public static string Intercept(string input, int p)
{
Encoding encode = Encoding.GetEncoding("gb2312");
byte[] byteArr = encode.GetBytes(input);
if (byteArr.Length <= p) return input;
int m = 0, n = 0;
foreach (byte b in byteArr)
{
if (n >= p) break;
if (b > 127) m++; //重要一步：对前p个字节中的值大于127的字符进行统计
n++;
}
if (m % 2 != 0) n = p + 1; //如果非偶：则说明末尾为双字节字符，截取位数加1
return encode.GetString(byteArr, 0, n);
}
Console.WriteLine(Intercept("ABC中国人", 7));
Console.WriteLine(Intercept("ABCD中国人", 7));
Console.WriteLine(Intercept("ABC中D国人", 7));
string HalfSubstring(string str, int strLength)
{
if (System.Text.Encoding.Unicode.GetByteCount(str) < strLength)
return str;
byte[] bytesStr = System.Text.Encoding.Unicode.GetBytes(str);
List<byte> list = new List<byte>();
int count = 0;
for (int i = 0; i < bytesStr.Length; i += 2)
{
if (count == strLength)
break;
if (bytesStr[i + 1] == 0)
{
if (count + 1 == strLength)
{
list.Add(46);
list.Add(0);
count++;
}
else
{
list.Add(bytesStr[i]);
list.Add(bytesStr[i + 1]);
count++;
}
}
else
{
if (count + 2 > strLength)
{
list.Add(46);
list.Add(0);
count++;
}
else if (count + 2 == strLength)
{
list.Add(46);
list.Add(0);
list.Add(46);
list.Add(0);
count += 2;
}
else
{
list.Add(bytesStr[i]);
list.Add(bytesStr[i + 1]);
count += 2;
}
}
}
return System.Text.Encoding.Unicode.GetString(list.ToArray());
}
public static string hySubString(string str, int length)
{
string res = String.Empty;
int bytecount = System.Text.Encoding.GetEncoding("GB2312").GetByteCount(str);
if (length >= bytecount)
{
return str;
}
for (int i = str.Length - 1; i >= 0; i--)
{
if (System.Text.Encoding.GetEncoding("GB2312").GetByteCount(str.Substring(0, i)) <= length)
{
return str.Substring(0, i);
}
}
return string.Empty;
}
public static string Intercept(string input, int p)
{
Encoding encode = Encoding.GetEncoding("gb2312");
byte[] byteArr = encode.GetBytes(input);
if (byteArr.Length <= p) return input;
if (byteArr[p - 1] >> 7 == 1)
++p;
return encode.GetString(byteArr, 0, p);
}
