【求助】大文件的操作，类似于winhex 那样的

[shakaqrj]

需要编写类似于winhex那样的程序，用于显示和修改其中的数据。
比如首先创建8G字节文件，之后再通过载入其他文件或者手动修改的方式 改变其中的数据。
一般来说这8G中大部分数据都是无用的，可能是0x0 或0xFF 或其他一些值。所载入的文件有可能很大(比如6G） 也有可能很小（相对于8G)，手动的修改也有可能发生

最后可能还需要保存这8G文件。

那么我该如何做才能做才能使速度变快？如果是创建初始值为0x0的，用内存映射方式直接创建一个就行了 很快。但如果创建初始值是其他的 就不知道方法了。
并且保存的时候有没有方法？
我看类似的软件 初始值不为0x0的也非常快，保存下来的文件也很小 如果内容本身就几乎是空数据（0x0，0xFF或者其他的），怀疑是用压缩算法的，可问题是我自己用压缩工具压缩也没这么小。

[赵4老师]

Sparse File Operations [This is preliminary documentation and subject to change.] You can determine whether a file system supports sparse files by calling the GetVolumeInformation function and examining the FILE_SUPPORTS_SPARSE_FILES bit flag. Most applications are not aware of sparse-files and will not create sparse files. The fact that an application is reading a sparse file is transparent to the application. An application that is aware of sparse-files should determine whether its data set is suitable to be kept in a sparse file. After that determination is made, the application must explicitly declare a file as sparse, using the FSCTL_SET_SPARSE operation. After an application has set a file to be sparse, the application can use the FSCTL_SET_ZERO_DATA operation to set a region of the file to zero. In addition, the application can use the FSCTL_QUERY_ALLOCATED_RANGES operation to speed searches for nonzero data in the sparse file. When you perform a write operation (with a function or operation other than FSCTL_SET_ZERO_DATA) whose data consists nothing but zeros, zeros will be written to the disk for the entire length of the write. To zero out a range of the file and maintain sparseness, use FSCTL_SET_ZERO_DATA. A sparse aware application may also set an existing file to be sparse. If an application sets an existing file to be sparse, it should then scan the file for regions which contain zeros, and use FSCTL_SET_ZERO_DATA to reset those regions, and possibly deallocate some physical disk storage. An application upgraded to sparse file awareness should perform this conversion. When you perform a read operation from a zeroed-out portion of a sparse file may not read from the hard drive. Instead, the system recognizes that the portion of the file to be read contains zeros, and it returns a buffer full of zeros without actually reading from the disk. As with any other file, the system can write data to or read data from any position in a sparse file. Nonzero data being written to a previously zeroed portion of the file may result in allocation of disk space. Zeros being written over nonzero data (with FSCTL_SET_ZERO_DATA) may result in a deallocation of disk space. Note It is up to the application to maintain sparseness by writing zeros with FSCTL_SET_ZERO_DATA. Note Defragmenting tools which handle compressed files on NTFS file systems will correctly handle sparse files on NTFS 5.0 volumes.

[schlafenhamster]

Sparse File(稀疏文件) https://en.wikipedia.org/wiki/Sparse_file

[shakaqrj]

谢谢 但有时候比如8G文件中 大部分数据是0xff 这样用稀疏文件也可以吗？好像它是判断是否非0

[aa123654ss]

但有时候比如8G文件中 大部分数据是0xff 这样用稀疏文件也可以吗？好像它是判断是否非0

[line_us]

好像很强大的功能嘛

[lovep0515]

很好的，很不错！

[失散糖]

这个帖子的方法，把建立文件需要的磁盘空间申请好，但是省去了系统“好心帮忙”对占用空间的擦除操作，这就省去了大量的擦除时间，代价就是文件内容全是“乱码”，得到的好处就是文件可以立即拿来操作。（创建时需要管理员权限） 根据我的测试，Sparse File Operations啦，内存映射文件啦，这些看起来好像是把文件创建完了也都清零了，但是一旦使用fopen系列函数对文件进行操作，那么这种文件会转换成普通文件，然后会耗费大量的时间用于申请并擦除扇区，之后才能变成普通文件。 bbs.csdn.net/topics/391006799

[qq_35585262]

规划法规和 jkj123

[jm0527]

不懂，等大神

[baidu_35580160]

计价规范尽快快快快

[zkmcsdn]

好高大上的样子

[liLongZHEN123]

看不懂，什么

[qq_35601330]

[gz_qmc]

创建模式！！！！！！！！！！！！！！！！！ 无则创建，有则打开，这就是你说的初始值吧？

[gz_qmc]

CreateFile(fName, GENERIC_READ|GENERIC_WRITE,0,NULL,OPEN_EXISTING,FILE_ATTRIBUTE_NORMAL,NULL); 看红色，看红色，看红色

[qq_35604665]

很好，很不错

[A305106117]

搞什么，下个东西也下不了

[sinat_35613199]

不懂，等大神

[sinat_35613199]

不懂，等大神

[qq_35611513]

顶~~~~~~~~~~~~~`