src: major cleanups, introduce new eXtended Span class

- initial minimally invasive eXtended Span implementation
- rename ptr_diff to ptr_diff_bytes
- move some files to util subdir
- lots of cleanups
- start using the new checked pointers - this needs some real-world testing

src/util/membuffer.h

@@ -0,0 +1,127 @@
+/* membuffer.h --
+
+   This file is part of the UPX executable compressor.
+
+   Copyright (C) 1996-2022 Markus Franz Xaver Johannes Oberhumer
+   Copyright (C) 1996-2022 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>               <ezerotven+github@gmail.com>
+ */
+
+#pragma once
+
+/*************************************************************************
+// A MemBuffer allocates memory on the heap, and automatically
+// gets destructed when leaving scope or on exceptions.
+**************************************************************************/
+
+// provides some base functionality for treating a MemBuffer as a pointer
+template <class T>
+class MemBufferBase {
+public:
+    typedef T element_type;
+    typedef T *pointer;
+
+protected:
+    pointer b = nullptr;
+    unsigned b_size_in_bytes = 0;
+
+public:
+    // NOTE: implicit conversion to underlying pointer
+    // NOTE: for fully bound-checked pointer use SPAN_S from xspan.h
+    operator pointer() const { return b; }
+
+    template <class U, class V = typename std::enable_if<std::is_integral<U>::value, U>::type>
+    pointer operator+(V n) const {
+        size_t bytes = mem_size(sizeof(T), n); // check
+        return raw_bytes(bytes) + n;
+    }
+
+    // NOT allowed; use raw_bytes() instead
+    template <class U, class V = typename std::enable_if<std::is_integral<U>::value, U>::type>
+    pointer operator-(V n) const = delete;
+
+    pointer raw_bytes(size_t bytes) const {
+        if (bytes > 0) {
+            assert(b != nullptr);
+            assert(bytes <= b_size_in_bytes);
+        }
+        return b;
+    }
+};
+
+class MemBuffer : public MemBufferBase<unsigned char> {
+public:
+    MemBuffer() = default;
+    explicit MemBuffer(upx_uint64_t size_in_bytes);
+    ~MemBuffer();
+
+    static unsigned getSizeForCompression(unsigned uncompressed_size, unsigned extra = 0);
+    static unsigned getSizeForUncompression(unsigned uncompressed_size, unsigned extra = 0);
+
+    void alloc(upx_uint64_t size);
+    void allocForCompression(unsigned uncompressed_size, unsigned extra = 0);
+    void allocForUncompression(unsigned uncompressed_size, unsigned extra = 0);
+
+    void dealloc();
+    void checkState() const;
+    unsigned getSize() const { return b_size_in_bytes; }
+
+    // explicit converstion
+    void *getVoidPtr() { return (void *) b; }
+    const void *getVoidPtr() const { return (const void *) b; }
+
+    // util
+    void fill(unsigned off, unsigned len, int value);
+    void clear(unsigned off, unsigned len) { fill(off, len, 0); }
+    void clear() { fill(0, b_size_in_bytes, 0); }
+
+    // If the entire range [skip, skip+take) is inside the buffer,
+    // then return &b[skip]; else throwCantPack(sprintf(errfmt, skip, take)).
+    // This is similar to BoundedPtr, except only checks once.
+    // skip == offset, take == size_in_bytes
+    pointer subref(const char *errfmt, size_t skip, size_t take) {
+        return (pointer) subref_impl(errfmt, skip, take);
+    }
+
+private:
+    void *subref_impl(const char *errfmt, size_t skip, size_t take);
+
+    static unsigned global_alloc_counter;
+
+    // disable copy, assignment and move assignment
+    MemBuffer(const MemBuffer &) = delete;
+    MemBuffer &operator=(const MemBuffer &) = delete;
+    MemBuffer &operator=(MemBuffer &&) = delete;
+    // disable dynamic allocation
+    ACC_CXX_DISABLE_NEW_DELETE
+
+    // disable taking the address => force passing by reference
+    // [I'm not too sure about this design decision, but we can always allow it if needed]
+    MemBuffer *operator&() const = delete;
+};
+
+// raw_bytes overload
+template <class T>
+inline T *raw_bytes(const MemBufferBase<T> &a, size_t size_in_bytes) {
+    return a.raw_bytes(size_in_bytes);
+}
+
+/* vim:set ts=4 sw=4 et: */