File indexing completed on 2024-09-15 11:55:01

 /*  -*- c++ -*-
     SPDX-FileCopyrightText: 2001 Marc Mutz <mutz@kde.org>
 
     SPDX-License-Identifier: LGPL-2.0-or-later
 */
 /**
   @file
   This file is part of the API for handling @ref MIME data and
   defines the @ref Base64 and @ref RFC2047B @ref Codec classes.
 
   @brief
   Defines the Base64Codec and Rfc2047BEncodingCodec classes.
 
   @authors Marc Mutz \<mutz@kde.org\>
 */
 
 #include "kcodecsbase64.h"
 #include "kcodecs_p.h"
 
 #include <QDebug>
 
 #include <cassert>
 
 using namespace KCodecs;
 
 namespace KCodecs
 {
 // codec for base64 as specified in RFC 2045
 // class Base64Codec;
 // class Base64Decoder;
 // class Base64Encoder;
 
 // codec for the B encoding as specified in RFC 2047
 // class Rfc2047BEncodingCodec;
 // class Rfc2047BEncodingEncoder;
 // class Rfc2047BEncodingDecoder;
 
 //@cond PRIVATE
 static const uchar base64DecodeMap[128] = {
     64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64,
 
     64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 62, 64, 64, 64, 63, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 64, 64, 64, 64, 64, 64,
 
     64, 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, 64, 64, 64, 64, 64,
 
     64, 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, 64, 64, 64, 64, 64};
 
 static const char base64EncodeMap[64] = {'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V',
                                          'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r',
                                          's', 't', 'u', 'v', 'w', 'x', 'y', 'z', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '+', '/'};
 //@endcond
 
 class Base64Decoder : public Decoder
 {
     uint mStepNo;
     uchar mOutbits;
     bool mSawPadding : 1;
 
 protected:
     friend class Base64Codec;
     Base64Decoder(Codec::NewlineType newline = Codec::NewlineLF)
         : Decoder(newline)
         , mStepNo(0)
         , mOutbits(0)
         , mSawPadding(false)
     {
     }
 
 public:
     ~Base64Decoder() override
     {
     }
 
     bool decode(const char *&scursor, const char *const send, char *&dcursor, const char *const dend) override;
     // ### really needs no finishing???
     bool finish(char *&dcursor, const char *const dend) override
     {
         Q_UNUSED(dcursor);
         Q_UNUSED(dend);
         return true;
     }
 };
 
 class Base64Encoder : public Encoder
 {
     uint mStepNo;
     /** number of already written base64-quartets on current line */
     uint mWrittenPacketsOnThisLine;
     uchar mNextbits;
     bool mInsideFinishing : 1;
 
 protected:
     friend class Rfc2047BEncodingCodec;
     friend class Rfc2047BEncodingEncoder;
     friend class Base64Codec;
     Base64Encoder(Codec::NewlineType newline = Codec::NewlineLF)
         : Encoder(newline)
         , mStepNo(0)
         , mWrittenPacketsOnThisLine(0)
         , mNextbits(0)
         , mInsideFinishing(false)
     {
     }
 
     bool generic_finish(char *&dcursor, const char *const dend, bool withLFatEnd);
 
 public:
     ~Base64Encoder() override
     {
     }
 
     bool encode(const char *&scursor, const char *const send, char *&dcursor, const char *const dend) override;
 
     bool finish(char *&dcursor, const char *const dend) override;
 
 protected:
     bool writeBase64(uchar ch, char *&dcursor, const char *const dend)
     {
         return write(base64EncodeMap[ch], dcursor, dend);
     }
 };
 
 class Rfc2047BEncodingEncoder : public Base64Encoder
 {
 protected:
     friend class Rfc2047BEncodingCodec;
     Rfc2047BEncodingEncoder(Codec::NewlineType newline = Codec::NewlineLF)
         : Base64Encoder(newline)
     {
     }
 
 public:
     bool encode(const char *&scursor, const char *const send, char *&dcursor, const char *const dend) override;
     bool finish(char *&dcursor, const char *const dend) override;
 };
 
 Encoder *Base64Codec::makeEncoder(Codec::NewlineType newline) const
 {
     return new Base64Encoder(newline);
 }
 
