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 "flang/Common/optional.h"
16#include <cinttypes>
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 Fortran::common::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 Fortran::common::optional<std::int64_t> openRecl; // RECL= on OPEN
33
34 RT_API_ATTRS bool IsRecordFile() const {
35 // Formatted stream files are viewed as having records, at least on input
36 return access != Access::Stream || !isUnformatted.value_or(true);
37 }
38
39 template <typename CHAR = char> constexpr RT_API_ATTRS 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 RT_API_ATTRS bool
49 IsAtEOF() const; // true when read has hit EOF or endfile record
50 RT_API_ATTRS bool
51 IsAfterEndfile() const; // true after ENDFILE until repositioned
52
53 // All positions and measurements are always in units of bytes,
54 // not characters. Multi-byte character encodings are possible in
55 // both internal I/O (when the character kind of the variable is 2 or 4)
56 // and external formatted I/O (when the encoding is UTF-8).
57 RT_API_ATTRS std::size_t RemainingSpaceInRecord() const;
58 RT_API_ATTRS bool NeedAdvance(std::size_t) const;
59 RT_API_ATTRS void HandleAbsolutePosition(std::int64_t);
60 RT_API_ATTRS void HandleRelativePosition(std::int64_t);
61
62 RT_API_ATTRS void BeginRecord() {
63 positionInRecord = 0;
64 furthestPositionInRecord = 0;
65 unterminatedRecord = false;
66 }
67
68 RT_API_ATTRS Fortran::common::optional<std::int64_t>
69 EffectiveRecordLength() const {
70 // When an input record is longer than an explicit RECL= from OPEN
71 // it is effectively truncated on input.
72 return openRecl && recordLength && *openRecl < *recordLength ? openRecl
73 : recordLength;
74 }
75
76 Fortran::common::optional<std::int64_t> recordLength;
77
78 std::int64_t currentRecordNumber{1}; // 1 is first
79
80 // positionInRecord is the 0-based bytes offset in the current record
81 // to/from which the next data transfer will occur. It can be past
82 // furthestPositionInRecord if moved by an X or T or TR control edit
83 // descriptor.
84 std::int64_t positionInRecord{0};
85
86 // furthestPositionInRecord is the 0-based byte offset of the greatest
87 // position in the current record to/from which any data transfer has
88 // occurred, plus one. It can be viewed as a count of bytes processed.
89 std::int64_t furthestPositionInRecord{0}; // max(position+bytes)
90
91 // Set at end of non-advancing I/O data transfer
92 Fortran::common::optional<std::int64_t>
93 leftTabLimit; // offset in current record
94
95 // currentRecordNumber value captured after ENDFILE/REWIND/BACKSPACE statement
96 // or an end-of-file READ condition on a sequential access file
97 Fortran::common::optional<std::int64_t> endfileRecordNumber;
98
99 // Mutable modes set at OPEN() that can be overridden in READ/WRITE & FORMAT
100 MutableModes modes; // BLANK=, DECIMAL=, SIGN=, ROUND=, PAD=, DELIM=, kP
101
102 // Set when processing repeated items during list-directed & NAMELIST input
103 // in order to keep a span of records in frame on a non-positionable file,
104 // so that backspacing to the beginning of the repeated item doesn't require
105 // repositioning the external storage medium when that's impossible.
106 bool pinnedFrame{false};
107
108 // Set when the last record of a file is not properly terminated
109 // so that a non-advancing READ will not signal EOR.
110 bool unterminatedRecord{false};
111};
112
113// Utility class for capturing and restoring a position in an input stream.
114class SavedPosition {
115public:
116 explicit RT_API_ATTRS SavedPosition(IoStatementState &);
117 RT_API_ATTRS ~SavedPosition();
118 RT_API_ATTRS void Cancel() { cancelled_ = true; }
119
120private:
121 IoStatementState &io_;
122 ConnectionState saved_;
123 bool cancelled_{false};
124};
125
126} // namespace Fortran::runtime::io
127#endif // FORTRAN_RUNTIME_IO_CONNECTION_H_
128

source code of flang/runtime/connection.h