Repeat with fewer writes

Author: nineinchnick

encode.go

@@ -343,7 +343,7 @@ 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, enc.title.Width, maxWidth)
+		enc.writeAligned(enc.title.Buf, &rs, AlignRight, enc.title.Width, maxWidth)
 		enc.w.Write(enc.newline)
 	}
 	// draw top border
@@ -430,7 +430,7 @@ 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 {
@@ -498,9 +498,9 @@ func (enc *TableEncoder) row(vals []*Value, rs rowStyle) {
 					width += v.Width
 				}
 
-				enc.writeAligned(v.Buf[start:end], rs.filler, v.Align, width, enc.maxWidths[i])
+				enc.writeAligned(v.Buf[start:end], &rs, v.Align, width, enc.maxWidths[i])
 			} else {
-				repeat(enc.w, rs.filler, enc.maxWidths[i])
+				rs.filler = repeat(enc.w, rs.filler, enc.maxWidths[i])
 			}
 
 			// write newline wrap value
@@ -532,7 +532,7 @@ func (enc *TableEncoder) row(vals []*Value, rs rowStyle) {
 	}
 }
 
-func (enc *TableEncoder) writeAligned(b, filler []byte, a Align, width, max int) {
+func (enc *TableEncoder) writeAligned(b []byte, rs *rowStyle, a Align, width, max int) {
 	// calc padding
 	padding := max - width
 	paddingLeft := 0
@@ -551,15 +551,15 @@ func (enc *TableEncoder) writeAligned(b, filler []byte, a Align, width, max 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)
 	}
 }
 
@@ -780,7 +780,7 @@ 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)

util.go

@@ -108,8 +108,16 @@ 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 cap(b) >= c {
+		w.Write(b[:c])
+		return b
 	}
+	nb := b[:cap(b)]
+	for len(nb) < c {
+		nb = append(nb, nb...)
+	}
+	w.Write(nb[:c])
+	return nb[:len(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)
+	}
+}