diff --git a/src/conf.h b/src/conf.h
index 8c13418b..64df18f7 100644
--- a/src/conf.h
+++ b/src/conf.h
@@ -442,10 +442,13 @@ private:
 #define UPX_F_LINUX_ELF32_ARMBE 133
 
 
+// compression methods
+#define M_ALL           (-1)
+#define M_END           (-2)
+#define M_NONE          (-3)
+#define M_SKIP          (-4)
+#define M_ULTRA_BRUTE   (-5)
 // compression methods - DO NOT CHANGE
-#define M_END           (-1)
-#define M_SKIP          (-2)
-#define M_ULTRA_BRUTE   (-3)
 #define M_NRV2B_LE32    2
 #define M_NRV2B_8       3
 #define M_NRV2B_LE16    4
@@ -469,10 +472,11 @@ private:
 #define M_IS_DEFLATE(x) ((x) == M_DEFLATE)
 
 
-// filters - DO NOT CHANGE
+// filters
 #define FT_END          (-1)
-#define FT_SKIP         (-2)
-#define FT_ULTRA_BRUTE  (-3)
+#define FT_NONE         (-2)
+#define FT_SKIP         (-3)
+#define FT_ULTRA_BRUTE  (-4)
 
 
 /*************************************************************************
diff --git a/src/main.cpp b/src/main.cpp
index 31a4f17a..cd556c27 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -50,9 +50,9 @@ void options_t::reset()
     o->crp.reset();
 
     o->cmd = CMD_NONE;
-    o->method = -1;
+    o->method = M_NONE;
     o->level = -1;
-    o->filter = -1;
+    o->filter = FT_NONE;
 
     o->backup = -1;
     o->overlay = -1;
diff --git a/src/p_armpe.cpp b/src/p_armpe.cpp
index 8dfb9c83..f86f669c 100644
--- a/src/p_armpe.cpp
+++ b/src/p_armpe.cpp
@@ -123,7 +123,7 @@ const int *PackArmPe::getCompressionMethods(int method, int level) const
     if (!use_thumb_stub)
         return getDefaultCompressionMethods_8(method, level);
 
-    if (method == -1)       return m_all;
+    if (method == M_ALL)    return m_all;
     if (M_IS_LZMA(method))  return m_lzma;
     if (M_IS_NRV2B(method)) return m_nrv2b;
     if (M_IS_NRV2E(method)) return m_nrv2e;
@@ -133,7 +133,7 @@ const int *PackArmPe::getCompressionMethods(int method, int level) const
 
 const int *PackArmPe::getFilters() const
 {
-    static const int filters[] = { 0x50, -1 };
+    static const int filters[] = { 0x50, FT_END };
     return filters;
 }
 
@@ -710,7 +710,7 @@ void PackArmPe::pack(OutputFile *fo)
     upx_compress_config_t cconf; cconf.reset();
     cconf.conf_lzma.max_num_probs = 1846 + (768 << 4); // ushort: ~28KB stack
     compressWithFilters(&ft, 2048, &cconf, filter_strategy,
-                        ih.codebase, rvamin);
+                        ih.codebase, rvamin, 0, NULL, 0);
 // info: see buildLoader()
     newvsize = (ph.u_len + rvamin + ph.overlap_overhead + oam1) &~ oam1;
     /*
diff --git a/src/p_com.cpp b/src/p_com.cpp
index 427e943f..a6a4b538 100644
--- a/src/p_com.cpp
+++ b/src/p_com.cpp
@@ -58,7 +58,7 @@ const int *PackCom::getFilters() const
 {
     static const int filters[] = {
         0x06, 0x03, 0x04, 0x01, 0x05, 0x02,
-    -1 };
+    FT_END };
     return filters;
 }
 
diff --git a/src/p_djgpp2.cpp b/src/p_djgpp2.cpp
index 7986eb81..f48d53a6 100644
--- a/src/p_djgpp2.cpp
+++ b/src/p_djgpp2.cpp
@@ -69,7 +69,7 @@ const int *PackDjgpp2::getFilters() const
 {
     static const int filters[] = {
         0x26, 0x24, 0x11, 0x14, 0x13, 0x16, 0x25, 0x15, 0x12,
-    -1 };
+    FT_END };
     return filters;
 }
 
diff --git a/src/p_exe.cpp b/src/p_exe.cpp
index f39faae3..39d06887 100644
--- a/src/p_exe.cpp
+++ b/src/p_exe.cpp
@@ -63,7 +63,7 @@ const int *PackExe::getCompressionMethods(int method, int level) const
     static const int m_nrv2d[] = { M_NRV2D_8, M_END };
     static const int m_nrv2e[] = { M_NRV2E_8, M_END };
 
