file_io.c

avr MP3 的源程序,包含文件系统,适合初学者

/*-------------------------------------------------------------
FileName    : file_io.c
Created by  : Datazyb
Created Date: 2006.4.8
Function    : read or write file with fat filesystem
Comments    : These are high level operations.
LastModified: 2007.5.2, for printing file name to pc
--------------------------------------------------------------*/

#include "file_io.h"

//**************************************************************
//Read a sector of file(512 bytes)
void read_a_sector_file(unsigned char *buffer)
//**************************************************************
{
    dword sector;
    
    if(sectorPos==Sectors_Per_Cluster) 
    {   
      //if whole cluster is already read then
      //a new cluster must be read by looking into FAT 
      currentCluster=findNextCluster();
      readPos=0;                            
      sectorPos=0;
    }
    //get lba address
    sector=clust2LBA(currentCluster)+sectorPos;
    ATA_Read_Sector(sector, buffer);
    sectorPos++; 
    filePos += 512;
}        

//*********************************************************************
//Find UNICODE.BIN
//UNICODE.BIN is used for decoding chinese file name:)
byte findSystemFile(void)
//*********************************************************************
{
  byte i; dword extension;
  
  currentFileNum=0;
  i=0;
  while((i<1)&&(getDirEntry(0)==1)) 
  { 
  extension = (*(dword *)fileExtension) & 0x00FFFFFF;
  if((extension==0x004E4942)&&((fileName[0] & 0x55)==0x55))
  { 
    tableStartCluster=currentCluster;
    tableFileSize=FileSize; 
    i++; 
  } //UNICODE.BIN file address
  } //while((i<1)&&(getDirEntry(0)==1))                                            
  if(i==1) return 1; 
  else return 0; //Missing UNICODE.BIN
}

void save_file_info(void)
{      
    byte i;
    
    currentFileInfo.startCluster = currentCluster;
    currentFileInfo.fileSize = FileSize;
    for(i=0; i<3; i++) 
    {currentFileInfo.fileExtName[i] = fileExtension[i];};
    currentFileInfo.fileNumber = currentFileNum;
}

void load_file_info(void)
{
    byte i;
    
    currentCluster = currentFileInfo.startCluster;
    FileSize = currentFileInfo.fileSize;
    for(i=0; i<3; i++) 
    {fileExtension[i] = currentFileInfo.fileExtName[i];};
    currentFileNum = currentFileInfo.fileNumber;
}

/*------------------- end of file_io.c ----------------------*/