[Support] Add functions that operate on native file handles on Windows.

Windows' CRT has a limit of 512 open file descriptors, and fds which are
generated by converting a HANDLE via _get_osfhandle count towards this
limit as well.

Regardless, often you find yourself marshalling back and forth between
native HANDLE objects and fds anyway. If we know from the getgo that
we're going to need to work directly with the handle, we can cut out the
marshalling layer while also not contributing to filling up the CRT's
very limited handle table.

On Unix these functions just delegate directly to the existing set of
functions since an fd *is* the native file type. It would be nice, very
long term, if we could convert most uses of fds to file_t.

Differential Revision: https://reviews.llvm.org/D47688

llvm-svn: 333945

1 files changed, 49 insertions, 30 deletions

diff --git a/llvm/lib/Support/Windows/Path.inc b/llvm/lib/Support/Windows/Path.inc
index 0d1631d6bb0..3f6aa114505 100644
--- a/llvm/lib/Support/Windows/Path.inc
+++ b/llvm/lib/Support/Windows/Path.inc
@@ -123,6 +123,8 @@ std::error_code widenPath(const Twine &Path8,
 
 namespace fs {
 
+const file_t kInvalidFile = INVALID_HANDLE_VALUE;
+
 std::string getMainExecutable(const char *argv0, void *MainExecAddr) {
   SmallVector<wchar_t, MAX_PATH> PathName;
   DWORD Size = ::GetModuleFileNameW(NULL, PathName.data(), PathName.capacity());
@@ -1051,13 +1053,32 @@ static std::error_code directoryRealPath(const Twine &Name,
   return EC;
 }
 
+static std::error_code nativeFileToFd(Expected<HANDLE> H, int &ResultFD,
+                                      int OpenFlags) {
+  ResultFD = -1;
+  if (!H)
+    return errorToErrorCode(H.takeError());
+
+  ResultFD = ::_open_osfhandle(intptr_t(*H), OpenFlags);
+  if (ResultFD == -1) {
+    ::CloseHandle(*H);
+    return mapWindowsError(ERROR_INVALID_HANDLE);
+  }
+  return std::error_code();
+}
+
 std::error_code openFileForRead(const Twine &Name, int &ResultFD,
                                 SmallVectorImpl<char> *RealPath) {
-  ResultFD = -1;
+  Expected<HANDLE> NativeFile = openNativeFileForRead(Name, RealPath);
+  return nativeFileToFd(std::move(NativeFile), ResultFD, 0);
+}
+
+Expected<file_t> openNativeFileForRead(const Twine &Name,
+                                       SmallVectorImpl<char> *RealPath) {
   SmallVector<wchar_t, 128> PathUTF16;
 
   if (std::error_code EC = widenPath(Name, PathUTF16))
-    return EC;
+    return errorCodeToError(EC);
 
   HANDLE H =
       ::CreateFileW(PathUTF16.begin(), GENERIC_READ,
@@ -1070,36 +1091,42 @@ std::error_code openFileForRead(const Twine &Name, int &ResultFD,
     // This only runs if we failed to open the file, so there is probably
     // no performances issues.
     if (LastError != ERROR_ACCESS_DENIED)
-      return EC;
+      return errorCodeToError(EC);
     if (is_directory(Name))
-      return make_error_code(errc::is_a_directory);
-    return EC;
-  }
-
-  ResultFD = ::_open_osfhandle(intptr_t(H), 0);
-  if (ResultFD == -1) {
-    ::CloseHandle(H);
-    return mapWindowsError(ERROR_INVALID_HANDLE);
+      return errorCodeToError(make_error_code(errc::is_a_directory));
+    return errorCodeToError(EC);
   }
 
   // Fetch the real name of the file, if the user asked
   if (RealPath)
     realPathFromHandle(H, *RealPath);
 
-  return std::error_code();
+  return H;
 }
 
 std::error_code openFileForWrite(const Twine &Name, int &ResultFD,
                             sys::fs::OpenFlags Flags, unsigned Mode) {
+  int OpenFlags = 0;
+  if (Flags & F_Append)
+    OpenFlags |= _O_APPEND;
+
+  if (Flags & F_Text)
+    OpenFlags |= _O_TEXT;
+
+  Expected<HANDLE> NativeFile = openNativeFileForWrite(Name, Flags, Mode);
+  return nativeFileToFd(std::move(NativeFile), ResultFD, OpenFlags);
+}
+
+Expected<file_t> openNativeFileForWrite(const Twine &Name, OpenFlags Flags,
+                                        unsigned Mode) {
   // Verify that we don't have both "append" and "excl".
   assert((!(Flags & sys::fs::F_Excl) || !(Flags & sys::fs::F_Append)) &&
          "Cannot specify both 'excl' and 'append' file creation flags!");
 
-  ResultFD = -1;
   SmallVector<wchar_t, 128> PathUTF16;
 
   if (std::error_code EC = widenPath(Name, PathUTF16))
-    return EC;
+    return errorCodeToError(EC);
 
   DWORD CreationDisposition;
   if (Flags & F_Excl)
@@ -1130,26 +1157,18 @@ std::error_code openFileForWrite(const Twine &Name, int &ResultFD,
     // This only runs if we failed to open the file, so there is probably
     // no performances issues.
     if (LastError != ERROR_ACCESS_DENIED)
-      return EC;
+      return errorCodeToError(EC);
     if (is_directory(Name))
-      return make_error_code(errc::is_a_directory);
-    return EC;
+      return errorCodeToError(make_error_code(errc::is_a_directory));
+    return errorCodeToError(EC);
   }
 
-  int OpenFlags = 0;
-  if (Flags & F_Append)
-    OpenFlags |= _O_APPEND;
-
-  if (Flags & F_Text)
-    OpenFlags |= _O_TEXT;
-
-  ResultFD = ::_open_osfhandle(intptr_t(H), OpenFlags);
-  if (ResultFD == -1) {
-    ::CloseHandle(H);
-    return mapWindowsError(ERROR_INVALID_HANDLE);
-  }
+  return H;
+}
 
-  return std::error_code();
+void closeFile(file_t &F) {
+  ::CloseHandle(F);
+  F = kInvalidFile;
 }
 
 std::error_code remove_directories(const Twine &path, bool IgnoreErrors) {