#include?
#include?
#include?
#include?
#include?
#include?
#include?
#include?“parse_metafile.h“
#include?“bitfield.h“

extern?int??pieces_length;
extern?char?*file_name;

Bitmap??????*bitmap?=?NULL;?????????//?指向位圖
int?????????download_piece_num?=?0;?//?當前已下載的piece數(shù)?

//?如果存在一個位圖文件則讀位圖文件并把獲取的內(nèi)容保存到bitmap
//?如此一來就可以實現(xiàn)斷點續(xù)傳即上次下載的內(nèi)容不至于丟失
int?create_bitfield（）
{
	bitmap?=?（Bitmap?*）malloc（sizeof（Bitmap））;
	if（bitmap?==?NULL）?{?
		printf（“allocate?memory?for?bitmap?fiailed\n“）;?
		return?-1;
	}

	//?pieces_length除以20即為總的piece數(shù)
	bitmap->valid_length?=?pieces_length?/?20;
	bitmap->bitfield_length?=?pieces_length?/?20?/?8;
	if（?（pieces_length/20）?%?8?!=?0?）??bitmap->bitfield_length++;

	bitmap->bitfield?=?（unsigned?char?*）malloc（bitmap->bitfield_length）;
	if（bitmap->bitfield?==?NULL）??{?
		printf（“allocate?memory?for?bitmap->bitfield?fiailed\n“）;?
		if（bitmap?!=?NULL）??free（bitmap）;
		return?-1;
	}

	char?bitmapfile[64];
	sprintf（bitmapfile“%dbitmap“pieces_length）;
	
	int??i;
	FILE?*fp?=?fopen（bitmapfile“rb“）;
	if（fp?==?NULL）?{??//?若打開文件失敗說明開始的是一個全新的下載
		memset（bitmap->bitfield?0?bitmap->bitfield_length）;
	}?else?{
		fseek（fp0SEEK_SET）;
		for（i?=?0;?i?bitfield_length;?i++）
			（bitmap->bitfield）[i]?=?fgetc（fp）;
		fclose（fp）;?
		//?給download_piece_num賦新的初值
		download_piece_num?=?get_download_piece_num（）;
	}
	
	return?0;
}

int?get_bit_value（Bitmap?*bitmapint?index）??
{
	int???????????ret;
	int???????????byte_index;
	unsigned?char?byte_value;
	unsigned?char?inner_byte_index;

	if（index?>=?bitmap->valid_length）??return?-1;

	byte_index?=?index?/?8;
	byte_value?=?bitmap->bitfield[byte_index];
	inner_byte_index?=?index?%?8;

	byte_value?=?byte_value?>>?（7?-?inner_byte_index）;
	if（byte_value?%?2?==?0）?ret?=?0;
	else????????????????????ret?=?1;

	return?ret;
}

int?set_bit_value（Bitmap?*bitmapint?indexunsigned?char?v）
{
	int???????????byte_index;
	unsigned?char?inner_byte_index;

	if（index?>=?bitmap->valid_length）??return?-1;
	if（（v?!=?0）?&&?（v?!=?1））???return?-1;

	byte_index?=?index?/?8;
	inner_byte_index?=?index?%?8;

	v?=?v?<	bitmap->bitfield[byte_index]?=?bitmap->bitfield[byte_index]?|?v;

	return?0;
}

int?all_zero（Bitmap?*bitmap）
{
	if（bitmap->bitfield?==?NULL）??return?-1;
	memset（bitmap->bitfield0bitmap->bitfield_length）;
	return?0;
}
?
int?all_set（Bitmap?*bitmap）
{
	if（bitmap->bitfield?==?NULL）??return?-1;
	memset（bitmap->bitfield0xffbitmap->bitfield_length）;
	return?0;	
}

void?release_memory_in_bitfield（）
{
	if（bitmap->bitfield?!=?NULL）?free（bitmap->bitfield）;
	if（bitmap?!=?NULL）??free（bitmap）;
}

int?print_bitfield（Bitmap?*bitmap）
{
	int?i;

	for（i?=?0;?i?bitfield_length;?i++）?{
		printf（“%.2X?“bitmap->bitfield[i]）;
		if（?（i+1）?%?16?==?0）??printf（“\n“）;
	}
	printf（“\n“）;

	return?0;
}

int?