Question

I don’t know what is that, I found this in the openSSL source code.

Is those some sort of byte sequence? Basically I just need to convert my char * to that kind of style as a parameter.

Answer 1

If what you read was

char foo[] = "\x6d\xe3\x85";

then that is the same as

char foo[] = { 0x6d, 0xE3, 0x85, 0x00 };

Further, I can tell you that 0x6D is the ASCII code point for 'm', 0xE3 is the ISO 8859.1 code point for 'ã', and 0x85 is the Windows-1252 code point for '…'.

But without knowing more about the context, I can’t tell you how to “convert [your] char * to that kind of style as a parameter”, except to say that you might not need to do any conversion at all! The \x notation allows you to write string constants containing arbitrary byte sequences into your source code. If you already have an arbitrary byte sequence in a buffer in your program, I can’t imagine your needing to back-convert it to \x notation before feeding it to OpenSSL.