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