├── .travis.yml ├── CONTRIBUTING ├── LICENSE ├── README.md ├── vectorio.go ├── vectorio_buffered.go ├── vectorio_buffered_example_test.go ├── vectorio_buffered_test.go ├── vectorio_example_test.go └── vectorio_test.go /.travis.yml: -------------------------------------------------------------------------------- 1 | language: go 2 | -------------------------------------------------------------------------------- /CONTRIBUTING: -------------------------------------------------------------------------------- 1 | Want to contribute? Great! First, read this page (including the small print at the end). 2 | 3 | ### Before you contribute 4 | Before we can use your code, you must sign the 5 | [Google Individual Contributor License Agreement] 6 | (https://cla.developers.google.com/about/google-individual) 7 | (CLA), which you can do online. 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We also recommend that a 186 | file or class name and description of purpose be included on the 187 | same "printed page" as the copyright notice for easier 188 | identification within third-party archives. 189 | 190 | Copyright [yyyy] [name of copyright owner] 191 | 192 | Licensed under the Apache License, Version 2.0 (the "License"); 193 | you may not use this file except in compliance with the License. 194 | You may obtain a copy of the License at 195 | 196 | http://www.apache.org/licenses/LICENSE-2.0 197 | 198 | Unless required by applicable law or agreed to in writing, software 199 | distributed under the License is distributed on an "AS IS" BASIS, 200 | WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 201 | See the License for the specific language governing permissions and 202 | limitations under the License. 203 | -------------------------------------------------------------------------------- /README.md: -------------------------------------------------------------------------------- 1 | vectorio: Scatter/Gather I/O for Go 2 | === 3 | 4 | vectorio is a library for Go (aka "golang") to implement the writev(2), and in the future, readv(2) system calls. This enables a list of byte slices to be efficiently written to a file without first copying them to an intermediate buffer. Go's built-in [bufio](http://golang.org/pkg/bufio/) library is the standard approach to buffered I/O, but vectorio can be a replacement to achieve the same goal but without copying data. 5 | 6 | This is not an official Google product. Authored by Ted Behling as a personal project. 7 | 8 | [![Build Status](https://travis-ci.org/google/vectorio.svg)](https://travis-ci.org/google/vectorio) 9 | 10 | See [example usage](vectorio_example_test.go) for a demo. 11 | 12 | -------------------------------------------------------------------------------- /vectorio.go: -------------------------------------------------------------------------------- 1 | /* 2 | Copyright 2015 Google Inc. All Rights Reserved. 3 | 4 | Licensed under the Apache License, Version 2.0 (the "License"); 5 | you may not use this file except in compliance with the License. 6 | You may obtain a copy of the License at 7 | 8 | http://www.apache.org/licenses/LICENSE-2.0 9 | 10 | Unless required by applicable law or agreed to in writing, software 11 | distributed under the License is distributed on an "AS IS" BASIS, 12 | WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 | See the License for the specific language governing permissions and 14 | limitations under the License. 