prefixed_writer.go

Documentation: github.com/onsi/gomega/gexec

     1  // untested sections: 1
     2  
     3  package gexec
     4  
     5  import (
     6  	"io"
     7  	"sync"
     8  )
     9  
    10  /*
    11  PrefixedWriter wraps an io.Writer, emitting the passed in prefix at the beginning of each new line.
    12  This can be useful when running multiple gexec.Sessions concurrently - you can prefix the log output of each
    13  session by passing in a PrefixedWriter:
    14  
    15  gexec.Start(cmd, NewPrefixedWriter("[my-cmd] ", GinkgoWriter), NewPrefixedWriter("[my-cmd] ", GinkgoWriter))
    16  */
    17  type PrefixedWriter struct {
    18  	prefix        []byte
    19  	writer        io.Writer
    20  	lock          *sync.Mutex
    21  	atStartOfLine bool
    22  }
    23  
    24  func NewPrefixedWriter(prefix string, writer io.Writer) *PrefixedWriter {
    25  	return &PrefixedWriter{
    26  		prefix:        []byte(prefix),
    27  		writer:        writer,
    28  		lock:          &sync.Mutex{},
    29  		atStartOfLine: true,
    30  	}
    31  }
    32  
    33  func (w *PrefixedWriter) Write(b []byte) (int, error) {
    34  	w.lock.Lock()
    35  	defer w.lock.Unlock()
    36  
    37  	toWrite := []byte{}
    38  
    39  	for _, c := range b {
    40  		if w.atStartOfLine {
    41  			toWrite = append(toWrite, w.prefix...)
    42  		}
    43  
    44  		toWrite = append(toWrite, c)
    45  
    46  		w.atStartOfLine = c == '\n'
    47  	}
    48  
    49  	_, err := w.writer.Write(toWrite)
    50  	if err != nil {
    51  		return 0, err
    52  	}
    53  
    54  	return len(b), nil
    55  }
    56
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