FAT file system-read＆set

原创于 2008-05-27 21:10:00 发布 · 635 阅读

0 ·

CC 4.0 BY-SA版权

文章标签：

#file #byte

杂专栏收录该内容

17 篇文章

订阅专栏

本文详细介绍了如何读取和设置FAT16与FAT32文件系统的簇入口值，包括读取指定扇区并根据不同类型的文件系统（FAT16或FAT32）来解析簇入口值的方法。

read sector number ThisFATSecNum (remember this is a sector number relative to sector 0 of the FAT volume). Assume this is read into an 8-bit byte array named SecBuff

If(FATType == FAT16)
FAT16ClusEntryVal = *((WORD *) &SecBuff[ThisFATEntOffset]);
Else
FAT32ClusEntryVal = (*((DWORD *) &SecBuff[ThisFATEntOffset])) & 0x0FFFFFFF;

set the contents of this same cluster

If(FATType == FAT16)
    *((WORD *) &SecBuff[ThisFATEntOffset]) = FAT16ClusEntryVal;
Else {
     FAT32ClusEntryVal = FAT32ClusEntryVal & 0x0FFFFFFF;
    *((DWORD *) &SecBuff[ThisFATEntOffset]) =
        (*((DWORD *) &SecBuff[ThisFATEntOffset])) & 0xF0000000;
    *((DWORD *) &SecBuff[ThisFATEntOffset]) =
        (*((DWORD *) &SecBuff[ThisFATEntOffset])) | FAT32ClusEntryVal;
}