bufpool: Return bytes.Buffer, rather than a pointer to it

It's silly to allocate a bytes.Buffer struct, however small it is,
every time Borrow is called, since the entire purpose is to reduce
allocations.

3 files changed, 22 insertions, 21 deletions

diff --git a/internal/bufpool/buffers.go b/internal/bufpool/buffers.go
index 27c017bd..439e7e04 100644
--- a/internal/bufpool/buffers.go
+++ b/internal/bufpool/buffers.go
@@ -23,10 +23,11 @@ const (
 // pooled buffer, the caller should invoke Release() to return it to the pool.
 //
 // Buffers must not be copied after first use; doing so can cause double-returns
-// to the pool and data races. A zero-value Buffer is not valid for use. Use
-// the pointer type (*Buffer) returned by Borrow/FromOwned to avoid accidental
-// copies.
+// to the pool and data races.
+//
+//go:nocopy
 type Buffer struct {
+	_    struct{} // for nocopy
 	buf  []byte
 	pool poolIndex
 }
@@ -69,28 +70,28 @@ var bufferPools = func() []sync.Pool {
 // unpooled buffer is allocated.
 //
 // The caller must call Release() when finished using the returned Buffer.
-func Borrow(capHint int) *Buffer {
+func Borrow(capHint int) Buffer {
 	if capHint < DefaultBufferCap {
 		capHint = DefaultBufferCap
 	}
 	classIdx, classCap, pooled := classFor(capHint)
 	if !pooled {
 		newBuf := make([]byte, 0, capHint)
-		return &Buffer{buf: newBuf, pool: unpooled}
+		return Buffer{buf: newBuf, pool: unpooled}
 	}
 	buf := bufferPools[classIdx].Get().(*[]byte)
 	if cap(*buf) < classCap {
 		*buf = make([]byte, 0, classCap)
 	}
 	slice := (*buf)[:0]
-	return &Buffer{buf: slice, pool: poolIndex(classIdx)}
+	return Buffer{buf: slice, pool: poolIndex(classIdx)}
 }
 
 // FromOwned constructs a Buffer from a caller-owned byte slice. The resulting
 // Buffer does not participate in pooling and will never be returned to the
 // internal pool when released.
-func FromOwned(buf []byte) *Buffer {
-	return &Buffer{buf: buf, pool: unpooled}
+func FromOwned(buf []byte) Buffer {
+	return Buffer{buf: buf, pool: unpooled}
 }
 
 // Resize adjusts the length of the buffer to n bytes. If n exceeds the current
diff --git a/internal/flatex/decompress_bytes.go b/internal/flatex/decompress_bytes.go
index 0d95084c..9f1ffcfd 100644
--- a/internal/flatex/decompress_bytes.go
+++ b/internal/flatex/decompress_bytes.go
@@ -21,16 +21,16 @@ var bufferDecompressorPool = sync.Pool{
 	},
 }
 
-func Decompress(src []byte) (*bufpool.Buffer, int, error) {
+func Decompress(src []byte) (bufpool.Buffer, int, error) {
 	return DecompressSized(src, 0)
 }
 
-func DecompressSized(src []byte, sizeHint int) (*bufpool.Buffer, int, error) {
+func DecompressSized(src []byte, sizeHint int) (bufpool.Buffer, int, error) {
 	d := bufferDecompressorPool.Get().(*bufferDecompressor)
 	defer bufferDecompressorPool.Put(d)
 
 	if err := d.inflater.reset(src); err != nil {
-		return nil, 0, err
+		return bufpool.Buffer{}, 0, err
 	}
 
 	out := bufpool.Borrow(sizeHint)
@@ -47,7 +47,7 @@ func DecompressSized(src []byte, sizeHint int) (*bufpool.Buffer, int, error) {
 				return out, d.inflater.pos, nil
 			}
 			out.Release()
-			return nil, 0, d.inflater.err
+			return bufpool.Buffer{}, 0, d.inflater.err
 		}
 		d.inflater.step(&d.inflater)
 		if d.inflater.err != nil && len(d.inflater.toRead) == 0 {
diff --git a/internal/zlibx/decompress.go b/internal/zlibx/decompress.go
index df4a34be..9d4e5268 100644
--- a/internal/zlibx/decompress.go
+++ b/internal/zlibx/decompress.go
@@ -9,45 +9,45 @@ import (
 	"git.sr.ht/~runxiyu/furgit/internal/flatex"
 )
 
-func Decompress(src []byte) (*bufpool.Buffer, error) {
+func Decompress(src []byte) (bufpool.Buffer, error) {
 	return DecompressSized(src, 0)
 }
 
-func DecompressSized(src []byte, sizeHint int) (*bufpool.Buffer, error) {
+func DecompressSized(src []byte, sizeHint int) (bufpool.Buffer, error) {
 	if len(src) < 6 {
-		return nil, io.ErrUnexpectedEOF
+		return bufpool.Buffer{}, io.ErrUnexpectedEOF
 	}
 
 	cmf := src[0]
 	flg := src[1]
 	if (cmf&0x0f != zlibDeflate) || (cmf>>4 > zlibMaxWindow) || (binary.BigEndian.Uint16(src[:2])%31 != 0) {
-		return nil, ErrHeader
+		return bufpool.Buffer{}, ErrHeader
 	}
 
 	offset := 2
 	if flg&0x20 != 0 {
-		return nil, ErrHeader
+		return bufpool.Buffer{}, ErrHeader
 	}
 
 	if len(src[offset:]) < 4 {
-		return nil, io.ErrUnexpectedEOF
+		return bufpool.Buffer{}, io.ErrUnexpectedEOF
 	}
 
 	deflateData := src[offset:]
 	out, consumed, err := flatex.DecompressSized(deflateData, sizeHint)
 	if err != nil {
-		return nil, err
+		return bufpool.Buffer{}, err
 	}
 
 	checksumPos := offset + consumed
 	if checksumPos+4 > len(src) {
 		out.Release()
-		return nil, io.ErrUnexpectedEOF
+		return bufpool.Buffer{}, io.ErrUnexpectedEOF
 	}
 	expected := binary.BigEndian.Uint32(src[checksumPos : checksumPos+4])
 	if expected != adler32.Checksum(out.Bytes()) {
 		out.Release()
-		return nil, ErrChecksum
+		return bufpool.Buffer{}, ErrChecksum
 	}
 	return out, nil
 }