CODEWITHSUNDEEP
rubystringfilebinaryprepend
Ger Cas
Ger Cas

Reputation: 2298

Prepend hex string to the content of binary file

I have these 2 arrays representing hexadecimal numbers and I want to write to a file in binary format.

I convert to hexadecimal string like this:

a=["A2","48","04","03","EE","72","B4","6B"]
b=["1A","28","18","06","07","00","11","86","05","01","01","01","A0"]

hex_string1 = a.map{|b| b.to_i(16)}.pack("C*")
hex_string2 = b.map{|b| b.to_i(16)}.pack("C*")

Now I want to write to a file the hex_string2 first and then prepend (with offset "0") the hex_string1 to the file.

I'm proceeding like this but the output is incorrect.

File.binwrite("outfile.bin",hex_string2)
File.binwrite("outfile.bin",hex_string1,0)

The current output is:

A2 48 04 03 EE 72 B4 6B 05 01 01 01 A0

And the correct content within the "output.bin" would be like this:

A2 48 04 03 EE 72 B4 6B 1A 28 18 06 07 00 11 86 05 01 01 01 A0

How would be the way to do this?

Upvotes: 2

Views: 298

Answers (1)

Ivan Olshansky
Ivan Olshansky

Reputation: 959

You should write second string with the offset by the size of first string:

File.binwrite("outfile.bin",hex_string2,hex_string1.size)
File.binwrite("outfile.bin",hex_string1,0)

In this case you'll get exactly what you want:

A2 48 04 03 EE 72 B4 6B 1A 28 18 06 07 00 11 86 05 01 01 01 A0

Upvotes: 2

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