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Add 32-bit support for custom strtod

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This commit is contained in:
Milo Yip 2014-09-14 12:42:58 +08:00
parent 855da06d0f
commit 4c2128818f
1 changed files with 23 additions and 4 deletions
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27
include/rapidjson/internal/strtod.h
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@ -299,17 +299,36 @@ private:
static uint64_t MulAdd64(uint64_t a, uint64_t b, uint64_t k, uint64_t* outHigh) {
#if defined(_MSC_VER) && defined(_M_AMD64)
uint64_t low = _umul128(a, b, outHigh);
uint64_t outLow = low + k;
if (outLow < low)
low += k;
if (low < k)
(*outHigh)++;
return outLow;
return low;
#elif (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 6)) && defined(__x86_64__)
unsigned __int128 p = static_cast<unsigned __int128>(a) * static_cast<unsigned __int128>(b);
p += k;
*outHigh = p >> 64;
return static_cast<uint64_t>(p);
#else
// TODO
const uint64_t a0 = a & 0xFFFFFFFF;
const uint64_t a1 = a >> 32;
const uint64_t b0 = b & 0xFFFFFFFF;
const uint64_t b1 = b >> 32;
uint64_t x0 = a0 * b0;
uint64_t x1 = a0 * b1;
uint64_t x2 = a1 * b0;
uint64_t x3 = a1 * b1;
x1 += (x0 >> 32); // can't give carry
x1 += x2;
if (x1 < x2)
x3 += (static_cast<uint64_t>(1) << 32);
uint64_t lo = (x1 << 32) + (x0 & 0xFFFFFFFF);
uint64_t hi = x3 + (x1 >> 32);
lo += k;
if (lo < k)
hi++;
*outHigh = hi;
return lo;
#endif
}