1//===-- runtime/connection.h ------------------------------------*- C++ -*-===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8
9// Fortran I/O connection state (abstracted over internal & external units)
10
11#ifndef FORTRAN_RUNTIME_IO_CONNECTION_H_
12#define FORTRAN_RUNTIME_IO_CONNECTION_H_
13
14#include "format.h"
15#include <cinttypes>
16#include <optional>
17
18namespace Fortran::runtime::io {
19
20class IoStatementState;
21
22enum class Direction { Output, Input };
23enum class Access { Sequential, Direct, Stream };
24
25// These characteristics of a connection are immutable after being
26// established in an OPEN statement.
27struct ConnectionAttributes {
28 Access access{Access::Sequential}; // ACCESS='SEQUENTIAL', 'DIRECT', 'STREAM'
29 std::optional<bool> isUnformatted; // FORM='UNFORMATTED' if true
30 bool isUTF8{false}; // ENCODING='UTF-8'
31 unsigned char internalIoCharKind{0}; // 0->external, 1/2/4->internal
32 std::optional<std::int64_t> openRecl; // RECL= on OPEN
33
34 bool IsRecordFile() const {
35 // Formatted stream files are viewed as having records, at least on input
36 return access != Access::Stream || !isUnformatted.value_or(u: true);
37 }
38
39 template <typename CHAR = char> constexpr bool useUTF8() const {
40 // For wide CHARACTER kinds, always use UTF-8 for formatted I/O.
41 // For single-byte CHARACTER, encode characters >= 0x80 with
42 // UTF-8 iff the mode is set.
43 return internalIoCharKind == 0 && (sizeof(CHAR) > 1 || isUTF8);
44 }
45};
46
47struct ConnectionState : public ConnectionAttributes {
48 bool IsAtEOF() const; // true when read has hit EOF or endfile record
49 bool IsAfterEndfile() const; // true after ENDFILE until repositioned
50
51 // All positions and measurements are always in units of bytes,
52 // not characters. Multi-byte character encodings are possible in
53 // both internal I/O (when the character kind of the variable is 2 or 4)
54 // and external formatted I/O (when the encoding is UTF-8).
55 std::size_t RemainingSpaceInRecord() const;
56 bool NeedAdvance(std::size_t) const;
57 void HandleAbsolutePosition(std::int64_t);
58 void HandleRelativePosition(std::int64_t);
59
60 void BeginRecord() {
61 positionInRecord = 0;
62 furthestPositionInRecord = 0;
63 unterminatedRecord = false;
64 }
65
66 std::optional<std::int64_t> EffectiveRecordLength() const {
67 // When an input record is longer than an explicit RECL= from OPEN
68 // it is effectively truncated on input.
69 return openRecl && recordLength && *openRecl < *recordLength ? openRecl
70 : recordLength;
71 }
72
73 std::optional<std::int64_t> recordLength;
74
75 std::int64_t currentRecordNumber{1}; // 1 is first
76
77 // positionInRecord is the 0-based bytes offset in the current record
78 // to/from which the next data transfer will occur. It can be past
79 // furthestPositionInRecord if moved by an X or T or TR control edit
80 // descriptor.
81 std::int64_t positionInRecord{0};
82
83 // furthestPositionInRecord is the 0-based byte offset of the greatest
84 // position in the current record to/from which any data transfer has
85 // occurred, plus one. It can be viewed as a count of bytes processed.
86 std::int64_t furthestPositionInRecord{0}; // max(position+bytes)
87
88 // Set at end of non-advancing I/O data transfer
89 std::optional<std::int64_t> leftTabLimit; // offset in current record
90
91 // currentRecordNumber value captured after ENDFILE/REWIND/BACKSPACE statement
92 // or an end-of-file READ condition on a sequential access file
93 std::optional<std::int64_t> endfileRecordNumber;
94
95 // Mutable modes set at OPEN() that can be overridden in READ/WRITE & FORMAT
96 MutableModes modes; // BLANK=, DECIMAL=, SIGN=, ROUND=, PAD=, DELIM=, kP
97
98 // Set when processing repeated items during list-directed & NAMELIST input
99 // in order to keep a span of records in frame on a non-positionable file,
100 // so that backspacing to the beginning of the repeated item doesn't require
101 // repositioning the external storage medium when that's impossible.
102 bool pinnedFrame{false};
103
104 // Set when the last record of a file is not properly terminated
105 // so that a non-advancing READ will not signal EOR.
106 bool unterminatedRecord{false};
107};
108
109// Utility class for capturing and restoring a position in an input stream.
110class SavedPosition {
111public:
112 explicit SavedPosition(IoStatementState &);
113 ~SavedPosition();
114 void Cancel() { cancelled_ = true; }
115
116private:
117 IoStatementState &io_;
118 ConnectionState saved_;
119 bool cancelled_{false};
120};
121
122} // namespace Fortran::runtime::io
123#endif // FORTRAN_RUNTIME_IO_CONNECTION_H_
124

source code of flang/runtime/connection.h