adding rlimit resource limit facility to provide platform and architecture independent method for canceling activities

Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>

src/util/rlimit.cpp

@@ -0,0 +1,55 @@
+/*++
+Copyright (c) 2015 Microsoft Corporation
+
+Module Name:
+
+    rlimit.cpp
+
+Abstract:
+
+    Resource limit container.
+
+Author:
+
+    Nikolaj Bjorner (nbjorner) 2015-09-28
+
+Revision History:
+
+--*/
+#include "rlimit.h"
+
+reslimit::reslimit():
+    m_count(0),
+    m_limit(UINT_MAX) {
+}
+
+unsigned reslimit::count() const {
+    return m_count;
+}
+
+bool reslimit::inc() {
+    ++m_count;
+    return m_count <= m_limit;
+}
+
+bool reslimit::inc(unsigned offset) {
+    m_count += offset;
+    return m_count <= m_limit;
+}
+
+void reslimit::push(unsigned delta_limit) {
+    unsigned new_limit = UINT_MAX;
+    if (delta_limit > 0 && delta_limit + m_count > m_count) {
+        new_limit = delta_limit + m_count;
+    }
+    m_limits.push_back(m_limit);
+    m_limit = std::min(new_limit, m_limit);
+}
+
+void reslimit::pop() {
+    if (m_count > m_limit) {
+        m_count = m_limit;
+    }
+    m_limit = m_limits.back();
+    m_limits.pop_back();
+}

src/util/rlimit.h

@@ -0,0 +1,47 @@
+/*++
+Copyright (c) 2015 Microsoft Corporation
+
+Module Name:
+
+    rlimit.h
+
+Abstract:
+
+    Resource limit container.
+
+Author:
+
+    Nikolaj Bjorner (nbjorner) 2015-09-28
+
+Revision History:
+
+--*/
+#ifndef RLIMIT_H_
+#define RLIMIT_H_
+
+#include "vector.h"
+
+class reslimit {
+    unsigned        m_count;
+    unsigned        m_limit;
+    unsigned_vector m_limits;
+public:    
+    reslimit();
+    bool inc();
+    bool inc(unsigned offset);
+    void push(unsigned delta_limit);
+    void pop();
+    unsigned count() const; 
+};
+
+class scoped_rlimit {
+    reslimit& m_limit;
+public:
+    scoped_rlimit(reslimit& r, unsigned l): m_limit(r) {
+        r.push(l);
+    }
+    ~scoped_rlimit() { m_limit.pop(); }
+
+};
+
+#endif

src/util/statistics.cpp

@@ -236,3 +236,7 @@ void get_memory_statistics(statistics& st) {
     st.update("memory",      static_cast<double>(mem)/100.0);
     st.update("num allocs",  static_cast<double>(memory::get_allocation_count()));
 }
+
+void get_rlimit_statistics(reslimit& l, statistics& st) {
+    st.update("rlimit-count",     l.count());
+}

src/util/statistics.h

@@ -21,6 +21,7 @@ Notes:
 
 #include<iostream>
 #include"vector.h"
+#include"rlimit.h"
 
 class statistics {
     typedef std::pair<char const *, unsigned> key_val_pair;
@@ -43,5 +44,6 @@ public:
 };
 
 void get_memory_statistics(statistics& st);
+void get_rlimit_statistics(reslimit& l, statistics& st);
 
 #endif