Question about reading from socket

[raczzoli]

Hi.

I`m working on a socket server written in c, where I have to read (and parse) the header informations sent by a browser. The problem is that because of the possible POST and GET variables I don`t know exactly how long the header string will be so I can`t declare the read buffer statically (for ex. char buf[512]). I thought about two possibilities:

1. read the bytes from the socket one by one, and reallocate the space for the buffer each time.
2. allocate say 128 or 256 bytes for the buffer from the start, and increase it if necessary.


What do you think, what would be the best way to do this? Any suggestion is welcome.


Thank you.

[anduril462]

Something more like #2. Calling realloc repeatedly for individual bytes is silly. Read into an array of fixed size, like 1024. Base your malloc and realloc on how many bytes read returns so you can avoid any over-allocating. Just make sure to use a temporary pointer to store realloc's return value in case it fails for some reason. Otherwise, you lose the pointer to your original data.

[CommonTater]

Generally for input buffers on socket networking I allocate at least, 16k... of course you're not going to do that with char buf[16384]... you'll be using malloc().

[phantomotap]

O_o

Look into incremental parsing; just because you don't know how long the message will be or how many reads it may take doesn't mean you can't make use of it.

Say you are going to be copying "POST" into a buffer for later perusal. You don't necessarily need to continually repeat a `READ->COPY->ENLARGE' cycle for every byte in the message only to allocate additional memory for storing the "POST" portion of the message and copying that portion when you have already found the "POST" portion you conditionally copy to the buffer set aside for that information.

Soma