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Copy pathio.go
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117 lines (96 loc) · 2.34 KB
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Copy pathio.go
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117 lines (96 loc) · 2.34 KB
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package main
import (
"io"
)
type countingReader struct {
io.Reader
N int
}
func newCountingReader(r io.Reader) *countingReader {
return &countingReader{r, 0}
}
func (r *countingReader) Read(p []byte) (int, error) {
n, err := r.Reader.Read(p)
r.N += n
return n, err
}
type countingWriter struct {
io.Writer
N int
}
func newCountingWriter(w io.Writer) *countingWriter {
return &countingWriter{w, 0}
}
func (w *countingWriter) Write(p []byte) (int, error) {
n, err := w.Writer.Write(p)
w.N += n
return n, err
}
type eofReader struct{}
func (r eofReader) Read(p []byte) (int, error) {
return 0, io.EOF
}
func (r eofReader) Close() error {
return nil
}
type concatFileReader struct {
filenames []string
opener func(string) (io.ReadCloser, error)
sep []byte
cur io.ReadCloser
sepLeft int
}
// NewConcatFileReader reads from a list of filenames, and lazily loads files as it needs it.
// It is a reader that reads a concatenation of those files separated by the separator.
// You must call Close to close the last file in the list.
func newConcatFileReader(filenames []string, opener func(string) (io.ReadCloser, error)) (*concatFileReader, error) {
var cur io.ReadCloser
if len(filenames) > 0 {
var filename string
filename, filenames = filenames[0], filenames[1:]
var err error
if cur, err = opener(filename); err != nil {
return nil, err
}
} else {
cur = eofReader{}
}
return &concatFileReader{filenames, opener, nil, cur, 0}, nil
}
func (r *concatFileReader) SetSeparator(sep []byte) {
r.sep = sep
}
func (r *concatFileReader) Read(p []byte) (int, error) {
m := r.writeSep(p)
n, err := r.cur.Read(p[m:])
n += m
// current reader is finished, load in the new reader
if err == io.EOF && len(r.filenames) > 0 {
if err := r.cur.Close(); err != nil {
return n, err
}
var filename string
filename, r.filenames = r.filenames[0], r.filenames[1:]
if r.cur, err = r.opener(filename); err != nil {
return n, err
}
r.sepLeft = len(r.sep)
// if previous read returned (0, io.EOF), read from the new reader
if n == 0 {
return r.Read(p)
}
n += r.writeSep(p[n:])
}
return n, err
}
func (r *concatFileReader) writeSep(p []byte) int {
m := 0
if r.sepLeft > 0 {
m = copy(p, r.sep[len(r.sep)-r.sepLeft:])
r.sepLeft -= m
}
return m
}
func (r *concatFileReader) Close() error {
return r.cur.Close()
}