15 | */ 16 | 17 | package vectorio 18 | 19 | import ( 20 | "fmt" 21 | "os" 22 | "syscall" 23 | "unsafe" 24 | ) 25 | 26 | // Writev calls writev() syscall, but first convert a [][]byte to []sycall.Iovec, return number of bytes written and an error 27 | func Writev(f *os.File, in [][]byte) (nw int, err error) { 28 | iovec := make([]syscall.Iovec, len(in)) 29 | for i, slice := range in { 30 | iovec[i] = syscall.Iovec{&slice[0], uint64(len(slice))} 31 | } 32 | nw, err = WritevRaw(uintptr(f.Fd()), iovec) 33 | return 34 | } 35 | 36 | // WritevRaw calls writev() syscall like Writev, but expects a slice of syscall.Iovec 37 | func WritevRaw(fd uintptr, iovec []syscall.Iovec) (nw int, err error) { 38 | nwRaw, _, errno := syscall.Syscall(syscall.SYS_WRITEV, fd, uintptr(unsafe.Pointer(&iovec[0])), uintptr(len(iovec))) 39 | nw = int(nwRaw) 40 | if errno != 0 { 41 | err = fmt.Errorf("writev failed with error: %d", errno) 42 | } 43 | return 44 | } 45 | -------------------------------------------------------------------------------- /vectorio_buffered.go: -------------------------------------------------------------------------------- 1 | /* 2 | Copyright 2015 Google Inc. All Rights Reserved. 3 | 4 | Licensed under the Apache License, Version 2.0 (the "License"); 5 | you may not use this file except in compliance with the License. 6 | You may obtain a copy of the License at 7 | 8 | http://www.apache.org/licenses/LICENSE-2.0 9 | 10 | Unless required by applicable law or agreed to in writing, software 11 | distributed under the License is distributed on an "AS IS" BASIS, 12 | WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 | See the License for the specific language governing permissions and 14 | limitations under the License. 15 | */ 16 | 17 | package vectorio 18 | 19 | import ( 20 | "errors" 21 | "net" 22 | "os" 23 | "sync" 24 | "syscall" 25 | ) 26 | 27 | // 1024 is the max size of an Iovec on Linux 28 | const defaultBufSize = 1024 29 | 30 | // just an alias so users don't have to import syscall to use this 31 | //type Iovec syscall.Iovec 32 | 33 | // BufferedWritev is similar to bufio.Writer. 34 | // after all data has been written, the client should call Flush to make sure everything is written. 35 | // Note: this is NOT concurrency safe. Concurrent access should use the embedded Lock object (w.Lock.Lock() / 36 | // w.Lock.Unlock()), or wrap this in a single goroutine that handles a channel of []byte. 37 | type BufferedWritev struct { 38 | buf []syscall.Iovec 39 | Lock *sync.Mutex 40 | fd uintptr 41 | } 42 | 43 | // NewBufferedWritev makes a new BufferedWritev from a net.TCPConn, os.File, or file descriptor (FD). 44 | func NewBufferedWritev(targetIn interface{}) (bw *BufferedWritev, err error) { 45 | switch target := targetIn.(type) { 46 | case *net.TCPConn: 47 | var f *os.File 48 | f, err = target.File() 49 | if err != nil { 50 | return 51 | } 52 | bw, err = NewBufferedWritev(f) 53 | case *os.File: 54 | bw, err = NewBufferedWritev(uintptr(target.Fd())) 55 | case uintptr: 56 | // refactor: make buffer size user-specified? 57 | bw = &BufferedWritev{buf: make([]syscall.Iovec, 0, defaultBufSize), Lock: new(sync.Mutex), fd: target} 58 | default: 59 | err = errors.New("NewBufferedWritev called with invalid type") 60 | } 61 | return 62 | } 63 | 64 | // Write implements the io.Writer interface. 