66 lines
1.5 KiB
C++
66 lines
1.5 KiB
C++
#include <cstdint>
|
|
#include <iostream>
|
|
|
|
#include <byteswap.h>
|
|
|
|
char b[8] = {1, 2, 3, 4, 0, 0, 0, 1};
|
|
|
|
int64_t safe_int64(const char* b) {
|
|
return int64_t(b[0]) << 56 | int64_t(b[1]) << 48 | int64_t(b[2]) << 40 |
|
|
int64_t(b[3]) << 32 | int64_t(b[4]) << 24 | int64_t(b[5]) << 16 |
|
|
int64_t(b[6]) << 8 | int64_t(b[7]);
|
|
}
|
|
|
|
int64_t unsafe_int64(const char* b) {
|
|
auto i = reinterpret_cast<const int64_t*>(b);
|
|
return __bswap_64(*i);
|
|
}
|
|
|
|
int32_t safe_int32(const char* b) {
|
|
return b[0] << 24 | b[1] << 16 | b[2] << 8 | b[3];
|
|
}
|
|
|
|
int32_t unsafe_int32(const char* b) {
|
|
auto i = reinterpret_cast<const int32_t*>(b);
|
|
return __bswap_32(*i);
|
|
}
|
|
|
|
[[clang::optnone]] void test(uint64_t n) {
|
|
for (uint64_t i = 0; i < n; ++i) unsafe_int64(b);
|
|
}
|
|
|
|
uint8_t f[8] = {0x3F, 0xF1, 0x99, 0x99, 0x99, 0x99, 0x99, 0x9A};
|
|
|
|
double ff = 1.1;
|
|
|
|
double get_double(const uint8_t* b) {
|
|
auto v = __bswap_64(*reinterpret_cast<const uint64_t*>(b));
|
|
return *reinterpret_cast<const double*>(&v);
|
|
}
|
|
|
|
void print_hex(const char* buf, size_t n) {
|
|
for (size_t i = 0; i < n; ++i) printf("%02X ", (unsigned char)buf[i]);
|
|
}
|
|
|
|
void print_hex(const uint8_t* buf, size_t n) { print_hex((const char*)buf, n); }
|
|
|
|
int main(void) {
|
|
auto dd = get_double(f);
|
|
|
|
print_hex(f, 8);
|
|
|
|
std::cout << std::endl;
|
|
print_hex((const uint8_t*)(&ff), 8);
|
|
|
|
std::cout << std::endl;
|
|
print_hex((const uint8_t*)(&dd), 8);
|
|
|
|
std::cout << "dd: " << dd << std::endl;
|
|
std::cout << "Safe: " << safe_int64(b) << std::endl;
|
|
std::cout << unsafe_int64(b) << std::endl;
|
|
|
|
test(1000000ull);
|
|
|
|
return 0;
|
|
}
|