Base64 and import/export keys

1 files changed, 91 insertions, 0 deletions

diff --git a/base64.cpp b/base64.cpp
new file mode 100644
index 0000000..80640f2
--- /dev/null
+++ b/base64.cpp
@@ -0,0 +1,91 @@
+#include "base64.h"
+
+using namespace std;
+
+namespace Base64{
+
+	char alphabet[65]="ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
+	uint8_t revbet[128]={
+#define XX (127)
+		XX,XX,XX,XX,XX,XX,XX,XX,XX,XX,XX,XX,XX,XX,XX,XX, //0-15
+		XX,XX,XX,XX,XX,XX,XX,XX,XX,XX,XX,XX,XX,XX,XX,XX, //16-31
+		XX,XX,XX,XX,XX,XX,XX,XX,XX,XX,XX,62,XX,XX,XX,63, //32-47
+		52,53,54,55,56,57,58,59,60,61,XX,XX,XX,XX,XX,XX, //48-63
+		XX, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9,10,11,12,13,14, //64-79
+		15,16,17,18,19,20,21,22,23,24,25,XX,XX,XX,XX,XX, //80-95
+		XX,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40, //96-111
+		41,42,43,44,45,46,47,48,49,50,51,XX,XX,XX,XX,XX, //112-127
+#undef XX
+	};
+
+	string encode(const string &data){
+		int sz=data.size();
+		if(sz==0)return {};
+		int blocks=sz/3;
+		string res(4*blocks+4*(sz%3!=0),'\0');
+		int x;
+		for(int i=0;i<blocks;i++){
+			x=((unsigned char)data[3*i]<<16)|((unsigned char)data[3*i+1]<<8)|(unsigned char)data[3*i+2];
+			res[4*i+3]=alphabet[x&0x3f]; x>>=6;
+			res[4*i+2]=alphabet[x&0x3f]; x>>=6;
+			res[4*i+1]=alphabet[x&0x3f]; x>>=6;
+			res[4*i+0]=alphabet[x];
+		}
+		switch(sz%3){
+			case 1:
+				res[4*blocks+0]=alphabet[(unsigned char)data[3*blocks]>>2];
+				res[4*blocks+1]=alphabet[((unsigned char)data[3*blocks]&0x3)<<4];
+				res[4*blocks+2]='=';
+				res[4*blocks+3]='=';
+				break;
+
+			case 2:
+				res[4*blocks+0]=alphabet[(unsigned char)data[3*blocks]>>2];
+				res[4*blocks+1]=alphabet[(((unsigned char)data[3*blocks]&0x3)<<4)|((unsigned char)data[3*blocks+1]>>4)];
+				res[4*blocks+2]=alphabet[(((unsigned char)data[3*blocks+1]&0xf)<<2)];
+				res[4*blocks+3]='=';
+				break;
+		}
+		return res;
+	}
+
+	string decode(const string &dataS){
+		int szS=dataS.size();
+		if(szS==0)return {};
+		uint8_t data[szS];
+		int sz=0;
+		for(char c : dataS){
+			if(revbet[c&0x7f]!=127)data[sz++]=revbet[c&0x7f];
+		}
+
+		int blocks=sz/4;
+		int endlen;
+		if(sz%4==0){
+			if(data[sz-1]=='='){
+				blocks--;
+				if(data[sz-2]=='=')endlen=1;
+				else endlen=2;
+			} else endlen=0;
+		} else endlen=sz%4-1;
+		string res(3*blocks+endlen,'\0');
+		int x;
+		for(int i=0;i<blocks;i++){
+			x=(data[4*i]<<18)|(data[4*i+1]<<12)|(data[4*i+2]<<6)|data[4*i+3];
+			res[3*i+2]=x&0xff; x>>=8;
+			res[3*i+1]=x&0xff; x>>=8;
+			res[3*i+0]=x;
+		}
+		switch(endlen){
+			case 1:
+				res[3*blocks+0]=(data[4*blocks]<<2)|(data[4*blocks+1]>>4);
+				break;
+
+			case 2:
+				res[3*blocks+0]=(data[4*blocks]<<2)|(data[4*blocks+1]>>4);
+				res[3*blocks+1]=(data[4*blocks+1]<<4)|(data[4*blocks+2]>>2);
+				break;
+		}
+		return res;
+	}
+
+}