fceugx/source/fceultra/utils/memorystream.h

303 lines
6.2 KiB
C
Raw Normal View History

2009-07-17 19:27:04 +02:00
#ifndef _memorystream_h_
#define _memorystream_h_
#include <iostream>
#include <string.h>
#include <vector>
#include <sstream>
#include <stdexcept>
template<typename T>
class memory_streambuf: public std::streambuf {
private:
friend class memorystream;
//the current buffer
T* buf;
//the current allocated capacity of the buffer
size_t capacity;
//whether the sequence is owned by the stringbuf
bool myBuf;
//the logical length of the buffer
size_t length;
//the current 'write window' starting position within the buffer for writing.
size_t ww;
//a vector that we have been told to use
std::vector<T>* usevec;
public:
memory_streambuf(int _capacity)
: buf(new T[capacity=_capacity])
, myBuf(true)
, length(_capacity)
, ww(0)
, usevec(0)
{
sync();
}
memory_streambuf()
: buf(new T[capacity = 128])
, myBuf(true)
, length(0)
, ww(0)
, usevec(0)
{
sync();
}
//constructs a non-expandable streambuf around the provided buffer
memory_streambuf(T* usebuf, int buflength)
: buf(usebuf)
, myBuf(false)
, length(buflength)
, ww(0)
, usevec(0)
{
sync();
}
//constructs an expandable streambuf around the provided buffer
memory_streambuf(std::vector<T>* _usevec)
: capacity(_usevec->size())
, myBuf(false)
, length(_usevec->size())
, ww(0)
, usevec(_usevec)
{
if(length>0)
buf = &(*_usevec)[0];
else buf = 0;
sync();
}
~memory_streambuf()
{
//only cleanup if we own the seq
if(myBuf) delete[] buf;
}
//the logical length of the buffer
size_t size()
{
sync();
return length;
}
//to avoid copying, rebuilds the provided vector and copies the streambuf contents into it
void toVector(std::vector<T>& out)
{
out.resize(length);
memcpy(&out[0],buf,length);
}
//maybe the compiler can avoid copying, but maybe not: returns a vector representing the current streambuf
std::vector<T> toVector()
{
return std::vector<T>(buf,buf+length);
}
//if the memorystream wraps a vector, the vector will be trimmed to the correct size,.
//you probably need to use this if you are using the vector wrapper
void trim()
{
if(!usevec) return;
usevec->resize(size());
}
//tells the current read or write position
std::streampos tell(std::ios::openmode which)
{
if(which == std::ios::in)
return tellRead();
else if(which == std::ios::out)
return tellWrite();
else return -1;
}
//tells the current read position
std::streampos tellRead()
{
return gptr()-eback();
}
//tells the current write position
std::streampos tellWrite()
{
return pptr()-pbase() + ww;
}
int sync()
{
dosync(-1);
return 0;
}
T* getbuf()
{
sync();
return buf;
}
//if we were provided a buffer, then calling this gives us ownership of it
void giveBuf() {
myBuf = true;
}
private:
void dosync(int c)
{
size_t wp = tellWrite();
size_t rp = tellRead();
//if we are supposed to insert a character..
if(c != -1)
{
buf[wp] = c;
wp++;
}
//the length is determined by the highest character that was ever inserted
length = std::max(length,wp);
//the write window advances to begin at the current write insertion point
ww = wp;
//set the new write and read windows
setp(buf+ww, buf + capacity);
setg(buf, buf+rp, buf + length);
}
void expand(size_t upto)
{
if(!myBuf && !usevec)
throw new std::runtime_error("memory_streambuf is not expandable");
size_t newcapacity;
if(upto == 0)
newcapacity = capacity + capacity/2 + 2;
else
newcapacity = std::max(upto,capacity);
if(newcapacity == capacity) return;
//if we are supposed to use the vector, then do it now
if(usevec)
{
usevec->resize(newcapacity);
capacity = usevec->size();
buf = &(*usevec)[0];
}
else
{
//otherwise, manage our own buffer
T* newbuf = new T[newcapacity];
memcpy(newbuf,buf,capacity);
delete[] buf;
capacity = newcapacity;
buf = newbuf;
}
}
protected:
int overflow(int c)
{
expand(-1);
dosync(c);
return 1;
}
std::streambuf::pos_type seekpos(pos_type pos, std::ios::openmode which)
{
//extend if we are seeking the write cursor
if(which & std::ios_base::out)
expand(pos);
sync();
if(which & std::ios_base::in)
setg(buf, buf+pos, buf + length);
if(which & std::ios_base::out)
{
ww = pos;
setp(buf+pos, buf + capacity);
}
return pos;
}
pos_type seekoff(off_type off, std::ios::seekdir way, std::ios::openmode which)
{
switch(way) {
case std::ios::beg:
return seekpos(off, which);
case std::ios::cur:
return seekpos(tell(which)+off, which);
case std::ios::end:
return seekpos(length+off, which);
default:
return -1;
}
}
};
//an iostream that uses the memory_streambuf to effectively act much like a c# memorystream
//please call sync() after writing data if you want to read it back
class memorystream : public std::basic_iostream<char, std::char_traits<char> >
{
public:
memorystream()
: std::basic_iostream<char, std::char_traits<char> >(&streambuf)
{}
memorystream(int size)
: std::basic_iostream<char, std::char_traits<char> >(&streambuf)
, streambuf(size)
{}
memorystream(char* usebuf, int buflength)
: std::basic_iostream<char, std::char_traits<char> >(&streambuf)
, streambuf(usebuf, buflength)
{}
memorystream(std::vector<char>* usevec)
: std::basic_iostream<char, std::char_traits<char> >(&streambuf)
, streambuf(usevec)
{}
//the underlying memory_streambuf
memory_streambuf<char> streambuf;
public:
size_t size() { return streambuf.size(); }
char* buf() { return streambuf.getbuf(); }
//flushes all the writing state and ensures the stream is ready for reading
void sync() { streambuf.sync(); }
//rewinds the cursors to offset 0
void rewind() { streambuf.seekpos(0,std::ios::in | std::ios::out); }
//if the memorystream wraps a vector, the vector will be trimmed to the correct size,.
//you probably need to use this if you are using the vector wrapper
void trim() { streambuf.trim(); }
void giveBuf() { streambuf.giveBuf(); }
};
#endif