From 199e274cacda53652294db828074d9934d955a58 Mon Sep 17 00:00:00 2001
From: "Markus F.X.J. Oberhumer" <markus@oberhumer.com>
Date: Mon, 8 Jan 2001 17:05:15 +0000
Subject: [PATCH] Added a simple delta filter.

committer: mfx <mfx> 978973515 +0000
---
 src/filter/ctoj.h  |   2 +-
 src/filter/ctojr.h |   2 +-
 src/filter/sub.h   | 151 +++++++++++++++++++++++++++++++++++++++++++++
 src/filteri.cpp    |   9 ++-
 4 files changed, 161 insertions(+), 3 deletions(-)
 create mode 100644 src/filter/sub.h

diff --git a/src/filter/ctoj.h b/src/filter/ctoj.h
index 40fa6222..5313a29c 100644
--- a/src/filter/ctoj.h
+++ b/src/filter/ctoj.h
@@ -64,7 +64,7 @@ static int F(Filter *f)
     }
     const unsigned char cto8 = f->cto;
 #ifdef U
-    const unsigned cto = (unsigned)cto8 << 24;
+    const unsigned cto = (unsigned)f->cto << 24;
 #endif
 
     for (ic = 0; ic < size - 5; ic++)
diff --git a/src/filter/ctojr.h b/src/filter/ctojr.h
index a155b54c..61e2a6b9 100644
--- a/src/filter/ctojr.h
+++ b/src/filter/ctojr.h
@@ -105,7 +105,7 @@ static int F(Filter *f)
     }
     const unsigned char cto8 = f->cto;
 #ifdef U
-    const unsigned cto = (unsigned)cto8 << 24;
+    const unsigned cto = (unsigned)f->cto << 24;
 #endif
 
     for (ic = 0; ic < size - 5; ic++)
diff --git a/src/filter/sub.h b/src/filter/sub.h
new file mode 100644
index 00000000..44268372
--- /dev/null
+++ b/src/filter/sub.h
@@ -0,0 +1,151 @@
+/* sub.h -- simple delta filter
+
+   This file is part of the UPX executable compressor.
+
+   Copyright (C) 1996-2001 Markus Franz Xaver Johannes Oberhumer
+   Copyright (C) 1996-2001 Laszlo Molnar
+   All Rights Reserved.
+
+   UPX and the UCL library are free software; you can redistribute them
+   and/or modify them under the terms of the GNU General Public License as
+   published by the Free Software Foundation; either version 2 of
+   the License, or (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; see the file COPYING.
+   If not, write to the Free Software Foundation, Inc.,
+   59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+
+   Markus F.X.J. Oberhumer   Laszlo Molnar
+   markus@oberhumer.com      ml1050@cdata.tvnet.hu
+ */
+
+
+
+/*************************************************************************
+//
+**************************************************************************/
+
+#define SUB(f, N) \
+    upx_byte *b = f->buf; \
+    unsigned l = f->buf_len; \
+    int i; \
+    unsigned char d[N]; \
+    \
+    i = N - 1; do d[i] = 0; while (--i >= 0); \
+    \
+    i = N - 1; \
+    do { \
+        *b -= d[i]; \
+        d[i] += *b++; \
+        if (--i < 0) \
+            i = N - 1; \
+    } while (--l > 0); \
+    f->calls = f->buf_len - 1; \
+    return 0;
+
+
+#define ADD(f, N) \
+    upx_byte *b = f->buf; \
+    unsigned l = f->buf_len; \
+    int i; \
+    unsigned char d[N]; \
+    \
+    i = N - 1; do d[i] = 0; while (--i >= 0); \
+    \
+    i = N - 1; \
+    do { \
+        d[i] += *b; \
+        *b++ = d[i]; \
+        if (--i < 0) \
+            i = N - 1; \
+    } while (--l > 0); \
+    f->calls = f->buf_len - 1; \
+    return 0;
+
+
+#define SCAN(f, N) \
+    f->calls = f->buf_len - 1; \
+    return 0;
+
+
+// filter
+static int f_sub1(Filter *f)
+{
+    SUB(f, 1)
+}
+
+static int f_sub2(Filter *f)
+{
+    SUB(f, 2)
+}
+
+static int f_sub3(Filter *f)
+{
+    SUB(f, 3)
+}
+
+static int f_sub4(Filter *f)
+{
+    SUB(f, 4)
+}
+
+
+// unfilter
+static int u_sub1(Filter *f)
+{
+    ADD(f, 1)
+}
+
+static int u_sub2(Filter *f)
+{
+    ADD(f, 2)
+}
+
+static int u_sub3(Filter *f)
+{
+    ADD(f, 3)
+}
+
+static int u_sub4(Filter *f)
+{
+    ADD(f, 4)
+}
+
+
+// scan
+static int s_sub1(Filter *f)
+{
+    SCAN(f, 1)
+}
+
+static int s_sub2(Filter *f)
+{
+    SCAN(f, 2)
+}
+
+static int s_sub3(Filter *f)
+{
+    SCAN(f, 3)
+}
+
+static int s_sub4(Filter *f)
+{
+    SCAN(f, 4)
+}
+
+
+#undef SUB
+#undef ADD
+#undef SCAN
+
+
+/*
+vi:ts=4:et:nowrap
+*/
+
diff --git a/src/filteri.cpp b/src/filteri.cpp
index 6fe3a406..d98fd2bf 100644
--- a/src/filteri.cpp
+++ b/src/filteri.cpp
@@ -41,12 +41,13 @@
 
 
 /*************************************************************************
-// calltrick / swaptrick
+// simple filters: calltrick / swaptrick / delta / ...
 **************************************************************************/
 
 #include "filter/ct.h"
 #include "filter/sw.h"
 #include "filter/ctsw.h"
+#include "filter/sub.h"
 
 
 /*************************************************************************
@@ -174,6 +175,12 @@ const FilterImp::FilterEntry FilterImp::filters[] = {
 
     // 32-bit cto calltrick with jmp and relative renumbering
     { 0x80, 8, 0x00ffffff, f_ctojr32_e8e9_bswap_le, u_ctojr32_e8e9_bswap_le, s_ctojr32_e8e9_bswap_le },
+
+    // simple delta filter
+    { 0x90, 2,          0, f_sub1, u_sub1, s_sub1 },
+    { 0x91, 3,          0, f_sub2, u_sub2, s_sub2 },
+    { 0x92, 4,          0, f_sub3, u_sub3, s_sub3 },
+    { 0x93, 5,          0, f_sub4, u_sub4, s_sub4 },
 };
 
 const int FilterImp::n_filters = HIGH(filters);