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sequential: refactor, and update godoc #127

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merged 5 commits into from
Jul 17, 2023
Merged

sequential: refactor, and update godoc #127

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67bd4fb
sequential: consistently use x/sys/windows for consts
thaJeztah Jun 10, 2023
3383186
sequential: open(File)Sequential: remove unused arg
thaJeztah Jun 10, 2023
7d0fcec
sequential: move error-handling to openFileSequential
thaJeztah Jun 10, 2023
ca7ec3f
sequential: simplify docs for non-Windows implementations
thaJeztah Jun 10, 2023
432b7c8
sequential: update docs for Windows-implementation
thaJeztah Jun 10, 2023
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27 changes: 4 additions & 23 deletions sequential/sequential_unix.go
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Original file line number Diff line number Diff line change
Expand Up @@ -5,41 +5,22 @@ package sequential

import "os"

// Create creates the named file with mode 0666 (before umask), truncating
// it if it already exists. If successful, methods on the returned
// File can be used for I/O; the associated file descriptor has mode
// O_RDWR.
// If there is an error, it will be of type *PathError.
// Create is an alias for [os.Create] on non-Windows platforms.
func Create(name string) (*os.File, error) {
return os.Create(name)
}

// Open opens the named file for reading. If successful, methods on
// the returned file can be used for reading; the associated file
// descriptor has mode O_RDONLY.
// If there is an error, it will be of type *PathError.
// Open is an alias for [os.Open] on non-Windows platforms.
func Open(name string) (*os.File, error) {
return os.Open(name)
}

// OpenFile is the generalized open call; most users will use Open
// or Create instead. It opens the named file with specified flag
// (O_RDONLY etc.) and perm, (0666 etc.) if applicable. If successful,
// methods on the returned File can be used for I/O.
// If there is an error, it will be of type *PathError.
// OpenFile is an alias for [os.OpenFile] on non-Windows platforms.
func OpenFile(name string, flag int, perm os.FileMode) (*os.File, error) {
return os.OpenFile(name, flag, perm)
}

// CreateTemp creates a new temporary file in the directory dir
// with a name beginning with prefix, opens the file for reading
// and writing, and returns the resulting *os.File.
// If dir is the empty string, TempFile uses the default directory
// for temporary files (see os.TempDir).
// Multiple programs calling TempFile simultaneously
// will not choose the same file. The caller can use f.Name()
// to find the pathname of the file. It is the caller's responsibility
// to remove the file when no longer needed.
// CreateTemp is an alias for [os.CreateTemp] on non-Windows platforms.
func CreateTemp(dir, prefix string) (f *os.File, err error) {
return os.CreateTemp(dir, prefix)
}
80 changes: 40 additions & 40 deletions sequential/sequential_windows.go
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Original file line number Diff line number Diff line change
Expand Up @@ -5,48 +5,52 @@ import (
"path/filepath"
"strconv"
"sync"
"syscall"
"time"
"unsafe"

"golang.org/x/sys/windows"
)

// Create creates the named file with mode 0666 (before umask), truncating
// it if it already exists. If successful, methods on the returned
// File can be used for I/O; the associated file descriptor has mode
// O_RDWR.
// If there is an error, it will be of type *PathError.
// Create is a copy of [os.Create], modified to use sequential file access.
//
// It uses [windows.FILE_FLAG_SEQUENTIAL_SCAN] rather than [windows.FILE_ATTRIBUTE_NORMAL]
// as implemented in golang. Refer to the [Win32 API documentation] for details
// on sequential file access.
//
// [Win32 API documentation]: https://learn.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-createfilea#FILE_FLAG_SEQUENTIAL_SCAN
func Create(name string) (*os.File, error) {
return OpenFile(name, os.O_RDWR|os.O_CREATE|os.O_TRUNC, 0)
return openFileSequential(name, windows.O_RDWR|windows.O_CREAT|windows.O_TRUNC)
}

// Open opens the named file for reading. If successful, methods on
// the returned file can be used for reading; the associated file
// descriptor has mode O_RDONLY.
// If there is an error, it will be of type *PathError.
// Open is a copy of [os.Open], modified to use sequential file access.
//
// It uses [windows.FILE_FLAG_SEQUENTIAL_SCAN] rather than [windows.FILE_ATTRIBUTE_NORMAL]
// as implemented in golang. Refer to the [Win32 API documentation] for details
// on sequential file access.
//
// [Win32 API documentation]: https://learn.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-createfilea#FILE_FLAG_SEQUENTIAL_SCAN
func Open(name string) (*os.File, error) {
return OpenFile(name, os.O_RDONLY, 0)
return openFileSequential(name, windows.O_RDONLY)
}

