fat.c

用89C51SND1C实现MP3播放器的源代码.用KEIL c51编写.

//******************************************************
//name : fat.c
//this flie include the commands for mass storage reading
//and analyze the system structe of the mass storage
//  zhdgps   wikee 2003.4.10
//******************************************************


//******************************************************
//include file
//******************************************************

#include "fat.h"
#include "testuart.h"
#include "flash.h"
#include "uart.h"

unsigned char FAT_TYPE;

unsigned char databuff[SectorLength];
void Init_File_System(unsigned int *Em_FAT,unsigned char *Em_DIR)
{
	unsigned int TotalCluster,BootSector,RsdSector,SectorofFatSize,i,j;

	///////////////////////////////////////////////////
	//得到引导扇区所在扇区号，如果介质是不带分区的，则0扇区就是BootSector了。
	ReadPage(ZeroCluster,0,databuff);
	if(!(databuff[0]==0xeb&&databuff[2]==0x90)){	//通过判断EB ?? 90来看是否已经是BPB了
		//带分区的介质
		BootSector=databuff[454]+databuff[455]*256+databuff[456]*(256*256)+databuff[457]*(256*256*256);
		}
	else BootSector=0;
	///////////////////////////////////////////////////

	////////////////////////////////////////////////
	//得到保留扇区数,总扇区数,总扇区数／每簇扇区数得到簇数，是FAT类型的依据
	ReadPage(ZeroCluster,BootSector,databuff);
	RsdSector=databuff[14]+databuff[15]*256;
	TotalCluster=(databuff[20]*256+databuff[19])/databuff[13];//FAT16的簇总数=扇区总数/每簇扇区数
	SectorofFatSize=((databuff[22]+databuff[23]*256));
	if(TotalCluster==0){  //FAT32的扇区总数和FAT表项长度
		TotalCluster=(databuff[32]+databuff[33]*256+databuff[34]*256*256+databuff[35]*256*256*256)/databuff[13];
		SectorofFatSize=(databuff[36]+databuff[37]*256+databuff[38]*256*256+databuff[39]*256*256*256);
		if(SectorofFatSize>(TotalCluster*16/512)) SectorofFatSize=((databuff[22]+databuff[23]*256));
		}
	////////////////////////////////////////////////////////////////
	
//	Uart_Printf("\nBootSector:%x RsdSector:%x,TotalCluster:%x  SectorofFatSize:%x\n",BootSector,RsdSector,TotalCluster,SectorofFatSize);
//	for(i=0;i<512;i++) {if(!(i%32)) Uart_Printf("\n");Uart_Printf("%x  ",databuff[i]);}
	/////////////////////////////////////////////////////////////
	//开始读取第一个FAT的第一个扇区
	ReadPage(ZeroCluster,BootSector+RsdSector,databuff);
	//根据总的簇数判断FAT类型，并进行FAT表项转换
	//decied which type of FAT this File System Belongs to
	if(TotalCluster==FAT32){	//FAT32
		FAT_TYPE=FAT32;
		for(i=0,j=0;j<(512-4);i++,j+=4) Em_FAT[i]=(databuff[j]&0x000000ff)|((databuff[j+1]&0x000000ff)<<8)|((databuff[j+2]&0x000000ff)<<16)|((databuff[j+3]&0x000000ff)<<24);
		}
	else if((TotalCluster>0)&&(TotalCluster<FAT12)) {//FAT12
		FAT_TYPE=FAT12;
		for(i=0,j=0;i<(512-3);i+=3) {		//f8  (f2 f1)  ff ---> f1 f8  ff f2  TotalCluster/3
			Em_FAT[j]=0;
			Em_FAT[j]=databuff[i+1]<<8;//ff00
			Em_FAT[j]=Em_FAT[j]|databuff[i];//fff8
			Em_FAT[j]=Em_FAT[j]&0x0fff;//0ff8
			
			Em_FAT[++j]=0;
			Em_FAT[j]=databuff[i+2]<<8;//ff00
			Em_FAT[j]=Em_FAT[j]|databuff[i+1];//ffff
			Em_FAT[j]=Em_FAT[j]>>4;//0fff
			j++;
			}
		}
	else {	//FAT16
		FAT_TYPE=FAT16;
		for(i=0,j=0;i<(512-2);i++,j+=2) Em_FAT[i]=(databuff[j]&0x00ff)|((databuff[j+1]&0x00ff)<<8);//如果是FAT16则直接赋值
		}
	//////////////////////////////////////////////////////////////

	////////////////////////////////////////////////
	//读根目录表的第一个扇区并进行相应的转换
	ReadPage(ZeroCluster,BootSector+RsdSector+2*SectorofFatSize,databuff);
	for(i=0;i<512;i++) *(Em_DIR+i)=databuff[i];//处理根目录

}

void ListName(unsigned char *Em_DIR)
{
	int i,j;
	j=0;
	for(;Em_DIR[j*32];) {
		if(Em_DIR[j*32]==0xe5) {j++;continue;}
		printuf("\n");for(i=0;i<11;i++) printuf("%x",Em_DIR[j*32+i]);
		j++;
		}
	
}