Base32 encoding/decoding

1 files changed, 187 insertions, 0 deletions

diff --git a/src/util.cpp b/src/util.cpp
index b07c9c1b7e..931d27ba00 100644
--- a/src/util.cpp
+++ b/src/util.cpp
@@ -702,6 +702,193 @@ string DecodeBase64(const string& str)
     return string((const char*)&vchRet[0], vchRet.size());
 }
 
+string EncodeBase32(const unsigned char* pch, size_t len)
+{
+    static const char *pbase32 = "ABCDEFGHIJKLMNOPQRSTUVWXYZ234567";
+
+    string strRet="";
+    strRet.reserve((len+4)/5*8);
+
+    int mode=0, left=0;
+    const unsigned char *pchEnd = pch+len;
+
+    while (pch<pchEnd)
+    {
+        int enc = *(pch++);
+        switch (mode)
+        {
+            case 0: // we have no bits
+                strRet += pbase32[enc >> 3];
+                left = (enc & 7) << 2;
+                mode = 1;
+                break;
+
+            case 1: // we have three bits
+                strRet += pbase32[left | (enc >> 6)];
+                strRet += pbase32[(enc >> 1) & 31];
+                left = (enc & 1) << 4;
+                mode = 2;
+                break;
+
+            case 2: // we have one bit
+                strRet += pbase32[left | (enc >> 4)];
+                left = (enc & 15) << 1;
+                mode = 3;
+                break;
+
+            case 3: // we have four bits
+                strRet += pbase32[left | (enc >> 7)];
+                strRet += pbase32[(enc >> 2) & 31];
+                left = (enc & 3) << 3;
+                mode = 4;
+                break;
+
+            case 4: // we have two bits
+                strRet += pbase32[left | (enc >> 5)];
+                strRet += pbase32[enc & 31];
+                mode = 0;
+        }
+    }
+
+    static const int nPadding[5] = {0, 6, 4, 3, 1};
+    if (mode)
+    {
+        strRet += pbase32[left];
+        for (int n=0; n<nPadding[mode]; n++)
+             strRet += '=';
+    }
+
+    return strRet;
+}
+
+string EncodeBase32(const string& str)
+{
+    return EncodeBase32((const unsigned char*)str.c_str(), str.size());
+}
+
+vector<unsigned char> DecodeBase32(const char* p, bool* pfInvalid)
+{
+    static const int decode32_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, -1, -1, -1, -1, -1, -1, -1, 26, 27, 28, 29, 30, 31, -1, -1, -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,  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, -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
+    };
+
+    if (pfInvalid)
+        *pfInvalid = false;
+
+    vector<unsigned char> vchRet;
+    vchRet.reserve((strlen(p))*5/8);
+
+    int mode = 0;
+    int left = 0;
+
+    while (1)
+    {
+         int dec = decode32_table[(unsigned char)*p];
+         if (dec == -1) break;
+         p++;
+         switch (mode)
+         {
+             case 0: // we have no bits and get 5
+                 left = dec;
+                 mode = 1;
+                 break;
+
+              case 1: // we have 5 bits and keep 2
+                  vchRet.push_back((left<<3) | (dec>>2));
+                  left = dec & 3;
+                  mode = 2;
+                  break;
+
+             case 2: // we have 2 bits and keep 7
+                 left = left << 5 | dec;
+                 mode = 3;
+                 break;
+
+             case 3: // we have 7 bits and keep 4
+                 vchRet.push_back((left<<1) | (dec>>4));
+                 left = dec & 15;
+                 mode = 4;
+                 break;
+
+             case 4: // we have 4 bits, and keep 1
+                 vchRet.push_back((left<<4) | (dec>>1));
+                 left = dec & 1;
+                 mode = 5;
+                 break;
+
+             case 5: // we have 1 bit, and keep 6
+                 left = left << 5 | dec;
+                 mode = 6;
+                 break;
+
+             case 6: // we have 6 bits, and keep 3
+                 vchRet.push_back((left<<2) | (dec>>3));
+                 left = dec & 7;
+                 mode = 7;
+                 break;
+
+             case 7: // we have 3 bits, and keep 0
+                 vchRet.push_back((left<<5) | dec);
+                 mode = 0;
+                 break;
+         }
+    }
+
+    if (pfInvalid)
+        switch (mode)
+        {
+            case 0: // 8n base32 characters processed: ok
+                break;
+
+            case 1: // 8n+1 base32 characters processed: impossible
+            case 3: //   +3
+            case 6: //   +6
+                *pfInvalid = true;
+                break;
+
+            case 2: // 8n+2 base32 characters processed: require '======'
+                if (left || p[0] != '=' || p[1] != '=' || p[2] != '=' || p[3] != '=' || p[4] != '=' || p[5] != '=' || decode32_table[(unsigned char)p[6]] != -1)
+                    *pfInvalid = true;
+                break;
+
+            case 4: // 8n+4 base32 characters processed: require '===='
+                if (left || p[0] != '=' || p[1] != '=' || p[2] != '=' || p[3] != '=' || decode32_table[(unsigned char)p[4]] != -1)
+                    *pfInvalid = true;
+                break;
+
+            case 5: // 8n+5 base32 characters processed: require '==='
+                if (left || p[0] != '=' || p[1] != '=' || p[2] != '=' || decode32_table[(unsigned char)p[3]] != -1)
+                    *pfInvalid = true;
+                break;
+
+            case 7: // 8n+7 base32 characters processed: require '='
+                if (left || p[0] != '=' || decode32_table[(unsigned char)p[1]] != -1)
+                    *pfInvalid = true;
+                break;
+        }
+
+    return vchRet;
+}
+
+string DecodeBase32(const string& str)
+{
+    vector<unsigned char> vchRet = DecodeBase32(str.c_str());
+    return string((const char*)&vchRet[0], vchRet.size());
+}
+
 
 bool WildcardMatch(const char* psz, const char* mask)
 {