From 02b84e9be9bef96f0b4a76ba3a83e595171add49 Mon Sep 17 00:00:00 2001
From: Tamir Duberstein <tamird@gmail.com>
Date: Tue, 12 Jul 2016 12:26:50 -0400
Subject: [PATCH] Revert "Optimize Patricia tree"
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This reverts commit 3bbbe9847675a1300cce193d9efe458b9f0bdd23.

Fixes race conditions in matchers. Impact on benchmarks:

name               old time/op    new time/op    delta
CMuxConnHTTP1-4       664ns ±19%     754ns ±59%     ~            (p=0.796 n=9+10)
CMuxConnHTTP2-4       745ns ±16%     822ns ±26%     ~            (p=0.252 n=9+10)
CMuxConnHTTP1n2-4     930ns ±28%     926ns ±19%     ~           (p=0.912 n=10+10)
CMuxConnHTTP2n1-4    1.18µs ±52%    0.92µs ±14%     ~           (p=0.469 n=10+10)

name               old alloc/op   new alloc/op   delta
CMuxConnHTTP1-4        256B ± 0%      260B ± 0%   +1.56%        (p=0.000 n=10+10)
CMuxConnHTTP2-4        288B ± 0%      288B ± 0%     ~     (all samples are equal)
CMuxConnHTTP1n2-4      288B ± 0%      290B ± 0%   +0.69%        (p=0.000 n=10+10)
CMuxConnHTTP2n1-4      288B ± 0%      292B ± 0%   +1.39%        (p=0.000 n=10+10)

name               old allocs/op  new allocs/op  delta
CMuxConnHTTP1-4        3.00 ± 0%      5.00 ± 0%  +66.67%        (p=0.000 n=10+10)
CMuxConnHTTP2-4        4.00 ± 0%      4.00 ± 0%     ~     (all samples are equal)
CMuxConnHTTP1n2-4      4.00 ± 0%      6.00 ± 0%  +50.00%        (p=0.000 n=10+10)
CMuxConnHTTP2n1-4      4.00 ± 0%      6.00 ± 0%  +50.00%        (p=0.000 n=10+10)
---
 patricia.go | 88 ++++++++++++++++++++++++++++-------------------------
 1 file changed, 46 insertions(+), 42 deletions(-)

diff --git a/patricia.go b/patricia.go
index ec10514..2bcc3f2 100644
--- a/patricia.go
+++ b/patricia.go
@@ -17,30 +17,18 @@ package cmux
 import (
 	"bytes"
 	"io"
-	"sync"
 )
 
 // patriciaTree is a simple patricia tree that handles []byte instead of string
 // and cannot be changed after instantiation.
 type patriciaTree struct {
 	root *ptNode
-	mu   struct {
-		sync.Mutex
-		buf []byte // preallocated buffer to read data while matching
-	}
 }
 
-func newPatriciaTree(bs ...[]byte) *patriciaTree {
-	max := 0
-	for _, b := range bs {
-		if max < len(b) {
-			max = len(b)
-		}
+func newPatriciaTree(b ...[]byte) *patriciaTree {
+	return &patriciaTree{
+		root: newNode(b),
 	}
-	t := patriciaTree{root: newNode(bs)}
-	t.mu.buf = make([]byte, max+1)
-
-	return &t
 }
 
 func newPatriciaTreeString(strs ...string) *patriciaTree {
@@ -48,23 +36,17 @@ func newPatriciaTreeString(strs ...string) *patriciaTree {
 	for i, s := range strs {
 		b[i] = []byte(s)
 	}
-	return newPatriciaTree(b...)
+	return &patriciaTree{
+		root: newNode(b),
+	}
 }
 
 func (t *patriciaTree) matchPrefix(r io.Reader) bool {
-	t.mu.Lock()
-	defer t.mu.Unlock()
-
-	n, _ := io.ReadFull(r, t.mu.buf)
-	return t.root.match(t.mu.buf[:n], true)
+	return t.root.match(r, true)
 }
 
 func (t *patriciaTree) match(r io.Reader) bool {
-	t.mu.Lock()
-	defer t.mu.Unlock()
-
-	n, _ := io.ReadFull(r, t.mu.buf)
-	return t.root.match(t.mu.buf[:n], false)
+	return t.root.match(r, false)
 }
 
 type ptNode struct {
@@ -154,30 +136,52 @@ func splitPrefix(bss [][]byte) (prefix []byte, rest [][]byte) {
 	return prefix, rest
 }
 
-func (n *ptNode) match(b []byte, prefix bool) bool {
-	l := len(n.prefix)
-	if l > 0 {
-		if l > len(b) {
-			l = len(b)
+func readBytes(r io.Reader, n int) (b []byte, err error) {
+	b = make([]byte, n)
+	o := 0
+	for o < n {
+		nr, err := r.Read(b[o:])
+		if err != nil && err != io.EOF {
+			return b, err
 		}
-		if !bytes.Equal(b[:l], n.prefix) {
+
+		o += nr
+
+		if err == io.EOF {
+			break
+		}
+	}
+	return b[:o], nil
+}
+
+func (n *ptNode) match(r io.Reader, prefix bool) bool {
+	if l := len(n.prefix); l > 0 {
+		b, err := readBytes(r, l)
+		if err != nil || len(b) != l || !bytes.Equal(b, n.prefix) {
 			return false
 		}
 	}
 
-	if n.terminal && (prefix || len(n.prefix) == len(b)) {
+	if prefix && n.terminal {
 		return true
 	}
 
-	nextN, ok := n.next[b[l]]
-	if !ok {
-		return false
+	b := make([]byte, 1)
+	for {
+		nr, err := r.Read(b)
+		if nr != 0 {
+			break
+		}
+
+		if err == io.EOF {
+			return n.terminal
+		}
+
+		if err != nil {
+			return false
+		}
 	}
 
-	if l == len(b) {
-		b = b[l:l]
-	} else {
-		b = b[l+1:]
-	}
-	return nextN.match(b, prefix)
+	nextN, ok := n.next[b[0]]
+	return ok && nextN.match(r, prefix)
 }