Source/cmBase32.cxx

   1 /* Distributed under the OSI-approved BSD 3-Clause License.  See accompanying
   2    file Copyright.txt or https://cmake.org/licensing for details.  */
   3 #include "cmBase32.h"
   4
   5 // -- Static functions
   6
   7 static const unsigned char Base32EncodeTable[33] =
   8   "ABCDEFGHIJKLMNOPQRSTUVWXYZ234567";
   9
  10 inline unsigned char Base32EncodeChar(int schar)
  11 {
  12   return Base32EncodeTable[schar];
  13 }
  14
  15 static void Base32Encode5(const unsigned char src[5], char dst[8])
  16 {
  17   // [0]:5 bits
  18   dst[0] = Base32EncodeChar((src[0] >> 3) & 0x1F);
  19   // [0]:3 bits + [1]:2 bits
  20   dst[1] = Base32EncodeChar(((src[0] << 2) & 0x1C) + ((src[1] >> 6) & 0x03));
  21   // [1]:5 bits
  22   dst[2] = Base32EncodeChar((src[1] >> 1) & 0x1F);
  23   // [1]:1 bit + [2]:4 bits
  24   dst[3] = Base32EncodeChar(((src[1] << 4) & 0x10) + ((src[2] >> 4) & 0x0F));
  25   // [2]:4 bits + [3]:1 bit
  26   dst[4] = Base32EncodeChar(((src[2] << 1) & 0x1E) + ((src[3] >> 7) & 0x01));
  27   // [3]:5 bits
  28   dst[5] = Base32EncodeChar((src[3] >> 2) & 0x1F);
  29   // [3]:2 bits + [4]:3 bit
  30   dst[6] = Base32EncodeChar(((src[3] << 3) & 0x18) + ((src[4] >> 5) & 0x07));
  31   // [4]:5 bits
  32   dst[7] = Base32EncodeChar((src[4] << 0) & 0x1F);
  33 }
  34
  35 // -- Class methods
  36
  37 cmBase32Encoder::cmBase32Encoder() = default;
  38
  39 std::string cmBase32Encoder::encodeString(const unsigned char* input,
  40                                           size_t len, bool padding)
  41 {
  42   std::string res;
  43
  44   static const size_t blockSize = 5;
  45   static const size_t bufferSize = 8;
  46   char buffer[bufferSize];
  47
  48   const unsigned char* end = input + len;
  49   while ((input + blockSize) <= end) {
  50     Base32Encode5(input, buffer);
  51     res.append(buffer, bufferSize);
  52     input += blockSize;
  53   }
  54
  55   size_t remain = static_cast<size_t>(end - input);
  56   if (remain != 0) {
  57     // Temporary source buffer filled up with 0s
  58     unsigned char extended[blockSize];
  59     for (size_t ii = 0; ii != remain; ++ii) {
  60       extended[ii] = input[ii];
  61     }
  62     for (size_t ii = remain; ii != blockSize; ++ii) {
  63       extended[ii] = 0;
  64     }
  65
  66     Base32Encode5(extended, buffer);
  67     size_t numPad(0);
  68     switch (remain) {
  69       case 1:
  70         numPad = 6;
  71         break;
  72       case 2:
  73         numPad = 4;
  74         break;
  75       case 3:
  76         numPad = 3;
  77         break;
  78       case 4:
  79         numPad = 1;
  80         break;
  81       default:
  82         break;
  83     }
  84     res.append(buffer, bufferSize - numPad);
  85     if (padding) {
  86       for (size_t ii = 0; ii != numPad; ++ii) {
  87         res.push_back(paddingChar);
  88       }
  89     }
  90   }
  91
  92   return res;
  93 }