throttle: use signed counters and assert that count never drops below 0

diff --git a/src/common/Throttle.h b/src/common/Throttle.h
index f05ae377018d130b0f23fbd366acc130b6abb66f..28320f2dec8e5bbaad5a76643e360f505eac9da0 100644 (file)
--- a/src/common/Throttle.h
+++ b/src/common/Throttle.h
@@ -5,27 +5,27 @@
 #include "Cond.h"
 
 class Throttle {
-  uint64_t count, max, waiting;
+  int64_t count, max, waiting;
   Mutex lock;
   Cond cond;
   
 public:
-  Throttle(uint64_t m = 0) : count(0), max(m), waiting(0),
+  Throttle(int64_t m = 0) : count(0), max(m), waiting(0),
                          lock("Throttle::lock") {}
 
 private:
-  void _reset_max(uint64_t m) {
+  void _reset_max(int64_t m) {
     if (m < max)
       cond.SignalOne();
     max = m;
   }
-  bool _should_wait(uint64_t c) {
+  bool _should_wait(int64_t c) {
     return
       max &&
       ((c < max && count + c > max) ||   // normally stay under max
        (c >= max && count > max));       // except for large c
   }
-  bool _wait(uint64_t c) {
+  bool _wait(int64_t c) {
     bool waited = false;
     if (_should_wait(c)) {
       waiting += c;
@@ -43,27 +43,27 @@ private:
   }
 
 public:
-  uint64_t get_current() {
+  int64_t get_current() {
     Mutex::Locker l(lock);
     return count;
   }
 
-  uint64_t get_max() { return max; }
+  int64_t get_max() { return max; }
 
-  bool wait(uint64_t m = 0) {
+  bool wait(int64_t m = 0) {
     Mutex::Locker l(lock);
     if (m)
       _reset_max(m);
     return _wait(0);
   }
 
-  uint64_t take(uint64_t c = 1) {
+  int64_t take(int64_t c = 1) {
     Mutex::Locker l(lock);
     count += c;
     return count;
   }
 
-  bool get(uint64_t c = 1, uint64_t m = 0) {
+  bool get(int64_t c = 1, int64_t m = 0) {
     Mutex::Locker l(lock);
     if (m)
       _reset_max(m);
@@ -72,10 +72,11 @@ public:
     return waited;
   }
 
-  uint64_t put(uint64_t c = 1) {
+  int64_t put(int64_t c = 1) {
     Mutex::Locker l(lock);
     cond.SignalOne();
     count -= c;
+    assert(c>=0); //if count goes negative, we failed somewhere!
     return count;
   }
 };