From d90024b17b59ee9b3e1668aa5ef13e45e0bad782 Mon Sep 17 00:00:00 2001
From: Tw <tw19881113@gmail.com>
Date: Wed, 11 Feb 2015 14:59:40 +0800
Subject: [PATCH] Delete unnecessary copy of input when enable fenced code
 extension

Copy of input waste time and memory.

Signed-off-by: Tw <tw19881113@gmail.com>
---
 block.go    | 29 ++++++++++++++++++++---------
 markdown.go |  5 +----
 2 files changed, 21 insertions(+), 13 deletions(-)

diff --git a/block.go b/block.go
index 9b00320..59c6d28 100644
--- a/block.go
+++ b/block.go
@@ -556,9 +556,12 @@ func (p *parser) isFencedCode(data []byte, syntax **string, oldmarker string) (s
 	skip = 0
 
 	// skip up to three spaces
-	for i < 3 && data[i] == ' ' {
+	for i < len(data) && i < 3 && data[i] == ' ' {
 		i++
 	}
+	if i >= len(data) {
+		return
+	}
 
 	// check for the marker characters: ~ or `
 	if data[i] != '~' && data[i] != '`' {
@@ -568,11 +571,15 @@ func (p *parser) isFencedCode(data []byte, syntax **string, oldmarker string) (s
 	c := data[i]
 
 	// the whole line must be the same char or whitespace
-	for data[i] == c {
+	for i < len(data) && data[i] == c {
 		size++
 		i++
 	}
 
+	if i >= len(data) {
+		return
+	}
+
 	// the marker char must occur at least 3 times
 	if size < 3 {
 		return
@@ -587,22 +594,26 @@ func (p *parser) isFencedCode(data []byte, syntax **string, oldmarker string) (s
 	if syntax != nil {
 		syn := 0
 
-		for data[i] == ' ' {
+		for i < len(data) && data[i] == ' ' {
 			i++
 		}
 
+		if i >= len(data) {
+			return
+		}
+
 		syntaxStart := i
 
 		if data[i] == '{' {
 			i++
 			syntaxStart++
 
-			for data[i] != '}' && data[i] != '\n' {
+			for i < len(data) && data[i] != '}' && data[i] != '\n' {
 				syn++
 				i++
 			}
 
-			if data[i] != '}' {
+			if i >= len(data) || data[i] != '}' {
 				return
 			}
 
@@ -619,7 +630,7 @@ func (p *parser) isFencedCode(data []byte, syntax **string, oldmarker string) (s
 
 			i++
 		} else {
-			for !isspace(data[i]) {
+			for i < len(data) && !isspace(data[i]) {
 				syn++
 				i++
 			}
@@ -629,10 +640,10 @@ func (p *parser) isFencedCode(data []byte, syntax **string, oldmarker string) (s
 		*syntax = &language
 	}
 
-	for data[i] == ' ' {
+	for i < len(data) && data[i] == ' ' {
 		i++
 	}
-	if data[i] != '\n' {
+	if i >= len(data) || data[i] != '\n' {
 		return
 	}
 
@@ -661,7 +672,7 @@ func (p *parser) fencedCode(out *bytes.Buffer, data []byte, doRender bool) int {
 
 		// copy the current line
 		end := beg
-		for data[end] != '\n' {
+		for end < len(data) && data[end] != '\n' {
 			end++
 		}
 		end++
diff --git a/markdown.go b/markdown.go
index d07e37c..4315488 100644
--- a/markdown.go
+++ b/markdown.go
@@ -327,10 +327,7 @@ func firstPass(p *parser, input []byte) []byte {
 			if p.flags&EXTENSION_FENCED_CODE != 0 {
 				// when last line was none blank and a fenced code block comes after
 				if beg >= lastFencedCodeBlockEnd {
-					// tmp var so we don't modify beyond bounds of `input`
-					var tmp = make([]byte, len(input[beg:]), len(input[beg:])+1)
-					copy(tmp, input[beg:])
-					if i := p.fencedCode(&out, append(tmp, '\n'), false); i > 0 {
+					if i := p.fencedCode(&out, input[beg:], false); i > 0 {
 						if !lastLineWasBlank {
 							out.WriteByte('\n') // need to inject additional linebreak
 						}