libslic3r utils: Add a Windows-proof file move function

xs/src/libslic3r/Utils.hpp

@@ -44,6 +44,11 @@ extern local_encoded_string encode_path(const char *src);
 extern std::string decode_path(const char *src);
 extern std::string normalize_utf8_nfc(const char *src);
 
+// Safely rename a file even if the target exists.
+// On Windows, the file explorer (or anti-virus or whatever else) often locks the file
+// for a short while, so the file may not be movable. Retry while we see recoverable errors.
+extern int rename_file(const std::string &from, const std::string &to);
+
 // File path / name / extension splitting utilities, working with UTF-8,
 // to be published to Perl.
 namespace PerlUtils {

xs/src/libslic3r/utils.cpp

@@ -23,6 +23,7 @@
 #include <boost/nowide/fstream.hpp>
 #include <boost/nowide/integration/filesystem.hpp>
 #include <boost/nowide/convert.hpp>
+#include <boost/nowide/cstdio.hpp>
 
 #include <tbb/task_scheduler_init.h>
 
@@ -149,6 +150,68 @@ const std::string& data_dir()
     return g_data_dir;
 }
 
+// borrowed from LLVM lib/Support/Windows/Path.inc
+int rename_file(const std::string &from, const std::string &to)
+{
+    int ec = 0;
+
+#ifdef _WIN32
+
+    // Convert to utf-16.
+    std::wstring wide_from = boost::nowide::widen(from);
+    std::wstring wide_to   = boost::nowide::widen(to);
+
+    // Retry while we see recoverable errors.
+    // System scanners (eg. indexer) might open the source file when it is written
+    // and closed.
+    bool TryReplace = true;
+
+    // This loop may take more than 2000 x 1ms to finish.
+    for (int i = 0; i < 2000; ++ i) {
+        if (i > 0)
+            // Sleep 1ms
+            ::Sleep(1);
+        if (TryReplace) {
+            // Try ReplaceFile first, as it is able to associate a new data stream
+            // with the destination even if the destination file is currently open.
+            if (::ReplaceFileW(wide_to.data(), wide_from.data(), NULL, 0, NULL, NULL))
+                return 0;
+            DWORD ReplaceError = ::GetLastError();
+            ec = -1; // ReplaceError
+            // If ReplaceFileW returned ERROR_UNABLE_TO_MOVE_REPLACEMENT or
+            // ERROR_UNABLE_TO_MOVE_REPLACEMENT_2, retry but only use MoveFileExW().
+            if (ReplaceError == ERROR_UNABLE_TO_MOVE_REPLACEMENT ||
+                ReplaceError == ERROR_UNABLE_TO_MOVE_REPLACEMENT_2) {
+                TryReplace = false;
+                continue;
+            }
+            // If ReplaceFileW returned ERROR_UNABLE_TO_REMOVE_REPLACED, retry
+            // using ReplaceFileW().
+            if (ReplaceError == ERROR_UNABLE_TO_REMOVE_REPLACED)
+                continue;
+            // We get ERROR_FILE_NOT_FOUND if the destination file is missing.
+            // MoveFileEx can handle this case.
+            if (ReplaceError != ERROR_ACCESS_DENIED && ReplaceError != ERROR_FILE_NOT_FOUND && ReplaceError != ERROR_SHARING_VIOLATION)
+                break;
+        }
+        if (::MoveFileExW(wide_from.c_str(), wide_to.c_str(), MOVEFILE_COPY_ALLOWED | MOVEFILE_REPLACE_EXISTING))
+            return 0;
+        DWORD MoveError = ::GetLastError();
+        ec = -1; // MoveError
+        if (MoveError != ERROR_ACCESS_DENIED && MoveError != ERROR_SHARING_VIOLATION)
+            break;
+    }
+
+#else
+
+    boost::nowide::remove(to.c_str());
+    ec = boost::nowide::rename(from.c_str(), to.c_str());
+
+#endif
+
+    return ec;
+}
+
 } // namespace Slic3r
 
 #include <xsinit.h>