// Copyright 2016 Tom Thorogood. All rights reserved.
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// Use of this source code is governed by a
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// Modified BSD License license that can be found in
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// the LICENSE file.
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package shm
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import (
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"os"
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"sync/atomic"
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"unsafe"
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"golang.org/x/sys/unix"
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)
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func CreateSimplex(name string, perm os.FileMode, blockCount, blockSize int) (*ReadWriteCloser, error) {
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if blockSize&0x3f != 0 {
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return nil, ErrNotMultipleOf64
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}
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file, err := Open(name, unix.O_CREAT|unix.O_EXCL|unix.O_TRUNC|unix.O_RDWR, perm)
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if err != nil {
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return nil, err
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}
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defer file.Close()
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fullBlockSize := blockHeaderSize + uint64(blockSize)
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size := sharedHeaderSize + fullBlockSize*uint64(blockCount)
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if err = file.Truncate(int64(size)); err != nil {
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return nil, err
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}
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data, err := unix.Mmap(int(file.Fd()), 0, int(size), unix.PROT_READ|unix.PROT_WRITE, unix.MAP_SHARED)
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if err != nil {
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return nil, err
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}
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shared := (*sharedMem)(unsafe.Pointer(&data[0]))
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/*
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* memset already set:
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* shared.ReadStart, shared.ReadEnd = 0, 0
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* shared.WriteStart, shared.WriteEnd = 0, 0
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* shared.block[i].Size = 0
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* shared.block[i].DoneRead, shared.block[i].DoneWrite = 0, 0
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*/
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*(*uint32)(&shared.BlockCount), *(*uint64)(&shared.BlockSize) = uint32(blockCount), uint64(blockSize)
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if err = ((*Semaphore)(&shared.SemSignal)).Init(0); err != nil {
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return nil, err
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}
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if err = ((*Semaphore)(&shared.SemAvail)).Init(0); err != nil {
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return nil, err
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}
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for i := uint32(0); i < uint32(blockCount); i++ {
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block := (*sharedBlock)(unsafe.Pointer(&data[sharedHeaderSize+uint64(i)*fullBlockSize]))
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switch i {
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case 0:
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block.Next, *(*uint32)(&block.Prev) = 1, uint32(blockCount-1)
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case uint32(blockCount - 1):
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block.Next, *(*uint32)(&block.Prev) = 0, uint32(blockCount-2)
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default:
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*(*uint32)(&block.Next), *(*uint32)(&block.Prev) = i+1, i-1
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}
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}
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atomic.StoreUint32((*uint32)(&shared.Version), version)
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return &ReadWriteCloser{
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name: name,
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data: data,
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readShared: shared,
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writeShared: shared,
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size: size,
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fullBlockSize: fullBlockSize,
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Flags: (*[len(shared.Flags)]uint32)(unsafe.Pointer(&shared.Flags[0])),
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}, nil
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}
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func CreateDuplex(name string, perm os.FileMode, blockCount, blockSize int) (*ReadWriteCloser, error) {
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if blockSize&0x3f != 0 {
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return nil, ErrNotMultipleOf64
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}
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file, err := Open(name, unix.O_CREAT|unix.O_EXCL|unix.O_TRUNC|unix.O_RDWR, perm)
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if err != nil {
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return nil, err
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}
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defer file.Close()
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fullBlockSize := blockHeaderSize + uint64(blockSize)
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sharedSize := sharedHeaderSize + fullBlockSize*uint64(blockCount)
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size := 2 * sharedSize
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if err = file.Truncate(int64(size)); err != nil {
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return nil, err
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}
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data, err := unix.Mmap(int(file.Fd()), 0, int(size), unix.PROT_READ|unix.PROT_WRITE, unix.MAP_SHARED)
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if err != nil {
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return nil, err
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}
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for i := uint64(0); i < 2; i++ {
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shared := (*sharedMem)(unsafe.Pointer(&data[i*sharedSize]))
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/*
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* memset already set:
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* shared.ReadStart, shared.ReadEnd = 0, 0
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* shared.WriteStart, shared.WriteEnd = 0, 0
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* shared.Blocks[i].Size = 0
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* shared.Blocks[i].DoneRead, shared.Blocks[i].DoneWrite = 0, 0
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*/
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*(*uint32)(&shared.BlockCount), *(*uint64)(&shared.BlockSize) = uint32(blockCount), uint64(blockSize)
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if err = ((*Semaphore)(&shared.SemSignal)).Init(0); err != nil {
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return nil, err
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}
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if err = ((*Semaphore)(&shared.SemAvail)).Init(0); err != nil {
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return nil, err
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}
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for j := uint32(0); j < uint32(blockCount); j++ {
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block := (*sharedBlock)(unsafe.Pointer(&data[i*sharedSize+sharedHeaderSize+uint64(j)*fullBlockSize]))
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switch j {
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case 0:
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block.Next, *(*uint32)(&block.Prev) = 1, uint32(blockCount-1)
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case uint32(blockCount - 1):
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block.Next, *(*uint32)(&block.Prev) = 0, uint32(blockCount-2)
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default:
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*(*uint32)(&block.Next), *(*uint32)(&block.Prev) = j+1, j-1
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}
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}
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}
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readShared := (*sharedMem)(unsafe.Pointer(&data[0]))
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atomic.StoreUint32((*uint32)(&readShared.Version), version)
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return &ReadWriteCloser{
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name: name,
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data: data,
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readShared: readShared,
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writeShared: (*sharedMem)(unsafe.Pointer(&data[sharedSize])),
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size: size,
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fullBlockSize: fullBlockSize,
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Flags: (*[len(readShared.Flags)]uint32)(unsafe.Pointer(&readShared.Flags[0])),
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}, nil
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}
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