protobuf/src/google/protobuf/io/strtod.cc

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// Protocol Buffers - Google's data interchange format
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// https://developers.google.com/protocol-buffers/
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#include <google/protobuf/io/strtod.h>
 
#include <cstdio>
#include <cstring>
#include <limits>
#include <string>
 
#include <google/protobuf/stubs/logging.h>
#include <google/protobuf/stubs/common.h>
 
#include <google/protobuf/stubs/strutil.h>
 
namespace google {
namespace protobuf {
namespace io {
 
// This approximately 0x1.ffffffp127, but we don't use 0x1.ffffffp127 because
// it won't compile in MSVC.
const double MAX_FLOAT_AS_DOUBLE_ROUNDED = 3.4028235677973366e+38;
 
float SafeDoubleToFloat(double value) {
  // static_cast<float> on a number larger than float can result in illegal
  // instruction error, so we need to manually convert it to infinity or max.
  if (value > std::numeric_limits<float>::max()) {
    // Max float value is about 3.4028234664E38 when represented as a double.
    // However, when printing float as text, it will be rounded as
    // 3.4028235e+38. If we parse the value of 3.4028235e+38 from text and
    // compare it to 3.4028234664E38, we may think that it is larger, but
    // actually, any number between these two numbers could only be represented
    // as the same max float number in float, so we should treat them the same
    // as max float.
    if (value <= MAX_FLOAT_AS_DOUBLE_ROUNDED) {
      return std::numeric_limits<float>::max();
    }
    return std::numeric_limits<float>::infinity();
  } else if (value < -std::numeric_limits<float>::max()) {
    if (value >= -MAX_FLOAT_AS_DOUBLE_ROUNDED) {
      return -std::numeric_limits<float>::max();
    }
    return -std::numeric_limits<float>::infinity();
  } else {
    return static_cast<float>(value);
  }
}
 
double NoLocaleStrtod(const char* str, char** endptr) {
  return google::protobuf::internal::NoLocaleStrtod(str, endptr);
}
 
}  // namespace io
}  // namespace protobuf
}  // namespace google