how to retrieve all the ascii characters from a binary file.

[varun aggarwal]

Hi i have a binary file that i need to parse.
The situation is that i need all the ascii characters from that binary file, the way that is to be implemented should be very efficient as the binary files are big.
Is there a function in php that can do that or a php script that can do the work.
Thanks
Varun

[kovik]

The situation is that i need all the ascii characters from that binary file

Look at ord(), chr(), and unpack().

[varun aggarwal]

Hi what i am using now is the regular expression.
But that doesnt seem to work.

my regular expresson is :
preg_match("/Description\x20\x02\x20\x16(.*)Q/",$content,$match).
but the expression doesnt seem to work with hexadecimal values.
Is there something wrong in this one?
Thanks
Varun

[pbmods]

Heya, Varun.

My recommendation would be to parse the string manually:

• Create an empty target string.
• For each character in the binary string:
  • Check its value with ord().
  • If it is a printable character, append it to the target string.

[kovik]

Hi what i am using now is the regular expression.

Why? unpack() is suited specifically for handling binary data. Are you not familiar with data types? They should give you the syntax for the CHAR type in the documentation for the pack() function.

[varun aggarwal]

Why? unpack() is suited specifically for handling binary data. Are you not familiar with data types? They should give you the syntax for the CHAR type in the documentation for the pack() function.

The data i am trying to parse is a video file that has information contained within. Could you tell me what query should i write in unpack so that all the relevant information (Clip Information) can be retrieved from the binary file?

I am very new to php and have never worked on a problem like that. Sorry if that sounds too stupid.
Thanks
Varun

[jx2]

The data i am trying to parse is a video file that has information contained within. Could you tell me what query should i write in unpack so that all the relevant information (Clip Information) can be retrieved from the binary file?

I am very new to php and have never worked on a problem like that. Sorry if that sounds too stupid.
Thanks
Varun

its not as easy as unpack() i understand you want to read exif data from "video" file - in my knowledge there is no such function in php u need to handle binary data on your own
1. u need to know file format
2. u need to read specification of this file format
3. u need to write function which can read the data you need

well i know i didnt helped but i hope i gave you an idea of the problem

regards
jx2

[kovik]

The data i am trying to parse is a video file that has information contained within. Could you tell me what query should i write in unpack so that all the relevant information (Clip Information) can be retrieved from the binary file?

Hehe. I see the problem.

I am very new to php and have never worked on a problem like that. Sorry if that sounds too stupid.

Dealing with binary data is beyond regular programming, and if you are new to programming, I'm sure that it's safe to assume that you are almost completely inexperienced with binary data. Dealing with binary data is up there with ASM and disassembly, as you are dealing with the raw data instead of human-readable code.

Files have formats. It's usually in the style of "Header" then "Data." You have to be familiar with the file format and the data types in order to decipher which bits are what, and then you have to be familiar with the storage types in order to translate the data into a usable format. I've been planning on writing a tutorial for dealing with binary data in PHP, but the interest is low and the extent of work necessary to teach it is not.

If you'd really like to deal with file formats in PHP without having to learn anything in-depth about file formats, search GoogleCode, SourceForge, or PHPClasses for pre-made scripts and APIs that deal with the file format that you are after.