确定一个字节[]是否是一个pdf文件 [英] Determine if a byte[] is a pdf file

问题描述

有没有什么办法不用打开就可以检查一个byte[]是否是pdf文件?

Is there any way of checking if a byte[] is a pdf without opening?

我有一些代码可以将 byte[] 列表显示为 pdf 缩略图.我以前知道所有字节 [] 都是 pdf 的，因为我们过滤了 servlet 以仅返回这些.现在要求已经改变，我需要恢复所有文件类型.有什么方法可以检查 byte[] 是什么，或者更具体地说，确定它不是 pdf?

I have some code to display a list of byte[] as pdf thumbnails. I previously knew all the byte[] were pdf's because we filtered the servlet to only return these. Now the requirement has changed and I need to bring all file types back. Is there any way of checking what the byte[] is, or more specifically determining if it isn't, a pdf?

推荐答案

检查数组的前 4 个字节.

Check the first 4 bytes of the array.

如果那些是 0x25 0x50 0x44 0x46 那么它很可能是一个 PDF 文件.

If those are 0x25 0x50 0x44 0x46 then it's most probably a PDF file.

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