updater: Clean up char* with std::string.

So we can remove a few free()s. And also replace a few pointers with
references.

Change-Id: I4b6332216704f4f9ea4a044b8d4bb7aa42a7ef26
diff --git a/print_sha1.h b/print_sha1.h
new file mode 100644
index 0000000..9e37c5f
--- /dev/null
+++ b/print_sha1.h
@@ -0,0 +1,43 @@
+/*
+ * Copyright (C) 2015 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef RECOVERY_PRINT_SHA1_H
+#define RECOVERY_PRINT_SHA1_H
+
+#include <stdint.h>
+#include <string>
+
+#include "mincrypt/sha.h"
+
+static std::string print_sha1(const uint8_t sha1[SHA_DIGEST_SIZE], size_t len) {
+    const char* hex = "0123456789abcdef";
+    std::string result = "";
+    for (size_t i = 0; i < len; ++i) {
+        result.push_back(hex[(sha1[i]>>4) & 0xf]);
+        result.push_back(hex[sha1[i] & 0xf]);
+    }
+    return result;
+}
+
+static std::string print_sha1(const uint8_t sha1[SHA_DIGEST_SIZE]) {
+    return print_sha1(sha1, SHA_DIGEST_SIZE);
+}
+
+static std::string short_sha1(const uint8_t sha1[SHA_DIGEST_SIZE]) {
+    return print_sha1(sha1, 4);
+}
+
+#endif  // RECOVERY_PRINT_SHA1_H