35 lines
874 B
Go
35 lines
874 B
Go
package updates
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import "sync"
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// outputTailMax bounds the package-manager output carried back in a
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// PatchResult. The end of the output is where apt and dnf say what failed, so
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// the newest bytes are the ones kept.
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const outputTailMax = 64 << 10
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// tailBuffer is an io.Writer that retains only the last max bytes written.
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// Stdout and stderr are both pointed at one, so it is safe for concurrent use.
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type tailBuffer struct {
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mu sync.Mutex
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max int
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buf []byte
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}
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func newTailBuffer(max int) *tailBuffer { return &tailBuffer{max: max} }
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func (t *tailBuffer) Write(p []byte) (int, error) {
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t.mu.Lock()
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defer t.mu.Unlock()
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t.buf = append(t.buf, p...)
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if over := len(t.buf) - t.max; over > 0 {
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t.buf = append([]byte(nil), t.buf[over:]...)
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}
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return len(p), nil
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}
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func (t *tailBuffer) String() string {
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t.mu.Lock()
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defer t.mu.Unlock()
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return string(t.buf)
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}
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