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#include <iostream>
#include <cassert>
using namespace std;
namespace B64 {
static const char cb64[]="ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
static const char cd64[]="|$$$}rstuvwxyz{$$$$$$$>?@ABCDEFGHIJKLMNOPQRSTUVW$$$$$$XYZ[\\]^_`abcdefghijklmnopq";
static void encodeblock(const unsigned char* in, ostream* os, int len) {
char out[4];
out[0] = cb64[ in[0] >> 2 ];
out[1] = cb64[ ((in[0] & 0x03) << 4) | ((in[1] & 0xf0) >> 4) ];
out[2] = (len > 1 ? cb64[ ((in[1] & 0x0f) << 2) | ((in[2] & 0xc0) >> 6) ] : '=');
out[3] = (len > 2 ? cb64[ in[2] & 0x3f ] : '=');
os->write(out, 4);
}
void b64encode(const char* data, const size_t size, ostream* out) {
size_t cur = 0;
while(cur < size) {
int len = min(static_cast<size_t>(3), size - cur);
encodeblock(reinterpret_cast<const unsigned char*>(&data[cur]), out, len);
cur += len;
}
}
static void decodeblock(const unsigned char* in, unsigned char* out) {
out[0] = (unsigned char ) (in[0] << 2 | in[1] >> 4);
out[1] = (unsigned char ) (in[1] << 4 | in[2] >> 2);
out[2] = (unsigned char ) (((in[2] << 6) & 0xc0) | in[3]);
}
bool b64decode(const unsigned char* data, const size_t insize, char* out, const size_t outsize) {
size_t cur = 0;
size_t ocur = 0;
unsigned char in[4];
while(cur < insize) {
assert(ocur < outsize);
for (int i = 0; i < 4; ++i) {
unsigned char v = data[cur];
v = (unsigned char) ((v < 43 || v > 122) ? '\0' : cd64[ v - 43 ]);
if (!v) {
cerr << "B64 decode error at offset " << cur << " offending character: " << (int)data[cur] << endl;
return false;
}
v = (unsigned char) ((v == '$') ? '\0' : v - 61);
if (v) in[i] = v - 1; else in[i] = 0;
++cur;
}
decodeblock(in, reinterpret_cast<unsigned char*>(&out[ocur]));
ocur += 3;
}
return true;
}
}
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