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fq/internal/asciiwriter/asciiwriter.go
Mattias Wadman 970465996c Init
2021-09-12 13:08:42 +02:00

83 lines
1.6 KiB
Go

package asciiwriter
import (
"io"
)
type Writer struct {
w io.Writer
width int
startLineOffset int
fn func(v byte) string
offset int
buf []byte
bufOffset int
}
func SafeASCII(c byte) string {
if c < 32 || c > 126 {
return "."
}
return string(c)
}
func New(w io.Writer, width int, startLineOffset int, fn func(v byte) string) *Writer {
return &Writer{
w: w,
width: width,
startLineOffset: startLineOffset,
fn: fn,
offset: 0,
buf: make([]byte, width*11+2), // worst case " " or "\n" + width*(c+ansi) + "\n"
bufOffset: 0,
}
}
func (h *Writer) Write(p []byte) (n int, err error) {
for h.offset < h.startLineOffset {
b := []byte(" ")
if h.offset%h.width == h.width-1 {
b = []byte("\n")
}
if _, err := h.w.Write(b); err != nil {
return 0, err
}
h.offset++
}
if h.offset > h.startLineOffset && h.offset%h.width == 0 {
h.buf[0] = '\n'
h.bufOffset = 1
}
for i := 0; i < len(p); i++ {
lineOffset := h.offset % h.width
s := []byte(h.fn(p[i]))
copy(h.buf[h.bufOffset:], s)
h.bufOffset += len(s)
var b []byte
switch {
case i < len(p)-1 && lineOffset == h.width-1:
h.buf[h.bufOffset] = '\n'
h.bufOffset++
b = h.buf[:h.bufOffset]
case i == len(p)-1:
b = h.buf[:h.bufOffset]
}
//log.Printf("i=%d h.bufOffset=%d lineOffset=%d h.width-1=%d b=%q\n", i, h.bufOffset, lineOffset, h.width-1, b)
if b != nil {
if _, err := h.w.Write(b); err != nil {
return 0, err
}
h.bufOffset = 0
}
h.offset++
}
return len(p), nil
}