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package text
import (
"io"
)
// Indent inserts prefix at the beginning of each non-empty line of s. The
// end-of-line marker is NL.
func Indent(s, prefix string) string {
return string(IndentBytes([]byte(s), []byte(prefix)))
}
// IndentBytes inserts prefix at the beginning of each non-empty line of b.
// The end-of-line marker is NL.
func IndentBytes(b, prefix []byte) []byte {
var res []byte
bol := true
for _, c := range b {
if bol && c != '\n' {
res = append(res, prefix...)
}
res = append(res, c)
bol = c == '\n'
}
return res
}
// Writer indents each line of its input.
type indentWriter struct {
w io.Writer
bol bool
pre [][]byte
sel int
off int
}
// NewIndentWriter makes a new write filter that indents the input
// lines. Each line is prefixed in order with the corresponding
// element of pre. If there are more lines than elements, the last
// element of pre is repeated for each subsequent line.
func NewIndentWriter(w io.Writer, pre ...[]byte) io.Writer {
return &indentWriter{
w: w,
pre: pre,
bol: true,
}
}
// The only errors returned are from the underlying indentWriter.
func (w *indentWriter) Write(p []byte) (n int, err error) {
for _, c := range p {
if w.bol {
var i int
i, err = w.w.Write(w.pre[w.sel][w.off:])
w.off += i
if err != nil {
return n, err
}
}
_, err = w.w.Write([]byte{c})
if err != nil {
return n, err
}
n++
w.bol = c == '\n'
if w.bol {
w.off = 0
if w.sel < len(w.pre)-1 {
w.sel++
}
}
}
return n, nil
}
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