/Users/baford/proj/netsteria/sst/lib/chk32.h

#ifndef SST_CHK32_H
#define SST_CHK32_H

#include <stdint.h>

namespace SST {


// Default initialization value for unkeyed use: b = 0, a = 1
//#define CHK32_INIT    ((uint32_t)0x00000001)


class Chk32
{
private:
        // Counter initialization values
        static const uint32_t InitA = 0;
        static const uint32_t InitB = 0;

        // Prime modulus for our wraparound checksum arithmetic
        static const int Modulus = 65537;

        // Number of words we can process before our 64-bit counters overflow.
        // Actually 23726746, but just to be safe...
        static const int MaxRun = 23726740;

        uint64_t a;
        uint64_t b;
        int run;
        union {
                uint8_t b[2];
                uint16_t w;
        } oddbuf;
        bool haveodd;

public:
        inline Chk32() : a(InitA), b(InitB), run(MaxRun), haveodd(false) { }

        // Primitive init/update/final API for 
        inline void init16()
                { a = InitA; b = InitB; run = MaxRun; haveodd = false; }
        void update16(const uint16_t *buf, int nwords);
        uint32_t final16();

        // Standard init/update/final API for byte streams
        inline void init() { init16(); }
        void update(const void *buf, size_t size);
        uint32_t final();

        // Compute a checksum over a single data block
        static inline uint32_t sum(const void *buf, size_t size) {
                Chk32 c; c.update(buf, size); return c.final(); }
};


} // namespace SST

#endif  // SST_CHK32_H

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