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/*
* Copyright (c) 2012 Nicira, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at:
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include <config.h>
#include "token-bucket.h"
#include "poll-loop.h"
#include "sat-math.h"
#include "timeval.h"
#include "util.h"
/* Initializes 'tb' to accumulate 'rate' tokens per millisecond, with a
* maximum of 'burst' tokens.
*
* The token bucket is initially full.
*
* It may be more convenient to use TOKEN_BUCKET_INIT. */
void
token_bucket_init(struct token_bucket *tb,
unsigned int rate, unsigned int burst)
{
tb->rate = rate;
tb->burst = burst;
tb->tokens = 0;
tb->last_fill = LLONG_MIN;
}
/* Changes 'tb' to accumulate 'rate' tokens per millisecond, with a maximum of
* 'burst' tokens.
*
* 'tb' must already have been initialized with TOKEN_BUCKET_INIT or
* token_bucket_init(). */
void
token_bucket_set(struct token_bucket *tb,
unsigned int rate, unsigned int burst)
{
tb->rate = rate;
tb->burst = burst;
if (burst > tb->tokens) {
tb->tokens = burst;
}
}
/* Attempts to remove 'n' tokens from 'tb'. Returns true if successful, false
* if 'tb' contained fewer than 'n' tokens (and thus 'n' tokens could not be
* removed) . */
bool
token_bucket_withdraw(struct token_bucket *tb, unsigned int n)
{
if (tb->tokens < n) {
long long int now = time_msec();
if (now > tb->last_fill) {
unsigned long long int elapsed_ull
= (unsigned long long int) now - tb->last_fill;
unsigned int elapsed = MIN(UINT_MAX, elapsed_ull);
unsigned int add = sat_mul(tb->rate, elapsed);
unsigned int tokens = sat_add(tb->tokens, add);
tb->tokens = MIN(tokens, tb->burst);
tb->last_fill = now;
}
if (tb->tokens < n) {
return false;
}
}
tb->tokens -= n;
return true;
}
/* Causes the poll loop to wake up when at least 'n' tokens will be available
* for withdrawal from 'tb'. */
void
token_bucket_wait(struct token_bucket *tb, unsigned int n)
{
if (tb->tokens >= n) {
poll_immediate_wake();
} else {
unsigned int need = n - tb->tokens;
poll_timer_wait_until(tb->last_fill + need / tb->rate + 1);
}
}
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