106 lines
3.1 KiB
C++
106 lines
3.1 KiB
C++
#include "dtoa.hpp"
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#include <rapidjson/internal/dtoa.h>
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namespace mbgl {
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namespace util {
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namespace {
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// From https://github.com/miloyip/rapidjson/blob/master/include/rapidjson/internal/dtoa.h
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char* Prettify(char* buffer, int length, int k) {
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constexpr int maxDecimalPlaces = 324;
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const int kk = length + k; // 10^(kk-1) <= v < 10^kk
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if (0 <= k && kk <= 21) {
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// 1234e7 -> 12340000000
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for (int i = length; i < kk; i++)
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buffer[i] = '0';
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return &buffer[kk];
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}
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else if (0 < kk && kk <= 21) {
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// 1234e-2 -> 12.34
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std::memmove(&buffer[kk + 1], &buffer[kk], static_cast<size_t>(length - kk));
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buffer[kk] = '.';
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if (0 > k + maxDecimalPlaces) {
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// When maxDecimalPlaces = 2, 1.2345 -> 1.23, 1.102 -> 1.1
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// Remove extra trailing zeros (at least one) after truncation.
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for (int i = kk + maxDecimalPlaces; i > kk + 1; i--)
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if (buffer[i] != '0')
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return &buffer[i + 1];
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return &buffer[kk + 2]; // Reserve one zero
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}
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else
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return &buffer[length + 1];
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}
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else if (-6 < kk && kk <= 0) {
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// 1234e-6 -> 0.001234
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const int offset = 2 - kk;
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std::memmove(&buffer[offset], &buffer[0], static_cast<size_t>(length));
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buffer[0] = '0';
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buffer[1] = '.';
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for (int i = 2; i < offset; i++)
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buffer[i] = '0';
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if (length - kk > maxDecimalPlaces) {
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// When maxDecimalPlaces = 2, 0.123 -> 0.12, 0.102 -> 0.1
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// Remove extra trailing zeros (at least one) after truncation.
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for (int i = maxDecimalPlaces + 1; i > 2; i--)
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if (buffer[i] != '0')
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return &buffer[i + 1];
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return &buffer[3]; // Reserve one zero
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}
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else
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return &buffer[length + offset];
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}
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else if (kk < -maxDecimalPlaces) {
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// Truncate to zero
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buffer[0] = '0';
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return &buffer[1];
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}
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else if (length == 1) {
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// 1e30
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buffer[1] = 'e';
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return rapidjson::internal::WriteExponent(kk - 1, &buffer[2]);
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}
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else {
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// 1234e30 -> 1.234e33
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std::memmove(&buffer[2], &buffer[1], static_cast<size_t>(length - 1));
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buffer[1] = '.';
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buffer[length + 1] = 'e';
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return rapidjson::internal::WriteExponent(kk - 1, &buffer[0 + length + 2]);
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}
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}
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} // namespace
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char* dtoa(double value, char* buffer) {
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rapidjson::internal::Double d(value);
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if (d.IsZero()) {
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if (d.Sign())
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*buffer++ = '-'; // -0.0, Issue #289
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buffer[0] = '0';
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return &buffer[1];
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}
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else {
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if (value < 0) {
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*buffer++ = '-';
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value = -value;
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}
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int length, K;
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rapidjson::internal::Grisu2(value, buffer, &length, &K);
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return Prettify(buffer, length, K);
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}
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}
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std::string dtoa(double value) {
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std::string data;
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data.resize(25);
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auto end = dtoa(value, const_cast<char*>(data.data()));
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data.resize(end - data.data());
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return data;
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}
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} // namespace util
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} // namespace mbgl
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