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| 3bd1f2 | 1 | // Copyright 2016 Tom Thorogood. All rights reserved. |
| Z | 2 | // Use of this source code is governed by a |
| 3 | // Modified BSD License license that can be found in | |
| 4 | // the LICENSE file. | |
| 5 | ||
| 6 | package shm | |
| 7 | ||
| 8 | import ( | |
| 9 | "io" | |
| 10 | "sync/atomic" | |
| 11 | "unsafe" | |
| 12 | ||
| a0123f | 13 | "golang.org/x/sys/unix" |
| 3bd1f2 | 14 | ) |
| Z | 15 | |
| 16 | const ( | |
| 17 | eofFlagIndex = 0 | |
| 18 | eofFlagMask = 0x01 | |
| 19 | ) | |
| 20 | ||
| 21 | type Buffer struct { | |
| 22 | block *sharedBlock | |
| 23 | write bool | |
| 24 | ||
| 25 | Data []byte | |
| 26 | Flags *[blockFlagsSize]byte | |
| 27 | } | |
| 28 | ||
| 29 | type ReadWriteCloser struct { | |
| 30 | name string | |
| 31 | ||
| 32 | data []byte | |
| 33 | readShared *sharedMem | |
| 34 | writeShared *sharedMem | |
| 35 | size uint64 | |
| 36 | fullBlockSize uint64 | |
| 37 | ||
| 38 | // Must be accessed using atomic operations | |
| 39 | Flags *[sharedFlagsSize]uint32 | |
| 40 | ||
| 41 | closed uint32 | |
| 42 | } | |
| 43 | ||
| 44 | func (rw *ReadWriteCloser) Close() error { | |
| 45 | if !atomic.CompareAndSwapUint32(&rw.closed, 0, 1) { | |
| 46 | return nil | |
| 47 | } | |
| 48 | ||
| 49 | // finish all sends before close! | |
| 50 | ||
| 51 | return unix.Munmap(rw.data) | |
| 52 | } | |
| 53 | ||
| 54 | // Name returns the name of the shared memory. | |
| 55 | func (rw *ReadWriteCloser) Name() string { | |
| 56 | return rw.name | |
| 57 | } | |
| 58 | ||
| a7b93e | 59 | // DirectRead create byte in func |
| Z | 60 | func (rw *ReadWriteCloser) DirectRead() ([]byte, error) { |
| 61 | buf, err := rw.GetReadBuffer() | |
| 62 | if err != nil { | |
| 63 | return nil, err | |
| 64 | } | |
| 3bd1f2 | 65 | |
| a7b93e | 66 | data := make([]byte, len(buf.Data)) |
| Z | 67 | |
| 68 | copy(data, buf.Data) | |
| 69 | isEOF := buf.Flags[eofFlagIndex]&eofFlagMask != 0 | |
| 70 | ||
| 71 | if err = rw.SendReadBuffer(buf); err != nil { | |
| 72 | return nil, err | |
| 73 | } | |
| 74 | ||
| 75 | if isEOF { | |
| 7db9ab | 76 | return data, io.EOF |
| a7b93e | 77 | } |
| Z | 78 | |
| 79 | return data, nil | |
| 80 | } | |
| 81 | ||
| 82 | // Peek get length | |
| 83 | func (rw *ReadWriteCloser) Peek() (n int, err error) { | |
| 84 | buf, err := rw.GetReadBuffer() | |
| 85 | if err != nil { | |
| 86 | return 0, err | |
| 87 | } | |
| 88 | ||
| 89 | return len(buf.Data), nil | |
| 90 | } | |
| 91 | ||
| 92 | // Read | |
| 3bd1f2 | 93 | func (rw *ReadWriteCloser) Read(p []byte) (n int, err error) { |
| Z | 94 | buf, err := rw.GetReadBuffer() |
| 95 | if err != nil { | |
| 96 | return 0, err | |
| 97 | } | |
