vendor: update buildkit to master@8b7bcb900d3c

Signed-off-by: Justin Chadwell <me@jedevc.com>

vendor/k8s.io/klog/v2/internal/buffer/buffer.go

@@ -40,44 +40,33 @@ type Buffer struct {
 	next *Buffer
 }
 
-// Buffers manages the reuse of individual buffer instances. It is thread-safe.
-type Buffers struct {
-	// mu protects the free list. It is separate from the main mutex
-	// so buffers can be grabbed and printed to without holding the main lock,
-	// for better parallelization.
-	mu sync.Mutex
-
-	// freeList is a list of byte buffers, maintained under mu.
-	freeList *Buffer
+var buffers = sync.Pool{
+	New: func() interface{} {
+		return new(Buffer)
+	},
 }
 
 // GetBuffer returns a new, ready-to-use buffer.
-func (bl *Buffers) GetBuffer() *Buffer {
-	bl.mu.Lock()
-	b := bl.freeList
-	if b != nil {
-		bl.freeList = b.next
-	}
-	bl.mu.Unlock()
-	if b == nil {
-		b = new(Buffer)
-	} else {
-		b.next = nil
-		b.Reset()
-	}
+func GetBuffer() *Buffer {
+	b := buffers.Get().(*Buffer)
+	b.Reset()
 	return b
 }
 
 // PutBuffer returns a buffer to the free list.
-func (bl *Buffers) PutBuffer(b *Buffer) {
+func PutBuffer(b *Buffer) {
 	if b.Len() >= 256 {
-		// Let big buffers die a natural death.
+		// Let big buffers die a natural death, without relying on
+		// sync.Pool behavior. The documentation implies that items may
+		// get deallocated while stored there ("If the Pool holds the
+		// only reference when this [= be removed automatically]
+		// happens, the item might be deallocated."), but
+		// https://github.com/golang/go/issues/23199 leans more towards
+		// having such a size limit.
 		return
 	}
-	bl.mu.Lock()
-	b.next = bl.freeList
-	bl.freeList = b
-	bl.mu.Unlock()
+
+	buffers.Put(b)
 }
 
 // Some custom tiny helper functions to print the log header efficiently.
@@ -121,7 +110,8 @@ func (buf *Buffer) someDigits(i, d int) int {
 	return copy(buf.Tmp[i:], buf.Tmp[j:])
 }
 
-// FormatHeader formats a log header using the provided file name and line number.
+// FormatHeader formats a log header using the provided file name and line number
+// and writes it into the buffer.
 func (buf *Buffer) FormatHeader(s severity.Severity, file string, line int, now time.Time) {
 	if line < 0 {
 		line = 0 // not a real line number, but acceptable to someDigits
@@ -157,3 +147,30 @@ func (buf *Buffer) FormatHeader(s severity.Severity, file string, line int, now
 	buf.Tmp[n+2] = ' '
 	buf.Write(buf.Tmp[:n+3])
 }
+
+// SprintHeader formats a log header and returns a string. This is a simpler
+// version of FormatHeader for use in ktesting.
+func (buf *Buffer) SprintHeader(s severity.Severity, now time.Time) string {
+	if s > severity.FatalLog {
+		s = severity.InfoLog // for safety.
+	}
+
+	// Avoid Fprintf, for speed. The format is so simple that we can do it quickly by hand.
+	// It's worth about 3X. Fprintf is hard.
+	_, month, day := now.Date()
+	hour, minute, second := now.Clock()
+	// Lmmdd hh:mm:ss.uuuuuu threadid file:line]
+	buf.Tmp[0] = severity.Char[s]
+	buf.twoDigits(1, int(month))
+	buf.twoDigits(3, day)
+	buf.Tmp[5] = ' '
+	buf.twoDigits(6, hour)
+	buf.Tmp[8] = ':'
+	buf.twoDigits(9, minute)
+	buf.Tmp[11] = ':'
+	buf.twoDigits(12, second)
+	buf.Tmp[14] = '.'
+	buf.nDigits(6, 15, now.Nanosecond()/1000, '0')
+	buf.Tmp[21] = ']'
+	return string(buf.Tmp[:22])
+}