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stdio.go
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stdio.go
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package sys
import (
"io"
"os"
"syscall"
"time"
"github.com/tetratelabs/wazero/internal/fsapi"
"github.com/tetratelabs/wazero/internal/platform"
"github.com/tetratelabs/wazero/internal/sysfs"
)
// StdinFile is a fs.ModeDevice file for use implementing FdStdin.
// This is safer than reading from os.DevNull as it can never overrun
// operating system file descriptors.
type StdinFile struct {
noopStdinFile
io.Reader
}
// Read implements the same method as documented on internalapi.File
func (f *StdinFile) Read(buf []byte) (int, syscall.Errno) {
n, err := f.Reader.Read(buf)
return n, platform.UnwrapOSError(err)
}
type writerFile struct {
noopStdoutFile
w io.Writer
}
// Write implements the same method as documented on internalapi.File
func (f *writerFile) Write(buf []byte) (int, syscall.Errno) {
n, err := f.w.Write(buf)
return n, platform.UnwrapOSError(err)
}
// noopStdinFile is a fs.ModeDevice file for use implementing FdStdin. This is
// safer than reading from os.DevNull as it can never overrun operating system
// file descriptors.
type noopStdinFile struct {
noopStdioFile
}
// AccessMode implements the same method as documented on internalapi.File
func (noopStdinFile) AccessMode() int {
return syscall.O_RDONLY
}
// Read implements the same method as documented on internalapi.File
func (noopStdinFile) Read([]byte) (int, syscall.Errno) {
return 0, 0 // Always EOF
}
// PollRead implements the same method as documented on internalapi.File
func (noopStdinFile) PollRead(*time.Duration) (ready bool, errno syscall.Errno) {
return true, 0 // always ready to read nothing
}
// noopStdoutFile is a fs.ModeDevice file for use implementing FdStdout and
// FdStderr.
type noopStdoutFile struct {
noopStdioFile
}
// AccessMode implements the same method as documented on internalapi.File
func (noopStdoutFile) AccessMode() int {
return syscall.O_WRONLY
}
// Write implements the same method as documented on internalapi.File
func (noopStdoutFile) Write(buf []byte) (int, syscall.Errno) {
return len(buf), 0 // same as io.Discard
}
type noopStdioFile struct {
fsapi.UnimplementedFile
}
// Stat implements the same method as documented on internalapi.File
func (noopStdioFile) Stat() (fsapi.Stat_t, syscall.Errno) {
return fsapi.Stat_t{Mode: modeDevice, Nlink: 1}, 0
}
// IsDir implements the same method as documented on internalapi.File
func (noopStdioFile) IsDir() (bool, syscall.Errno) {
return false, 0
}
// Close implements the same method as documented on internalapi.File
func (noopStdioFile) Close() (errno syscall.Errno) { return }
func stdinFile(r io.Reader) (*FileEntry, error) {
if r == nil {
return &FileEntry{Name: "stdin", IsPreopen: true, File: &noopStdinFile{}}, nil
} else if f, ok := r.(*os.File); ok {
if f, err := sysfs.NewStdioFile(true, f); err != nil {
return nil, err
} else {
return &FileEntry{Name: "stdin", IsPreopen: true, File: f}, nil
}
} else {
return &FileEntry{Name: "stdin", IsPreopen: true, File: &StdinFile{Reader: r}}, nil
}
}
func stdioWriterFile(name string, w io.Writer) (*FileEntry, error) {
if w == nil {
return &FileEntry{Name: name, IsPreopen: true, File: &noopStdoutFile{}}, nil
} else if f, ok := w.(*os.File); ok {
if f, err := sysfs.NewStdioFile(false, f); err != nil {
return nil, err
} else {
return &FileEntry{Name: name, IsPreopen: true, File: f}, nil
}
} else {
return &FileEntry{Name: name, IsPreopen: true, File: &writerFile{w: w}}, nil
}
}