internal/zstd: optimize skipFrame by using io.CopyN

Replaced the manual byte skipping logic with io.CopyN
to improve performance and reduce memory allocation.
This change simplifies the code by directly discarding
the bytes read, enhancing readability and efficiency.

Change-Id: Id11496d072fb554c394947d08e63616ca48ecab4
GitHub-Last-Rev: dc5f836
GitHub-Pull-Request: #69619
Reviewed-on: https://go-review.googlesource.com/c/go/+/615716
Auto-Submit: Ian Lance Taylor <[email protected]>
Reviewed-by: Ian Lance Taylor <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>
Reviewed-by: Carlos Amedee <[email protected]>

Author: aimuz

src/internal/zstd/zstd.go

@@ -358,30 +358,12 @@ func (r *Reader) skipFrame() error {
 		return nil
 	}
 
-	var skip []byte
-	const chunk = 1 << 20 // 1M
-	for size >= chunk {
-		if len(skip) == 0 {
-			skip = make([]byte, chunk)
-		}
-		if _, err := io.ReadFull(r.r, skip); err != nil {
-			return r.wrapNonEOFError(relativeOffset, err)
-		}
-		relativeOffset += chunk
-		size -= chunk
-	}
-	if size > 0 {
-		if len(skip) == 0 {
-			skip = make([]byte, size)
-		}
-		if _, err := io.ReadFull(r.r, skip); err != nil {
-			return r.wrapNonEOFError(relativeOffset, err)
-		}
-		relativeOffset += int(size)
+	n, err := io.CopyN(io.Discard, r.r, int64(size))
+	relativeOffset += int(n)
+	if err != nil {
+		return r.wrapNonEOFError(relativeOffset, err)
 	}
-
 	r.blockOffset += int64(relativeOffset)
-
 	return nil
 }