73b193aec2
Add a header-only implementation of Briggs & Torczon's fast small integer set data structure to flang/include/flang/Common, and use it in the runtime to manage a pool of Fortran unit numbers with recycling. This replaces the bit set previously used for that purpose. The set is initialized on demand with the negations of all the NEWUNIT= unit numbers that can be returned to any kind of integer variable. For programs that require more concurrently open NEWUNIT= unit numbers than the pool can hold, they are now allocated with a non-recycling counter. This allows as many open units as the operating system provides. Many of the top-line comments in flang/unittests/Runtime had the wrong path name. I noticed this while adding a unit test for the fast integer set data structure, and cleaned them up. Differential Revision: https://reviews.llvm.org/D120685
100 lines
3 KiB
C++
100 lines
3 KiB
C++
//===-- runtime/unit-map.h --------------------------------------*- C++ -*-===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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// Maps Fortran unit numbers to their ExternalFileUnit instances.
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// A simple hash table with forward-linked chains per bucket.
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#ifndef FORTRAN_RUNTIME_UNIT_MAP_H_
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#define FORTRAN_RUNTIME_UNIT_MAP_H_
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#include "lock.h"
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#include "unit.h"
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#include "flang/Common/fast-int-set.h"
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#include "flang/Runtime/memory.h"
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#include <cstdint>
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#include <cstdlib>
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namespace Fortran::runtime::io {
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class UnitMap {
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public:
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ExternalFileUnit *LookUp(int n) {
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CriticalSection critical{lock_};
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return Find(n);
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}
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ExternalFileUnit &LookUpOrCreate(
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int n, const Terminator &terminator, bool &wasExtant) {
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CriticalSection critical{lock_};
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auto *p{Find(n)};
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wasExtant = p != nullptr;
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return p ? *p : Create(n, terminator);
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}
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// Unit look-up by name is needed for INQUIRE(FILE="...")
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ExternalFileUnit *LookUp(const char *path) {
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CriticalSection critical{lock_};
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return Find(path);
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}
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ExternalFileUnit &NewUnit(const Terminator &);
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// To prevent races, the unit is removed from the map if it exists,
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// and put on the closing_ list until DestroyClosed() is called.
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ExternalFileUnit *LookUpForClose(int);
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void DestroyClosed(ExternalFileUnit &);
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void CloseAll(IoErrorHandler &);
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void FlushAll(IoErrorHandler &);
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private:
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struct Chain {
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explicit Chain(int n) : unit{n} {}
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ExternalFileUnit unit;
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OwningPtr<Chain> next{nullptr};
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};
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static constexpr int buckets_{1031}; // must be prime
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// The pool of recyclable new unit numbers uses the range that
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// works even with INTEGER(kind=1). 0 and -1 are never used.
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static constexpr int maxNewUnits_{129}; // [ -128 .. 0 ]
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int Hash(int n) { return std::abs(n) % buckets_; }
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void Initialize();
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ExternalFileUnit *Find(int n) {
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Chain *previous{nullptr};
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int hash{Hash(n)};
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for (Chain *p{bucket_[hash].get()}; p; previous = p, p = p->next.get()) {
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if (p->unit.unitNumber() == n) {
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if (previous) {
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// Move found unit to front of chain for quicker lookup next time
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previous->next.swap(p->next); // now p->next.get() == p
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bucket_[hash].swap(p->next); // now bucket_[hash].get() == p
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}
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return &p->unit;
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}
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}
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return nullptr;
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}
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ExternalFileUnit *Find(const char *path);
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ExternalFileUnit &Create(int, const Terminator &);
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Lock lock_;
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bool isInitialized_{false};
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OwningPtr<Chain> bucket_[buckets_]{}; // all owned by *this
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OwningPtr<Chain> closing_{nullptr}; // units during CLOSE statement
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common::FastIntSet<maxNewUnits_> freeNewUnits_;
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int emergencyNewUnit_{maxNewUnits_}; // not recycled
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};
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} // namespace Fortran::runtime::io
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#endif // FORTRAN_RUNTIME_UNIT_MAP_H_
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