dolphin/Source/Core/Common/Src/ChunkFile.cpp

// Copyright (C) 2003-2008 Dolphin Project.

// This program 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, version 2.0.

// 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 2.0 for more details.

// A copy of the GPL 2.0 should have been included with the program.
// If not, see http://www.gnu.org/licenses/

// Official SVN repository and contact information can be found at
// http://code.google.com/p/dolphin-emu/

#include "Common.h"
#include "ChunkFile.h"

#include <stdio.h>

// Not using file mapping, just bog standard fopen and friends. We trust them to be fast
// enough to not be the bottleneck.

ChunkFile::ChunkFile(const char *filename, ChunkFileMode _mode)
{
	mode = _mode;
	data = 0;

	didFail = false;
	f = fopen(filename, mode == MODE_WRITE ? "wb" : "rb");
	if (!f) {
		didFail = true;
		return;
	}
	
	fseek(f, 0, SEEK_END);
	size = ftell(f);
	eof = size;

	stack_ptr = 0;
}

ChunkFile::~ChunkFile()
{
	if (f)
		fclose(f);
}

int ChunkFile::ReadInt()
{
	int x;
	fread(&x, 4, 1, f);
	return x;
}

void ChunkFile::WriteInt(int x)
{
	fwrite(&x, 4, 1, f);
}

bool ChunkFile::Do(void *ptr, int size)
{
	int sz;
	switch (mode) {
	case MODE_READ:
		sz = ReadInt();
		if (sz != size)
			return false;
		fread(ptr, size, 1, f);
		fseek(f, ((size + 3) & ~3) - size, SEEK_CUR);
		break;
	case MODE_WRITE:
		WriteInt(size);
		fwrite(ptr, size, 1, f);
		fseek(f, ((size + 3) & ~3) - size, SEEK_CUR);
		break;
	case MODE_VERIFY:
		sz = ReadInt();
		if (sz != size)
			return false;
		fseek(f, (size + 3) & ~3, SEEK_CUR);
		break;
	}
	return true;
}

//let's get into the business
bool ChunkFile::Descend(const char *cid)
{
	int id = *((int*)cid);
	if (mode == MODE_READ)
	{
		bool found = false;
		int startPos = ftell(f);
		ChunkInfo temp = stack[stack_ptr];

		//save information to restore after the next Ascend
		stack[stack_ptr].parentStartLocation = startPos;
		stack[stack_ptr].parentEOF = eof;

		int firstID = 0;
		//let's search through children..
		while (ftell(f) < eof)
		{
			stack[stack_ptr].ID = ReadInt();
			if (firstID == 0)
				firstID = stack[stack_ptr].ID|1;
			stack[stack_ptr].length = ReadInt();
			stack[stack_ptr].startLocation = ftell(f);
			if (stack[stack_ptr].ID == id)
			{
				found = true;
				break;
			}
			else
			{
				fseek(f, stack[stack_ptr].length, SEEK_CUR); //try next block
			}
		} 

		//if we found nothing, return false so the caller can skip this
		if (!found)
		{
			stack[stack_ptr] = temp;
			fseek(f, stack[stack_ptr].parentStartLocation, SEEK_SET);
			return false;
		}

		//descend into it
		//pos was set inside the loop above
		eof = stack[stack_ptr].startLocation + stack[stack_ptr].length;
		stack_ptr++;
		return true;
	}
	else
	{
		//write a chunk id, and prepare for filling in length later
		WriteInt(id);
		WriteInt(0); //will be filled in by Ascend
		stack[stack_ptr].startLocation = ftell(f);
		stack_ptr++;
		return true;
	}
}

//let's ascend out
void ChunkFile::Ascend()
{
	if (mode == MODE_READ)
	{
		//ascend, and restore information
		stack_ptr--;
		fseek(f, stack[stack_ptr].parentStartLocation, SEEK_SET);
		eof = stack[stack_ptr].parentEOF;
	}
	else 
	{
		stack_ptr--;
		//now fill in the written length automatically
		int posNow = ftell(f);
		fseek(f, stack[stack_ptr].startLocation - 4, SEEK_SET);
		WriteInt(posNow - stack[stack_ptr].startLocation);
		fseek(f, posNow, SEEK_SET);
	}
}

int ChunkFile::GetCurrentChunkSize()
{
	if (stack_ptr)
		return stack[stack_ptr - 1].length;
	else
		return 0;
}