65 | // Number of bytes written (nw) is usually 0 except for the times we flush the buffer, which will reflect the quantity of all bytes written in that writev() call 66 | func (bw *BufferedWritev) Write(p []byte) (nw int, err error) { 67 | nw, err = bw.WriteIovec(syscall.Iovec{&p[0], uint64(len(p))}) 68 | return 69 | } 70 | 71 | // WriteIovec takes a user-composed syscall.Iovec struct instead of []byte; functionally the same as Write 72 | func (bw *BufferedWritev) WriteIovec(iov syscall.Iovec) (nw int, err error) { 73 | //bw.lock.Lock() 74 | // normally append will reallocate a slice if it exceeds its cap, but that should not happen here because of our logic below 75 | bw.buf = append(bw.buf, iov) 76 | 77 | if len(bw.buf) == cap(bw.buf) { 78 | // maxed out the slice; write it and reset the slice 79 | nw, err = bw.flush() 80 | } 81 | 82 | //bw.lock.Unlock() 83 | return 84 | } 85 | 86 | // Flush writes the contents of buffer to underlying file handle and resets buffer. 87 | // This must be called at the end of writing before closing the underlying file, or data will be lost. 88 | func (bw *BufferedWritev) Flush() (nw int, err error) { 89 | // TODO: if we're not going to use a lock, collapse Flush() and flush() 90 | //bw.Lock.Lock() 91 | nw, err = bw.flush() 92 | //bw.Lock.Unlock() 93 | return 94 | } 95 | 96 | // FUTURE: check to make sure the number of bytes written matches the sum of the iovec's 97 | // Note: must be wrapped in a mutex to be concurrency safe 98 | func (bw *BufferedWritev) flush() (nw int, err error) { 99 | nw, err = WritevRaw(bw.fd, bw.buf) 100 | bw.buf = bw.buf[:0] 101 | return 102 | } 103 | -------------------------------------------------------------------------------- /vectorio_buffered_example_test.go: -------------------------------------------------------------------------------- 1 | /* 2 | Copyright 2015 Google Inc. All Rights Reserved. 3 | 4 | Licensed under the Apache License, Version 2.0 (the "License"); 5 | you may not use this file except in compliance with the License. 6 | You may obtain a copy of the License at 7 | 8 | http://www.apache.org/licenses/LICENSE-2.0 9 | 10 | Unless required by applicable law or agreed to in writing, software 11 | distributed under the License is distributed on an "AS IS" BASIS, 12 | WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 | See the License for the specific language governing permissions and 14 | limitations under the License. 15 | */ 16 | 17 | package vectorio_test 18 | 19 | import ( 20 | "fmt" 21 | "io/ioutil" 22 | "syscall" 23 | 24 | "github.com/google/vectorio" 25 | ) 26 | 27 | func ExampleBufferedVectorio() { 28 | // Create a temp file to use 29 | f, err := ioutil.TempFile("", "vectorio") 30 | if err != nil { 31 | panic(err) 32 | } 33 | defer f.Close() 34 | 35 | data1 := []byte("foobarbaz") 36 | data2 := []byte("foobazbar") 37 | 38 | w, err := vectorio.NewBufferedWritev(f) 39 | nw, err := w.Write(data2) 40 | nw, err = w.WriteIovec(syscall.Iovec{&data1[0], 9}) 41 | nw, err = w.Flush() 42 | 43 | if err != nil { 44 | fmt.Printf("Flush threw error: %s", err) 45 | } 46 | if nw == 9*2 { 47 | fmt.Println("Wrote", nw, "bytes to file!") 48 | } else { 49 | fmt.Println("did not write 9 * 2 bytes, wrote ", nw) 50 | } 51 | 52 | // Output: 53 | // Wrote 18 bytes to file! 54 | } 55 | 56 | func ExampleBufferedVectorioUnsafe() { 57 | // Create a temp file to use 58 | f, _ := ioutil.TempFile("", "vectorio") 59 | defer f.Close() 60 | 61 | data1 := []byte("foobarbaz") 62 | data2 := []byte("foobazbar") 63 | 64 | w, _ := vectorio.NewBufferedWritev(f) 65 | w.Write(data2) 66 | w.WriteIovec(syscall.Iovec{&data1[0], 9}) 67 | nw, _ := w.Flush() 68 | fmt.Println("Wrote", nw, "bytes to file!") 69 | 70 | // Output: 71 | // Wrote 18 bytes to file! 72 | } 73 | -------------------------------------------------------------------------------- /vectorio_buffered_test.go: -------------------------------------------------------------------------------- 1 | /* 2 | Copyright 2015 Google Inc. All Rights Reserved. 