intial release

asar/integrity.go

@@ -0,0 +1,42 @@
+package asar
+
+import (
+	"crypto"
+	"fmt"
+)
+
+const (
+	ALGORITHM  = "SHA256"
+	BLOCK_SIZE = 4 * 1024 * 1024
+)
+
+type FileIntegrity struct {
+	Algorithm string   `json:"algorithm"`
+	Hash      string   `json:"hash"`
+	BlockSize int      `json:"blockSize"`
+	Blocks    []string `json:"blocks"`
+}
+
+func getFileIntegrity(data []byte) *FileIntegrity {
+	blockHashes := []string{}
+	for i := 0; i < len(data); i += BLOCK_SIZE {
+		end := i + BLOCK_SIZE
+		if end > len(data) {
+			end = len(data)
+		}
+		blockHashes = append(blockHashes, hashBlock(data[i:end]))
+	}
+
+	return &FileIntegrity{
+		Algorithm: ALGORITHM,
+		Hash:      hashBlock(data),
+		BlockSize: BLOCK_SIZE,
+		Blocks:    blockHashes,
+	}
+}
+
+func hashBlock(block []byte) string {
+	hash := crypto.SHA256.New()
+	hash.Write(block)
+	return fmt.Sprintf("%x", hash.Sum(nil))
+}