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utils: Add fsbridge fstream function wrapper
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‎src/fs.cpp‎

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@@ -113,4 +113,106 @@ std::string get_filesystem_error_message(const fs::filesystem_error& e)
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#endif
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}
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#ifdef WIN32
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#ifdef __GLIBCXX__
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// reference: https://github.com/gcc-mirror/gcc/blob/gcc-7_3_0-release/libstdc%2B%2B-v3/include/std/fstream#L270
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static std::string openmodeToStr(std::ios_base::openmode mode)
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{
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switch (mode & ~std::ios_base::ate) {
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case std::ios_base::out:
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case std::ios_base::out | std::ios_base::trunc:
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return "w";
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case std::ios_base::out | std::ios_base::app:
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case std::ios_base::app:
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return "a";
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case std::ios_base::in:
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return "r";
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case std::ios_base::in | std::ios_base::out:
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return "r+";
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case std::ios_base::in | std::ios_base::out | std::ios_base::trunc:
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return "w+";
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case std::ios_base::in | std::ios_base::out | std::ios_base::app:
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case std::ios_base::in | std::ios_base::app:
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return "a+";
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case std::ios_base::out | std::ios_base::binary:
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case std::ios_base::out | std::ios_base::trunc | std::ios_base::binary:
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return "wb";
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case std::ios_base::out | std::ios_base::app | std::ios_base::binary:
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case std::ios_base::app | std::ios_base::binary:
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return "ab";
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case std::ios_base::in | std::ios_base::binary:
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return "rb";
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case std::ios_base::in | std::ios_base::out | std::ios_base::binary:
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return "r+b";
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case std::ios_base::in | std::ios_base::out | std::ios_base::trunc | std::ios_base::binary:
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return "w+b";
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case std::ios_base::in | std::ios_base::out | std::ios_base::app | std::ios_base::binary:
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case std::ios_base::in | std::ios_base::app | std::ios_base::binary:
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return "a+b";
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default:
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return std::string();
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}
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}
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void ifstream::open(const fs::path& p, std::ios_base::openmode mode)
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{
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close();
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m_file = fsbridge::fopen(p, openmodeToStr(mode).c_str());
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if (m_file == nullptr) {
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return;
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}
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m_filebuf = __gnu_cxx::stdio_filebuf<char>(m_file, mode);
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rdbuf(&m_filebuf);
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if (mode & std::ios_base::ate) {
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seekg(0, std::ios_base::end);
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}
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}
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void ifstream::close()
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{
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if (m_file != nullptr) {
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m_filebuf.close();
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fclose(m_file);
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}
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m_file = nullptr;
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}
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void ofstream::open(const fs::path& p, std::ios_base::openmode mode)
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{
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close();
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m_file = fsbridge::fopen(p, openmodeToStr(mode).c_str());
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if (m_file == nullptr) {
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return;
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}
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m_filebuf = __gnu_cxx::stdio_filebuf<char>(m_file, mode);
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rdbuf(&m_filebuf);
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if (mode & std::ios_base::ate) {
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seekp(0, std::ios_base::end);
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}
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}
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void ofstream::close()
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{
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if (m_file != nullptr) {
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m_filebuf.close();
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fclose(m_file);
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}
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m_file = nullptr;
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}
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#else // __GLIBCXX__
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static_assert(sizeof(*fs::path().BOOST_FILESYSTEM_C_STR) == sizeof(wchar_t),
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"Warning: This build is using boost::filesystem ofstream and ifstream "
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"implementations which will fail to open paths containing multibyte "
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"characters. You should delete this static_assert to ignore this warning, "
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"or switch to a different C++ standard library like the Microsoft C++ "
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"Standard Library (where boost uses non-standard extensions to construct "
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"stream objects with wide filenames), or the GNU libstdc++ library (where "
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"a more complicated workaround has been implemented above).");
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#endif // __GLIBCXX__
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#endif // WIN32
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} // fsbridge

‎src/fs.h‎

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Original file line numberDiff line numberDiff line change
@@ -7,6 +7,9 @@
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#include <stdio.h>
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#include <string>
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#if defined WIN32 && defined __GLIBCXX__
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#include <ext/stdio_filebuf.h>
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#endif
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#include <boost/filesystem.hpp>
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#include <boost/filesystem/fstream.hpp>
@@ -39,6 +42,54 @@ namespace fsbridge {
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};
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std::string get_filesystem_error_message(const fs::filesystem_error& e);
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// GNU libstdc++ specific workaround for opening UTF-8 paths on Windows.
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//
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// On Windows, it is only possible to reliably access multibyte file paths through
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// `wchar_t` APIs, not `char` APIs. But because the C++ standard doesn't
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// require ifstream/ofstream `wchar_t` constructors, and the GNU library doesn't
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// provide them (in contrast to the Microsoft C++ library, see
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// https://stackoverflow.com/questions/821873/how-to-open-an-stdfstream-ofstream-or-ifstream-with-a-unicode-filename/822032#822032),
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// Boost is forced to fall back to `char` constructors which may not work properly.
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//
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// Work around this issue by creating stream objects with `_wfopen` in
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// combination with `__gnu_cxx::stdio_filebuf`. This workaround can be removed
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// with an upgrade to C++17, where streams can be constructed directly from
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// `std::filesystem::path` objects.
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#if defined WIN32 && defined __GLIBCXX__
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class ifstream : public std::istream
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{
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public:
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ifstream() = default;
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explicit ifstream(const fs::path& p, std::ios_base::openmode mode = std::ios_base::in) { open(p, mode); }
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~ifstream() { close(); }
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void open(const fs::path& p, std::ios_base::openmode mode = std::ios_base::in);
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bool is_open() { return m_filebuf.is_open(); }
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void close();
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private:
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__gnu_cxx::stdio_filebuf<char> m_filebuf;
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FILE* m_file = nullptr;
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};
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class ofstream : public std::ostream
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{
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public:
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ofstream() = default;
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explicit ofstream(const fs::path& p, std::ios_base::openmode mode = std::ios_base::out) { open(p, mode); }
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~ofstream() { close(); }
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void open(const fs::path& p, std::ios_base::openmode mode = std::ios_base::out);
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bool is_open() { return m_filebuf.is_open(); }
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void close();
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private:
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__gnu_cxx::stdio_filebuf<char> m_filebuf;
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FILE* m_file = nullptr;
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};
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#else // !(WIN32 && __GLIBCXX__)
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typedef fs::ifstream ifstream;
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typedef fs::ofstream ofstream;
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#endif // WIN32 && __GLIBCXX__
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};
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#endif // BITCOIN_FS_H

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