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// 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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} |