zstd: Trigger BCE by switching on lengths (#716)

This patches reduces the number of bounds checks in zstd, as reported by go build -gcflags="-d=ssa/check_bce/debug=1" |& wc -l from 723 to 693.
klauspost · Dec 19, 2022 · b2d7bff · b2d7bff
1 parent b3140ce
commit b2d7bff
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Showing 2 changed files with 4 additions and 4 deletions.
diff --git a/zstd/decodeheader.go b/zstd/decodeheader.go
@@ -152,7 +152,7 @@ func (h *Header) Decode(in []byte) error {
 		}
 		b, in = in[:size], in[size:]
 		h.HeaderSize += int(size)
-		switch size {
+		switch len(b) {
 		case 1:
 			h.DictionaryID = uint32(b[0])
 		case 2:
@@ -182,7 +182,7 @@ func (h *Header) Decode(in []byte) error {
 		}
 		b, in = in[:fcsSize], in[fcsSize:]
 		h.HeaderSize += int(fcsSize)
-		switch fcsSize {
+		switch len(b) {
 		case 1:
 			h.FrameContentSize = uint64(b[0])
 		case 2:

diff --git a/zstd/framedec.go b/zstd/framedec.go
@@ -167,7 +167,7 @@ func (d *frameDec) reset(br byteBuffer) error {
 			return err
 		}
 		var id uint32
-		switch size {
+		switch len(b) {
 		case 1:
 			id = uint32(b[0])
 		case 2:
@@ -204,7 +204,7 @@ func (d *frameDec) reset(br byteBuffer) error {
 			println("Reading Frame content", err)
 			return err
 		}
-		switch fcsSize {
+		switch len(b) {
 		case 1:
 			d.FrameContentSize = uint64(b[0])
 		case 2: