此代码在 w/ 行产生中等警告return
:
// Checks if the symbol defines two-symbols Unicode sequence
bool doubleSymbol(const char c) {
static const char TWO_SYMBOLS_MASK = 0b110;
return (c >> 5) == TWO_SYMBOLS_MASK;
}
// Checks if the symbol defines three-symbols Unicode sequence
bool tripleSymbol(const char c) {
static const char THREE_SYMBOLS_MASK = 0b1110;
return (c >> 4) == THREE_SYMBOLS_MASK;
}
// Checks if the symbol defines four-symbols Unicode sequence
bool quadrupleSymbol(const char c) {
static const char FOUR_SYMBOLS_MASK = 0b11110;
return (c >> 3) == FOUR_SYMBOLS_MASK;
}
PVS 说表达式总是错误的(V547),但实际上不是:char
可能是读取到的 Unicode 符号的一部分std::string
!以下是符号的 Unicode 表示:
1 byte - 0xxx'xxxx - 7 bits
2 bytes - 110x'xxxx 10xx'xxxx - 11 bits
3 bytes - 1110'xxxx 10xx'xxxx 10xx'xxxx - 16 bits
4 bytes - 1111'0xxx 10xx'xxxx 10xx'xxxx 10xx'xxxx - 21 bits
以下代码计算 Unicode 文本中的符号数:
size_t symbolCount = 0;
std::string s;
while (getline(std::cin, s)) {
for (size_t i = 0; i < s.size(); ++i) {
const char c = s[i];
++symbolCount;
if (doubleSymbol(c)) {
i += 1;
} else if (tripleSymbol(c)) {
i += 2;
} else if (quadrupleSymbol(c)) {
i += 3;
}
}
}
std::cout << symbolCount << "\n";
对于Hello!
输入,输出是6
,对于Привет, мир!
是12
——这是正确的!
我错了还是 PVS 不知道什么?;)