Sequence Numbers helper class

libraries/networking/src/udt/SeqNum.cpp

@@ -0,0 +1,38 @@
+//
+//  SeqNum.cpp
+//
+//
+//  Created by Clement on 7/23/15.
+//  Copyright 2015 High Fidelity, Inc.
+//
+//  Distributed under the Apache License, Version 2.0.
+//  See the accompanying file LICENSE or http://www.apache.org/licenses/LICENSE-2.0.html
+//
+
+#include "SeqNum.h"
+
+namespace udt {
+
+int seqcmp(const SeqNum& seq1, const SeqNum& seq2) {
+    return (glm::abs(seq1._value - seq2._value) < SeqNum::THRESHOLD) ? (seq1._value - seq2._value)
+    : (seq2._value - seq1._value);
+}
+
+int seqlen(const SeqNum& seq1, const SeqNum& seq2) {
+    return (seq1._value <= seq2._value) ? (seq2._value - seq1._value + 1)
+    : (seq2._value - seq1._value + SeqNum::MAX + 2);
+}
+
+int seqoff(const SeqNum& seq1, const SeqNum& seq2) {
+    if (glm::abs(seq1._value - seq2._value) < SeqNum::THRESHOLD) {
+        return seq2._value - seq1._value;
+    }
+    
+    if (seq1._value < seq2._value) {
+        return seq2._value - seq1._value - SeqNum::MAX - 1;
+    }
+    
+    return seq2._value - seq1._value + SeqNum::MAX + 1;
+}
+
+}

libraries/networking/src/udt/SeqNum.h

@@ -0,0 +1,84 @@
+//
+//  SeqNum.h
+//  libraries/networking/src/udt
+//
+//  Created by Clement on 7/23/15.
+//  Copyright 2015 High Fidelity, Inc.
+//
+//  Distributed under the Apache License, Version 2.0.
+//  See the accompanying file LICENSE or http://www.apache.org/licenses/LICENSE-2.0.html
+//
+
+#ifndef hifi_SeqNum_h
+#define hifi_SeqNum_h
+
+#include <glm/detail/func_common.hpp>
+
+namespace udt {
+
+class SeqNum {
+public:
+    // Base type of sequence numbers
+    using Type = uint32_t;
+    
+    // Values are for 29 bit SeqNum
+    static const Type THRESHOLD = 0x0FFFFFFF; // threshold for comparing sequence numbers
+    static const Type MAX = 0x1FFFFFFF; // maximum sequence number used in UDT
+    
+    SeqNum() : _value(0) {}
+    
+    // Only explicit conversions
+    explicit SeqNum(Type value) { *this = value; }
+    explicit operator Type() { return _value; }
+    
+    inline SeqNum& operator++() {
+        _value = (_value == MAX) ? 0 : ++_value;
+        return *this;
+    }
+    inline SeqNum& operator--() {
+        _value = (_value == 0) ? MAX : --_value;
+        return *this;
+    }
+    inline SeqNum operator++(int) {
+        SeqNum before = *this;
+        (*this)++;
+        return before;
+    }
+    inline SeqNum operator--(int) {
+        SeqNum before = *this;
+        (*this)--;
+        return before;
+    }
+    
+    inline SeqNum& operator=(Type value) {
+        _value = (value <= MAX) ? value : MAX;
+        return *this;
+    }
+    inline SeqNum& operator=(SeqNum& other) {
+        _value = other._value;
+        return *this;
+    }
+    inline SeqNum& operator+=(Type inc) {
+        _value = (_value + inc > MAX) ? _value + inc - (MAX + 1) : _value + inc;
+        return *this;
+    }
+    inline SeqNum& operator-=(Type dec) {
+        _value = (_value < dec) ? MAX - (dec - _value + 1) : _value - dec;
+        return *this;
+    }
+    
+    friend int seqcmp(const SeqNum& seq1, const SeqNum& seq2);
+    friend int seqlen(const SeqNum& seq1, const SeqNum& seq2);
+    friend int seqoff(const SeqNum& seq1, const SeqNum& seq2);
+    
+private:
+    Type _value;
+};
+    
+int seqcmp(const SeqNum& seq1, const SeqNum& seq2);
+int seqlen(const SeqNum& seq1, const SeqNum& seq2);
+int seqoff(const SeqNum& seq1, const SeqNum& seq2);
+
+}
+
+#endif // hifi_SeqNum_h