68 lines
1.6 KiB
C++
68 lines
1.6 KiB
C++
|
#pragma once
|
|||
|
|
|
|||
|
|
#include <atomic>
|
|||
|
|
|
|||
|
|
#include "sync.hh"
|
|||
|
|
|
|||
|
|
/* This class hands out tokens. There are only ‘maxTokens’ tokens
|
|||
|
|
available. Calling get() will return a Token object, representing
|
|||
|
|
ownership of a token. If no token is available, get() will sleep
|
|||
|
|
until another thread returns a token. */
|
|||
|
|
|
|||
|
|
class TokenServer
|
|||
|
|
{
|
|||
|
|
unsigned int maxTokens;
|
|||
|
|
|
|||
|
|
Sync<unsigned int> curTokens{0};
|
|||
|
|
std::condition_variable_any wakeup;
|
|||
|
|
|
|||
|
|
public:
|
|||
|
|
TokenServer(unsigned int maxTokens) : maxTokens(maxTokens) { }
|
|||
|
|
|
|||
|
|
class Token
|
|||
|
|
{
|
|||
|
|
friend TokenServer;
|
|||
|
|
|
|||
|
|
TokenServer * ts;
|
|||
|
|
|
|||
|
|
bool acquired = false;
|
|||
|
|
|
|||
|
|
Token(TokenServer * ts, unsigned int timeout) : ts(ts)
|
|||
|
|
{
|
|||
|
|
auto curTokens(ts->curTokens.lock());
|
|||
|
|
while (*curTokens >= ts->maxTokens)
|
|||
|
|
if (timeout) {
|
|||
|
|
if (!curTokens.wait_for(ts->wakeup, std::chrono::seconds(timeout),
|
|||
|
|
[&]() { return *curTokens < ts->maxTokens; }))
|
|||
|
|
return;
|
|||
|
|
} else
|
|||
|
|
curTokens.wait(ts->wakeup);
|
|||
|
|
(*curTokens)++;
|
|||
|
|
acquired = true;
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
public:
|
|||
|
|
|
|||
|
|
Token(Token && t) : ts(t.ts) { t.ts = 0; }
|
|||
|
|
Token(const Token & l) = delete;
|
|||
|
|
|
|||
|
|
~Token()
|
|||
|
|
{
|
|||
|
|
if (!ts || !acquired) return;
|
|||
|
|
{
|
|||
|
|
auto curTokens(ts->curTokens.lock());
|
|||
|
|
assert(*curTokens);
|
|||
|
|
(*curTokens)--;
|
|||
|
|
}
|
|||
|
|
ts->wakeup.notify_one();
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
bool operator ()() { return acquired; }
|
|||
|
|
};
|
|||
|
|
|
|||
|
|
Token get(unsigned int timeout = 0)
|
|||
|
|
{
|
|||
|
|
return Token(this, timeout);
|
|||
|
|
}
|
|||
|
|
};
|