From 8c53711fbeeab5eab537a794b351c5839de43197 Mon Sep 17 00:00:00 2001
From: Jordan Orelli <jordanorelli@gmail.com>
Date: Sat, 30 Jul 2016 11:36:13 -0400
Subject: [PATCH] check header again

---
 main.go   | 10 +++-------
 parser.go | 24 ++++++++++++++++++++++++
 2 files changed, 27 insertions(+), 7 deletions(-)
 create mode 100644 parser.go

diff --git a/main.go b/main.go
index fd6618b..fb533fb 100644
--- a/main.go
+++ b/main.go
@@ -68,12 +68,8 @@ func main() {
 		bail(1, "input error: %v", err)
 	}
 
-	buf := make([]byte, 8)
-	if _, err := r.Read(buf); err != nil {
-		bail(1, "error reading header: %v", err)
+	p := newParser(r)
+	if _, err := p.checkHeader(); err != nil {
+		bail(1, "parse error: %v", err)
 	}
-	if string(buf) != replay_header {
-		bail(1, "unexpected replay header: %s", string(buf))
-	}
-	fmt.Println(string(buf))
 }
diff --git a/parser.go b/parser.go
new file mode 100644
index 0000000..7788b4e
--- /dev/null
+++ b/parser.go
@@ -0,0 +1,24 @@
+package main
+
+import (
+	"fmt"
+	"io"
+)
+
+type parser struct {
+	// the source of replay bytes. Must NOT be compressed.
+	source io.Reader
+}
+
+func newParser(r io.Reader) *parser {
+	return &parser{source: r}
+}
+
+// checks whether we have an acceptable header at the current reader position.
+func (p *parser) checkHeader() (bool, error) {
+	buf := make([]byte, 8)
+	if _, err := p.source.Read(buf); err != nil {
+		return false, fmt.Errorf("unable to read header bytes: %v", err)
+	}
+	return string(buf) == replay_header, nil
+}