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Implement our string builder
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18bd350dab
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@ -1,16 +1,32 @@
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package m
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import "unicode/utf8"
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type reusableStringBuilder struct {
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buf []byte
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length int // Number of used bytes in buf
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}
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func (rsb reusableStringBuilder) Reset() {
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panic("Unimplemented")
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func (rsb *reusableStringBuilder) Reset() {
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rsb.length = 0
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}
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func (rsb reusableStringBuilder) WriteRune(char rune) {
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panic("Unimplemented")
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// Inspired by the source code of strings.Builder
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func (rsb *reusableStringBuilder) WriteRune(r rune) {
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availableBytes := cap(rsb.buf) - rsb.length
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if availableBytes < utf8.UTFMax {
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newLength := 2*cap(rsb.buf) + utf8.UTFMax
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newBuf := make([]byte, newLength)
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for i := 0; i < rsb.length; i++ {
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newBuf[i] = rsb.buf[i]
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}
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rsb.buf = newBuf
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}
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encodedBytesCount := utf8.EncodeRune(rsb.buf[rsb.length:rsb.length+utf8.UTFMax], r)
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rsb.length += encodedBytesCount
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}
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func (rsb reusableStringBuilder) String() string {
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panic("Unimplemented")
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func (rsb *reusableStringBuilder) String() string {
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return string(rsb.buf[0:rsb.length])
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}
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@ -15,6 +15,10 @@ func TestReusableStringBuilder_Basics(t *testing.T) {
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testMe.Reset()
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assert.Equal(t, "", testMe.String())
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// Reset again to make sure it works when empty
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testMe.Reset()
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assert.Equal(t, "", testMe.String())
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}
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// Ensure the strings returned by our builder are real, rather than just being
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@ -32,3 +36,18 @@ func TestReusableStringBuilder_Copies(t *testing.T) {
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assert.Equal(t, s1, "a")
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assert.Equal(t, s2, "b")
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}
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func TestReusableStringBuilder_AddMultiple(t *testing.T) {
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testMe := reusableStringBuilder{}
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// Should be more than utf8.UTFMax = 4 to force one expansion when we
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// already have data
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testMe.WriteRune('a')
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testMe.WriteRune('b')
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testMe.WriteRune('c')
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testMe.WriteRune('d')
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testMe.WriteRune('e')
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testMe.WriteRune('f')
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assert.Equal(t, testMe.String(), "abcdef")
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}
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