Repeat with fewer writes

Author: nineinchnick

encode.go

@@ -410,7 +410,7 @@ func (enc *TableEncoder) header() {
 
 	if enc.title != nil && enc.title.Width != 0 {
 		maxWidth := ((enc.tableWidth() - enc.title.Width) / 2) + enc.title.Width
-		enc.writeAligned(enc.title.Buf, rs.filler, AlignRight, maxWidth-enc.title.Width)
+		enc.writeAligned(enc.title.Buf, &rs, AlignRight, maxWidth-enc.title.Width)
 		enc.w.Write(enc.newline)
 	}
 	// draw top border
@@ -472,7 +472,7 @@ func (enc TableEncoder) rowStyle(r [4]rune) rowStyle {
 		wrapper:     []byte(string(enc.lineStyle.Wrap[1])),
 		middle:      []byte(middle),
 		right:       []byte(right + string(enc.newline)),
-		filler:      []byte(filler),
+		filler:      bytes.Repeat([]byte(filler), 8),
 		hasWrapping: runewidth.RuneWidth(enc.lineStyle.Row[1]) > 0,
 	}
 }
@@ -497,11 +497,11 @@ func (enc *TableEncoder) divider(rs rowStyle) {
 
 	for i, width := range enc.maxWidths {
 		// column
-		repeat(enc.w, rs.filler, width)
+		rs.filler = repeat(enc.w, rs.filler, width)
 
 		// line feed indicator
 		if rs.hasWrapping && enc.border >= 1 {
-			enc.w.Write(rs.filler)
+			enc.w.Write(rs.filler[:1])
 		}
 
 		// middle separator
@@ -614,11 +614,10 @@ func (enc *TableEncoder) row(vals []*Value, rs rowStyle) {
 				if enc.border <= 1 && i == len(vals)-1 && (!rs.hasWrapping || l >= len(v.Newlines)) {
 					padding = 0
 				}
-				enc.writeAligned(v.Buf[start:end], rs.filler, v.Align, padding)
+				enc.writeAligned(v.Buf[start:end], &rs, v.Align, padding)
 			} else {
 				if enc.border > 1 || i != len(vals)-1 {
-					enc.w.Write(bytes.Repeat(rs.filler, enc.maxWidths[i]))
-					repeat(enc.w, rs.filler, enc.maxWidths[i])
+					rs.filler = repeat(enc.w, rs.filler, enc.maxWidths[i])
 				}
 			}
 
@@ -627,7 +626,7 @@ func (enc *TableEncoder) row(vals []*Value, rs rowStyle) {
 				if l < len(v.Newlines) {
 					enc.w.Write(rs.wrapper)
 				} else {
-					enc.w.Write(rs.filler)
+					enc.w.Write(rs.filler[:1])
 				}
 			}
 
@@ -651,7 +650,7 @@ func (enc *TableEncoder) row(vals []*Value, rs rowStyle) {
 	}
 }
 
-func (enc *TableEncoder) writeAligned(b, filler []byte, a Align, padding int) {
+func (enc *TableEncoder) writeAligned(b []byte, rs *rowStyle, a Align, padding int) {
 	// calc padding
 	paddingLeft := 0
 	paddingRight := 0
@@ -669,15 +668,15 @@ func (enc *TableEncoder) writeAligned(b, filler []byte, a Align, padding int) {
 
 	// add padding left
 	if paddingLeft > 0 {
-		repeat(enc.w, filler, paddingLeft)
+		rs.filler = repeat(enc.w, rs.filler, paddingLeft)
 	}
 
 	// write
 	enc.w.Write(b)
 
 	// add padding right
 	if paddingRight > 0 {
-		repeat(enc.w, filler, paddingRight)
+		rs.filler = repeat(enc.w, rs.filler, paddingRight)
 	}
 }
 
@@ -950,10 +949,10 @@ func (enc *ExpandedEncoder) record(i int, vals []*Value, rs rowStyle) {
 		enc.w.WriteString(header)
 		padding := enc.maxWidths[0] + enc.maxWidths[1] + runewidth.StringWidth(string(headerRS.middle))*2 - len(header) - 1
 		if padding > 0 {
-			repeat(enc.w, headerRS.filler, padding)
+			headerRS.filler = repeat(enc.w, headerRS.filler, padding)
 		}
 		// write newline wrap value
-		enc.w.Write(headerRS.filler)
+		enc.w.Write(headerRS.filler[:1])
 		enc.w.Write(headerRS.right)
 	}
 

util.go

@@ -108,8 +108,15 @@ func condWrite(w io.Writer, repeat int, runes ...rune) error {
 	return err
 }
 
-func repeat(w io.Writer, b []byte, c int) {
-	for i := 0; i < c; i++ {
-		w.Write(b)
+// repeat b c times and write it to w, returning b with increased capacity
+func repeat(w io.Writer, b []byte, c int) []byte {
+	if len(b) >= c {
+		w.Write(b[:c])
+		return b
 	}
+	for len(b) < c {
+		b = append(b, b...)
+	}
+	w.Write(b[:c])
+	return b
 }

util_test.go

@@ -12,6 +12,7 @@ import (
 	"os/exec"
 	"strconv"
 	"strings"
+	"testing"
 	"time"
 	"unicode"
 )
@@ -356,3 +357,20 @@ type noopWriter struct {
 func (*noopWriter) Write(buf []byte) (int, error) {
 	return len(buf), nil
 }
+
+func TestRepeat(t *testing.T) {
+	buf := new(bytes.Buffer)
+	filler := []byte("x")
+	filler = repeat(buf, filler, 10)
+	filler = repeat(buf, filler, 10)
+	if cap(filler) != 16 {
+		t.Errorf("Expected filler to have cap of 16, got %d", cap(filler))
+	}
+	if len(filler) != 1 {
+		t.Errorf("Expected filler to have len of 1, got %d", len(filler))
+	}
+	actual := buf.String()
+	if actual != "xxxxxxxxxxxxxxxxxxxx" {
+		t.Errorf("Expected buf to be 20 x's, got %s", actual)
+	}
+}