libfduserdata

associate file descriptors with user defined data

This small library permits to associate user defined data to file descriptors. This library is thread safe.

The library uses a hash table.

Initialization/Termination

The function fduserdata_create sets up the data structure. e.g.

FDUSERDATA table = fduserdata_create(0);

The optional parameter (here 0) is the size of the hashtable. The default size if 64.

When the data structure is no longer needed it can be deleted/freed using:

fduserdata_destroy(table);

create a new element:

Allocate a struct mydata element connected to the file descriptor fd in table:

struct mydata *data = fduserdata_new(table, fd, struct mydata);
// mydata.xxxx = yyyy
// intialize all mydata  fields
fduserdata_put(data)

Please note that fduserdata_put is required to close the critical section. No other threads can add, read or modify elements in table until the current element has been completely initialized and fduserdata_put has been called.

search an element/modify

struct mydata *fddata = fduserdata_get(table, fd);
if (fddata) {
    //... read/update user defined data (data->fields)
    fduserdata_put(data);
}

Again fduserdata_put closes the critical section. Slow or blocking operations should not take place between fduserdata_get and fduserdata_put

delete an element

struct mydata *fddata = fduserdata_get(table, fd);
if (fddata)
    fduserdata_del(data);

fduserdata_get (or fduserdata_new) is needed before fduserdata_del because fduserdata_del deletes the element while it closes the critical section. (in this way it is not possible to delete an element twice).

compile and install the library:

This is a sequence of commands that can be used to compile install the library.

mkdir build
cd build
cmake ..
make
sudo make install

rd235 / libfduserdata