3 | 4 | Licensed under the Apache License, Version 2.0 (the "License"); 5 | you may not use this file except in compliance with the License. 6 | You may obtain a copy of the License at 7 | 8 | http://www.apache.org/licenses/LICENSE-2.0 9 | 10 | Unless required by applicable law or agreed to in writing, software 11 | distributed under the License is distributed on an "AS IS" BASIS, 12 | WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 | See the License for the specific language governing permissions and 14 | limitations under the License. 15 | */ 16 | 17 | package vectorio_test 18 | 19 | import ( 20 | "bytes" 21 | "io/ioutil" 22 | "os" 23 | "syscall" 24 | "testing" 25 | 26 | "github.com/google/vectorio" 27 | ) 28 | 29 | func TestBufferedWritev(t *testing.T) { 30 | f, err := os.Create("testbufferedwritev") 31 | if err != nil { 32 | panic(err) 33 | } 34 | defer f.Close() 35 | 36 | data := []byte("foobarbaz") 37 | data_desired := []byte("foobazbar") 38 | 39 | bw, _ := vectorio.NewBufferedWritev(f) 40 | 41 | bw.WriteIovec(syscall.Iovec{&data[0], 3}) 42 | bw.WriteIovec(syscall.Iovec{&data[6], 3}) 43 | bw.Write(data[3:6]) 44 | 45 | nw, err := bw.Flush() 46 | if err != nil { 47 | t.Errorf("Flush threw error: %s", err) 48 | } 49 | if nw != 3*3 { 50 | t.Errorf("Flush wrote wrong number of bytes, expected 3 * 3 but got %d", nw) 51 | } 52 | 53 | stats, err := f.Stat() 54 | if err != nil { 55 | t.Errorf("Stat threw error: %s", err) 56 | } 57 | filesize := stats.Size() 58 | if filesize != int64(len(data)) { 59 | t.Errorf("Length %d of input does not match %d written bytes", len(data), filesize) 60 | } 61 | 62 | f.Seek(0, 0) 63 | fromdisk, err := ioutil.ReadAll(f) 64 | if err != nil { 65 | t.Errorf("can't read file back, %s", err) 66 | } 67 | if bytes.Compare(fromdisk, data_desired) != 0 { 68 | t.Errorf("contents of file don't match input, %s != %s or %d != %d", fromdisk, data_desired, len(fromdisk), len(data_desired)) 69 | } 70 | os.Remove("testbufferedwritev") 71 | } 72 | 73 | func TestBufferedWritevHuge(t *testing.T) { 74 | f, err := os.Create("testbufferedwritevhuge") 75 | if err != nil { 76 | panic(err) 77 | } 78 | defer f.Close() 79 | 80 | data := []byte("foobarba") 81 | final := []byte("attheend") 82 | 83 | bw, _ := vectorio.NewBufferedWritev(f) 84 | 85 | // write a little more than our buffer size 86 | for i := 0; i < 1024; i++ { 87 | bw.Write(data) 88 | } 89 | bw.Write(final) 90 | 91 | _, err = bw.Flush() 92 | if err != nil { 93 | t.Errorf("Flush threw error: %s", err) 94 | } 95 | 96 | stats, err := f.Stat() 97 | if err != nil { 98 | t.Errorf("Stat threw error: %s", err) 99 | } 100 | filesize := stats.Size() 101 | if filesize != int64(1024*len(data)+len(final)) { 102 | t.Errorf("Length %d of input does not match %d written bytes", len(data), filesize) 103 | } 104 | 105 | // Maybe make this validate file contents later?? 