tests: contentenc: add TestSizeToSize

TestSizeToSize tests CipherSizeToPlainSize and PlainSizeToCipherSize.

Fails at the moment due to CipherSizeToPlainSize non-moniticity.

internal/contentenc/offsets_test.go

@@ -0,0 +1,52 @@
+package contentenc
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/rfjakob/gocryptfs/internal/cryptocore"
+)
+
+// TestSizeToSize tests CipherSizeToPlainSize and PlainSizeToCipherSize
+func TestSizeToSize(t *testing.T) {
+	key := make([]byte, cryptocore.KeyLen)
+	cc := cryptocore.New(key, cryptocore.BackendGoGCM, DefaultIVBits, true, false)
+	ce := New(cc, DefaultBS, false)
+
+	const rangeMax = 10000
+
+	var c2p [rangeMax]uint64
+	var p2c [rangeMax]uint64
+
+	// Calculate values
+	for i := range c2p {
+		c2p[i] = ce.CipherSizeToPlainSize(uint64(i))
+		p2c[i] = ce.PlainSizeToCipherSize(uint64(i))
+	}
+
+	// Print data table
+	fmt.Print("x\tToPlainSize\tToCipherSize\n")
+	for i := range c2p {
+		if i > 1 && i < rangeMax-1 {
+			// If the point before has value-1 and the point after has value+1,
+			// it is not interesting. Don't print it out.
+			if c2p[i] == c2p[i-1]+1 && p2c[i] == p2c[i-1]+1 && c2p[i+1] == c2p[i]+1 && p2c[i+1] == p2c[i]+1 {
+				continue
+			}
+		}
+		fmt.Printf("%d\t%d\t%d\n", i, c2p[i], p2c[i])
+	}
+
+	// Monotonicity check
+	for i := range c2p {
+		if i < 1 {
+			continue
+		}
+		if c2p[i-1] > c2p[i] {
+			t.Errorf("error: c2p is non-monotonic: c2p[%d]=%d c2p[%d]=%d ", i-1, c2p[i-1], i, c2p[i])
+		}
+		if p2c[i-1] > p2c[i] {
+			t.Errorf("error: p2c is non-monotonic: p2c[%d]=%d p2c[%d]=%d ", i-1, p2c[i-1], i, p2c[i])
+		}
+	}
+}