在有 < 强度 > 全球 < / 强度 > < code > FILE 指针/描述符的地方,我有一个要求。其中一项功能将从此指针/描述符中读取。 < 强度% em > 内部指针 与 < code > FILE 指针/ 描述符进步相关联的 < fILE < /code > 指针/描述符/描述符。此函数返回后, < 强度@ em > 我要从同一个 < code > FILE > < /code > 指针/描述符中读取, 以及其它函数所读的相同数据。
但我无法读取与内部指示器前进相同的精确数据 。 迭代描述符不工作 ,因为重复的反照原始。在阅读前保存 FILE 指针也无效,因为它是一个指针,并且将再次开始引用相同的东西 。
一种替代办法是在阅读前使用 fgetpos () 保存文件位置,然后在下次阅读前使用 fsetpos () () 。
但这对文件指针而不是描述符有效。
通常的指针很容易。 但用 < code> FILE 指针, 事情就变得困难了 。
是否有其他的unt-lumsy 方法可以做到这一点?
如果您指的是 POSIX 文件描述符, 听起来您正在寻找 lseek () 。
off_t off;
off = lseek(fd, 0, SEEK_CUR); /* get current offset */
/* do some read(s) */
lseek(fd, off, SEEK_SET);
另一个选项是使用“http://linux.die.net/man/2/mmap” rel=“nofollow”\\ code>mmap () 来绘制文件的内存图。
这将允许您随机阅读文件中的任何位置, 而不必使用 lseek () 或 fseek () 。
在 基于您的描述, 我会将文件指针隐藏在另一个界面后面, 缓冲最后读取的数据块, 这样代码的不同区域就可以访问相同的数据, 而不必倒转流 。
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mmap () at linux questions 上,您将会在mmap ()
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