mostream.h

// This file is part of the uSTL library, an STL implementation.
//
// Copyright (c) 2005 by Mike Sharov <msharov@users.sourceforge.net>
// This file is free software, distributed under the MIT License.

#pragma once
#include "memlink.h"
#include "uexception.h"
#include "utf8.h"
#include "uios.h"
#include "strmsize.h"
#if WANT_STREAM_BOUNDS_CHECKING
    #include "typeinfo.h"
#endif

namespace ustl {

class istream;
class string;

/// \class ostream mostream.h ustl.h
/// \ingroup BinaryStreams
///
/// \brief Helper class to write packed binary streams.
///
/// This class contains a set of functions to write integral types into an
/// unstructured memory block. Packing binary file data can be done this
/// way, for instance. aligning the data is your responsibility, and can
/// be accomplished by proper ordering of writes and by calling align.
/// Unaligned access is usually slower by orders of magnitude and,
/// on some architectures, such as PowerPC, can cause your program to crash.
/// Therefore, all write functions have asserts to check alignment.
/// See \ref istream documentation for rules on designing your data format.
/// Overwriting the end of the stream will also cause a crash (an assert in
/// debug builds). Oh, and don't be intimidated by the size of the inlines
/// here. In the assembly code the compiler will usually chop everything down
/// to five instructions each.
///
/// Example code:
/// \code
///     memblock b;
///     ostream os (b);
///     os << boolVar << ios::talign<int>();
///     os << intVar << floatVar;
///     os.write (binaryData, binaryDataSize);
///     os.align();
///     b.resize (os.pos());
///     b.write_file ("test.file");
/// \endcode
///
class ostream : public memlink, public ios_base {
public:
    inline		ostream (void)			: memlink(), _pos(0) {}
    inline		ostream (void* p, streamsize n)	: memlink (p, n), _pos (0) {}
    inline explicit	ostream (const memlink& source)	: memlink (source), _pos (0) {}
    inline iterator	end (void)			{ return memlink::end(); }
    inline const_iterator end (void) const		{ return memlink::end(); }
    inline void		seek (uoff_t newPos);
    inline void		iseek (const_iterator newPos);
    inline void		skip (streamsize nBytes);
    inline uoff_t	pos (void) const		{ return _pos; }
    inline iterator	ipos (void)			{ return begin() + pos(); }
    inline const_iterator ipos (void) const		{ return begin() + pos(); }
    inline streamsize	remaining (void) const;
    inline bool		aligned (streamsize grain = c_DefaultAlignment) const;
    bool		verify_remaining (const char* op, const char* type, size_t n);
    inline streamsize	align_size (streamsize grain = c_DefaultAlignment) const;
    void		align (streamsize grain = c_DefaultAlignment);
    inline void		write (const void* buffer, streamsize size);
    inline void		write (const cmemlink& buf);
    void		write_strz (const char* str);
    void		read (istream& is);
    inline void		write (ostream& os) const	{ os.write (begin(), pos()); }
    void		text_write (ostringstream& os) const;
    inline size_t	stream_size (void) const	{ return pos(); }
    void		insert (iterator start, streamsize size);
    void		erase (iterator start, streamsize size);
    inline void		swap (ostream& os);
    template <typename T>
    inline void		iwrite (const T& v);
    inline virtual ostream&	flush (void)		{ return *this; }
    inline virtual streamsize	overflow (streamsize=1)	{ return remaining(); }
    virtual void	unlink (void) noexcept override;
    inline void		link (void* p, streamsize n)	{ memlink::link (p, n); }
    inline void		link (memlink& l)		{ memlink::link (l.data(), l.writable_size()); }
    inline void		link (void* f, void* l)		{ memlink::link (f, l); }
    inline void		relink (void* p, streamsize n)	{ memlink::relink (p, n); _pos = 0; }
    inline void		relink (memlink& l)		{ relink (l.data(), l.writable_size()); }
    inline void		seekp (off_t p, seekdir d = beg);
    inline off_t	tellp (void) const		{ return pos(); }
protected:
    inline void		SetPos (uoff_t newPos)		{ _pos = newPos; }
private:
    streamoff		_pos;	///< Current write position.
};

