Use protozero for tile decoding

protozero/byteswap.hpp

@@ -0,0 +1,71 @@
+#ifndef PROTOZERO_BYTESWAP_HPP
+#define PROTOZERO_BYTESWAP_HPP
+
+/*****************************************************************************
+
+protozero - Minimalistic protocol buffer decoder and encoder in C++.
+
+This file is from https://github.com/mapbox/protozero where you can find more
+documentation.
+
+*****************************************************************************/
+
+/**
+ * @file byteswap.hpp
+ *
+ * @brief Contains functions to swap bytes in values (for different endianness).
+ */
+
+#include <cstdint>
+#include <cassert>
+
+#include <protozero/config.hpp>
+
+namespace protozero {
+
+/**
+ * Swap N byte value between endianness formats. This template function must
+ * be specialized to actually work.
+ */
+template <int N>
+inline void byteswap(const char* /*data*/, char* /*result*/) {
+    static_assert(N == 1, "Can only swap 4 or 8 byte values");
+}
+
+/**
+ * Swap 4 byte value (int32_t, uint32_t, float) between endianness formats.
+ */
+template <>
+inline void byteswap<4>(const char* data, char* result) {
+#ifdef PROTOZERO_USE_BUILTIN_BSWAP
+    *reinterpret_cast<uint32_t*>(result) = __builtin_bswap32(*reinterpret_cast<const uint32_t*>(data));
+#else
+    result[3] = data[0];
+    result[2] = data[1];
+    result[1] = data[2];
+    result[0] = data[3];
+#endif
+}
+
+/**
+ * Swap 8 byte value (int64_t, uint64_t, double) between endianness formats.
+ */
+template <>
+inline void byteswap<8>(const char* data, char* result) {
+#ifdef PROTOZERO_USE_BUILTIN_BSWAP
+    *reinterpret_cast<uint64_t*>(result) = __builtin_bswap64(*reinterpret_cast<const uint64_t*>(data));
+#else
+    result[7] = data[0];
+    result[6] = data[1];
+    result[5] = data[2];
+    result[4] = data[3];
+    result[3] = data[4];
+    result[2] = data[5];
+    result[1] = data[6];
+    result[0] = data[7];
+#endif
+}
+
+} // end namespace protozero
+
+#endif // PROTOZERO_BYTESWAP_HPP