65 lines
1.4 KiB
Go
65 lines
1.4 KiB
Go
package mailyak
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import (
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"io"
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)
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const maxLineLen = 60
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// lineSplitter breaks the given input into lines of maxLineLen characters
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// before writing a "\r\n" newline
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type lineSplitter struct {
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w io.Writer
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wrote uint
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maxLen int
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}
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type lineSplitterBuilder struct{}
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func (b lineSplitterBuilder) new(w io.Writer) io.Writer {
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return &lineSplitter{w: w, maxLen: maxLineLen}
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}
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func (w *lineSplitter) Write(p []byte) (int, error) {
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// Calculate the previously wrote line length
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leftover := w.wrote % uint(w.maxLen)
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// Calculate the amount of bytes remaining for this line
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lineSize := w.maxLen - int(leftover)
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// Break p into chunks
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for i := 0; i < len(p); i += lineSize {
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// Reset linesize
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if i%w.maxLen != 0 && lineSize < w.maxLen {
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lineSize = w.maxLen
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}
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// Calculate the end of the chunk offset
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end := i + lineSize
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if end > len(p) {
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end = len(p)
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}
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// Slice chunk out of p
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chunk := p[i:end]
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// Increment the amount wrote so far by the chunk size
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w.wrote += uint(len(chunk))
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// Write the chunk
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if n, err := w.w.Write(chunk); err != nil {
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return i + n, err
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}
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// If this finishes a line, add linebreaks
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if end == i+lineSize {
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if _, err := w.w.Write([]byte("\r\n")); err != nil {
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// If this errors, return the bytes wrote so far from the
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// caller's perspective (it is unaware newlines are being added)
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return i + len(chunk), err
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}
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}
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}
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return len(p), nil
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}
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