-    if (method == -1)       return m_all;
+    if (method == M_ALL)    return m_all;
     if (M_IS_NRV2B(method)) return m_nrv2b;
     if (M_IS_NRV2D(method)) return m_nrv2d;
     if (M_IS_NRV2E(method)) return m_nrv2e;
diff --git a/src/p_lx_elf.cpp b/src/p_lx_elf.cpp
index a0879cbd..cdacc094 100644
--- a/src/p_lx_elf.cpp
+++ b/src/p_lx_elf.cpp
@@ -249,8 +249,8 @@ int const *
 PackLinuxElf32ppc::getFilters() const
 {
     static const int filters[] = {
-        0xd0, -1
-    };
+        0xd0,
+    FT_END };
     return filters;
 }
 
@@ -258,8 +258,8 @@ int const *
 PackLinuxElf64amd::getFilters() const
 {
     static const int filters[] = {
-        0x49, -1
-    };
+        0x49,
+    FT_END };
     return filters;
 }
 
@@ -1424,8 +1424,8 @@ using namespace N_BELE_CTP;
 static const int *
 ARM_getFilters(bool const isBE)
 {
-    static const int f50[] = { 0x50, -1 };
-    static const int f51[] = { 0x51, -1 };
+    static const int f50[] = { 0x50, FT_END };
+    static const int f51[] = { 0x51, FT_END };
     if (isBE)
         return f51;
     return f50;
@@ -1857,7 +1857,7 @@ PackLinuxElf32x86::getFilters() const
         0x82, 0x85,
         0x24, 0x16, 0x13, 0x14, 0x11, 0x25, 0x15, 0x12,
 #endif
-    -1 };
+    FT_END };
     return filters;
 }
 
diff --git a/src/p_lx_exc.cpp b/src/p_lx_exc.cpp
index ce5fe816..bad4cedc 100644
--- a/src/p_lx_exc.cpp
+++ b/src/p_lx_exc.cpp
@@ -100,7 +100,7 @@ const int *PackLinuxI386::getFilters() const
         0x83, 0x86, 0x80, 0x84, 0x87, 0x81, 0x82, 0x85,
         0x24, 0x16, 0x13, 0x14, 0x11, 0x25, 0x15, 0x12,
 #endif
-    -1 };
+    FT_END };
     return filters;
 }
 
diff --git a/src/p_lx_sh.cpp b/src/p_lx_sh.cpp
index dfc132a6..e6c2f320 100644
--- a/src/p_lx_sh.cpp
+++ b/src/p_lx_sh.cpp
@@ -85,7 +85,7 @@ PackLinuxI386sh::buildLoader(Filter const *ft)
     // get fresh filter
     Filter fold_ft = *ft;
     fold_ft.init(ft->id, ft->addvalue);
-    int preferred_ctos[2] = {ft->cto, -1};
+    int preferred_ctos[2] = { ft->cto, -1 };
     fold_ft.preferred_ctos = preferred_ctos;
 
     // filter
diff --git a/src/p_mach.cpp b/src/p_mach.cpp
index e81a73bd..0039dd1c 100644
--- a/src/p_mach.cpp
+++ b/src/p_mach.cpp
@@ -60,7 +60,7 @@ const int *PackMachPPC32::getCompressionMethods(int /*method*/, int /*level*/) c
 
 const int *PackMachPPC32::getFilters() const
 {
-    static const int filters[] = { 0xd0, -1 };
+    static const int filters[] = { 0xd0, FT_END };
     return filters;
 }
 
diff --git a/src/p_tmt.cpp b/src/p_tmt.cpp
index 6f390661..30659f93 100644
--- a/src/p_tmt.cpp
+++ b/src/p_tmt.cpp
@@ -60,7 +60,7 @@ const int *PackTmt::getFilters() const
 {
     static const int filters[] = {
         0x26, 0x24, 0x11, 0x14, 0x13, 0x16, 0x25, 0x12, 0x15,
-    -1 };
+    FT_END };
     return filters;
 }
 
