Faster Base64 decoder.

1 files changed, 59 insertions, 0 deletions

diff --git a/src/util.cpp b/src/util.cpp
index a5e3d30995..5b6d26bb89 100644
--- a/src/util.cpp
+++ b/src/util.cpp
@@ -470,6 +470,65 @@ void ParseParameters(int argc, char* argv[])
     }
 }
 
+static const int decode64_table[256]=
+{
+ -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+ -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+ -1, -1, -1, 62, -1, -1, -1, 63, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1,
+ -1, -1, -1, -1, -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14,
+ 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1, -1, 26, 27, 28,
+ 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48,
+ 49, 50, 51, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+ -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+ -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+ -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+ -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+ -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+ -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1
+};
+
+std::string DecodeBase64(const std::string &s)
+{
+    char buf[1024];
+    if(s.length()>512) return "";
+    char *optr=buf;
+
+    int dec, mode=0, left=0;
+    size_t index=0;
+    for (int i=0; i<s.length(); i++)
+    {
+         dec=decode64_table[s[i]];
+         if(dec==-1) break;
+         switch(mode)
+         {
+             case 0: // we have no bits and get 6
+                 left = dec;
+                 mode = 1;
+                 break;
+
+              case 1: // we have 6 bits and keep 4
+                 *optr++ = (left<<2) | (dec>>4);
+                  left = dec & 15;
+                  mode = 2;
+                  break;
+                  
+             case 2: // we have 4 bits and get 6, we keep 2            
+                  *optr++ = (left<<4) | (dec>>2);
+                 left = dec & 3;
+                 mode = 3;
+                 break;
+                 
+             case 3: // we have 2 bits and get 6
+                 *optr++ = (left<<6) | dec;
+                 mode=0;
+                 break;
+         }
+    }
+
+    *optr=0;   
+    return buf;
+}
+
 
 
 bool WildcardMatch(const char* psz, const char* mask)