| 98 | ||
| 99 | n = copy(p, buf.Data) | |
| 100 | isEOF := buf.Flags[eofFlagIndex]&eofFlagMask != 0 | |
| 101 | ||
| 102 | if err = rw.SendReadBuffer(buf); err != nil { | |
| 103 | return n, err | |
| 104 | } | |
| 105 | ||
| 106 | if isEOF { | |
| 107 | return n, io.EOF | |
| 108 | } | |
| 109 | ||
| 110 | return n, nil | |
| 111 | } | |
| 112 | ||
| 113 | func (rw *ReadWriteCloser) WriteTo(w io.Writer) (n int64, err error) { | |
| 114 | for { | |
| 115 | buf, err := rw.GetReadBuffer() | |
| 116 | if err != nil { | |
| 117 | return n, err | |
| 118 | } | |
| 119 | ||
| 120 | nn, err := w.Write(buf.Data) | |
| 121 | n += int64(nn) | |
| 122 | ||
| 123 | isEOF := buf.Flags[eofFlagIndex]&eofFlagMask != 0 | |
| 124 | ||
| 125 | if putErr := rw.SendReadBuffer(buf); putErr != nil { | |
| 126 | return n, putErr | |
| 127 | } | |
| 128 | ||
| 129 | if err != nil || isEOF { | |
| 130 | return n, err | |
| 131 | } | |
| 132 | } | |
| 133 | } | |
| 134 | ||
| 135 | func (rw *ReadWriteCloser) GetReadBuffer() (Buffer, error) { | |
| 136 | if atomic.LoadUint32(&rw.closed) != 0 { | |
| 137 | return Buffer{}, io.ErrClosedPipe | |
| 138 | } | |
| 139 | ||
| 140 | var block *sharedBlock | |
| 141 | ||
| 142 | blocks := uintptr(unsafe.Pointer(rw.readShared)) + sharedHeaderSize | |
| 143 | ||
| 144 | for { | |
| 145 | blockIndex := atomic.LoadUint32((*uint32)(&rw.readShared.ReadStart)) | |
| 146 | if blockIndex > uint32(rw.readShared.BlockCount) { | |
| 147 | return Buffer{}, ErrInvalidSharedMemory | |
| 148 | } | |
| 149 | ||
| 150 | block = (*sharedBlock)(unsafe.Pointer(blocks + uintptr(uint64(blockIndex)*rw.fullBlockSize))) | |
| 151 | ||
| 152 | if blockIndex == atomic.LoadUint32((*uint32)(&rw.readShared.WriteEnd)) { | |
| a0123f | 153 | if err := ((*Semaphore)(&rw.readShared.SemSignal)).Wait(); err != nil { |
| 3bd1f2 | 154 | return Buffer{}, err |
| Z | 155 | } |
| 156 | ||
| 157 | continue | |
| 158 | } | |
| 159 | ||
| 160 | if atomic.CompareAndSwapUint32((*uint32)(&rw.readShared.ReadStart), blockIndex, uint32(block.Next)) { | |
| 161 | break | |
| 162 | } | |
| 163 | } | |
| 164 | ||
| 165 | data := (*[1 << 30]byte)(unsafe.Pointer(uintptr(unsafe.Pointer(block)) + blockHeaderSize)) | |
| 166 | flags := (*[len(block.Flags)]byte)(unsafe.Pointer(&block.Flags[0])) | |
| 167 | return Buffer{ | |
| 168 | block: block, | |
| 169 | ||
| 170 | Data: data[:block.Size:rw.readShared.BlockSize], | |
| 171 | Flags: flags, | |
| 172 | }, nil | |
| 173 | } | |
| 174 | ||
| 175 | func (rw *ReadWriteCloser) SendReadBuffer(buf Buffer) error { | |
| 176 | if atomic.LoadUint32(&rw.closed) != 0 { | |
| 177 | return io.ErrClosedPipe | |
| 178 | } | |
| 179 | ||
| 180 | if buf.write { | |
| 181 | return ErrInvalidBuffer | |