diff --git a/src/p_unix.cpp b/src/p_unix.cpp
index 6cb48ec6..238500b3 100644
--- a/src/p_unix.cpp
+++ b/src/p_unix.cpp
@@ -346,10 +346,10 @@ void PackUnix::packExtent(
             ft->cto = 0;
 
             compressWithFilters(ft, OVERHEAD, NULL_cconf, filter_strategy,
-                                0, 0, hdr_ibuf, hdr_u_len);
+                                0, 0, 0, hdr_ibuf, hdr_u_len);
         }
         else {
-            (void) compress(ibuf, obuf);    // ignore return value
+            (void) compress(ibuf, ph.u_len, obuf);    // ignore return value
         }
 
         if (ph.c_len < ph.u_len) {
diff --git a/src/p_vmlinx.cpp b/src/p_vmlinx.cpp
index dc203b9c..94aa1fb4 100644
--- a/src/p_vmlinx.cpp
+++ b/src/p_vmlinx.cpp
@@ -68,7 +68,7 @@ const int *PackVmlinuxI386::getFilters() const
 {
     static const int filters[] = {
         0x49, 0x46,
-    -1 };
+    FT_END };
     return filters;
 }
 
@@ -358,7 +358,7 @@ void PackVmlinuxI386::pack(OutputFile *fo)
     ph.u_len = phdri[0].p_offset;
     fi->seek(0, SEEK_SET);
     fi->readx(ibuf, ph.u_len);
-    compress(ibuf, obuf);
+    compress(ibuf, ph.u_len, obuf);
 
     while (0!=*p++) ;
     shdro[2].sh_name = ptr_diff(p, shstrtab);
@@ -383,7 +383,7 @@ void PackVmlinuxI386::pack(OutputFile *fo)
             ph.level = 1;
         }
     }
-    compress(ibuf, obuf, &cconf);
+    compress(ibuf, ph.u_len, obuf, &cconf);
     ph.level = old_level;
 
     // while (0!=*p++) ;  // name is the same
diff --git a/src/p_vmlinz.cpp b/src/p_vmlinz.cpp
index 92c224ae..972dcccf 100644
--- a/src/p_vmlinz.cpp
+++ b/src/p_vmlinz.cpp
@@ -69,7 +69,7 @@ const int *PackVmlinuzI386::getFilters() const
     static const int filters[] = {
         0x49,
         0x26, 0x24, 0x11, 0x14, 0x13, 0x16, 0x25, 0x15, 0x12,
-    -1 };
+    FT_END };
     return filters;
 }
 
diff --git a/src/p_w32pe.cpp b/src/p_w32pe.cpp
index 534211d4..0b6fe3a6 100644
--- a/src/p_w32pe.cpp
+++ b/src/p_w32pe.cpp
@@ -804,7 +804,7 @@ void PackW32Pe::pack(OutputFile *fo)
     }
 
     compressWithFilters(&ft, 2048, NULL_cconf, filter_strategy,
-                        ih.codebase, rvamin);
+                        ih.codebase, rvamin, 0, NULL, 0);
 // info: see buildLoader()
     newvsize = (ph.u_len + rvamin + ph.overlap_overhead + oam1) &~ oam1;
     if (tlsindex && ((newvsize - ph.c_len - 1024 + oam1) &~ oam1) > tlsindex + 4)
diff --git a/src/p_wcle.cpp b/src/p_wcle.cpp
index d9c42d81..f64c299a 100644
--- a/src/p_wcle.cpp
+++ b/src/p_wcle.cpp
@@ -77,7 +77,7 @@ const int *PackWcle::getFilters() const
 {
     static const int filters[] = {
         0x26, 0x24, 0x14, 0x11, 0x16, 0x13, 0x25, 0x12, 0x15,
-    -1 };
+    FT_END };
     return filters;
 }
 
@@ -428,7 +428,7 @@ void PackWcle::preprocessFixups()
 
 
 #define RESERVED 0x1000
-void PackWcle::encodeImage(const Filter *ft)
+void PackWcle::encodeImage(Filter *ft)
 {
     // concatenate image & preprocessed fixups
     unsigned isize = soimage + sofixups;
@@ -438,16 +438,18 @@ void PackWcle::encodeImage(const Filter *ft)
 
     delete[] ifixups; ifixups = NULL;
 
