github.com/mh-cbon/go@v0.0.0-20160603070303-9e112a3fe4c0/src/io/multi.go (about)

     1  // Copyright 2010 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package io
     6  
     7  type multiReader struct {
     8  	readers []Reader
     9  }
    10  
    11  func (mr *multiReader) Read(p []byte) (n int, err error) {
    12  	for len(mr.readers) > 0 {
    13  		// Optimization to flatten nested multiReaders (Issue 13558)
    14  		if len(mr.readers) == 1 {
    15  			if r, ok := mr.readers[0].(*multiReader); ok {
    16  				mr.readers = r.readers
    17  				continue
    18  			}
    19  		}
    20  		n, err = mr.readers[0].Read(p)
    21  		if n > 0 || err != EOF {
    22  			if err == EOF {
    23  				// Don't return EOF yet. There may be more bytes
    24  				// in the remaining readers.
    25  				err = nil
    26  			}
    27  			return
    28  		}
    29  		mr.readers = mr.readers[1:]
    30  	}
    31  	return 0, EOF
    32  }
    33  
    34  // MultiReader returns a Reader that's the logical concatenation of
    35  // the provided input readers. They're read sequentially. Once all
    36  // inputs have returned EOF, Read will return EOF.  If any of the readers
    37  // return a non-nil, non-EOF error, Read will return that error.
    38  func MultiReader(readers ...Reader) Reader {
    39  	r := make([]Reader, len(readers))
    40  	copy(r, readers)
    41  	return &multiReader{r}
    42  }
    43  
    44  type multiWriter struct {
    45  	writers []Writer
    46  }
    47  
    48  func (t *multiWriter) Write(p []byte) (n int, err error) {
    49  	for _, w := range t.writers {
    50  		n, err = w.Write(p)
    51  		if err != nil {
    52  			return
    53  		}
    54  		if n != len(p) {
    55  			err = ErrShortWrite
    56  			return
    57  		}
    58  	}
    59  	return len(p), nil
    60  }
    61  
    62  var _ stringWriter = (*multiWriter)(nil)
    63  
    64  func (t *multiWriter) WriteString(s string) (n int, err error) {
    65  	var p []byte // lazily initialized if/when needed
    66  	for _, w := range t.writers {
    67  		if sw, ok := w.(stringWriter); ok {
    68  			n, err = sw.WriteString(s)
    69  		} else {
    70  			if p == nil {
    71  				p = []byte(s)
    72  			}
    73  			n, err = w.Write(p)
    74  		}
    75  		if err != nil {
    76  			return
    77  		}
    78  		if n != len(s) {
    79  			err = ErrShortWrite
    80  			return
    81  		}
    82  	}
    83  	return len(s), nil
    84  }
    85  
    86  // MultiWriter creates a writer that duplicates its writes to all the
    87  // provided writers, similar to the Unix tee(1) command.
    88  func MultiWriter(writers ...Writer) Writer {
    89  	w := make([]Writer, len(writers))
    90  	copy(w, writers)
    91  	return &multiWriter{w}
    92  }