/
io.go
233 lines (198 loc) · 4.7 KB
/
io.go
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package otk
import (
"bufio"
"encoding/json"
"io"
"os"
"path/filepath"
"sync"
"golang.org/x/xerrors"
)
// PipeRd is an io.Pipe helper, returns a io.ReadCloser
func PipeRd(writeFn func(io.Writer) error) io.ReadCloser {
rd, wr := io.Pipe()
go func() { wr.CloseWithError(writeFn(wr)) }()
return rd
}
// PipeWr is an io.Pipe helper, returns a io.WriteCloser
func PipeWr(readerFn func(io.Reader) error) io.WriteCloser {
rd, wr := io.Pipe()
go func() { rd.CloseWithError(readerFn(rd)) }()
return wr
}
type multiWriter struct {
writers []io.Writer
errs []error
}
func (t *multiWriter) Write(p []byte) (n int, err error) {
for i, w := range t.writers {
if w == nil {
continue
}
n, err = w.Write(p)
if err == nil && n != len(p) {
err = io.ErrShortWrite
}
if err != nil {
t.errs = append(t.errs, xerrors.Errorf("writer #%d: %w", i, err))
t.writers[i] = nil
}
}
return len(p), nil
}
var _ io.StringWriter = (*multiWriter)(nil)
func (t *multiWriter) WriteString(s string) (n int, err error) {
var (
p []byte // lazily initialized if/when needed
ln = len(s)
)
for i, w := range t.writers {
if w == nil {
continue
}
if sw, ok := w.(io.StringWriter); ok {
n, err = sw.WriteString(s)
} else {
if p == nil {
p = []byte(s)
ln = len(p)
}
n, err = w.Write(p)
}
if err == nil && n != ln {
err = io.ErrShortWrite
}
if err != nil {
t.errs = append(t.errs, xerrors.Errorf("writer #%d: %w", i, err))
t.writers[i] = nil
}
}
return len(s), nil
}
func (t *multiWriter) getErrs() []error { return t.errs }
// MultiWriter creates a writer that duplicates its writes to all the
// provided writers, similar to the Unix tee(1) command.
//
// Each write is written to each listed writer, one at a time.
// If a listed writer returns an error, that writer will be ignored
// for later writes.
// returns the multi writer and a func that returns a slice of errors if there were any.
func MultiWriter(writers ...io.Writer) (io.Writer, func() []error) {
allWriters := make([]io.Writer, 0, len(writers))
for _, w := range writers {
if mw, ok := w.(*multiWriter); ok {
allWriters = append(allWriters, mw.writers...)
} else {
allWriters = append(allWriters, w)
}
}
mw := &multiWriter{allWriters, nil}
return mw, mw.getErrs
}
type nopCloser struct {
io.Writer
}
func (nopCloser) Close() error { return nil }
func NopWriteCloser(w io.Writer) io.WriteCloser { return nopCloser{w} }
func CopyOnWriteFile(fp string, fn func(w io.Writer) error) (err error) {
return CopyOnWriteFilePerms(fp, func(w *bufio.Writer) error { return fn(w) }, 0644)
}
var bufWriterPool = sync.Pool{
New: func() interface{} {
return bufio.NewWriterSize(nil, 32768)
},
}
func CopyOnWriteFilePerms(fp string, fn func(bw *bufio.Writer) error, mode os.FileMode) (err error) {
var f *os.File
dir, fname := filepath.Split(fp)
if f, err = os.CreateTemp(dir, fname); err != nil {
return
}
bw := bufWriterPool.Get().(*bufio.Writer)
bw.Reset(f)
defer func() {
bw.Reset(nil)
bufWriterPool.Put(bw)
os.Remove(f.Name()) // clean our trash if we errored out
}()
if err = fn(bw); err != nil {
f.Close()
return
}
if err = bw.Flush(); err != nil {
f.Close()
return
}
if err = f.Chmod(mode); err != nil {
f.Close()
return
}
if err = f.Close(); err != nil {
return
}
return os.Rename(f.Name(), fp)
}
type (
FileDecoder interface {
Decode(interface{}) error
}
FileEncoder interface {
Encode(interface{}) error
}
)
func ReadFileWithDecoder(fp string, dec func(r io.Reader) FileDecoder, out interface{}) error {
f, err := os.Open(fp)
if err != nil {
return err
}
defer f.Close()
return dec(f).Decode(out)
}
func WriteFileWithEncoder(fp string, enc func(w io.Writer) FileEncoder, in interface{}) error {
f, err := os.Create(fp)
if err != nil {
return err
}
defer f.Close()
return enc(f).Encode(in)
}
func ReadJSONFile(fp string, out interface{}) error {
return ReadFileWithDecoder(fp, func(r io.Reader) FileDecoder {
return json.NewDecoder(r)
}, out)
}
func WriteJSONFile(fp string, in interface{}, indent bool) error {
return WriteFileWithEncoder(fp, func(w io.Writer) FileEncoder {
enc := json.NewEncoder(w)
if indent {
enc.SetIndent("", "\t")
}
return enc
}, in)
}
type CachedReader struct {
R io.Reader
tmp []byte
rewind bool
}
func (cr *CachedReader) Read(p []byte) (int, error) {
if !cr.rewind {
if cr.tmp == nil {
cr.tmp = make([]byte, 0, len(p))
}
n, err := cr.R.Read(p)
cr.tmp = append(cr.tmp, p[:n]...)
return n, err
}
if len(cr.tmp) > 0 {
n := copy(p, cr.tmp)
if cr.tmp = cr.tmp[n:]; len(cr.tmp) == 0 {
cr.tmp = nil
}
return n, nil
}
return cr.R.Read(p)
}
func (cr *CachedReader) Rewind() {
cr.rewind = true
}