-    // compress
     oimage.allocForCompression(isize, RESERVED+512);
-    ph.filter = ft->id;
-    ph.filter_cto = ft->cto;
+    // prepare packheader
     ph.u_len = isize;
-    // reserve RESERVED bytes for the decompressor
-    if (!compress(ibuf,oimage+RESERVED))
-        throwNotCompressible();
-    ph.overlap_overhead = findOverlapOverhead(oimage+RESERVED, 512);
-    buildLoader(ft);
+    // prepare filter [already done]
+    // compress
+    upx_compress_config_t cconf; cconf.reset();
+    cconf.conf_lzma.max_num_probs = 1846 + (768 << 4); // ushort: ~28KB stack
+    compressWithFilters(ibuf, isize,
+                        oimage + RESERVED,
+                        ibuf + ft->addvalue, ft->buf_len,
+                        NULL, 0,
+                        ft, 512, &cconf, 0);
 
     ibuf.dealloc();
     soimage = ph.c_len;
@@ -506,15 +508,13 @@ void PackWcle::pack(OutputFile *fo)
     ifixups[sofixups+12] = (unsigned char) (unsigned) objects;
     sofixups += 13;
 
-    // filter
+    // prepare filter
     Filter ft(ph.level);
-    tryFilters(&ft, iimage+text_vaddr, text_size, text_vaddr);
-
+    ft.buf_len = text_size;
+    ft.addvalue = text_vaddr;
+    // compress
     encodeImage(&ft);
 
-    // verify filter
-    ft.verifyUnfilter();
-
     const unsigned lsize = getLoaderSize();
     neweip = getLoaderSection("WCLEMAIN");
     int e_len = getLoaderSectionStart("WCLECUTP");
diff --git a/src/p_wcle.h b/src/p_wcle.h
index b13c8c89..1455b591 100644
--- a/src/p_wcle.h
+++ b/src/p_wcle.h
@@ -74,7 +74,7 @@ protected:
     virtual void encodeFixups();
     virtual void decodeFixups();
 
-    virtual void encodeImage(const Filter *ft);
+    virtual void encodeImage(Filter *ft);
     virtual void decodeImage();
 
     static void virt2rela(const le_object_table_entry_t *, unsigned *objn, unsigned *addr);
diff --git a/src/packer.cpp b/src/packer.cpp
index ba4d660a..8730cf88 100644
--- a/src/packer.cpp
+++ b/src/packer.cpp
@@ -177,9 +177,10 @@ bool ph_skipVerify(const PackHeader &ph)
 // compress - wrap call to low-level upx_compress()
 **************************************************************************/
 
-bool Packer::compress(upx_bytep in, upx_bytep out,
+bool Packer::compress(upx_bytep i_ptr, unsigned i_len, upx_bytep o_ptr,
                       const upx_compress_config_t *cconf_parm)
 {
+    ph.u_len = i_len;
     ph.c_len = 0;
     assert(ph.level >= 1); assert(ph.level <= 10);
 
@@ -190,7 +191,7 @@ bool Packer::compress(upx_bytep in, upx_bytep out,
     ph.saved_u_adler = ph.u_adler;
     ph.saved_c_adler = ph.c_adler;
     // update checksum of uncompressed data
-    ph.u_adler = upx_adler32(in, ph.u_len, ph.u_adler);
+    ph.u_adler = upx_adler32(i_ptr, ph.u_len, ph.u_adler);
 
     // set compression paramters
     upx_compress_config_t cconf; cconf.reset();
@@ -236,7 +237,7 @@ bool Packer::compress(upx_bytep in, upx_bytep out,
     //OutputFile::dump("data.raw", in, ph.u_len);
 
     // compress
-    int r = upx_compress(in, ph.u_len, out, &ph.c_len,
+    int r = upx_compress(i_ptr, ph.u_len, o_ptr, &ph.c_len,
                          uip->getCallback(),
                          ph.method, ph.level, &cconf, &ph.compress_result);
 
@@ -274,13 +275,13 @@ bool Packer::compress(upx_bytep in, upx_bytep out,
         return false;
 
