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 18 namespace Fortran::runtime::io { 19 20 class IoStatementState; 21 22 enum class Direction { Output, Input }; 23 enum class Access { Sequential, Direct, Stream }; 24 25 // These characteristics of a connection are immutable after being 26 // established in an OPEN statement. 27 struct 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 IsRecordFileConnectionAttributes34 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 useUTF8ConnectionAttributes39 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 47 struct 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 BeginRecordConnectionState62 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> EffectiveRecordLengthConnectionState69 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. 114 class SavedPosition { 115 public: 116 explicit RT_API_ATTRS SavedPosition(IoStatementState &); 117 RT_API_ATTRS ~SavedPosition(); Cancel()118 RT_API_ATTRS void Cancel() { cancelled_ = true; } 119 120 private: 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