1//===-- runtime/unit-map.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// Maps Fortran unit numbers to their ExternalFileUnit instances.
10// A simple hash table with forward-linked chains per bucket.
11
12#ifndef FORTRAN_RUNTIME_UNIT_MAP_H_
13#define FORTRAN_RUNTIME_UNIT_MAP_H_
14
15#include "lock.h"
16#include "unit.h"
17#include "flang/Common/fast-int-set.h"
18#include "flang/Runtime/memory.h"
19#include <cstdint>
20#include <cstdlib>
21
22namespace Fortran::runtime::io {
23
24class UnitMap {
25public:
26 ExternalFileUnit *LookUp(int n) {
27 CriticalSection critical{lock_};
28 return Find(n);
29 }
30
31 ExternalFileUnit *LookUpOrCreate(
32 int n, const Terminator &terminator, bool &wasExtant) {
33 CriticalSection critical{lock_};
34 if (auto *p{Find(n)}) {
35 wasExtant = true;
36 return p;
37 } else {
38 wasExtant = false;
39 return n >= 0 ? &Create(n, terminator) : nullptr;
40 }
41 }
42
43 // Unit look-up by name is needed for INQUIRE(FILE="...")
44 ExternalFileUnit *LookUp(const char *path, std::size_t pathLen) {
45 CriticalSection critical{lock_};
46 return Find(path, pathLen);
47 }
48
49 ExternalFileUnit &NewUnit(const Terminator &);
50
51 // To prevent races, the unit is removed from the map if it exists,
52 // and put on the closing_ list until DestroyClosed() is called.
53 ExternalFileUnit *LookUpForClose(int);
54
55 void DestroyClosed(ExternalFileUnit &);
56 void CloseAll(IoErrorHandler &);
57 void FlushAll(IoErrorHandler &);
58
59private:
60 struct Chain {
61 explicit Chain(int n) : unit{n} {}
62 ExternalFileUnit unit;
63 OwningPtr<Chain> next{nullptr};
64 };
65
66 static constexpr int buckets_{1031}; // must be prime
67
68 // The pool of recyclable new unit numbers uses the range that
69 // works even with INTEGER(kind=1). 0 and -1 are never used.
70 static constexpr int maxNewUnits_{129}; // [ -128 .. 0 ]
71
72 int Hash(int n) { return std::abs(x: n) % buckets_; }
73
74 void Initialize();
75
76 ExternalFileUnit *Find(int n) {
77 Chain *previous{nullptr};
78 int hash{Hash(n)};
79 for (Chain *p{bucket_[hash].get()}; p; previous = p, p = p->next.get()) {
80 if (p->unit.unitNumber() == n) {
81 if (previous) {
82 // Move found unit to front of chain for quicker lookup next time
83 previous->next.swap(p->next); // now p->next.get() == p
84 bucket_[hash].swap(p->next); // now bucket_[hash].get() == p
85 }
86 return &p->unit;
87 }
88 }
89 return nullptr;
90 }
91 ExternalFileUnit *Find(const char *path, std::size_t pathLen);
92
93 ExternalFileUnit &Create(int, const Terminator &);
94
95 Lock lock_;
96 bool isInitialized_{false};
97 OwningPtr<Chain> bucket_[buckets_]{}; // all owned by *this
98 OwningPtr<Chain> closing_{nullptr}; // units during CLOSE statement
99 common::FastIntSet<maxNewUnits_> freeNewUnits_;
100 int emergencyNewUnit_{maxNewUnits_}; // not recycled
101};
102} // namespace Fortran::runtime::io
103#endif // FORTRAN_RUNTIME_UNIT_MAP_H_
104

source code of flang/runtime/unit-map.h