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ReadFrom: keep the bytes returned together with a read error #33

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Merged
smallnest merged 1 commit into from
Sep 28, 2026
Merged

ReadFrom: keep the bytes returned together with a read error #33

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6 changes: 6 additions & 0 deletions ring_buffer.go
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Original file line number Diff line number Diff line change
Expand Up @@ -553,6 +553,12 @@ func (r *RingBuffer) ReadFrom(rd io.Reader) (n int64, err error) {
continue
}
if rerr != nil && rerr != io.EOF {
// Keep the bytes that came with the error.
if nr > 0 {
r.w = (startW + nr) % r.size
r.isFull = r.r == r.w
n += int64(nr)
}
err = r.setErr(rerr, true)
r.mu.Unlock()
break
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17 changes: 17 additions & 0 deletions ring_buffer_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -973,6 +973,7 @@ func (e *errormock) Read(p []byte) (n int, err error) {

case len(p) > e.rleft:
n = e.rleft
err = e.rerr

default:
n = len(p)
Expand Down Expand Up @@ -1031,6 +1032,22 @@ func TestRingBuffer_ReadFrom_Error(t *testing.T) {
}
}

func TestRingBuffer_ReadFrom_ErrorKeepsData(t *testing.T) {
rb := New(16).SetBlocking(true)
tester := &errormock{rerr: io.ErrUnexpectedEOF, rleft: 5}

copied, err := rb.ReadFrom(tester)
if err != io.ErrUnexpectedEOF {
t.Errorf("expect io.ErrUnexpectedEOF but got %v", err)
}
if copied != 5 {
t.Errorf("expect 5 bytes copied but got %d", copied)
}
if got := rb.Length(); got != 5 {
t.Errorf("expect 5 bytes buffered but got %d", got)
}
}

func TestRingBuffer_WriteTo_Error(t *testing.T) {
const bufsize = 4 << 10

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