getbit.h

DVD转换到AVI的源代码

/* 
 *	Copyright (C) Chia-chen Kuo - Jan 2001
 *
 *  This file is part of DVD2AVI, a free MPEG-2 decoder
 *	
 *  DVD2AVI is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2, or (at your option)
 *  any later version.
 *   
 *  DVD2AVI 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 GNU Make; see the file COPYING.  If not, write to
 *  the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA. 
 *
 */

void Initialize_Buffer(void);
void Fill_Buffer(void);
void Next_Packet(void);
void Flush_Buffer_All(unsigned int N);
unsigned int Get_Bits_All(unsigned int N);
void Next_File(void);

__forceinline static unsigned int Show_Bits(unsigned int N);
__forceinline static unsigned int Get_Bits(unsigned int N);
__forceinline static void Flush_Buffer(unsigned int N);
__forceinline static void Fill_Next(void);
__forceinline static unsigned int Get_Byte(void);

unsigned char Rdbfr[BUFFER_SIZE], *Rdptr, *Rdmax;
unsigned int CurrentBfr, NextBfr, BitsLeft, Val, Read;

static unsigned int Show_Bits(unsigned int N)
{
	if (N <= BitsLeft)
		return (CurrentBfr << (32 - BitsLeft)) >> (32 - N);
	else
	{
		N -= BitsLeft;
		return (((CurrentBfr << (32 - BitsLeft)) >> (32 - BitsLeft)) << N) + (NextBfr >> (32 - N));
	}
}

static unsigned int Get_Bits(unsigned int N)
{
	if (N < BitsLeft)
	{
		Val = (CurrentBfr << (32 - BitsLeft)) >> (32 - N);
		BitsLeft -= N;
		return Val;
	}
	else
		return Get_Bits_All(N);
}

static void Flush_Buffer(unsigned int N)
{
	if (N < BitsLeft)
		BitsLeft -= N;
	else
		Flush_Buffer_All(N);	
}

static void Fill_Next()
{
	if (SystemStream_Flag && Rdptr>=Rdmax-4)
	{
		if (Rdptr >= Rdmax)
			Next_Packet();
		NextBfr = Get_Byte() << 24;

		if (Rdptr >= Rdmax)
			Next_Packet();
		NextBfr += Get_Byte() << 16;

		if (Rdptr >= Rdmax)
			Next_Packet();
		NextBfr += Get_Byte() << 8;

		if (Rdptr >= Rdmax)
			Next_Packet();
		NextBfr += Get_Byte();
	}
	else if (Rdptr < Rdbfr+BUFFER_SIZE-4)
	{
		NextBfr = (*Rdptr << 24) + (*(Rdptr+1) << 16) + (*(Rdptr+2) << 8) + *(Rdptr+3);
		Rdptr += 4;
	}
	else
	{
		if (Rdptr >= Rdbfr+BUFFER_SIZE)
			Fill_Buffer();
		NextBfr = *Rdptr++ << 24;

		if (Rdptr >= Rdbfr+BUFFER_SIZE)
			Fill_Buffer();
		NextBfr += *Rdptr++ << 16;

		if (Rdptr >= Rdbfr+BUFFER_SIZE)
			Fill_Buffer();
		NextBfr += *Rdptr++ << 8;

		if (Rdptr >= Rdbfr+BUFFER_SIZE)
			Fill_Buffer();
		NextBfr += *Rdptr++;
	}
}

static unsigned int Get_Byte()
{
	while (Rdptr >= (Rdbfr + BUFFER_SIZE))
	{
		Read = _read(Infile[File_Flag], Rdbfr, BUFFER_SIZE);

		if (Read < BUFFER_SIZE)
			Next_File();

		Rdptr -= BUFFER_SIZE;
		Rdmax -= BUFFER_SIZE;
	}

	return *Rdptr++;
}