如何将字节数组转换为十六进制字符串,反之亦然?
当前回答
我将参加这个比特拨弄比赛,因为我有一个同样使用比特拨弄来解码十六进制的答案。请注意,使用字符数组可能会更快,因为调用StringBuilder方法也需要时间。
public static String ToHex (byte[] data)
{
int dataLength = data.Length;
// pre-create the stringbuilder using the length of the data * 2, precisely enough
StringBuilder sb = new StringBuilder (dataLength * 2);
for (int i = 0; i < dataLength; i++) {
int b = data [i];
// check using calculation over bits to see if first tuple is a letter
// isLetter is zero if it is a digit, 1 if it is a letter
int isLetter = (b >> 7) & ((b >> 6) | (b >> 5)) & 1;
// calculate the code using a multiplication to make up the difference between
// a digit character and an alphanumerical character
int code = '0' + ((b >> 4) & 0xF) + isLetter * ('A' - '9' - 1);
// now append the result, after casting the code point to a character
sb.Append ((Char)code);
// do the same with the lower (less significant) tuple
isLetter = (b >> 3) & ((b >> 2) | (b >> 1)) & 1;
code = '0' + (b & 0xF) + isLetter * ('A' - '9' - 1);
sb.Append ((Char)code);
}
return sb.ToString ();
}
public static byte[] FromHex (String hex)
{
// pre-create the array
int resultLength = hex.Length / 2;
byte[] result = new byte[resultLength];
// set validity = 0 (0 = valid, anything else is not valid)
int validity = 0;
int c, isLetter, value, validDigitStruct, validDigit, validLetterStruct, validLetter;
for (int i = 0, hexOffset = 0; i < resultLength; i++, hexOffset += 2) {
c = hex [hexOffset];
// check using calculation over bits to see if first char is a letter
// isLetter is zero if it is a digit, 1 if it is a letter (upper & lowercase)
isLetter = (c >> 6) & 1;
// calculate the tuple value using a multiplication to make up the difference between
// a digit character and an alphanumerical character
// minus 1 for the fact that the letters are not zero based
value = ((c & 0xF) + isLetter * (-1 + 10)) << 4;
// check validity of all the other bits
validity |= c >> 7; // changed to >>, maybe not OK, use UInt?
validDigitStruct = (c & 0x30) ^ 0x30;
validDigit = ((c & 0x8) >> 3) * (c & 0x6);
validity |= (isLetter ^ 1) * (validDigitStruct | validDigit);
validLetterStruct = c & 0x18;
validLetter = (((c - 1) & 0x4) >> 2) * ((c - 1) & 0x2);
validity |= isLetter * (validLetterStruct | validLetter);
// do the same with the lower (less significant) tuple
c = hex [hexOffset + 1];
isLetter = (c >> 6) & 1;
value ^= (c & 0xF) + isLetter * (-1 + 10);
result [i] = (byte)value;
// check validity of all the other bits
validity |= c >> 7; // changed to >>, maybe not OK, use UInt?
validDigitStruct = (c & 0x30) ^ 0x30;
validDigit = ((c & 0x8) >> 3) * (c & 0x6);
validity |= (isLetter ^ 1) * (validDigitStruct | validDigit);
validLetterStruct = c & 0x18;
validLetter = (((c - 1) & 0x4) >> 2) * ((c - 1) & 0x2);
validity |= isLetter * (validLetterStruct | validLetter);
}
if (validity != 0) {
throw new ArgumentException ("Hexadecimal encoding incorrect for input " + hex);
}
return result;
}
从Java代码转换而来。
其他回答
这个问题也可以使用查找表来解决。这将需要编码器和解码器的少量静态存储器。然而,这种方法很快:
编码器表512字节或1024字节(两次大小写(如果是大写和小写)需要)解码器表256字节或64 KiB(单个字符查找或双字符查找)
我的解决方案使用1024字节作为编码表,256字节用于解码。
解码
private static readonly byte[] LookupTable = new byte[] {
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
0xFF, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
0xFF, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF
};
private static byte Lookup(char c)
{
var b = LookupTable[c];
if (b == 255)
throw new IOException("Expected a hex character, got " + c);
return b;
}
public static byte ToByte(char[] chars, int offset)
{
return (byte)(Lookup(chars[offset]) << 4 | Lookup(chars[offset + 1]));
}
编码
private static readonly char[][] LookupTableUpper;
private static readonly char[][] LookupTableLower;
