From ff16782fb7421d1af8120d5f519bc1b4e6453e71 Mon Sep 17 00:00:00 2001
From: Jochen Topf <jochen@topf.org>
Date: Mon, 23 Jul 2018 16:36:34 +0200
Subject: [PATCH] Rewrite code to be byte-order independent.

Fixes #263.
---
 include/osmium/io/detail/pbf_input_format.hpp  | 15 ++++++++-------
 include/osmium/io/detail/pbf_output_format.hpp | 14 ++++++++------
 2 files changed, 16 insertions(+), 13 deletions(-)

diff --git a/include/osmium/io/detail/pbf_input_format.hpp b/include/osmium/io/detail/pbf_input_format.hpp
index 0f1ca22df..e146dd776 100644
--- a/include/osmium/io/detail/pbf_input_format.hpp
+++ b/include/osmium/io/detail/pbf_input_format.hpp
@@ -44,7 +44,6 @@ DEALINGS IN THE SOFTWARE.
 #include <osmium/thread/util.hpp>
 #include <osmium/util/config.hpp>
 
-#include <protozero/byteswap.hpp>
 #include <protozero/pbf_message.hpp>
 #include <protozero/types.hpp>
 
@@ -97,18 +96,20 @@ namespace osmium {
                  * the length of the following BlobHeader.
                  */
                 uint32_t read_blob_header_size_from_file() {
-                    uint32_t size_in_network_byte_order;
+                    uint32_t size;
 
                     try {
-                        const std::string input_data{read_from_input_queue(sizeof(size_in_network_byte_order))};
-                        size_in_network_byte_order = *reinterpret_cast<const uint32_t*>(input_data.data());
+                        // size is encoded in network byte order
+                        const std::string input_data{read_from_input_queue(sizeof(size))};
+                        const char* d = input_data.data();
+                        size = (static_cast<uint32_t>(d[3])) |
+                               (static_cast<uint32_t>(d[2]) << 8u) |
+                               (static_cast<uint32_t>(d[1]) << 16u) |
+                               (static_cast<uint32_t>(d[0]) << 24u);
                     } catch (const osmium::pbf_error&) {
                         return 0; // EOF
                     }
 
-                    uint32_t size = size_in_network_byte_order;
-                    ::protozero::byteswap_inplace(&size);
-
                     if (size > static_cast<uint32_t>(max_blob_header_size)) {
                         throw osmium::pbf_error{"invalid BlobHeader size (> max_blob_header_size)"};
                     }
diff --git a/include/osmium/io/detail/pbf_output_format.hpp b/include/osmium/io/detail/pbf_output_format.hpp
index 4239667a1..4af7134a3 100644
--- a/include/osmium/io/detail/pbf_output_format.hpp
+++ b/include/osmium/io/detail/pbf_output_format.hpp
@@ -62,7 +62,6 @@ DEALINGS IN THE SOFTWARE.
 #include <osmium/util/misc.hpp>
 #include <osmium/visitor.hpp>
 
-#include <protozero/byteswap.hpp>
 #include <protozero/pbf_builder.hpp>
 #include <protozero/pbf_writer.hpp>
 #include <protozero/types.hpp>
@@ -193,13 +192,16 @@ namespace osmium {
                     // data plus a few header bytes (https://zlib.net/zlib_tech.html).
                     pbf_blob_header.add_int32(FileFormat::BlobHeader::required_int32_datasize, static_cast<int32_t>(blob_data.size()));
 
-                    auto sz = static_cast<uint32_t>(blob_header_data.size());
-                    ::protozero::byteswap_inplace(&sz);
+                    const auto size = static_cast<uint32_t>(blob_header_data.size());
 
-                    // write to output: the 4-byte BlobHeader-Size followed by the BlobHeader followed by the Blob
+                    // write to output: the 4-byte BlobHeader size in network
+                    // byte order followed by the BlobHeader followed by the Blob
                     std::string output;
-                    output.reserve(sizeof(sz) + blob_header_data.size() + blob_data.size());
-                    output.append(reinterpret_cast<const char*>(&sz), sizeof(sz));
+                    output.reserve(4 + blob_header_data.size() + blob_data.size());
+                    output += static_cast<char>((size >> 24u) & 0xffu);
+                    output += static_cast<char>((size >> 16u) & 0xffu);
+                    output += static_cast<char>((size >>  8u) & 0xffu);
+                    output += static_cast<char>( size         & 0xffu);
                     output.append(blob_header_data);
                     output.append(blob_data);