106 | f.Seek(0, 0) 107 | fromdisk, err := ioutil.ReadAll(f) 108 | if err != nil { 109 | t.Errorf("can't read file back, %s", err) 110 | } 111 | compared := fromdisk[1024*8:] 112 | if bytes.Compare(compared, final) != 0 { 113 | t.Errorf("contents of file don't match input, %s != %s or %d != %d", compared, final, len(compared), len(final)) 114 | } 115 | os.Remove("testbufferedwritevhuge") 116 | } 117 | -------------------------------------------------------------------------------- /vectorio_example_test.go: -------------------------------------------------------------------------------- 1 | package vectorio_test 2 | 3 | import ( 4 | "fmt" 5 | "io/ioutil" 6 | "syscall" 7 | 8 | "github.com/google/vectorio" 9 | ) 10 | 11 | func ExampleVectorioCombined() { 12 | // Create a temp file for demo purposes 13 | f, err := ioutil.TempFile("", "vectorio") 14 | if err != nil { 15 | panic(err) 16 | } 17 | defer f.Close() 18 | 19 | data1 := []byte("foobarbaz_buf\n") 20 | data2 := []byte("barbazfoo_buf\n") 21 | 22 | // This demonstrates the "buffered" form of the library, similar to bufio. 23 | // w implements io.Writer. 24 | w, err := vectorio.NewBufferedWritev(f) 25 | if err != nil { 26 | panic(err) 27 | } 28 | 29 | // The simple method is to just write a byte slice; 30 | // this is converted to a syscall.Iovec and queued 31 | // for writing 32 | w.Write(data2) 33 | 34 | // The user can also gain more control with WriteIovec, 35 | // although this does not have a significant advantage over Write. 36 | // This is what Write does on your behalf. 37 | w.WriteIovec(syscall.Iovec{&data1[0], uint64(len(data1))}) 38 | 39 | // Flush must be called after writes are complete, to empty out 40 | // the buffer of pending Iovec. 41 | // Returns the total number of bytes written, as reported by the underlying syscall. 42 | nw1, err := w.Flush() 43 | if err != nil { 44 | panic(err) 45 | } 46 | 47 | // One can also write a slice of byte slices ([][]byte) all at once. 48 | // Note, this usage does *not* implement io.Writer, but if you have a slice 49 | // of byte slices to write, this is a way to do that without looping. 50 | 51 | multiple := [][]byte{ 52 | []byte("foobarbaz_slice\n"), 53 | []byte("foobazbar_slice\n"), 54 | } 55 | 56 | // we return the number of bytes written, as reported by the underlying syscall. 57 | nw2, err := vectorio.Writev(f, multiple) 58 | if err != nil { 59 | panic(err) 60 | } 61 | 62 | fmt.Println("Wrote", nw1+nw2, "bytes to file") 63 | // Output: 64 | // Wrote 60 bytes to file 65 | } 66 | -------------------------------------------------------------------------------- /vectorio_test.go: -------------------------------------------------------------------------------- 1 | /* 2 | Copyright 2015 Google Inc. All Rights Reserved. 3 | 4 | Licensed under the Apache License, Version 2.0 (the "License"); 5 | you may not use this file except in compliance with the License. 6 | You may obtain a copy of the License at 7 | 8 | http://www.apache.org/licenses/LICENSE-2.0 9 | 10 | Unless required by applicable law or agreed to in writing, software 11 | distributed under the License is distributed on an "AS IS" BASIS, 12 | WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 | See the License for the specific language governing permissions and 14 | limitations under the License. 