truncate.c

来自「嵌入式系统中文件系统源代码」· C语言 代码 · 共 101 行

/*************************************************************
File Name: truncate.C                                         *
**************************************************************
Programmer: Huang Giun-Haur
Last Modified Date: 1999/06/15
Compiler : Gnu Cross-compiler
Platform : X86 protection mode
Usage :
	int rename(const char *oldname, const char *newname)
*************************************************************/

/*************************************************************
 		  	Header Files
**************************************************************/
#include <sys/syscall.h>
//#include "../../RDebug/include/RDebug.h"

#include "../../FileSys/include/FileSys.h"

#include "../include/fat1x.h"
#include "../include/cluster.h"



#ifdef FAT_ID



/* init.c */
extern unsigned long   	FATBytesPerCluster[];
extern unsigned char	FATType[];

extern int		FATDirSemaphoreID;

extern unsigned short	FATEndOfChain[];

/* fat1x.c */
extern struct FAT_FILE **FATHandleTable;


/*************************************************************
Function : FAT_truncate
Description:
	cut a file to the given size
Input:
	fHandle - the file handle of the target file
	size - the new size of the file in bytes
Output:
	0	SUCCESS
	-1	FAILURE
**************************************************************/
int FAT_truncate(int fHandle, unsigned long size)
{
  unsigned short nThCluster;
  unsigned short traceCluster;
  unsigned short actualCluster;
  unsigned short freeCluster;
  short drive;

#ifdef FAT1X_DEBUG
  SprintStringLn("[FAT_truncate]");
#endif

  FATErrno = 0;

  if (InitFAT == FALSE)
  {
	FATErrno = ERROR_FILE_SYSTEM_NOT_INIT;
	return -1;
  }

  if ((fHandle < 0) || (fHandle >= MAX_OPEN_FILE) || (FATHandleTable[fHandle] == NULL))
  {
	FATErrno = ERROR_INVALID_HANDLE;
	return -1;
  }

  if (FATHandleTable[fHandle]->deviceID != FAT_ID)
  {
	FATErrno = ERROR_INVALID_DEVICE;
	return -1;
  }

  if ( (FATHandleTable[fHandle]->fileFlag & O_RDWR) == 0)
  {
  	FATErrno = ERROR_FILE_FLAG;
  	return -1;
  }
  
  sc_waitSemaphore(FATDirSemaphoreID);

  /**** added by chilong 02/05/2002 ****/
  if (size == 0)
  {
	FATHandleTable[fHandle]->dirEntry.fsize = 0;
	FATHandleTable[fHandle]->fpos = 0;
	FAT_clear_fat_cluster_chain(fHandle);
	
	FATHandleTable[fHandle]->dirEntry.startCluster = 0;
	
	FAT_update_file_info(FATHandleTable[fHandle]);	//