u32lim.h

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#ifndef _RE2C_UTIL_U32LIM_
#define _RE2C_UTIL_U32LIM_

#include "src/util/c99_stdint.h"

// uint32_t truncated to LIMIT
// any overflow (either result of a binary operation
// or conversion from another type) results in LIMIT
// LIMIT is a fixpoint
template<uint32_t LIMIT>
class u32lim_t
{
    uint32_t value;
    explicit u32lim_t (uint32_t x)
        : value (x < LIMIT ? x : LIMIT)
    {}
    explicit u32lim_t (uint64_t x)
        : value (x < LIMIT ? static_cast<uint32_t> (x) : LIMIT)
    {}

public:
    // implicit conversion is forbidden, because
    // operands should be converted before operation:
    //     uint32_t x, y; ... u32lim_t z = x + y;
    // will result in 32-bit addition and may overflow
    // Don't export overloaded constructors: it breaks OS X builds
    // ('size_t' causes resolution ambiguity)
    static u32lim_t from32 (uint32_t x) { return u32lim_t(x); }
    static u32lim_t from64 (uint64_t x) { return u32lim_t(x); }

    static u32lim_t limit ()
    {
        return u32lim_t (LIMIT);
    }

    uint32_t uint32 () const
    {
        return value;
    }

    bool overflow () const
    {
        return value == LIMIT;
    }

    friend u32lim_t operator + (u32lim_t x, u32lim_t y)
    {
        const uint64_t z
            = static_cast<uint64_t> (x.value)
            + static_cast<uint64_t> (y.value);
        return z < LIMIT
            ? u32lim_t (z)
            : u32lim_t (LIMIT);
    }

    friend u32lim_t operator * (u32lim_t x, u32lim_t y)
    {
        const uint64_t z
            = static_cast<uint64_t> (x.value)
            * static_cast<uint64_t> (y.value);
        return z < LIMIT
            ? u32lim_t (z)
            : u32lim_t (LIMIT);
    }

    friend bool operator < (u32lim_t x, u32lim_t y)
    {
        return x.value < y.value;
    }
};

#endif // _RE2C_UTIL_U32LIM_