PDF格式. ％起始序列的功能 [英] PDF format. function of %-started sequence

问题描述

在某些文档的开头发现的十六进制序列"25 E2 E3 CF D3"的功能是什么?据我了解，这应该是评论，但其内容不是任何有意义的文本，并且在许多文档中都采用相同的顺序.

What is a function of hex sequence "25 E2 E3 CF D3", found at the beginning of some documents? It should be a comment as far as I understand, but it's content is not any meaningful text and the same sequence occurs in many documents.

推荐答案

它将PDF文件标识为包含二进制数据.

It identifies the PDF file as containing binary data.

来自免费提供的PDF参考(第7.5.2节，第40页):

From the freely available PDF Reference (section 7.5.2, p. 40):

如果PDF文件像大多数一样包含二进制数据(请参见7.2，词法约定")，则标题行应为 紧随其后的是至少包含四个二进制字符的注释行，即，其字符 代码为128或更大.这样可确保检查文件附近的数据的文件传输应用程序的正常行为. 文件开头以确定是否将文件内容视为文本还是二进制.

If a PDF file contains binary data, as most do (see 7.2, "Lexical Conventions"), the header line shall be immediately followed by a comment line containing at least four binary characters—that is, characters whose codes are 128 or greater. This ensures proper behaviour of file transfer applications that inspect data near the beginning of a file to determine whether to treat the file’s contents as text or as binary.

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