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
如果你想得到wcoenen报告的“4倍速度增长”,那么如果不明显:用hex[i]+hex[i+1]替换hex.Substring(i,2)
您还可以再进一步,通过在两个地方使用i++来消除i+=2。
其他回答
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();
}
我猜它的速度值16个额外的字节。
static char[] hexes = new char[]{'0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F'};
public static string ToHexadecimal (this byte[] Bytes)
{
char[] Result = new char[Bytes.Length << 1];
int Offset = 0;
for (int i = 0; i != Bytes.Length; i++) {
Result[Offset++] = hexes[Bytes[i] >> 4];
Result[Offset++] = hexes[Bytes[i] & 0x0F];
}
return new string(Result);
}
.NET 5已添加Convert.ToHexString方法。
对于使用旧版本.NET的用户
internal static class ByteArrayExtensions
{
public static string ToHexString(this byte[] bytes, Casing casing = Casing.Upper)
{
Span<char> result = stackalloc char[0];
if (bytes.Length > 16)
{
var array = new char[bytes.Length * 2];
result = array.AsSpan();
}
else
{
result = stackalloc char[bytes.Length * 2];
}
int pos = 0;
foreach (byte b in bytes)
{
ToCharsBuffer(b, result, pos, casing);
pos += 2;
}
return result.ToString();
}
private static void ToCharsBuffer(byte value, Span<char> buffer, int startingIndex = 0, Casing casing = Casing.Upper)
{
uint difference = (((uint)value & 0xF0U) << 4) + ((uint)value & 0x0FU) - 0x8989U;
uint packedResult = ((((uint)(-(int)difference) & 0x7070U) >> 4) + difference + 0xB9B9U) | (uint)casing;
buffer[startingIndex + 1] = (char)(packedResult & 0xFF);
buffer[startingIndex] = (char)(packedResult >> 8);
}
}
public enum Casing : uint
{
// Output [ '0' .. '9' ] and [ 'A' .. 'F' ].
Upper = 0,
// Output [ '0' .. '9' ] and [ 'a' .. 'f' ].
Lower = 0x2020U,
}
改编自.NET存储库https://github.com/dotnet/runtime/blob/v5.0.3/src/libraries/System.Private.CoreLib/src/System/Convert.cshttps://github.com/dotnet/runtime/blob/v5.0.3/src/libraries/Common/src/System/HexConverter.cs
在编写加密代码时,通常避免依赖数据的分支和表查找,以确保运行时不依赖于数据,因为依赖数据的计时可能会导致侧通道攻击。
它也很快。
static string ByteToHexBitFiddle(byte[] bytes)
{
char[] c = new char[bytes.Length * 2];
int b;
for (int i = 0; i < bytes.Length; i++) {
b = bytes[i] >> 4;
c[i * 2] = (char)(55 + b + (((b-10)>>31)&-7));
b = bytes[i] & 0xF;
c[i * 2 + 1] = (char)(55 + b + (((b-10)>>31)&-7));
}
return new string(c);
}
Ph'nglui mglw'naph Cthulhu R'lieh wgah'nagl fhtagn公司
你们这些进入这里的人,放弃一切希望吧
一个奇怪的拨弄解释:
bytes[i]>>4提取字节的高位半字节bytes[i]&0xF提取字节的低位半字节b-10对于值b<10,为<0,将变为十进制数字对于值b>10,为>=0,这将成为从a到F的字母。在有符号32位整数上使用i>>31可以提取符号,这得益于符号扩展。当i<0时为-1,当i>=0时为0。结合2)和3),表明(b-10)>>31将是字母0,数字-1。看看字母的大小写,最后一个被加数变为0,b在10到15的范围内。我们希望将其映射到A(65)到F(70),这意味着添加55('A'-10)。看看数字的情况,我们希望调整最后一个被加数,使其将b从范围0到9映射到范围0(48)到9(57)。这意味着它需要变为-7('0'-55)。现在我们可以乘以7。但由于-1由所有位表示为1,因此我们可以改用&-7,因为(0&-7)==0和(-1&-7)==-7。
进一步考虑:
