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// Copyright 2014-2022 Ulrich Kunitz. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package randtxt
import (
"bufio"
"io"
"unicode"
)
// GroupReader groups the incoming text in groups of 5, whereby the
// number of groups per line can be controlled.
type GroupReader struct {
R io.ByteReader
GroupsPerLine int
off int64
eof bool
}
// NewGroupReader creates a new group reader.
func NewGroupReader(r io.Reader) *GroupReader {
return &GroupReader{R: bufio.NewReader(r)}
}
// Read formats the data provided by the internal reader in groups of 5
// characters. If GroupsPerLine hasn't been initialized 8 groups per
// line will be produced.
func (r *GroupReader) Read(p []byte) (n int, err error) {
if r.eof {
return 0, io.EOF
}
groupsPerLine := r.GroupsPerLine
if groupsPerLine < 1 {
groupsPerLine = 8
}
lineLen := int64(groupsPerLine * 6)
var c byte
for i := range p {
switch {
case r.off%lineLen == lineLen-1:
if i+1 == len(p) && len(p) > 1 {
return i, nil
}
c = '\n'
case r.off%6 == 5:
if i+1 == len(p) && len(p) > 1 {
return i, nil
}
c = ' '
default:
c, err = r.R.ReadByte()
if err == io.EOF {
r.eof = true
if i > 0 {
switch p[i-1] {
case ' ':
p[i-1] = '\n'
fallthrough
case '\n':
return i, io.EOF
}
}
p[i] = '\n'
return i + 1, io.EOF
}
if err != nil {
return i, err
}
switch {
case c == ' ':
c = '_'
case !unicode.IsPrint(rune(c)):
c = '-'
}
}
p[i] = c
r.off++
}
return len(p), nil
}
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