15 | */ 16 | 17 | package vectorio_test 18 | 19 | import ( 20 | "bytes" 21 | "io/ioutil" 22 | "net" 23 | "os" 24 | "syscall" 25 | "testing" 26 | "time" 27 | 28 | "github.com/google/vectorio" 29 | ) 30 | 31 | func TestWritevRaw(t *testing.T) { 32 | f, err := os.Create("testwritevraw") 33 | if err != nil { 34 | panic(err) 35 | } 36 | defer f.Close() 37 | 38 | data := []byte("foobarbaz") 39 | data_desired := []byte("foobazbar") 40 | iovec := []syscall.Iovec{syscall.Iovec{&data[0], 3}, syscall.Iovec{&data[6], 3}, syscall.Iovec{&data[3], 3}} 41 | 42 | nw, err := vectorio.WritevRaw(uintptr(f.Fd()), iovec) 43 | f.Seek(0, 0) 44 | if err != nil { 45 | t.Errorf("WritevRaw threw error: %s", err) 46 | } 47 | 48 | if nw != len(data) { 49 | t.Errorf("Length %d of input does not match %d written bytes", len(data), nw) 50 | } 51 | 52 | fromdisk, err := ioutil.ReadAll(f) 53 | if err != nil { 54 | t.Errorf("can't read file back, %s", err) 55 | } 56 | if bytes.Compare(fromdisk, data_desired) != 0 { 57 | t.Errorf("contents of file don't match input, %s != %s or %d != %d", fromdisk, data_desired, len(fromdisk), len(data_desired)) 58 | } 59 | os.Remove("testwritevraw") 60 | } 61 | 62 | func TestWritev(t *testing.T) { 63 | f, err := os.Create("testwritev") 64 | if err != nil { 65 | panic(err) 66 | } 67 | defer f.Close() 68 | 69 | data := [][]byte{[]byte("foo"), []byte("bar"), []byte("baz")} 70 | 71 | nw, err := vectorio.Writev(f, data) 72 | f.Seek(0, 0) 73 | if err != nil { 74 | t.Errorf("WritevRaw threw error: %s", err) 75 | } 76 | 77 | if nw != 9 { 78 | t.Errorf("Length %d of input does not match %d written bytes", 9, nw) 79 | } 80 | 81 | fromdisk, err := ioutil.ReadAll(f) 82 | if err != nil { 83 | t.Errorf("can't read file back, %s", err) 84 | } 85 | should := []byte("foobarbaz") 86 | if bytes.Compare(fromdisk, should) != 0 { 87 | t.Errorf("contents of file don't match input, %s != %s", fromdisk, should) 88 | } 89 | os.Remove("testwritev") 90 | } 91 | 92 | func TestWritevSocket(t *testing.T) { 93 | go func() { 94 | ln, err := net.Listen("tcp", "127.0.0.1:9999") 95 | if err != nil { 96 | t.Errorf("could not listen on 127.0.0.1:9999: %s", err) 97 | } 98 | 99 | conn, err := ln.Accept() 100 | if err != nil { 101 | t.Errorf("could not accept conn: %s", err) 102 | } 103 | defer conn.Close() 104 | 105 | buf := make([]byte, 9) 106 | nr, err := conn.Read(buf) 107 | if nr != len(buf) { 108 | t.Errorf("read was wrong length: %d != %d", nr, len(buf)) 109 | } 110 | 111 | good := []byte("foobarbaz") 112 | if bytes.Compare(buf, good) != 0 { 113 | t.Errorf("read got wrong data: %s != %s", buf, good) 114 | } else { 115 | t.Logf("read got correct data: %s == %s", buf, good) 116 | } 117 | }() 118 | 119 | time.Sleep(1 * time.Second) 120 | addr, _ := net.ResolveTCPAddr("tcp4", "127.0.0.1:9999") 121 | conn, err := net.DialTCP("tcp4", nil, addr) 122 | if err != nil { 123 | t.Errorf("error connecting to 127.0.0.1:9999: %s", err) 124 | } else { 125 | t.Logf("connected to server") 126 | } 127 | defer conn.Close() 128 | data := [][]byte{[]byte("foo"), []byte("bar"), []byte("baz")} 129 | 130 | f, err := conn.File() 131 | if err != nil { 132 | t.Errorf("could not get file handle for TCP client: %s", err) 133 | } 134 | defer f.Close() 135 | nw, err := vectorio.Writev(f, data) 136 | f.Seek(0, 0) 137 | if err != nil { 138 | t.Errorf("WritevRaw threw error: %s", err) 139 | } 140 | 141 | if nw != 9 { 142 | t.Errorf("Length %d of input does not match %d written bytes", len(data), nw) 143 | } else { 144 | t.Logf("right number of bytes written") 145 | } 146 | time.Sleep(1 * time.Second) 147 | } 148 | --------------------------------------------------------------------------------