From 9cb3bbcb0728ee78f8432052ad7bbc2506e9641f Mon Sep 17 00:00:00 2001
From: Lion <chenxin619315@gmail.com>
Date: Sat, 18 Jun 2022 19:36:45 +0800
Subject: [PATCH] add load header func

---
 binding/golang/xdb/util.go      | 30 ++++++++++++++++++++++++++++++
 binding/golang/xdb/util_test.go | 11 +++++++++++
 2 files changed, 41 insertions(+)

diff --git a/binding/golang/xdb/util.go b/binding/golang/xdb/util.go
index ddc8688..8cde3df 100644
--- a/binding/golang/xdb/util.go
+++ b/binding/golang/xdb/util.go
@@ -89,6 +89,36 @@ func LoadVectorIndexFromFile(dbFile string) ([][]*VectorIndexBlock, error) {
 	return LoadVectorIndex(handle)
 }
 
+// LoadHeader load the header info from the specified handle
+func LoadHeader(handle *os.File) ([]byte, error) {
+	_, err := handle.Seek(0, 0)
+	if err != nil {
+		return nil, fmt.Errorf("seek to the header: %w", err)
+	}
+
+	var buff = make([]byte, HeaderInfoLength)
+	rLen, err := handle.Read(buff)
+	if err != nil {
+		return nil, err
+	}
+
+	if rLen != len(buff) {
+		return nil, fmt.Errorf("incomplete read: readed bytes should be %d", len(buff))
+	}
+
+	return buff, nil
+}
+
+// LoadHeaderFromFile load header info from the specified db file path
+func LoadHeaderFromFile(dbFile string) ([]byte, error) {
+	handle, err := os.OpenFile(dbFile, os.O_RDONLY, 0600)
+	if err != nil {
+		return nil, fmt.Errorf("open xdb file `%s`: %w", dbFile, err)
+	}
+
+	return LoadHeader(handle)
+}
+
 // LoadContent load the whole xdb content from the specified file handle
 func LoadContent(handle *os.File) ([]byte, error) {
 	// get file size
diff --git a/binding/golang/xdb/util_test.go b/binding/golang/xdb/util_test.go
index beb1553..a8ea453 100644
--- a/binding/golang/xdb/util_test.go
+++ b/binding/golang/xdb/util_test.go
@@ -23,6 +23,17 @@ func TestLoadContent(t *testing.T) {
 	buff, err := LoadContentFromFile("../../../data/ip2region.xdb")
 	if err != nil {
 		fmt.Printf("failed to load xdb content: %s\n", err)
+		return
+	}
+
+	fmt.Printf("buff length: %d\n", len(buff))
+}
+
+func TestLoadHeader(t *testing.T) {
+	buff, err := LoadHeaderFromFile("../../../data/ip2region.xdb")
+	if err != nil {
+		fmt.Printf("failed to load xdb header info: %s\n", err)
+		return
 	}
 
 	fmt.Printf("buff length: %d\n", len(buff))