我没有使用第二个循环变量来索引c,因为测量表明从I计算它更便宜。正好使用i<bytes.Length作为循环的上限允许JITter消除对bytes[i]的边界检查,所以我选择了这个变量。将b设为int允许不必要的从和到字节的转换。
测试:十六进制字符串到字节数组
我注意到,大多数测试都是在将Bytes数组转换为十六进制字符串的函数上执行的。因此,在这篇文章中,我将关注另一方面:将十六进制字符串转换为字节数组的函数。若您只对结果感兴趣,可以跳到“摘要”部分。测试代码文件在文章末尾提供。
标签
我想根据接受的答案(Tomalak)将函数命名为StringToByteArrayV1,或将其快捷到V1。其余函数将以相同的方式命名:V2、V3、V4、…、。。。,等
参与功能索引
Tomalak的StringToByteArrayV1(公认答案)Mykroft的StringToByteArrayV2(使用SoapHexBinary)drphrozen的StringToByteArrayV3(查找表)CoperNick的StringToByteArrayV4(字节操作)Chris F编写的StringToByteArrayV5_1(字节操作)Chris F的StringToByteArrayV5_2(V5_1+根据Amir Rezaei的评论修改)Chris F的StringToByteArrayV5_3(V5_2+根据Ben Voigt的评论对其进行了修改)(您可以在发布后的测试代码中看到它的最终形状)Ben Mosher编写的StringToByteArrayV6(字节操作)Maratius的StringToByteArrayV7(字节操作-安全版本)Maratius的StringToByteArrayV8(字节操作-不安全版本)StringToByteArrayV9(按Geograph)AlejandroAlis编写的StringToByteArrayV10Fredrik Hu编写的StringToByteArrayV11Maarten Bodewes编写的StringToByteArrayV12ClausAndersen编写的StringToByteArrayV13Stas Makutin编写的StringToByteArrayV14JJJ的StringToByteArrayV15JamieSee的StringToByteArrayV16spacepille的StringToByteArrayV17Gregory Morse编写的StringToByteArrayV18Rick编写的StringToByteArrayV19SandRock的StringToByteArrayV20Paul编写的StringToByteArrayV21
正确性测试
我通过传递1字节的所有256个可能值来测试正确性,然后检查输出是否正确。结果:
V18中以“00”开头的字符串有问题(请参阅Roger Stewart对此的评论)。除了通过所有测试。如果十六进制字符串字母是大写的:所有函数都成功传递如果十六进制字符串字母是小写的,则以下函数失败:V5_1、V5_2、v7、V8、V15、V19
注:V5_3解决了这个问题(V5_1和V5_2)
性能测试
我已经使用Stopwatch类进行了性能测试。
长字符串的性能
input length: 10,000,000 bytes
runs: 100
average elapsed time per run:
V1 = 136.4ms
V2 = 104.5ms
V3 = 22.0ms
V4 = 9.9ms
V5_1 = 10.2ms
V5_2 = 9.0ms
V5_3 = 9.3ms
V6 = 18.3ms
V7 = 9.8ms
V8 = 8.8ms
V9 = 10.2ms
V10 = 19.0ms
V11 = 12.2ms
V12 = 27.4ms
V13 = 21.8ms
V14 = 12.0ms
V15 = 14.9ms
V16 = 15.3ms
V17 = 9.5ms
V18 got excluded from this test, because it was very slow when using very long string
V19 = 222.8ms
V20 = 66.0ms
V21 = 15.4ms
V1 average ticks per run: 1363529.4
V2 is more fast than V1 by: 1.3 times (ticks ratio)
V3 is more fast than V1 by: 6.2 times (ticks ratio)
V4 is more fast than V1 by: 13.8 times (ticks ratio)
V5_1 is more fast than V1 by: 13.3 times (ticks ratio)
V5_2 is more fast than V1 by: 15.2 times (ticks ratio)
V5_3 is more fast than V1 by: 14.8 times (ticks ratio)
V6 is more fast than V1 by: 7.4 times (ticks ratio)
V7 is more fast than V1 by: 13.9 times (ticks ratio)
V8 is more fast than V1 by: 15.4 times (ticks ratio)
V9 is more fast than V1 by: 13.4 times (ticks ratio)
V10 is more fast than V1 by: 7.2 times (ticks ratio)
V11 is more fast than V1 by: 11.1 times (ticks ratio)
V12 is more fast than V1 by: 5.0 times (ticks ratio)
V13 is more fast than V1 by: 6.3 times (ticks ratio)
V14 is more fast than V1 by: 11.4 times (ticks ratio)
V15 is more fast than V1 by: 9.2 times (ticks ratio)
V16 is more fast than V1 by: 8.9 times (ticks ratio)