static Hex()
{
LookupTableLower = new char[256][];
LookupTableUpper = new char[256][];
for (var i = 0; i < 256; i++)
{
LookupTableLower[i] = i.ToString("x2").ToCharArray();
LookupTableUpper[i] = i.ToString("X2").ToCharArray();
}
}
public static char[] ToCharLower(byte[] b, int bOffset)
{
return LookupTableLower[b[bOffset]];
}
public static char[] ToCharUpper(byte[] b, int bOffset)
{
return LookupTableUpper[b[bOffset]];
}
比较
StringBuilderToStringFromBytes: 106148
BitConverterToStringFromBytes: 15783
ArrayConvertAllToStringFromBytes: 54290
ByteManipulationToCharArray: 8444
TableBasedToCharArray: 5651 *
*这个解决方案
Note
在解码过程中,可能会发生IOException和IndexOutOfRangeException(如果字符的值太高>256)。应该实现对流或数组进行去/编码的方法,这只是概念的证明。
我没有得到你建议的代码,Olipro。hex[i]+hex[i+1]显然返回了int。
然而,我确实从Waleeds代码中得到了一些提示,并将其结合在一起,取得了一些成功。这很难看,但根据我的测试(使用patricges测试机制),与其他测试相比,它似乎有1/3的时间在工作和执行。取决于输入大小。切换?:s首先将0-9分隔开可能会产生稍微更快的结果,因为数字比字母多。
public static byte[] StringToByteArray2(string hex)
{
byte[] bytes = new byte[hex.Length/2];
int bl = bytes.Length;
for (int i = 0; i < bl; ++i)
{
bytes[i] = (byte)((hex[2 * i] > 'F' ? hex[2 * i] - 0x57 : hex[2 * i] > '9' ? hex[2 * i] - 0x37 : hex[2 * i] - 0x30) << 4);
bytes[i] |= (byte)(hex[2 * i + 1] > 'F' ? hex[2 * i + 1] - 0x57 : hex[2 * i + 1] > '9' ? hex[2 * i + 1] - 0x37 : hex[2 * i + 1] - 0x30);
}
return bytes;
}
为了提高性能,我会选择drphrozens解决方案。解码器的一个微小的优化可能是为任一字符使用一个表,以消除“<<4”。
显然,这两个方法调用代价高昂。如果对输入或输出数据进行某种检查(可以是CRC、校验和或其他),则If(b==255)。。。可以跳过,从而也可以完全调用方法。
使用offset++和offset代替offset和offset+1可能会带来一些理论上的好处,但我怀疑编译器比我更好地处理这一点。
private static readonly byte[] LookupTableLow = new byte[] {
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
0xFF, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
0xFF, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF
};
private static readonly byte[] LookupTableHigh = new byte[] {
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
0x00, 0x10, 0x20, 0x30, 0x40, 0x50, 0x60, 0x70, 0x80, 0x90, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
0xFF, 0xA0, 0xB0, 0xC0, 0xD0, 0xE0, 0xF0, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
0xFF, 0xA0, 0xB0, 0xC0, 0xD0, 0xE0, 0xF0, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF
};
private static byte LookupLow(char c)
{
var b = LookupTableLow[c];
if (b == 255)
throw new IOException("Expected a hex character, got " + c);
return b;
}
private static byte LookupHigh(char c)
{
var b = LookupTableHigh[c];
if (b == 255)
throw new IOException("Expected a hex character, got " + c);
return b;
}
public static byte ToByte(char[] chars, int offset)
{
return (byte)(LookupHigh(chars[offset++]) | LookupLow(chars[offset]));
}
这只是我的头顶,没有经过测试或基准测试。
可以使用从.NET 5开始的Convert.ToHexString。还有一个用于反向操作的方法:Convert.FromHexString。
对于较旧版本的.NET,您可以使用:
public static string ByteArrayToString(byte[] ba)
{
StringBuilder hex = new StringBuilder(ba.Length * 2);
foreach (byte b in ba)
hex.AppendFormat("{0:x2}", b);
return hex.ToString();
}
or:
public static string ByteArrayToString(byte[] ba)
{
return BitConverter.ToString(ba).Replace("-","");
}
举个例子,这里有更多的方法。
反向转换如下:
public static byte[] StringToByteArray(String hex)
{
int NumberChars = hex.Length;
byte[] bytes = new byte[NumberChars / 2];
for (int i = 0; i < NumberChars; i += 2)
bytes[i / 2] = Convert.ToByte(hex.Substring(i, 2), 16);
return bytes;
}
使用Substring是与Convert.ToByte结合使用的最佳选项。有关详细信息,请参阅此答案。如果需要更好的性能,必须避免Convert.ToByte,然后才能删除SubString。
对于Java 8,我们可以使用Byte.toUnsignedInt
public static String convertBytesToHex(byte[] bytes) {
StringBuilder result = new StringBuilder();
for (byte byt : bytes) {
int decimal = Byte.toUnsignedInt(byt);
String hex = Integer.toHexString(decimal);
result.append(hex);
}
return result.toString();
}
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