| 182 | } | |
| 183 | ||
| 184 | block := buf.block | |
| 185 | ||
| 186 | atomic.StoreUint32((*uint32)(&block.DoneRead), 1) | |
| 187 | ||
| 188 | blocks := uintptr(unsafe.Pointer(rw.readShared)) + sharedHeaderSize | |
| 189 | ||
| 190 | for { | |
| 191 | blockIndex := atomic.LoadUint32((*uint32)(&rw.readShared.ReadEnd)) | |
| 192 | if blockIndex > uint32(rw.readShared.BlockCount) { | |
| 193 | return ErrInvalidSharedMemory | |
| 194 | } | |
| 195 | ||
| 196 | block = (*sharedBlock)(unsafe.Pointer(blocks + uintptr(uint64(blockIndex)*rw.fullBlockSize))) | |
| 197 | ||
| 198 | if !atomic.CompareAndSwapUint32((*uint32)(&block.DoneRead), 1, 0) { | |
| 199 | return nil | |
| 200 | } | |
| 201 | ||
| 202 | atomic.CompareAndSwapUint32((*uint32)(&rw.readShared.ReadEnd), blockIndex, uint32(block.Next)) | |
| 203 | ||
| 204 | if uint32(block.Prev) == atomic.LoadUint32((*uint32)(&rw.readShared.WriteStart)) { | |
| a0123f | 205 | if err := ((*Semaphore)(&rw.readShared.SemAvail)).Post(); err != nil { |
| 3bd1f2 | 206 | return err |
| Z | 207 | } |
| 208 | } | |
| 209 | } | |
| 210 | } | |
| 211 | ||
| 212 | // Write | |
| 213 | ||
| 214 | func (rw *ReadWriteCloser) Write(p []byte) (n int, err error) { | |
| 215 | buf, err := rw.GetWriteBuffer() | |
| 216 | if err != nil { | |
| 217 | return 0, err | |
| 218 | } | |
| 219 | ||
| 220 | n = copy(buf.Data[:cap(buf.Data)], p) | |
| 221 | buf.Data = buf.Data[:n] | |
| 222 | ||
| 223 | buf.Flags[eofFlagIndex] |= eofFlagMask | |
| 224 | ||
| 225 | _, err = rw.SendWriteBuffer(buf) | |
| 226 | return n, err | |
| 227 | } | |
| 228 | ||
| 229 | func (rw *ReadWriteCloser) ReadFrom(r io.Reader) (n int64, err error) { | |
| 230 | for { | |
| 231 | buf, err := rw.GetWriteBuffer() | |
| 232 | if err != nil { | |
| 233 | return n, err | |
| 234 | } | |
| 235 | ||
| 236 | nn, err := r.Read(buf.Data[:cap(buf.Data)]) | |
| 237 | buf.Data = buf.Data[:nn] | |
| 238 | n += int64(nn) | |
| 239 | ||
| 240 | if err == io.EOF { | |
| 241 | buf.Flags[eofFlagIndex] |= eofFlagMask | |
| 242 | } else { | |
| 243 | buf.Flags[eofFlagIndex] &^= eofFlagMask | |
| 244 | } | |
| 245 | ||
| 246 | if _, putErr := rw.SendWriteBuffer(buf); putErr != nil { | |
| 247 | return n, err | |
| 248 | } | |
| 249 | ||
| 250 | if err == io.EOF { | |
| 251 | return n, nil | |
| 252 | } else if err != nil { | |
| 253 | return n, err | |
| 254 | } | |
| 255 | } | |
| 256 | } | |
| 257 | ||
| 258 | func (rw *ReadWriteCloser) GetWriteBuffer() (Buffer, error) { | |
| 259 | if atomic.LoadUint32(&rw.closed) != 0 { | |
| 260 | return Buffer{}, io.ErrClosedPipe | |
| 261 | } | |
| 262 | ||
| 263 | var block *sharedBlock | |
| 264 | ||
| 265 | blocks := uintptr(unsafe.Pointer(rw.writeShared)) + sharedHeaderSize | |