V17 is more fast than V1 by: 14.4 times (ticks ratio)
V19 is more SLOW than V1 by: 1.6 times (ticks ratio)
V20 is more fast than V1 by: 2.1 times (ticks ratio)
V21 is more fast than V1 by: 8.9 times (ticks ratio)
V18的长串性能
V18 took long time at the previous test,
so let's decrease length for it:
input length: 1,000,000 bytes
runs: 100
average elapsed time per run: V1 = 14.1ms , V18 = 146.7ms
V1 average ticks per run: 140630.3
V18 is more SLOW than V1 by: 10.4 times (ticks ratio)
短字符串的性能
input length: 100 byte
runs: 1,000,000
V1 average ticks per run: 14.6
V2 is more fast than V1 by: 1.4 times (ticks ratio)
V3 is more fast than V1 by: 5.9 times (ticks ratio)
V4 is more fast than V1 by: 15.7 times (ticks ratio)
V5_1 is more fast than V1 by: 15.1 times (ticks ratio)
V5_2 is more fast than V1 by: 18.4 times (ticks ratio)
V5_3 is more fast than V1 by: 16.3 times (ticks ratio)
V6 is more fast than V1 by: 5.3 times (ticks ratio)
V7 is more fast than V1 by: 15.7 times (ticks ratio)
V8 is more fast than V1 by: 18.0 times (ticks ratio)
V9 is more fast than V1 by: 15.5 times (ticks ratio)
V10 is more fast than V1 by: 7.8 times (ticks ratio)
V11 is more fast than V1 by: 12.4 times (ticks ratio)
V12 is more fast than V1 by: 5.3 times (ticks ratio)
V13 is more fast than V1 by: 5.2 times (ticks ratio)
V14 is more fast than V1 by: 13.4 times (ticks ratio)
V15 is more fast than V1 by: 9.9 times (ticks ratio)
V16 is more fast than V1 by: 9.2 times (ticks ratio)
V17 is more fast than V1 by: 16.2 times (ticks ratio)
V18 is more fast than V1 by: 1.1 times (ticks ratio)
V19 is more SLOW than V1 by: 1.6 times (ticks ratio)
V20 is more fast than V1 by: 1.9 times (ticks ratio)
V21 is more fast than V1 by: 11.4 times (ticks ratio)
测试代码
在使用以下代码之前,最好先阅读本文下面的免责声明部分https://github.com/Ghosticollis/performance-tests/blob/main/MTestPerformance.cs
总结
由于性能良好,我建议使用以下函数之一,并支持大写和小写:
CoperNick的StringToByteArrayV4StringToByteArrayV9(按Geograph)spacepille的StringToByteArrayV17StringToByteArrayV5_3基本上由Chris F开发(它基于V5_1,但我根据Amir Rezaei和Ben Voigt的评论对其进行了增强)。
以下是V5_3的最终形状:
static byte[] HexStringToByteArrayV5_3(string hexString) {
int hexStringLength = hexString.Length;
byte[] b = new byte[hexStringLength / 2];
for (int i = 0; i < hexStringLength; i += 2) {
int topChar = hexString[i];
topChar = (topChar > 0x40 ? (topChar & ~0x20) - 0x37 : topChar - 0x30) << 4;
int bottomChar = hexString[i + 1];
bottomChar = bottomChar > 0x40 ? (bottomChar & ~0x20) - 0x37 : bottomChar - 0x30;
b[i / 2] = (byte)(topChar + bottomChar);
}
return b;
}
免责声明
警告:我没有适当的测试知识。这些原始测试的主要目的是快速概述所有发布的函数的优点。如果您需要准确的结果,请使用适当的测试工具。
最后,我想说,我是新来的,在斯塔科弗洛活跃,如果我的职位空缺,我很抱歉。如果您能发表评论,我们将不胜感激。
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