Question

Assuming I have a function that fills a buffer with binary data easily, how can I make that function return said buffer for further use?

The way I am currently doing it is by having it write the buffer (based off the content-length field from recv) write a temp file, then returning the name of that temp file so I can just read the tmp file into memory.

It would be nice however if I could just return the data directly rather than writing it to a tmp file, and using that. The only problem is if I return the binary data I have no way of knowing what the size of the buffer is (it’s not static) So my question is: is there a method of returning this binary data as well as maybe it’s size, or any way that I can work with it?

Or is my best bet just to stick with using tmp files?

Answer 1

In C you can either use a struct to encapsulate bunch of data items together, and pass that to your function, like:

/* Describes single I/O buffer */
struct buf {
    char* data; /* pointer to dynamically allocated memory */
    size_t mem_size; /* allocation size */
    size_t data_len; /* how much data is in the buffer */
    struct buf* next; /* can be used for buffer chaining */
};

/* Returns 0 on success, -1 on error */
int read_data( int sockfd, struct buf* pb );

Or use value-return arguments, like:

/* buffer receives data, len tells buffer length on input, and
 * how much was read on success. */
int read_data( int sockfd, char* buffer, size_t* len );