1 files changed, 91 insertions, 0 deletions
diff --git a/js/public/SliceBudget.h b/js/public/SliceBudget.h
new file mode 100644
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--- /dev/null
+++ b/js/public/SliceBudget.h
@@ -0,0 +1,91 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
+ * vim: set ts=8 sts=4 et sw=4 tw=99:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef js_SliceBudget_h
+#define js_SliceBudget_h
+
+#include <stdint.h>
+
+namespace js {
+
+struct JS_PUBLIC_API(TimeBudget)
+{
+    int64_t budget;
+
+    explicit TimeBudget(int64_t milliseconds) { budget = milliseconds; }
+};
+
+struct JS_PUBLIC_API(WorkBudget)
+{
+    int64_t budget;
+
+    explicit WorkBudget(int64_t work) { budget = work; }
+};
+
+/*
+ * This class records how much work has been done in a given collection slice,
+ * so that we can return before pausing for too long. Some slices are allowed
+ * to run for unlimited time, and others are bounded. To reduce the number of
+ * gettimeofday calls, we only check the time every 1000 operations.
+ */
+class JS_PUBLIC_API(SliceBudget)
+{
+    static const int64_t unlimitedDeadline = INT64_MAX;
+    static const intptr_t unlimitedStartCounter = INTPTR_MAX;
+
+    bool checkOverBudget();
+
+    SliceBudget();
+
+  public:
+    // Memory of the originally requested budget. If isUnlimited, neither of
+    // these are in use. If deadline==0, then workBudget is valid. Otherwise
+    // timeBudget is valid.
+    TimeBudget timeBudget;
+    WorkBudget workBudget;
+
+    int64_t deadline; /* in microseconds */
+    intptr_t counter;
+
+    static const intptr_t CounterReset = 1000;
+
+    static const int64_t UnlimitedTimeBudget = -1;
+    static const int64_t UnlimitedWorkBudget = -1;
+
+    /* Use to create an unlimited budget. */
+    static SliceBudget unlimited() { return SliceBudget(); }
+
+    /* Instantiate as SliceBudget(TimeBudget(n)). */
+    explicit SliceBudget(TimeBudget time);
+
+    /* Instantiate as SliceBudget(WorkBudget(n)). */
+    explicit SliceBudget(WorkBudget work);
+
+    void makeUnlimited() {
+        deadline = unlimitedDeadline;
+        counter = unlimitedStartCounter;
+    }
+
+    void step(intptr_t amt = 1) {
+        counter -= amt;
+    }
+
+    bool isOverBudget() {
+        if (counter > 0)
+            return false;
+        return checkOverBudget();
+    }
+
+    bool isWorkBudget() const { return deadline == 0; }
+    bool isTimeBudget() const { return deadline > 0 && !isUnlimited(); }
+    bool isUnlimited() const { return deadline == unlimitedDeadline; }
+
+    int describe(char* buffer, size_t maxlen) const;
+};
+
+} // namespace js
+
+#endif /* js_SliceBudget_h */