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61 lines
1.8 KiB
Go
61 lines
1.8 KiB
Go
// Copyright 2018 The go-ethereum Authors
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// This file is part of the go-ethereum library.
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//
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// The go-ethereum library is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Lesser General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// The go-ethereum library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Lesser General Public License for more details.
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//
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// You should have received a copy of the GNU Lesser General Public License
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// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
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// Platform-specific functions of the Etheruem database package
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package ethdb
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import (
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"fmt"
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"os"
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"syscall"
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"unsafe"
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)
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// mmap memory maps a HexHeap's data file.
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func mmap(f *os.File, sz int) ([]byte, error) {
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// Map the data file to memory.
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b, err := syscall.Mmap(int(f.Fd()), 0, sz, syscall.PROT_READ|syscall.PROT_WRITE, syscall.MAP_SHARED)
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if err != nil {
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return nil, err
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}
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// Advise the kernel that the mmap is accessed randomly.
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if err := madvise(b, syscall.MADV_RANDOM); err != nil {
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return nil, fmt.Errorf("madvise: %s", err)
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}
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return b, nil
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}
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// munmap unmaps a DB's data file from memory.
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func munmap(h []byte) error {
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// Ignore the unmap if we have no mapped data.
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if h == nil {
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return nil
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}
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// Unmap using the original byte slice.
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return syscall.Munmap(h)
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}
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func madvise(b []byte, advice int) (err error) {
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_, _, e1 := syscall.Syscall(syscall.SYS_MADVISE, uintptr(unsafe.Pointer(&b[0])), uintptr(len(b)), uintptr(advice))
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if e1 != 0 {
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err = e1
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}
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return
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}
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