[英]How do I convert a base64 string to hexadecimal string in C++?
I have a string that represents a value in base64. 我有一个表示base64中值的字符串。 I want to convert this string from base64 to hexadecimal.
我想将此字符串从base64转换为十六进制。 I'm working in C++ on Ubuntu 10.10.
我正在Ubuntu 10.10上使用C ++进行工作。 I have the following code:
我有以下代码:
std::string ssir = "DNQwSinfOUSSWd+U04r23A==";
std::string dec=(base64_decode(ssir));
std::stringstream ss;
for (int i=0; i<dec.size(); ++i) {
if (i != 0) ss << ':';
ss << std::hex << std::setw(2) << std::setfill('0') << static_cast<unsigned int>(dec[i]);//(int)(dec[i]);
}
std::string res;
res= ss.str();
cout<<"the ress is: "<<res<<std::endl;
The result is: 结果是:
0c:ffffffd4:30:4a:29:ffffffdf:39:44:ffffff92:59:ffffffdf:ffffff94:ffffffd3:ffffff8a:fffffff6:ffffffdc
0C:ffffffd4:30:4A:29:ffffffdf:39:44:ffffff92:59:ffffffdf:ffffff94:ffffffd3:ffffff8a:fffffff6:ffffffdc
It is correct, besides those ffffffff. 除了那些ffffffff,它是正确的。 What can I do to fix this?
我该怎么做才能解决此问题? If I want my hexadecimal result to be written to a
std::vector<unsigned char> x
, what do I have to do? 如果我想将十六进制结果写入
std::vector<unsigned char> x
,该怎么办?
Try using this cast instead: 尝试使用此强制转换:
static_cast<unsigned char>(dec[i])
int
is 32 bits wide and you only want to output 8 bits, which is how wide char
is. int
是32位宽,您只想输出8位,这就是char
宽度。 Presumably std::hex
is considering the input type when formatting the number. 在格式化数字时,大概
std::hex
正在考虑输入类型。 (Though I'm not quite sure where the sign extension is coming from, since you are casting to an unsigned type...) (尽管我不确定符号扩展名来自何处,因为您正在转换为无符号类型...)
@cdhowie's post is nearly correct. @cdhowie的帖子几乎正确。 However, if you cast to a
char
(signed or unsigned), the standard stream operators will attempt to write out the ASCII value of that character. 但是,如果强制转换为
char
(有符号或无符号),则标准流运算符将尝试写出该字符的ASCII值。 You will either need another cast: 您将需要另一个强制转换:
static_cast<int>(static_cast<unsigned char>(dec[i]))
or to explicitly truncate the value: 或显式截断值:
(static_cast<int>(dec[i]) & 0xFF)
(In both cases, your outer int
does not need to be unsigned
; in the first case, signed int
is wide enough to hold all unsigned char
values, and in the second, you are explicitly making the value positive.) (在两种情况下,都不需要对外部
int
进行unsigned
;在第一种情况下, signed int
足够宽,可以容纳所有unsigned char
值;在第二种情况下,您将使该值显式为正。)
You can try another string to hex conversion method. 您可以尝试其他字符串到十六进制的转换方法。 I wrote two functions.
我写了两个函数。 The str_to_hex - is my method.
str_to_hex-是我的方法。 str_to_hex2 - is your.
str_to_hex2-是您的。 I omit base64 encoding.
我省略了base64编码。 And then I invoked 1M times my function and your.
然后我调用了1M次函数和您的函数。 The execution time for str_to_hex is
str_to_hex的执行时间为
time ./a.out
real 0m0.365s
user 0m0.360s
sys 0m0.010s
And the execution time for str_to_hex2 is: 并且str_to_hex2的执行时间为:
time ./a.out
real 0m3.253s
user 0m3.220s
sys 0m0.000s
Ubuntu 10.04, 64bit, g++ 4.4.3, -O3 option. Ubuntu 10.04、64位,g ++ 4.4.3,-O3选项。
The code of testing programm is below. 测试程序的代码如下。
#include <string>
#include <iostream>
#include <sstream>
#include <iomanip>
void str_to_hex() {
std::string ssir = "DNQwSinfOUSSWd+U04r23A==";
static const char *hex = "0123456789ABCDEF";
std::string result;
result.reserve(ssir.size() * 3);
for (std::string::const_iterator i = ssir.begin(), end = ssir.end(); i != end; ++i) {
if (i != ssir.begin())
result.push_back(':');
result.push_back(hex[*i >> 4]);
result.push_back(hex[*i & 0xf]);
}
}
void str_to_hex2() {
std::string ssir = "DNQwSinfOUSSWd+U04r23A==";
std::stringstream ss;
for (int i=0; i<ssir.size(); ++i) {
if (i != 0) ss << ':';
ss << std::hex << std::setw(2) << std::setfill('0') << static_cast<unsigned int>(ssir[i] & 0xff);
}
}
int main() {
for (int i = 0; i < 1000000; ++i)
str_to_hex();
}
I am not sure if this is the best solution but this is how I did it. 我不确定这是否是最好的解决方案,但这就是我的方法。
#include <vector>
#include <bitset>
#include <string>
//hex->dec->bin8->bin6->dec->base64table
//HexToDec
unsigned int HexToDec(std::string hexInput)
{
//initlize variables
const int HexBaseASCCI = 48;
const int HexBase = 16;