// OpenFile is the generalized open call; most users will use Open
// or Create instead.
// If there is an error, it will be of type *PathError.
// OpenFile is a copy of [os.OpenFile], modified to use sequential file access.
//
// It uses [windows.FILE_FLAG_SEQUENTIAL_SCAN] rather than [windows.FILE_ATTRIBUTE_NORMAL]
// as implemented in golang. Refer to the [Win32 API documentation] for details
// on sequential file access.
//
// [Win32 API documentation]: https://learn.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-createfilea#FILE_FLAG_SEQUENTIAL_SCAN
func OpenFile(name string, flag int, _ os.FileMode) (*os.File, error) {
if name == "" {
return nil, &os.PathError{Op: "open", Path: name, Err: syscall.ENOENT}
}
r, err := openFileSequential(name, flag, 0)
if err == nil {
return r, nil
}
return nil, &os.PathError{Op: "open", Path: name, Err: err}
return openFileSequential(name, flag)
}

func openFileSequential(name string, flag int, _ os.FileMode) (file *os.File, err error) {
r, e := openSequential(name, flag|windows.O_CLOEXEC, 0)
func openFileSequential(name string, flag int) (file *os.File, err error) {
if name == "" {
return nil, &os.PathError{Op: "open", Path: name, Err: windows.ERROR_FILE_NOT_FOUND}
}
r, e := openSequential(name, flag|windows.O_CLOEXEC)
if e != nil {
return nil, e
return nil, &os.PathError{Op: "open", Path: name, Err: e}
}
return os.NewFile(uintptr(r), name), nil
}
Expand All @@ -58,7 +62,7 @@ func makeInheritSa() *windows.SecurityAttributes {
return &sa
}

func openSequential(path string, mode int, _ uint32) (fd windows.Handle, err error) {
func openSequential(path string, mode int) (fd windows.Handle, err error) {
if len(path) == 0 {
return windows.InvalidHandle, windows.ERROR_FILE_NOT_FOUND
}
Expand Down Expand Up @@ -101,7 +105,7 @@ func openSequential(path string, mode int, _ uint32) (fd windows.Handle, err err
createmode = windows.OPEN_EXISTING
}
// Use FILE_FLAG_SEQUENTIAL_SCAN rather than FILE_ATTRIBUTE_NORMAL as implemented in golang.
// https://msdn.microsoft.com/en-us/library/windows/desktop/aa363858(v=vs.85).aspx
// https://learn.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-createfilea#FILE_FLAG_SEQUENTIAL_SCAN
h, e := windows.CreateFile(pathp, access, sharemode, sa, createmode, windows.FILE_FLAG_SEQUENTIAL_SCAN, 0)
return h, e
}
Expand All @@ -126,17 +130,13 @@ func nextSuffix() string {
return strconv.Itoa(int(1e9 + r%1e9))[1:]
}

// CreateTemp is a copy of os.CreateTemp, modified to use sequential
// file access. Below is the original comment from golang:
// TempFile creates a new temporary file in the directory dir
// with a name beginning with prefix, opens the file for reading
// and writing, and returns the resulting *os.File.
// If dir is the empty string, TempFile uses the default directory
// for temporary files (see os.TempDir).
// Multiple programs calling TempFile simultaneously
// will not choose the same file. The caller can use f.Name()
// to find the pathname of the file. It is the caller's responsibility
// to remove the file when no longer needed.
// CreateTemp is a copy of [os.CreateTemp], modified to use sequential file access.
//
// It uses [windows.FILE_FLAG_SEQUENTIAL_SCAN] rather than [windows.FILE_ATTRIBUTE_NORMAL]
// as implemented in golang. Refer to the [Win32 API documentation] for details
// on sequential file access.
//
// [Win32 API documentation]: https://learn.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-createfilea#FILE_FLAG_SEQUENTIAL_SCAN
func CreateTemp(dir, prefix string) (f *os.File, err error) {
if dir == "" {
dir = os.TempDir()
Expand All @@ -145,7 +145,7 @@ func CreateTemp(dir, prefix string) (f *os.File, err error) {
nconflict := 0
for i := 0; i < 10000; i++ {
name := filepath.Join(dir, prefix+nextSuffix())
f, err = OpenFile(name, os.O_RDWR|os.O_CREATE|os.O_EXCL, 0o600)
f, err = openFileSequential(name, windows.O_RDWR|windows.O_CREAT|windows.O_EXCL)
if os.IsExist(err) {
if nconflict++; nconflict > 10 {
randmu.Lock()
Expand Down