     // update checksum of compressed data
-    ph.c_adler = upx_adler32(out, ph.c_len, ph.c_adler);
+    ph.c_adler = upx_adler32(o_ptr, ph.c_len, ph.c_adler);
     // Decompress and verify. Skip this when using the fastest level.
     if (!ph_skipVerify(ph))
     {
         // decompress
         unsigned new_len = ph.u_len;
-        r = upx_decompress(out, ph.c_len, in, &new_len, ph.method, &ph.compress_result);
+        r = upx_decompress(o_ptr, ph.c_len, i_ptr, &new_len, ph.method, &ph.compress_result);
         //printf("%d %d: %d %d %d\n", ph.method, r, ph.c_len, ph.u_len, new_len);
         if (r != UPX_E_OK)
             throwInternalError("decompression failed");
@@ -288,7 +289,7 @@ bool Packer::compress(upx_bytep in, upx_bytep out,
             throwInternalError("decompression failed (size error)");
 
         // verify decompression
-        if (ph.u_adler != upx_adler32(in, ph.u_len, ph.saved_u_adler))
+        if (ph.u_adler != upx_adler32(i_ptr, ph.u_len, ph.saved_u_adler))
             throwInternalError("decompression failed (checksum error)");
     }
     return true;
@@ -627,7 +628,7 @@ void Packer::initPackHeader()
     memset(&ph, 0, sizeof(ph));
     ph.version = getVersion();
     ph.format = getFormat();
-    ph.method = -1;
+    ph.method = M_NONE;
     ph.level = -1;
     ph.u_adler = ph.c_adler = ph.saved_u_adler = ph.saved_c_adler = upx_adler32(NULL,0);
     ph.buf_offset = -1;
@@ -1139,8 +1140,8 @@ void Packer::relocateLoader()
 //
 // - updates this->ph
 // - updates *ft
-// - ibuf[] is restored to the original unfiltered version
-// - obuf[] contains the best compressed version
+// - i_ptr[] is restored to the original unfiltered version
+// - o_ptr[] contains the best compressed version
 //
 // filter_strategy:
 //   n:  try the first N filters, use best one
@@ -1258,23 +1259,23 @@ done:
 }
 
 
-void Packer::compressWithFilters(Filter *parm_ft,
+void Packer::compressWithFilters(upx_bytep i_ptr, unsigned i_len,
+                                 upx_bytep o_ptr,
+                                 upx_bytep f_ptr, unsigned f_len,
+                                 const upx_bytep hdr_ptr, unsigned hdr_len,
+                                 Filter *parm_ft,
                                  const unsigned overlap_range,
                                  const upx_compress_config_t *cconf,
-                                 int filter_strategy,
-                                 unsigned filter_off, unsigned compress_buf_off,
-                                 const upx_bytep hdr_buf, unsigned hdr_u_len)
+                                 int filter_strategy)
 {
+    parm_ft->buf_len = f_len;
     // struct copies
     const PackHeader orig_ph = this->ph;
           PackHeader best_ph = this->ph;
     const Filter orig_ft = *parm_ft;
           Filter best_ft = *parm_ft;
     //
-    const unsigned compress_buf_len = orig_ph.u_len;
-    const unsigned filter_len = orig_ft.buf_len ? orig_ft.buf_len : compress_buf_len;
-    //
-    best_ph.c_len = orig_ph.u_len;
+    best_ph.c_len = i_len;
     best_ph.overlap_overhead = 0;
     unsigned best_ph_lsize = 0;
     unsigned best_hdr_c_len = 0;
@@ -1282,11 +1283,10 @@ void Packer::compressWithFilters(Filter *parm_ft,
     // preconditions
     assert(orig_ph.filter == 0);
     assert(orig_ft.id == 0);
-    assert(filter_off + filter_len <= compress_buf_off + compress_buf_len);
 
     // prepare methods and filters
     int methods[256];
-    int nmethods = prepareMethods(methods, ph.method, getCompressionMethods(-1, ph.level));
+    int nmethods = prepareMethods(methods, ph.method, getCompressionMethods(M_ALL, ph.level));
     assert(nmethods > 0); assert(nmethods < 256);
     int filters[256];
     int nfilters = prepareFilters(filters, filter_strategy, getFilters());
@@ -1307,9 +1307,9 @@ void Packer::compressWithFilters(Filter *parm_ft,
     else
         uip->ui_total_passes += nfilters * nmethods;
 
