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
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。
其他回答
您可以使用BitConverter.ToString方法:
byte[] bytes = {0, 1, 2, 4, 8, 16, 32, 64, 128, 256}
Console.WriteLine( BitConverter.ToString(bytes));
输出:
00-01-02-04-08-10-20-40-80-FF
更多信息:BitConverter.ToString方法(Byte[])
另一个快速功能。。。
private static readonly byte[] HexNibble = new byte[] {
0x0, 0x1, 0x2, 0x3, 0x4, 0x5, 0x6, 0x7,
0x8, 0x9, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,
0x0, 0xA, 0xB, 0xC, 0xD, 0xE, 0xF, 0x0,
0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,
0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,
0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0,
0x0, 0xA, 0xB, 0xC, 0xD, 0xE, 0xF
};
public static byte[] HexStringToByteArray( string str )
{
int byteCount = str.Length >> 1;
byte[] result = new byte[byteCount + (str.Length & 1)];
for( int i = 0; i < byteCount; i++ )
result[i] = (byte) (HexNibble[str[i << 1] - 48] << 4 | HexNibble[str[(i << 1) + 1] - 48]);
if( (str.Length & 1) != 0 )
result[byteCount] = (byte) HexNibble[str[str.Length - 1] - 48];
return result;
}
对于插入SQL字符串(如果不使用命令参数):
public static String ByteArrayToSQLHexString(byte[] Source)
{
return = "0x" + BitConverter.ToString(Source).Replace("-", "");
}
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。
我想出了一个不同的代码,它可以容忍额外的字符(空格、破折号…)。它的灵感主要来自这里一些可以接受的快速答案。它允许解析以下“文件”
00-aa-84-fb
12 32 FF CD
12 00
12_32_FF_CD
1200d5e68a
/// <summary>Reads a hex string into bytes</summary>
public static IEnumerable<byte> HexadecimalStringToBytes(string hex) {
if (hex == null)
throw new ArgumentNullException(nameof(hex));
char c, c1 = default(char);
bool hasc1 = false;
unchecked {
for (int i = 0; i < hex.Length; i++) {
c = hex[i];
bool isValid = 'A' <= c && c <= 'f' || 'a' <= c && c <= 'f' || '0' <= c && c <= '9';
if (!hasc1) {
if (isValid) {
hasc1 = true;
}
} else {
hasc1 = false;
if (isValid) {
yield return (byte)((GetHexVal(c1) << 4) + GetHexVal(c));
}
}
c1 = c;
}
}
}
/// <summary>Reads a hex string into a byte array</summary>
public static byte[] HexadecimalStringToByteArray(string hex)
{
if (hex == null)
throw new ArgumentNullException(nameof(hex));
var bytes = new List<byte>(hex.Length / 2);
foreach (var item in HexadecimalStringToBytes(hex)) {
bytes.Add(item);
}
return bytes.ToArray();
}
private static byte GetHexVal(char val)
{
return (byte)(val - (val < 0x3A ? 0x30 : val < 0x5B ? 0x37 : 0x57));
// ^^^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^^^ ^^^^
// digits 0-9 upper char A-Z a-z
}
复制时请参考完整代码。包括单元测试。
有些人可能会说它对额外的字符太宽容了。因此,不要依赖此代码来执行验证(或更改)。
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