[RESOLVED] Binary fopen Problem

jbrandt

Hey there! I have a variable containing some binary data. When I do echo strlen ($var) I get 20078, but when I try this:

$op = fopen ('file', 'wb');
fwrite ($op, $var);
fclose ($op);

the length of the file is only 20017! The first few binary characters are the same, and so are the last few (when I look at them in Notepad) but I have no idea how to tell which pieces of the file are different from the variable since its binary, not text.

Any help is greatly appreciated!

Thanks,
Jared

bpat1434

Just take the $var variable and use [man]file_get_contents/man to get the contents of the file to a string, and use [man]strcmp/man to compare the two strings. If they're different it will return either -1 or 1, and if they're the same it will return 0. So if you run:

echo strcmp($var, file_get_contents('file'));

If it's -1: $var is less than file
If it's 0 : $var is equal to file
If it's 1 : $var is greater than file

Hope that helps.

jbrandt

Well I can check using strcmp, and it will return a nonzero number, but I'm sorry, I don't see how that would help? It wouldn't fix the file.

$var = file_get_contents ('./file', FILE_BINARY); // ./file is originally 20078 bytes
echo strlen ($var); // this prints 20078 to the screen

$op = fopen ('./new', 'wb');
fwrite ($op, $var);
fclose ($op); // the file now contains only 20017 bytes and i can't tell which ones are missing

It's strange. 🙁

bpat1434

You could always do a loop that compares character to character.... then once one is found "wrong" you can mark that spot....

jbrandt

Well I tried it with a different file (with the same "scheme") with file size 18020. The output file, which should be identical, was only 17990. When I went through a loop to compare the two values, it went something like this:

index 10193: match => 155 vs 155
index 10194: match => 28 vs 28
index 10195: match => 113 vs 113
index 10196: match => 176 vs 176
index 10197: match => 127 vs 127
index 10198: match => 44 vs 44
index 10199: match => 17 vs 17
index 10200: NOT A MATCH => 92 vs 158
index 10201: NOT A MATCH => 158 vs 223
index 10202: NOT A MATCH => 223 vs 236
index 10203: NOT A MATCH => 236 vs 51
index 10204: NOT A MATCH => 51 vs 16
index 10205: NOT A MATCH => 16 vs 194

So the character (ASCII 92) was randomly omitted from the file?

bpat1434

Well, ASCII 92 is the back-slash character... could have something to do with need the character escaped... but I'm not sure.... what is the binary file you're trying to open & write? Is it an image or compiled code or what?

jbrandt

Well I don't know.. this is weird.. HOWEVER, file_put_contents () seems to work wonderfully! That function does write the file just fine.

bpat1434

Probably had to do with the \ not being escaped..... you probably could have used [man]addcslashes[/man] to see if that would work.... but glad you got it figured out.