-    // Working buffer for compressed data. Don't waste memory.
-    MemBuffer *otemp = &obuf;
-    MemBuffer otemp_buf;
+    // Working buffer for compressed data. Don't waste memory and allocate as needed.
+    upx_bytep o_tmp = o_ptr;
+    MemBuffer o_tmp_buf;
 
     // compress using all methods/filters
     int nfilters_success_total = 0;
@@ -1317,27 +1317,25 @@ void Packer::compressWithFilters(Filter *parm_ft,
     {
         assert(isValidCompressionMethod(methods[mm]));
         unsigned hdr_c_len = 0;
-        if (hdr_buf && hdr_u_len)
+        if (hdr_ptr != NULL && hdr_len)
         {
-            if (nfilters_success_total != 0 && otemp == &obuf)
+            if (nfilters_success_total != 0 && o_tmp == o_ptr)
             {
-                // do not overwrite obuf
-                otemp_buf.allocForCompression(compress_buf_len);
-                otemp = &otemp_buf;
+                // do not overwrite o_ptr
+                o_tmp_buf.allocForCompression(UPX_MAX(hdr_len, i_len));
+                o_tmp = o_tmp_buf;
             }
-            int r = upx_compress(hdr_buf, hdr_u_len, *otemp, &hdr_c_len,
+            int r = upx_compress(hdr_ptr, hdr_len, o_tmp, &hdr_c_len,
                                  NULL, methods[mm], 10, NULL, NULL);
             if (r != UPX_E_OK)
                 throwInternalError("header compression failed");
-            if (hdr_c_len >= hdr_u_len)
+            if (hdr_c_len >= hdr_len)
                 throwInternalError("header compression size increase");
         }
         int nfilters_success_mm = 0;
         for (int ff = 0; ff < nfilters; ff++) // for all filters
         {
             assert(isValidFilter(filters[ff]));
-            ibuf.checkState();
-            obuf.checkState();
             // get fresh packheader
             ph = orig_ph;
             ph.method = methods[mm];
@@ -1347,8 +1345,8 @@ void Packer::compressWithFilters(Filter *parm_ft,
             Filter ft = orig_ft;
             ft.init(ph.filter, orig_ft.addvalue);
             // filter
-            optimizeFilter(&ft, ibuf + filter_off, filter_len);
-            bool success = ft.filter(ibuf + filter_off, filter_len);
+            optimizeFilter(&ft, f_ptr, f_len);
+            bool success = ft.filter(f_ptr, f_len);
             if (ft.id != 0 && ft.calls == 0)
             {
                 // filter did not do anything - no need to call ft.unfilter()
@@ -1370,23 +1368,23 @@ void Packer::compressWithFilters(Filter *parm_ft,
             printf("filter: id 0x%02x size %6d, calls %5d/%5d/%3d/%5d/%5d, cto 0x%02x\n",
                    ft.id, ft.buf_len, ft.calls, ft.noncalls, ft.wrongcalls, ft.firstcall, ft.lastcall, ft.cto);
 #endif
-            if (nfilters_success_total != 0 && otemp == &obuf)
+            if (nfilters_success_total != 0 && o_tmp == o_ptr)
             {
-                otemp_buf.allocForCompression(compress_buf_len);
-                otemp = &otemp_buf;
+                o_tmp_buf.allocForCompression(i_len);
+                o_tmp = o_tmp_buf;
             }
             nfilters_success_total++;
             nfilters_success_mm++;
             ph.filter_cto = ft.cto;
             ph.n_mru = ft.n_mru;
             // compress
-            if (compress(ibuf + compress_buf_off, *otemp, cconf))
+            if (compress(i_ptr, i_len, o_tmp, cconf))
             {
                 unsigned lsize = 0;
                 if (ph.c_len + lsize + hdr_c_len <= best_ph.c_len + best_ph_lsize + best_hdr_c_len)
                 {
                     // get results
-                    ph.overlap_overhead = findOverlapOverhead(*otemp, overlap_range);
+                    ph.overlap_overhead = findOverlapOverhead(o_tmp, overlap_range);
                     buildLoader(&ft);
                     lsize = getLoaderSize();
                     assert(lsize > 0);
@@ -1414,9 +1412,9 @@ void Packer::compressWithFilters(Filter *parm_ft,
                 if (update)
                 {
                     assert((int)ph.overlap_overhead > 0);
-                    // update obuf[] with best version
-                    if (otemp != &obuf)
-                        memcpy(obuf, *otemp, ph.c_len);
+                    // update o_ptr[] with best version
+                    if (o_tmp != o_ptr)
+                        memcpy(o_ptr, o_tmp, ph.c_len);
                     // save compression results
                     best_ph = ph;
                     best_ph_lsize = lsize;
@@ -1424,13 +1422,8 @@ void Packer::compressWithFilters(Filter *parm_ft,
                     best_ft = ft;
                 }
             }
-            // restore ibuf[] - unfilter with verify
-            ft.unfilter(ibuf + filter_off, filter_len, true);
-            //
-            ibuf.checkState();
-            obuf.checkState();
-            otemp->checkState();
-            //
+            // restore - unfilter with verify
+            ft.unfilter(f_ptr, f_len, true);
             if (filter_strategy < 0)
                 break;
         }
@@ -1462,6 +1455,49 @@ void Packer::compressWithFilters(Filter *parm_ft,
 }
 
