fixes #1

pkg/bspatch/bspatch.go

@@ -172,7 +172,8 @@ func patchb(oldfile, patch []byte) ([]byte, error) {
 		}
 
 		// Read diff string
-		lenread, err = dpfbz2.Read(pnew[newpos : newpos+ctrl[0]])
+		// lenread, err = dpfbz2.Read(pnew[newpos : newpos+ctrl[0]])
+		lenread, err = bzreadall(dpfbz2, pnew[newpos:newpos+ctrl[0]], ctrl[0])
 		if lenread < ctrl[0] || (err != nil && err != io.EOF) {
 			e0 := ""
 			if err != nil {
@@ -197,7 +198,9 @@ func patchb(oldfile, patch []byte) ([]byte, error) {
 		}
 
 		// Read extra string
-		lenread, err = epfbz2.Read(pnew[newpos : newpos+ctrl[1]])
+		// epfbz2.Read was not reading all the requested bytes, probably an internal buffer limitation ?
+		// it was encapsulated by bzreadall to work around the issue
+		lenread, err = bzreadall(epfbz2, pnew[newpos:newpos+ctrl[1]], ctrl[1])
 		if lenread < ctrl[1] || (err != nil && err != io.EOF) {
 			e0 := ""
 			if err != nil {
@@ -254,3 +257,22 @@ func offtin(buf []byte) int {
 	}
 	return y
 }
+
+func bzreadall(r io.Reader, b []byte, expected int) (int, error) {
+	var allread int
+	var offset int
+	for {
+		nread, err := r.Read(b[offset:])
+		if nread == expected {
+			return nread, err
+		}
+		if err != nil {
+			return allread + nread, err
+		}
+		allread += nread
+		if allread >= expected {
+			return allread, nil
+		}
+		offset += nread
+	}
+}

pkg/bspatch/bspatch_test.go

@@ -249,3 +249,43 @@ func TestCorruptHeader(t *testing.T) {
 		t.Fatal("header should be corrupt (6)")
 	}
 }
+
+type lowcaprdr struct {
+	read []byte
+	n    int
+}
+
+func (r *lowcaprdr) Read(b []byte) (int, error) {
+	if len(b) > 8 {
+		copy(r.read[r.n:], b[:8])
+		r.n += 8
+		return 8, nil
+	}
+	copy(r.read[r.n:], b)
+	r.n += len(b)
+	return len(b), nil
+}
+
+func TestBZReadAll(t *testing.T) {
+	buf := []byte{
+		0x10, 0x10, 0x10, 0x10, 0x20, 0x20, 0x20, 0x20,
+		0x30, 0x30, 0x30, 0x30, 0x40, 0x40, 0x40, 0x40,
+		0x43,
+	}
+	rr := &lowcaprdr{
+		read: make([]byte, 1024),
+	}
+	nr, err := bzreadall(rr, buf, len(buf))
+	if err != nil {
+		t.Fail()
+	}
+	if nr != len(buf) {
+		t.Fail()
+	}
+	if buf[16] != rr.read[16] {
+		t.Fail()
+	}
+	if buf[7] != rr.read[7] {
+		t.Fail()
+	}
+}