2 files changed, 43 insertions, 0 deletions
diff --git a/lib/Support/Windows/PathV2.inc b/lib/Support/Windows/PathV2.inc
index c618dbf520..f4629a15c4 100644
--- a/lib/Support/Windows/PathV2.inc
+++ b/lib/Support/Windows/PathV2.inc
@@ -616,6 +616,48 @@ retry_create_file:
   return success;
 }
 
+error_code get_magic(const Twine &path, uint32_t len,
+                     SmallVectorImpl<char> &result) {
+  SmallString<128> path_storage;
+  SmallVector<wchar_t, 128> path_utf16;
+  result.set_size(0);
+
+  // Convert path to UTF-16.
+  if (error_code ec = UTF8ToUTF16(path.toStringRef(path_storage),
+                                  path_utf16))
+    return ec;
+
+  // Open file.
+  HANDLE file = ::CreateFileW(c_str(path_utf16),
+                              GENERIC_READ,
+                              FILE_SHARE_READ,
+                              NULL,
+                              OPEN_EXISTING,
+                              FILE_ATTRIBUTE_READONLY,
+                              NULL);
+  if (file == INVALID_HANDLE_VALUE)
+    return windows_error(::GetLastError());
+
+  // Allocate buffer.
+  result.reserve(len);
+
+  // Get magic!
+  DWORD bytes_read = 0;
+  BOOL read_success = ::ReadFile(file, result.data(), len, &bytes_read, NULL);
+  error_code ec = windows_error(::GetLastError());
+  ::CloseHandle(file);
+  if (!read_success || (bytes_read != len)) {
+    // Set result size to the number of bytes read if it's valid.
+    if (bytes_read >= 0 && bytes_read <= len)
+      result.set_size(bytes_read);
+    // ERROR_HANDLE_EOF is mapped to errc::value_too_large.
+    return ec;
+  }
+
+  result.set_size(len);
+  return success;
+}
+
 error_code directory_iterator_construct(directory_iterator &it, StringRef path){
   SmallVector<wchar_t, 128> path_utf16;
 
diff --git a/lib/Support/Windows/system_error.inc b/lib/Support/Windows/system_error.inc
index 73304d517f..64753d0eea 100644
--- a/lib/Support/Windows/system_error.inc
+++ b/lib/Support/Windows/system_error.inc
@@ -79,6 +79,7 @@ _system_error_category::default_error_condition(int ev) const {
   MAP_ERR_TO_COND(ERROR_FILE_EXISTS,         file_exists);
   MAP_ERR_TO_COND(ERROR_FILE_NOT_FOUND,      no_such_file_or_directory);
   MAP_ERR_TO_COND(ERROR_HANDLE_DISK_FULL,    no_space_on_device);
+  MAP_ERR_TO_COND(ERROR_HANDLE_EOF,          value_too_large);
   MAP_ERR_TO_COND(ERROR_INVALID_ACCESS,      permission_denied);
   MAP_ERR_TO_COND(ERROR_INVALID_DRIVE,       no_such_device);
   MAP_ERR_TO_COND(ERROR_INVALID_FUNCTION,    function_not_supported);