 
+/*************************************************************************
+//
+**************************************************************************/
+
+void Packer::compressWithFilters(Filter *ft,
+                                 const unsigned overlap_range,
+                                 const upx_compress_config_t *cconf,
+                                 int filter_strategy)
+{
+    compressWithFilters(ft, overlap_range, cconf, filter_strategy,
+                        0, 0, 0, NULL, 0);
+}
+
+
+void Packer::compressWithFilters(Filter *ft,
+                                 const unsigned overlap_range,
+                                 const upx_compress_config_t *cconf,
+                                 int filter_strategy,
+                                 unsigned filter_off,
+                                 unsigned ibuf_off,
+                                 unsigned obuf_off,
+                                 const upx_bytep hdr_ptr, unsigned hdr_len)
+{
+    ibuf.checkState(); obuf.checkState();
+
+    upx_bytep i_ptr = ibuf + ibuf_off;
+    unsigned  i_len = ph.u_len;
+    upx_bytep o_ptr = obuf + obuf_off;
+    upx_bytep f_ptr = ibuf + filter_off;
+    unsigned  f_len = ft->buf_len ? ft->buf_len : i_len;
+
+    assert(f_ptr + f_len <= i_ptr + i_len);
+
+    compressWithFilters(i_ptr, i_len,
+                        o_ptr,
+                        f_ptr, f_len,
+                        hdr_ptr, hdr_len,
+                        ft, overlap_range, cconf, filter_strategy);
+
+    ibuf.checkState(); obuf.checkState();
+}
+
+
 /*
 vi:ts=4:et:nowrap
 */
diff --git a/src/packer.h b/src/packer.h
index c25b23e6..5033964f 100644
--- a/src/packer.h
+++ b/src/packer.h
@@ -169,7 +169,7 @@ public:
 
 protected:
     // main compression drivers
-    virtual bool compress(upx_bytep in, upx_bytep out,
+    virtual bool compress(upx_bytep i_ptr, unsigned i_len, upx_bytep o_ptr,
                           const upx_compress_config_t *cconf = NULL);
     virtual void decompress(const upx_bytep in, upx_bytep out,
                             bool verify_checksum = true, Filter *ft = NULL);
@@ -181,11 +181,24 @@ protected:
     void compressWithFilters(Filter *ft,
                              const unsigned overlap_range,
                              const upx_compress_config_t *cconf,
-                             int filter_strategy = 0,
-                             unsigned filter_buf_off = 0,
-                             unsigned compress_buf_off = 0,
-                             const upx_bytep header_buffer = NULL,
-                             unsigned header_length = 0);
+                             int filter_strategy = 0);
+    void compressWithFilters(Filter *ft,
+                             const unsigned overlap_range,
+                             const upx_compress_config_t *cconf,
+                             int filter_strategy,
+                             unsigned filter_buf_off,
+                             unsigned compress_ibuf_off,
+                             unsigned compress_obuf_off,
+                             const upx_bytep hdr_ptr, unsigned hdr_len);
+    // real compression driver
+    void compressWithFilters(upx_bytep i_ptr, unsigned i_len,
+                             upx_bytep o_ptr,
+                             upx_bytep f_ptr, unsigned f_len,
+                             const upx_bytep hdr_ptr, unsigned hdr_len,
+                             Filter *ft,
+                             const unsigned overlap_range,
+                             const upx_compress_config_t *cconf,
+                             int filter_strategy);
 
