmap[h1]; ok {
+				we = s
+				fi = n
+			}
+
 		case state == expectColon && b[i] == ':':
 			state = expectValue
 
@@ -120,13 +108,15 @@ func Replace(w *bytes.Buffer, b []byte, from, to []Field) error {
 
 		if e != 0 {
 			e++
+
 			h2 := sha1.Sum(b[s:e])
+			replace := false
 
 			if n, ok1 := fmap[h2]; ok1 && n == fi {
 				ti, ok2 := tmap[h2]
 
 				if ok2 {
-						if _, err := w.Write(b[ws:we]); err != nil {
+					if _, err := w.Write(b[ws:(we + 1)]); err != nil {
 						return err
 					}
 					if _, err := w.Write(to[ti].Key); err != nil {
@@ -138,19 +128,21 @@ func Replace(w *bytes.Buffer, b []byte, from, to []Field) error {
 					if _, err := w.Write(to[ti].Value); err != nil {
 						return err
 					}
+					replace = true
 					ws = e
 				}
 			}
 
-				if ws != e && (b[s] == '[' || b[s] == '{') {
+			if !replace && (b[s] == '[' || b[s] == '{') {
+				// the i++ in the for loop will add 1 so we account for that (s - 1)
 				i = s - 1
 			}
 
 			state = expectKey
 			we = len(b)
 			fi = -1
-				break
+			e = 0
-			}
+			d = 0
 		}
 	}
 

json/strip.go

@@ -9,41 +9,15 @@ func Strip(b []byte, path []string) []byte {
 	state := expectKey
 
 	kb := make([][]byte, 0, len(path))
-	ki := 0
 	for _, k := range path {
 		kb = append(kb, []byte(k))
 	}
 
+	s, e, d := 0, 0, 0
+	ki := 0
+	pm := false
+
 	for i := 0; i < len(b); i++ {
-		switch {
-		case state == expectKey && b[i] == '"':
-			state = expectKeyClose
-			s = i + 1
-			continue
-
-		case state == expectKeyClose && b[i] == '"':
-			state = expectColon
-		}
-
-		if state != expectColon {
-			continue
-		}
-
-		if ki >= len(kb) {
-			return nil
-		}
-
-		if !bytes.Equal(b[s:i], kb[ki]) {
-			state = expectKey
-			continue
-		}
-
-		ki++
-
-		e := 0
-		d := 0
-		s := 0
-		for ; i < len(b); i++ {
 		if state == expectObjClose || state == expectListClose {
 			switch b[i] {
 			case '{', '[':
@@ -54,6 +28,20 @@ func Strip(b []byte, path []string) []byte {
 		}
 
 		switch {
+		case state == expectKey && b[i] == '"':
+			state = expectKeyClose
+			s = i
+
+		case state == expectKeyClose && b[i] == '"':
+			state = expectColon
+			if ki == len(kb) {
+				ki = 0
+			}
+			pm = bytes.Equal(b[(s+1):i], kb[ki])
+			if pm {
+				ki++
+			}
+
 		case state == expectColon && b[i] == ':':
 			state = expectValue
 
@@ -99,18 +87,18 @@ func Strip(b []byte, path []string) []byte {
 			e = i
 		}
 
-			if e != 0 && (b[s] == '[' || b[s] == '{') {
+		if e != 0 {
-				e++
+			if pm && (b[s] == '[' || b[s] == '{') {
-				b = b[s:e]
+				b = b[s:(e + 1)]
 				i = 0
 
 				if ki == len(kb) {
 					return b
 				}
+			}
 
 			state = expectKey
-				break
+			e = 0
-			}
 		}
 	}