diff --git a/src/file.cpp b/src/file.cpp
index 88663175..8962ac39 100644
--- a/src/file.cpp
+++ b/src/file.cpp
@@ -407,11 +407,10 @@ void OutputFile::set_extent(off_t offset, off_t length)
     }
 }
 
-off_t OutputFile::clear_offset()
+off_t OutputFile::unset_extent()
 {
     _offset = 0;
-    ::lseek(_fd, 0, SEEK_END);
-    _length = tell();
+    _length = ::lseek(_fd, 0, SEEK_END);
     return _length;
 }
 
diff --git a/src/file.h b/src/file.h
index b6382ddc..66b614ef 100644
--- a/src/file.h
+++ b/src/file.h
@@ -61,7 +61,6 @@ public:
     const char *getName() const { return _name; }
     virtual off_t st_size() const;  // { return _length; }
     virtual void set_extent(off_t offset, off_t length);
-    virtual off_t tell() const;
 
 protected:
     void sopen();
@@ -69,6 +68,7 @@ protected:
     virtual int readx(void *buf, int len);
     virtual void write(const void *buf, int len);
     virtual void seek(off_t off, int whence);
+    virtual off_t tell() const;
 
     int _fd;
     int _flags;
@@ -133,7 +133,7 @@ public:
     virtual void write(const MemBuffer *buf, int len);
     virtual void write(const MemBuffer &buf, int len);
     virtual void set_extent(off_t offset, off_t length);
-    virtual off_t clear_offset();  // returns actual length
+    virtual off_t unset_extent();  // returns actual length
 
     off_t getBytesWritten() const { return bytes_written; }
     virtual off_t st_size() const;  // { return _length; }
diff --git a/src/p_mach.cpp b/src/p_mach.cpp
index 1ca66eeb..8b44c8f1 100644
--- a/src/p_mach.cpp
+++ b/src/p_mach.cpp
@@ -648,7 +648,7 @@ void PackMachFat::pack(OutputFile *fo)
         fat_head.fat.nfat_arch * sizeof(fat_head.arch[0]));
     unsigned length;
     for (unsigned j=0; j < fat_head.fat.nfat_arch; ++j) {
-        unsigned base = fo->clear_offset();  // actual length
+        unsigned base = fo->unset_extent();  // actual length
         base += ~(~0u<<fat_head.arch[j].align) & -base;  // align up
         fo->seek(base, SEEK_SET);
         fo->set_extent(base, ~0u);
@@ -672,10 +672,10 @@ void PackMachFat::pack(OutputFile *fo)
         } break;
         }  // switch cputype
         fat_head.arch[j].offset = base;
-        length = fo->clear_offset();
+        length = fo->unset_extent();
         fat_head.arch[j].size = length - base;
     }
-    ph.u_file_size = in_size;;
+    ph.u_file_size = in_size;
     fi->set_extent(0, in_size);
 
     fo->seek(0, SEEK_SET);
@@ -694,12 +694,6 @@ bool PackMachFat::canPack()
     struct Mach_fat_arch *arch = &fat_head.arch[0];
 
     fi->readx(&fat_head, sizeof(fat_head));
-    if (Mach_fat_header::FAT_MAGIC_SWAB==fat_head.fat.magic) {
-        unsigned *const p = &fat_head.fat.magic;
-        for (unsigned j = 0; j < sizeof(fat_head)/sizeof(unsigned); ++j) {
-            p[j] = acc_swab32(p[j]);
-        }
-    }
     if (Mach_fat_header::FAT_MAGIC!=fat_head.fat.magic
     ||  N_FAT_ARCH < fat_head.fat.nfat_arch) {
         return false;
diff --git a/src/p_mach.h b/src/p_mach.h
index 38eb0528..5b13c9d4 100644
--- a/src/p_mach.h
+++ b/src/p_mach.h
@@ -29,22 +29,20 @@
 #ifndef __UPX_P_MACHO_H
 #define __UPX_P_MACHO_H
 
-// Apparently, Mach_fat_header and Mach_fat_arch have the endianness
-// of the machine on which they were created.  We must deal with both kinds.
 struct Mach_fat_header {
-    unsigned magic;
+    BE32 magic;
         enum e8 {  // note conflict with java bytecode PackLinuxI386
             FAT_MAGIC      = 0xcafebabe,
             FAT_MAGIC_SWAB = 0xbebafeca,
         };
-    unsigned nfat_arch;  // Number of Mach_fat_arch which follow.
+    BE32 nfat_arch;  // Number of Mach_fat_arch which follow.
 };
 struct Mach_fat_arch {
-    unsigned cputype;
-    unsigned cpusubtype;
-    unsigned offset;
-    unsigned size;
-    unsigned align;  /* shift count; log base 2 */
+    BE32 cputype;
+    BE32 cpusubtype;
+    BE32 offset;
+    BE32 size;
+    BE32 align;  /* shift count; log base 2 */
 };
 
 /*************************************************************************
@@ -281,8 +279,6 @@ typedef N_Mach::MachClass_64<N_BELE_CTP::LEPolicy>   MachClass_LE64;
 // shortcuts
 typedef MachClass_Host32::Mach_segment_command Mach32_segment_command;
 typedef MachClass_Host32::Mach_section_command Mach32_section_command;
-typedef MachClass_Host32::Mach_ppc_thread_state Mach_ppc_thread_state;
-typedef MachClass_Host32::Mach_i386_thread_state Mach_i386_thread_state;
 
 typedef MachClass_Host64::Mach_segment_command Mach64_segment_command;
 typedef MachClass_Host64::Mach_section_command Mach64_section_command;
@@ -299,6 +295,8 @@ typedef MachClass_LE32::Mach_section_command   MachLE32_section_command;
 typedef MachClass_LE64::Mach_segment_command   MachLE64_segment_command;
 typedef MachClass_LE64::Mach_section_command   MachLE64_section_command;
 
+typedef MachClass_BE32::Mach_ppc_thread_state  Mach_ppc_thread_state;
+typedef MachClass_LE32::Mach_i386_thread_state Mach_i386_thread_state;
 #include "p_unix.h"
 
 
@@ -367,6 +365,32 @@ protected:
 
     Mach_header mhdro;
     Mach_segment_command segcmdo;
+
+    struct b_info { // 12-byte header before each compressed block
+        U32 sz_unc;  // uncompressed_size
+        U32 sz_cpr;  //   compressed_size
+        unsigned char b_method;  // compression algorithm
+        unsigned char b_ftid;  // filter id
+        unsigned char b_cto8;  // filter parameter
+        unsigned char b_unused;
+    }
+    __attribute_packed;
+    struct l_info { // 12-byte trailer in header for loader
+        U32  l_checksum;
+        LE32 l_magic;
+        U16  l_lsize;
+        unsigned char l_version;
+        unsigned char l_format;
+    }
+    __attribute_packed;
+
+    struct p_info { // 12-byte packed program header
+        U32 p_progid;
+        U32 p_filesize;
+        U32 p_blocksize;
+    }
+    __attribute_packed;
+
     struct l_info linfo;
 };