Initial QSfera import

Server/vendor/github.com/lestrrat-go/jwx/v3/jwe/compress.go

@@ -0,0 +1,62 @@
+package jwe
+
+import (
+	"bytes"
+	"compress/flate"
+	"fmt"
+	"io"
+
+	"github.com/lestrrat-go/jwx/v3/internal/pool"
+)
+
+func uncompress(src []byte, maxBufferSize int64) ([]byte, error) {
+	var dst bytes.Buffer
+	r := flate.NewReader(bytes.NewReader(src))
+	defer r.Close()
+	var buf [16384]byte
+	var sofar int64
+	for {
+		n, readErr := r.Read(buf[:])
+		sofar += int64(n)
+		if sofar > maxBufferSize {
+			return nil, fmt.Errorf(`compressed payload exceeds maximum allowed size`)
+		}
+		if readErr != nil {
+			// if we have a read error, and it's not EOF, then we need to stop
+			if readErr != io.EOF {
+				return nil, fmt.Errorf(`failed to read inflated data: %w`, readErr)
+			}
+		}
+
+		if _, err := dst.Write(buf[:n]); err != nil {
+			return nil, fmt.Errorf(`failed to write inflated data: %w`, err)
+		}
+
+		if readErr != nil {
+			// if it got here, then readErr == io.EOF, we're done
+			return dst.Bytes(), nil
+		}
+	}
+}
+
+func compress(plaintext []byte) ([]byte, error) {
+	buf := pool.BytesBuffer().Get()
+	defer pool.BytesBuffer().Put(buf)
+
+	w, _ := flate.NewWriter(buf, 1)
+	in := plaintext
+	for len(in) > 0 {
+		n, err := w.Write(in)
+		if err != nil {
+			return nil, fmt.Errorf(`failed to write to compression writer: %w`, err)
+		}
+		in = in[n:]
+	}
+	if err := w.Close(); err != nil {
+		return nil, fmt.Errorf(`failed to close compression writer: %w`, err)
+	}
+
+	ret := make([]byte, buf.Len())
+	copy(ret, buf.Bytes())
+	return ret, nil
+}