     // util for verifying overlapping decompresion
     //   non-destructive test
@@ -233,10 +246,6 @@ protected:
 
     // filter handling [see packer_f.cpp]
     virtual bool isValidFilter(int filter_id) const;
-    virtual void tryFilters(Filter *ft, upx_byte *buf, unsigned buf_len,
-                            unsigned addvalue=0) const;
-    virtual void scanFilters(Filter *ft, const upx_byte *buf, unsigned buf_len,
-                             unsigned addvalue=0) const;
     virtual void optimizeFilter(Filter *, const upx_byte *, unsigned) const
         { }
     virtual void addFilter32(int filter_id);
diff --git a/src/packer_c.cpp b/src/packer_c.cpp
index 0bb4890d..d05325ec 100644
--- a/src/packer_c.cpp
+++ b/src/packer_c.cpp
@@ -60,7 +60,7 @@ const int *Packer::getDefaultCompressionMethods_8(int method, int level, int sma
     static const int m_nrv2d[] = { M_NRV2D_8, M_END };
     static const int m_nrv2e[] = { M_NRV2E_8, M_END };
 
-    if (method == -1)       return m_all;
+    if (method == M_ALL)    return m_all;
     //if (M_IS_CL1B(method))  return m_cl1b;
     if (M_IS_LZMA(method))  return m_lzma;
     if (M_IS_NRV2B(method)) return m_nrv2b;
@@ -83,7 +83,7 @@ const int *Packer::getDefaultCompressionMethods_le32(int method, int level, int
     static const int m_nrv2d[] = { M_NRV2D_LE32, M_END };
     static const int m_nrv2e[] = { M_NRV2E_LE32, M_END };
 
-    if (method == -1)       return m_all;
+    if (method == M_ALL)    return m_all;
     //if (M_IS_CL1B(method))  return m_cl1b;
     if (M_IS_LZMA(method))  return m_lzma;
     if (M_IS_NRV2B(method)) return m_nrv2b;
diff --git a/src/packer_f.cpp b/src/packer_f.cpp
index 52dc407b..77ec9b2d 100644
--- a/src/packer_f.cpp
+++ b/src/packer_f.cpp
@@ -41,54 +41,6 @@ bool Packer::isValidFilter(int filter_id) const
 }
 
 
-void Packer::tryFilters(Filter *ft, upx_byte *buf, unsigned buf_len,
-                        unsigned addvalue) const
-{
-    // debug
-    //scanFilters(ft, buf, buf_len, addvalue);
-
-    ft->init();
-    if (opt->filter == 0)
-        return;
-    for (const int *f = getFilters(); f && *f >= 0; f++)
-    {
-        if (*f == 0)        // skip no-filter
-            continue;
-        if (opt->filter < 0 || *f == opt->filter)
-        {
-            ft->init(*f, addvalue);
-            optimizeFilter(ft, buf, buf_len);
-            if (ft->filter(buf, buf_len) && ft->calls > 0)
-                break;                      // success
-            ft->init();
-        }
-    }
-}
-
-
-void Packer::scanFilters(Filter *ft, const upx_byte *buf, unsigned buf_len,
-                         unsigned addvalue) const
-{
-    ft->init();
-    if (opt->filter == 0)
-        return;
-    for (const int *f = getFilters(); f && *f >= 0; f++)
-    {
-        if (*f == 0)        // skip no-filter
-            continue;
-        ft->init(*f, addvalue);
-        //static const int ctos[] = { 0xff, 0xfe, 0x80, 0x22, -1 };
-        //ft->preferred_ctos = ctos;
-        if (ft->scan(buf, buf_len))
-        {
-            printf("scanFilters: id 0x%02x size: %6d: calls %5d/%5d/%3d, cto 0x%02x\n",
-                   ft->id, ft->buf_len, ft->calls, ft->noncalls, ft->wrongcalls, ft->cto);
-        }
-        ft->init();
-    }
-}
-
-
 /*************************************************************************
 // addFilter32
 **************************************************************************/