| 266 | ||
| 267 | for { | |
| 268 | blockIndex := atomic.LoadUint32((*uint32)(&rw.writeShared.WriteStart)) | |
| 269 | if blockIndex > uint32(rw.writeShared.BlockCount) { | |
| 270 | return Buffer{}, ErrInvalidSharedMemory | |
| 271 | } | |
| 272 | ||
| 273 | block = (*sharedBlock)(unsafe.Pointer(blocks + uintptr(uint64(blockIndex)*rw.fullBlockSize))) | |
| 274 | ||
| 275 | if uint32(block.Next) == atomic.LoadUint32((*uint32)(&rw.writeShared.ReadEnd)) { | |
| a0123f | 276 | if err := ((*Semaphore)(&rw.writeShared.SemAvail)).Wait(); err != nil { |
| 3bd1f2 | 277 | return Buffer{}, err |
| Z | 278 | } |
| 279 | ||
| 280 | continue | |
| 281 | } | |
| 282 | ||
| 283 | if atomic.CompareAndSwapUint32((*uint32)(&rw.writeShared.WriteStart), blockIndex, uint32(block.Next)) { | |
| 284 | break | |
| 285 | } | |
| 286 | } | |
| 287 | ||
| 288 | data := (*[1 << 30]byte)(unsafe.Pointer(uintptr(unsafe.Pointer(block)) + blockHeaderSize)) | |
| 289 | flags := (*[len(block.Flags)]byte)(unsafe.Pointer(&block.Flags[0])) | |
| 290 | return Buffer{ | |
| 291 | block: block, | |
| 292 | write: true, | |
| 293 | ||
| 294 | Data: data[:0:rw.writeShared.BlockSize], | |
| 295 | Flags: flags, | |
| 296 | }, nil | |
| 297 | } | |
| 298 | ||
| 299 | func (rw *ReadWriteCloser) SendWriteBuffer(buf Buffer) (n int, err error) { | |
| 300 | if atomic.LoadUint32(&rw.closed) != 0 { | |
| 301 | return 0, io.ErrClosedPipe | |
| 302 | } | |
| 303 | ||
| 304 | if !buf.write { | |
| 305 | return 0, ErrInvalidBuffer | |
| 306 | } | |
| 307 | ||
| 308 | block := buf.block | |
| 309 | ||
| 310 | *(*uint64)(&block.Size) = uint64(len(buf.Data)) | |
| 311 | ||
| 312 | atomic.StoreUint32((*uint32)(&block.DoneWrite), 1) | |
| 313 | ||
| 314 | blocks := uintptr(unsafe.Pointer(rw.writeShared)) + sharedHeaderSize | |
| 315 | ||
| 316 | for { | |
| 317 | blockIndex := atomic.LoadUint32((*uint32)(&rw.writeShared.WriteEnd)) | |
| 318 | if blockIndex > uint32(rw.writeShared.BlockCount) { | |
| 319 | return len(buf.Data), ErrInvalidSharedMemory | |
| 320 | } | |
| 321 | ||
| 322 | block = (*sharedBlock)(unsafe.Pointer(blocks + uintptr(uint64(blockIndex)*rw.fullBlockSize))) | |
| 323 | ||
| 324 | if !atomic.CompareAndSwapUint32((*uint32)(&block.DoneWrite), 1, 0) { | |
| 325 | return len(buf.Data), nil | |
| 326 | } | |
| 327 | ||
| 328 | atomic.CompareAndSwapUint32((*uint32)(&rw.writeShared.WriteEnd), blockIndex, uint32(block.Next)) | |
| 329 | ||
| 330 | if blockIndex == atomic.LoadUint32((*uint32)(&rw.writeShared.ReadStart)) { | |
| a0123f | 331 | if err := ((*Semaphore)(&rw.writeShared.SemSignal)).Post(); err != nil { |
| 3bd1f2 | 332 | return len(buf.Data), err |
| Z | 333 | } |
| 334 | } | |
| 335 | } | |
| 336 | } | |
