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# 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
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