1 files changed, 50 insertions, 0 deletions
diff --git a/flang/runtime/connection.h b/flang/runtime/connection.h
new file mode 100644
index 000000000000..85372dfa610d
--- /dev/null
+++ b/flang/runtime/connection.h
@@ -0,0 +1,50 @@
+//===-- runtime/connection.h ------------------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// Fortran I/O connection state (internal & external)
+
+#ifndef FORTRAN_RUNTIME_IO_CONNECTION_H_
+#define FORTRAN_RUNTIME_IO_CONNECTION_H_
+
+#include "format.h"
+#include <cinttypes>
+#include <optional>
+
+namespace Fortran::runtime::io {
+
+enum class Access { Sequential, Direct, Stream };
+
+inline bool IsRecordFile(Access a) { return a != Access::Stream; }
+
+// These characteristics of a connection are immutable after being
+// established in an OPEN statement.
+struct ConnectionAttributes {
+  Access access{Access::Sequential};  // ACCESS='SEQUENTIAL', 'DIRECT', 'STREAM'
+  std::optional<std::size_t> recordLength;  // RECL= when fixed-length
+  bool isUnformatted{false};  // FORM='UNFORMATTED'
+  bool isUTF8{false};  // ENCODING='UTF-8'
+};
+
+struct ConnectionState : public ConnectionAttributes {
+  std::size_t RemainingSpaceInRecord() const;
+  // Positions in a record file (sequential or direct, but not stream)
+  std::int64_t recordOffsetInFile{0};
+  std::int64_t currentRecordNumber{1};  // 1 is first
+  std::int64_t positionInRecord{0};  // offset in current record
+  std::int64_t furthestPositionInRecord{0};  // max(positionInRecord)
+  bool nonAdvancing{false};  // ADVANCE='NO'
+  // Set at end of non-advancing I/O data transfer
+  std::optional<std::int64_t> leftTabLimit;  // offset in current record
+  // currentRecordNumber value captured after ENDFILE/REWIND/BACKSPACE statement
+  // on a sequential access file
+  std::optional<std::int64_t> endfileRecordNumber;
+  // Mutable modes set at OPEN() that can be overridden in READ/WRITE & FORMAT
+  MutableModes modes;  // BLANK=, DECIMAL=, SIGN=, ROUND=, PAD=, DELIM=, kP
+};
+}
+#endif  // FORTRAN_RUNTIME_IO_CONNECTION_H_