size_t hexCharPlace = hexInput.size() -1;
int result = 0;
//reading the hexInput
for (int i = 0; i < hexInput.size(); i++)
{
char hexChar = hexInput.at(i);
int dec = 0;
//Finde the equvilcey of the char hex u read from the HexNum string
if (hexChar>='0' && hexChar<='9'){dec = (int)hexChar - HexBaseASCCI;}
else
{ switch (hexChar)
{ case ('A') :
case ('a') : {dec = 10; break;}
case ('B') :
case ('b') : {dec = 11; break;}
case ('C') :
case ('c') : {dec = 12; break;}
case ('D') :
case ('d') : {dec = 13; break;}
case ('E') :
case ('e') : {dec = 14; break;}
case ('F') :
case ('f') : {dec = 15; break;}
case ('X') :
case ('x') : {dec = 0; break;}
default : {
std::string msg ("is not in hex format");
throw std::logic_error(msg);};
}
}
//calculating the final dec
result += dec * pow(HexBase,hexCharPlace);
hexCharPlace--;
}
return result;
}
//HexToDec vector version
std::vector<unsigned int> HexToDec(std::vector<std::string> hex)
{
std::vector<unsigned int> dec;
for( auto x : hex){
dec.push_back(HexToDec(x));
}
return dec;
}
//BreakHexStringIntoGroups TODO .. needs to imporve
std::vector<std::string> BreakHexStringIntoGroups(std::string hexInput, unsigned long lengthOfBreaks)
{
std::vector<std::string> hexGroups;
if(!(hexInput.size() % 2)){
for (auto index(0); index < hexInput.size(); index+=lengthOfBreaks )
{
hexGroups.push_back(hexInput.substr(index,lengthOfBreaks));
}
}
else
{
for (auto index(0); index < hexInput.size()-1; index+=lengthOfBreaks )
{
hexGroups.push_back(hexInput.substr(index,lengthOfBreaks));
}
hexGroups.push_back(hexInput.substr(hexInput.size()-1));
}
return hexGroups;
}
//DecTo8BitsBin
std::vector<std::string> DecTo8BitsBin(std::vector<unsigned int> dec)
{
std::vector<std::string> bin;
for (auto x: dec)
{
bin.push_back(std::bitset<8>(x).to_string());
}
return bin;
}
//FuseStringVector
std::string FuseStringVector(std::vector<std::string> vec)
{
std::string res;
for (auto str: vec)
{
res+=str;
}
return res;
}
//BreakBinStringInto6BitsGroups TODO .. needs to imporve
std::vector<std::string> BreakBinStringInto6BitsGroups(std::string longBin){
std::vector<std::string> res;
if (!(longBin.size() % 6))
{
for (unsigned int i(0) ; i < longBin.size(); i+=6){
res.push_back(longBin.substr(i,6));
}
}
else
{
unsigned int max6AlignedIndex = (longBin.size() / 6)*6;
unsigned int paddingZeros = 6 -(longBin.size() % 6);
for (unsigned int i(0) ; i < max6AlignedIndex; i+=6){
res.push_back(longBin.substr(i,6));
}
res.push_back(longBin.substr(max6AlignedIndex) + std::string(paddingZeros, '0'));
}
return res;
}
//Bin6BitsToDec
unsigned int Bin6BitsToDec(std::string bin6Bit){
unsigned int decimalNumber(0), i(0), remainder(0);
unsigned int n (std::stoi(bin6Bit));
while (n!=0)
{
remainder = n%10;
n /= 10;
decimalNumber += remainder*pow(2,i);
++i;
}
return decimalNumber;
}
//Bin6BitsToDec vector
std::vector<unsigned int> Bin6BitsToDec(std::vector<std::string> bin6Bits)
{
std::vector<unsigned int> dec;
for(auto bin: bin6Bits)
{
dec.push_back(Bin6BitsToDec(bin));
}
return dec;
}
//DecToBase64
std::vector<char> DecToBase64(std::vector<unsigned int> dec)
{
const std::string base64Table("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/");
std::vector<char> res;
for(auto x: dec)
{
res.push_back(base64Table.at(x));
}
return res;
}
//FuseCharVector
std::string FuseCharVector(std::vector<char> vec)
{
return std::string(vec.begin(), vec.end());
}
std::string HexToBase64(std::string hex){
std::vector<std::string> brokenHexGroups(BreakHexStringIntoGroups(hex,2));
std::vector<unsigned int> brokenHexGroupsInDec(HexToDec(brokenHexGroups));
std::vector<std::string> bin8bits= DecTo8BitsBin(brokenHexGroupsInDec);
std::string fusedBin8bits = FuseStringVector(bin8bits);
std::vector<std::string> bin6Bits = BreakBinStringInto6BitsGroups(fusedBin8bits);
std::vector<unsigned int> bin6BitsInDec(Bin6BitsToDec(bin6Bits));
std::vector<char> decToBase64Chars = DecToBase64(bin6BitsInDec);
std::string finalString = FuseCharVector(decToBase64Chars);
return finalString;
}
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.