c++使用Poco实现字符串的base64解码，输出为字节数组

使用Poco库将Base64字符串解码成字节数组可以分为以下几个步骤：

1. 引入Poco库头文件和命名空间：

#include "Poco/Base64Decoder.h"
#include <iostream>

using namespace Poco;
using namespace std;

2. 定义待解码的Base64字符串和解码后的字节数组：

string base64Str = "SGVsbG8gV29ybGQh";
vector<unsigned char> decodedBytes;

3. 创建Base64解码器和输出流，并将解码后的字节输出到流中：

Base64Decoder decoder;
decoder.attach(new StringStream(base64Str));
char buffer[1024];
int bytesRead = decoder.read(buffer, sizeof(buffer));
while (bytesRead > 0)
{
    for (int i = 0; i < bytesRead; i++)
    {
        decodedBytes.push_back(static_cast<unsigned char>(buffer[i]));
    }
    bytesRead = decoder.read(buffer, sizeof(buffer));
}

4. 输出解码后的字节数组：

for (int i = 0; i < decodedBytes.size(); i++)
{
    cout << static_cast<int>(decodedBytes[i]) << " ";
}
cout << endl;

完整代码如下：

#include "Poco/Base64Decoder.h"
#include <iostream>

using namespace Poco;
using namespace std;

int main()
{
    string base64Str = "SGVsbG8gV29ybGQh";
    vector<unsigned char> decodedBytes;
    
    Base64Decoder decoder;
    decoder.attach(new StringStream(base64Str));
    char buffer[1024];
    int bytesRead = decoder.read(buffer, sizeof(buffer));
    while (bytesRead > 0)
    {
        for (int i = 0; i < bytesRead; i++)
        {
            decodedBytes.push_back(static_cast<unsigned char>(buffer[i]));
        }
        bytesRead = decoder.read(buffer, sizeof(buffer));
    }
    
    for (int i = 0; i < decodedBytes.size(); i++)
    {
        cout << static_cast<int>(decodedBytes[i]) << " ";
    }
    cout << endl;
    
    return 0;
}