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s2: Fix callbacks for skippable blocks and disallow 0xfe (Padding) fo…
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…r custom use (#916)

The spec writes that 0xfe must not be interpreted by decompressors, so
setting up a callback should be denied.

I left 0xfe open for use by the Writer, as it could maybe be valid for a
user to handle padding manually.
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Jille authored Jan 25, 2024
1 parent 01b2a79 commit 515f153
Showing 1 changed file with 6 additions and 6 deletions.
12 changes: 6 additions & 6 deletions s2/reader.go
Original file line number Diff line number Diff line change
Expand Up @@ -109,7 +109,7 @@ func ReaderSkippableCB(id uint8, fn func(r io.Reader) error) ReaderOption {
if id < 0x80 || id > 0xfd {
return fmt.Errorf("ReaderSkippableCB: Invalid id provided, must be 0x80-0xfd (inclusive)")
}
r.skippableCB[id] = fn
r.skippableCB[id-0x80] = fn
return nil
}
}
Expand All @@ -128,7 +128,7 @@ type Reader struct {
err error
decoded []byte
buf []byte
skippableCB [0x80]func(r io.Reader) error
skippableCB [0xff - 0x80]func(r io.Reader) error
blockStart int64 // Uncompressed offset at start of current.
index *Index

Expand Down Expand Up @@ -201,7 +201,7 @@ func (r *Reader) readFull(p []byte, allowEOF bool) (ok bool) {
// The supplied slice does not need to be the size of the read.
func (r *Reader) skippable(tmp []byte, n int, allowEOF bool, id uint8) (ok bool) {
if id < 0x80 {
r.err = fmt.Errorf("interbal error: skippable id < 0x80")
r.err = fmt.Errorf("internal error: skippable id < 0x80")
return false
}
if fn := r.skippableCB[id-0x80]; fn != nil {
Expand Down Expand Up @@ -1048,15 +1048,15 @@ func (r *Reader) ReadByte() (byte, error) {
}

// SkippableCB will register a callback for chunks with the specified ID.
// ID must be a Reserved skippable chunks ID, 0x80-0xfe (inclusive).
// ID must be a Reserved skippable chunks ID, 0x80-0xfd (inclusive).
// For each chunk with the ID, the callback is called with the content.
// Any returned non-nil error will abort decompression.
// Only one callback per ID is supported, latest sent will be used.
// Sending a nil function will disable previous callbacks.
func (r *Reader) SkippableCB(id uint8, fn func(r io.Reader) error) error {
if id < 0x80 || id > chunkTypePadding {
if id < 0x80 || id >= chunkTypePadding {
return fmt.Errorf("ReaderSkippableCB: Invalid id provided, must be 0x80-0xfe (inclusive)")
}
r.skippableCB[id] = fn
r.skippableCB[id-0x80] = fn
return nil
}

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