larbin源码分析--Fifo
标准Fifo结构
template <class T>
class Fifo {
public:
uint in, out; //入口和出口的标识符
uint size;
T **tab;
/* Specific constructor */
Fifo (uint size=maxUrlsBySite);
/* Destructor */
~Fifo ();
/* give the first object and let it in */
inline T* read () { return tab[out]; }
/* read the first obj if exist */
T *tryRead ();
/* get the first object */
T *get ();
/* get the first object (non totally blocking)
* return NULL if there is none
*/
T *tryGet ();
/* add an object in the Fifo */
void put (T *obj);
/* put an obj that has just been get
* this function must be called only to put back an obj
* that has just been tken with get */
void rePut (T *obj);
/* how many items are there inside ? */
int getLength ();
/* is this fifo empty ? */
inline bool isEmpty () { return in == out; }
};
template <class T>
Fifo<T>::Fifo (uint size) {
tab = new T*[size];
this->size = size;
in = 0;
out = 0;
}
template <class T>
Fifo<T>::~Fifo () {
delete [] tab;
}
template <class T>
T *Fifo<T>::tryRead () {
if (in == out) {
return NULL;
} else {
return tab[out];
}
}
template <class T>
T *Fifo<T>::get () {
T *tmp;
assert (in != out);
tmp = tab[out];
out = (out + 1) % size;
return tmp;
}
template <class T>
T *Fifo<T>::tryGet () {
T *tmp = NULL;
if (in != out) {
// The stack is not empty
tmp = tab[out];
out = (out + 1) % size;
}
return tmp;
}
template <class T>
void Fifo<T>::put (T *obj) {
tab[in] = obj;
in = (in + 1) % size;
if (in == out) {
T **tmp;
tmp = new T*[2*size];
for (uint i=out; i<size; i++) {
tmp[i] = tab[i];
}
for (uint i=0; i<in; i++) {
tmp[i+size] = tab[i];
}
in += size;
size *= 2;
delete [] tab;
tab = tmp;
}
}
template <class T>
void Fifo<T>::rePut (T *obj) {
out = (out + size - 1) % size;
tab[out] = obj;
}
template <class T>
int Fifo<T>::getLength () {
return (in + size - out) % size;
}