Move the ifstream wrapper to common

1 files changed, 70 insertions, 0 deletions

diff --git a/common/alfstream.h b/common/alfstream.h
new file mode 100644
index 00000000..046a6e2a
--- /dev/null
+++ b/common/alfstream.h
@@ -0,0 +1,70 @@
+#ifndef AL_FSTREAM_H
+#define AL_FSTREAM_H
+
+#ifdef _WIN32
+
+#define WIN32_LEAN_AND_MEAN
+#include <windows.h>
+
+#include <array>
+#include <string>
+#include <fstream>
+
+
+namespace al {
+
+// Windows' std::ifstream fails with non-ANSI paths since the standard only
+// specifies names using const char* (or std::string). MSVC has a non-standard
+// extension using const wchar_t* (or std::wstring?) to handle Unicode paths,
+// but not all Windows compilers support it. So we have to make our own istream
+// that accepts UTF-8 paths and forwards to Unicode-aware I/O functions.
+class filebuf final : public std::streambuf {
+    std::array<char_type,4096> mBuffer;
+    HANDLE mFile{INVALID_HANDLE_VALUE};
+
+    int_type underflow() override;
+    pos_type seekoff(off_type offset, std::ios_base::seekdir whence, std::ios_base::openmode mode) override;
+    pos_type seekpos(pos_type pos, std::ios_base::openmode mode) override;
+
+public:
+    filebuf() = default;
+    ~filebuf() override;
+
+    bool open(const wchar_t *filename, std::ios_base::openmode mode);
+    bool open(const char *filename, std::ios_base::openmode mode);
+
+    bool is_open() const noexcept { return mFile != INVALID_HANDLE_VALUE; }
+};
+
+// Inherit from std::istream to use our custom streambuf
+class ifstream final : public std::istream {
+    filebuf mStreamBuf;
+
+public:
+    ifstream(const wchar_t *filename, std::ios_base::openmode mode = std::ios_base::in);
+    ifstream(const std::wstring &filename, std::ios_base::openmode mode = std::ios_base::in)
+      : ifstream(filename.c_str(), mode) { }
+    ifstream(const char *filename, std::ios_base::openmode mode = std::ios_base::in);
+    ifstream(const std::string &filename, std::ios_base::openmode mode = std::ios_base::in)
+      : ifstream(filename.c_str(), mode) { }
+    ~ifstream() override;
+
+    bool is_open() const noexcept { return mStreamBuf.is_open(); }
+};
+
+} // namespace al
+
+#else /* _WIN32 */
+
+#include <fstream>
+
+namespace al {
+
+using filebuf = std::filebuf;
+using ifstream = std::ifstream;
+
+} // namespace al
+
+#endif /* _WIN32 */
+
+#endif /* AL_FSTREAM_H */