//----------------------------------------------------------------------

/// \class ostream_iterator mostream.h ustl.h
/// \ingroup BinaryStreamIterators
///
/// \brief An iterator over an ostream to use with uSTL algorithms.
///
template <typename T, typename Stream = ostream>
class ostream_iterator {
public:
    typedef T			value_type;
    typedef ptrdiff_t		difference_type;
    typedef value_type*		pointer;
    typedef value_type&		reference;
    typedef typename Stream::size_type	size_type;
    typedef output_iterator_tag	iterator_category;
public:
    inline explicit		ostream_iterator (Stream& os)
				    : _os (os) {}
    inline			ostream_iterator (const ostream_iterator& iter)
				    : _os (iter._os) {}
    /// Writes \p v into the stream.
    inline ostream_iterator&	operator= (const T& v)
				    { _os << v; return *this; }
    inline ostream_iterator&	operator* (void) { return *this; }
    inline ostream_iterator&	operator++ (void) { return *this; }
    inline ostream_iterator	operator++ (int) { return *this; }
    inline ostream_iterator&	operator+= (streamsize n) { _os.skip (n); return *this; }
    inline bool			operator== (const ostream_iterator& i) const
				    { return _os.pos() == i._os.pos(); }
    inline bool			operator< (const ostream_iterator& i) const
				    { return _os.pos() < i._os.pos(); }
private:
    Stream&	_os;
};

//----------------------------------------------------------------------

typedef ostream_iterator<utf8subchar_t> ostream_iterator_for_utf8;
typedef utf8out_iterator<ostream_iterator_for_utf8> utf8ostream_iterator;

/// Returns a UTF-8 adaptor writing to \p os.
inline utf8ostream_iterator utf8out (ostream& os)
{
    ostream_iterator_for_utf8 si (os);
    return utf8ostream_iterator (si);
}

//----------------------------------------------------------------------

/// Checks that \p n bytes are available in the stream, or else throws.
inline bool ostream::verify_remaining (const char* op, const char* type, size_t n)
{
    const size_t rem = remaining();
    bool enough = n <= rem;
    if (!enough) overrun (op, type, n, pos(), rem);
    return enough;
}

/// Move the write pointer to \p newPos
inline void ostream::seek (uoff_t newPos)
{
#if WANT_STREAM_BOUNDS_CHECKING
    if (newPos > size())
	return overrun ("seekp", "byte", newPos, pos(), size());
#else
    assert (newPos <= size());
#endif
    SetPos (newPos);
}

/// Sets the current write position to \p newPos
inline void ostream::iseek (const_iterator newPos)
{
    seek (distance (begin(), const_cast<iterator>(newPos)));
}

/// Sets the current write position to \p p based on \p d.
inline void ostream::seekp (off_t p, seekdir d)
{
    switch (d) {
	case beg:	seek (p); break;
	case cur:	seek (pos() + p); break;
	case ios_base::end:	seek (size() - p); break;
    }
}

/// Skips \p nBytes without writing anything.
inline void ostream::skip (streamsize nBytes)
{
    seek (pos() + nBytes);
}

/// Returns number of bytes remaining in the write buffer.
inline streamsize ostream::remaining (void) const
{
    return size() - pos();
}

/// Returns \c true if the write pointer is aligned on \p grain
inline bool ostream::aligned (streamsize grain) const
{
    return pos() % grain == 0;
}

/// Returns the number of bytes to skip to be aligned on \p grain.
inline streamsize ostream::align_size (streamsize grain) const
{
    return Align (pos(), grain) - pos();
}

/// Writes \p n bytes from \p buffer.
inline void ostream::write (const void* buffer, size_type n)
{
#if WANT_STREAM_BOUNDS_CHECKING
    if (!verify_remaining ("write", "binary data", n))
	return;
#else
    assert (remaining() >= n && "Buffer overrun. Check your stream size calculations.");
#endif
    memcpy (ipos(), const_iterator(buffer), n);
    _pos += n;
}

/// Writes the contents of \p buf into the stream as a raw dump.
inline void ostream::write (const cmemlink& buf)
{
    write (buf.begin(), buf.size());
}

/// Writes type T into the stream via a direct pointer cast.
template <typename T>
inline void ostream::iwrite (const T& v)
{
    assert (aligned (stream_align_of (v)));
#if WANT_STREAM_BOUNDS_CHECKING
    if (!verify_remaining ("write", typeid(v).name(), sizeof(T)))
	return;
#else
    assert (remaining() >= sizeof(T));
#endif
    *reinterpret_cast<T*>(ipos()) = v;
    SetPos (pos() + sizeof(T));
}

/// Swaps with \p os
inline void ostream::swap (ostream& os)
{
    memlink::swap (os);
    ::ustl::swap (_pos, os._pos);
}

//----------------------------------------------------------------------

template <typename T> struct object_writer {
    inline void operator()(ostream& os, const T& v) const { v.write (os); }
};
template <typename T> struct integral_object_writer {
    inline void operator()(ostream& os, const T& v) const { os.iwrite (v); }
};
template <typename T>
inline ostream& operator<< (ostream& os, const T& v) {
    typedef typename tm::Select <numeric_limits<T>::is_integral,
	integral_object_writer<T>, object_writer<T> >::Result object_writer_t;
    object_writer_t()(os, v);
    return os;
}

//----------------------------------------------------------------------

} // namespace ustl