49 lines
1.2 KiB
Go
49 lines
1.2 KiB
Go
package terminal
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import "sync"
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// defaultRingMax caps per-terminal replay history. A late subscriber gets at
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// most this many bytes of recent output so it can paint a usable screen without
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// the whole session backlog. Matches the legacy 50KB ring.
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const defaultRingMax = 50 * 1024
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// ringBuffer is a byte ring holding the most recent output of one terminal. It
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// keeps a contiguous tail capped at max bytes; snapshot returns a copy for
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// replay-on-subscribe.
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type ringBuffer struct {
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mu sync.Mutex
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buf []byte
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max int
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}
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func newRingBuffer(maxBytes int) *ringBuffer {
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if maxBytes <= 0 {
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maxBytes = defaultRingMax
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}
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return &ringBuffer{max: maxBytes}
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}
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// append adds p and drops the oldest bytes beyond max. A single write larger
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// than max is truncated to its last max bytes.
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func (r *ringBuffer) append(p []byte) {
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r.mu.Lock()
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defer r.mu.Unlock()
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if len(p) >= r.max {
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r.buf = append(r.buf[:0], p[len(p)-r.max:]...)
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return
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}
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r.buf = append(r.buf, p...)
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if len(r.buf) > r.max {
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r.buf = append(r.buf[:0], r.buf[len(r.buf)-r.max:]...)
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}
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}
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// snapshot returns a copy of the current contents (oldest first).
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func (r *ringBuffer) snapshot() []byte {
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r.mu.Lock()
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defer r.mu.Unlock()
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out := make([]byte, len(r.buf))
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copy(out, r.buf)
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return out
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}
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