Parsing Binary C Data

[Anon]

Hi, I'm kind of new at this. I searched the archives, but to no avail.

I have a blob in a mysql db that is a memory copy of a C struct.

I simplified it a bit, below is the struct map:

typedef struct {
char name[24];
unsigned short index;
node n[1024];
short last;
} map;

typedef struct {
unsigned char Edges[32];
short numEdges;
unsigned short x, y;
} node;

Now, I want to be able to pull this out of the db and parse it out into a nice HTML display. What's the best way to do this? For the char arrays it's pretty easy. But even if I put in assumptions about how many bytes each data type is, how do I tell php that 'These next 4 bytes are a short, and I want you to grab this and treat it as such, and not just 4 bytes of characters'.

Are there any built-in commands that understand C data types?

[Anon]

I think what you are looking for is unpack() ..

http://www.php.net/manual/en/function.unpack.php

Hope that helps

Chris King

[Anon]

I have a MySQL Blob that contains binary data. I have extracted this blob into a PHP variable using:
$line = mysql_fetch_next($query, MYSQL_ASSOC);

Now, $line is an array of columns, with the variable:

$line['binary_column'] referencing my binary data.

The format of the binary data is:

[Double] : Average A,
[Double] : Average B,
[Double] : Average C,
[Unsigned Int] : Count A Pairs to Follow,
[char] : x1,
[char] : y1,
[char] : v1,
[char] : ...
[char] : xN,
[char] : yN,
[char] : vN,
[Unsigned Int] : Count B Pairs to Follow,
[char] : x1,
[char] : y1,
[char] : v1,
[char] : ...
[char] : xN,
[char] : yN,
[char] : vN,
[Unsigned Int] : Count C Pairs to Follow,
[char] : x1,
[char] : y1,
[char] : v1,
[char] : ...
[char] : xN,
[char] : yN,
[char] : vN

I want to construct PHP variables out of the binary blob data -- construct 'php variables' from the three initial doubles, extract the chars-to-follow, and then build up array of the coefficient elements (each char in the binary stream is a coefficient).

any clue on how to do this? I was looking into the fread functions, but I don't know how to map a file handle over the php object representing the blob...?

Then I found "pack" from this thread, but I'm not sure if I can do this with pack... Anyone know of non-trivial examples using pack?