libbase: hex.h adds HexString
This requires a few lines of code to implement in C++, but the
'standard' implementation also triggers ubsan implicit-conversion, so it
can be more involved in some places. It's really common to convert
binary data into hex strings.
Future considerations:
- adding the reverse direction (parse binary data into uint8_t*)
- adding templated versions, which can be useful while debugging certain
issues (though, perhaps a bit overkill)
template <typename T>
std::string HexObject(const T& t) {
return HexString(reinterpret_cast<void*>(&t), sizeof(T));
}
Bug: N/A
Test: libbase_test
Change-Id: I93d3708a9740a0682c8cbd91f067e2dfeab35380
diff --git a/hex.cpp b/hex.cpp
new file mode 100644
index 0000000..a4b7715
--- /dev/null
+++ b/hex.cpp
@@ -0,0 +1,42 @@
+/*
+ * Copyright (C) 2021 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.
+ */
+
+#include "android-base/hex.h"
+
+#include "android-base/logging.h"
+
+namespace android {
+namespace base {
+
+std::string HexString(const void* bytes, size_t len) {
+ CHECK(bytes != nullptr || len == 0) << bytes << " " << len;
+
+ // b/132916539: Doing this the 'C way', std::setfill triggers ubsan implicit conversion
+ const uint8_t* bytes8 = static_cast<const uint8_t*>(bytes);
+ const char chars[] = "0123456789abcdef";
+ std::string result;
+ result.resize(len * 2);
+
+ for (size_t i = 0; i < len; i++) {
+ result[2 * i] = chars[bytes8[i] >> 4];
+ result[2 * i + 1] = chars[bytes8[i] & 0xf];
+ }
+
+ return result;
+}
+
+} // namespace base
+} // namespace android