 Decoder *Base64Codec::makeDecoder(Codec::NewlineType newline) const
 {
     return new Base64Decoder(newline);
 }
 
 Encoder *Rfc2047BEncodingCodec::makeEncoder(Codec::NewlineType newline) const
 {
     return new Rfc2047BEncodingEncoder(newline);
 }
 
 /********************************************************/
 /********************************************************/
 /********************************************************/
 
 bool Base64Decoder::decode(const char *&scursor, const char *const send, char *&dcursor, const char *const dend)
 {
     while (dcursor != dend && scursor != send) {
         uchar ch = *scursor++;
         uchar value;
 
         // try converting ch to a 6-bit value:
         if (ch < 128) {
             value = base64DecodeMap[ch];
         } else {
             value = 64;
         }
 
         // ch isn't of the base64 alphabet, check for other significant chars:
         if (value >= 64) {
             if (ch == '=') {
                 // padding:
                 if (mStepNo == 0 || mStepNo == 1) {
                     if (!mSawPadding) {
                         // malformed
                         // qWarning() << "Base64Decoder: unexpected padding"
                         //              "character in input stream";
                     }
                     mSawPadding = true;
                     break;
                 } else if (mStepNo == 2) {
                     // ok, there should be another one
                 } else if (mStepNo == 3) {
                     // ok, end of encoded stream
                     mSawPadding = true;
                     break;
                 }
                 mSawPadding = true;
                 mStepNo = (mStepNo + 1) % 4;
                 continue;
             } else {
                 // non-base64 alphabet
                 continue;
             }
         }
 
         if (mSawPadding) {
             // qWarning() << "Base64Decoder: Embedded padding character"
             //              "encountered!";
             return true;
         }
 
         // add the new bits to the output stream and flush full octets:
         switch (mStepNo) {
         case 0:
             mOutbits = value << 2;
             break;
         case 1:
             *dcursor++ = (char)(mOutbits | value >> 4);
             mOutbits = value << 4;
             break;
         case 2:
             *dcursor++ = (char)(mOutbits | value >> 2);
             mOutbits = value << 6;
             break;
         case 3:
             *dcursor++ = (char)(mOutbits | value);
             mOutbits = 0;
             break;
         default:
             assert(0);
         }
         mStepNo = (mStepNo + 1) % 4;
     }
 
     // return false when caller should call us again:
     return scursor == send;
 } // Base64Decoder::decode()
 
 bool Base64Encoder::encode(const char *&scursor, const char *const send, char *&dcursor, const char *const dend)
 {
     const uint maxPacketsPerLine = 76 / 4;
 
     // detect when the caller doesn't adhere to our rules:
     if (mInsideFinishing) {
         return true;
     }
 
     while (scursor != send && dcursor != dend) {
         // properly empty the output buffer before starting something new:
         // ### fixme: we can optimize this away, since the buffer isn't
         // written to anyway (most of the time)
         if (d->outputBufferCursor && !flushOutputBuffer(dcursor, dend)) {
             return scursor == send;
         }
 
         uchar ch = *scursor++;
         // mNextbits   // (part of) value of next sextet
 
         // check for line length;
         if (mStepNo == 0 && mWrittenPacketsOnThisLine >= maxPacketsPerLine) {
             writeCRLF(dcursor, dend);
             mWrittenPacketsOnThisLine = 0;
         }
 
         // depending on mStepNo, extract value and mNextbits from the
         // octet stream:
         switch (mStepNo) {
         case 0:
             assert(mNextbits == 0);
             writeBase64(ch >> 2, dcursor, dend); // top-most 6 bits -> output
             mNextbits = (ch & 0x3) << 4; // 0..1 bits -> 4..5 in mNextbits
             break;
         case 1:
             assert((mNextbits & ~0x30) == 0);
             writeBase64(mNextbits | ch >> 4, dcursor, dend); // 4..7 bits -> 0..3 in value
             mNextbits = (ch & 0xf) << 2; // 0..3 bits -> 2..5 in mNextbits
             break;
         case 2:
             assert((mNextbits & ~0x3C) == 0);
             writeBase64(mNextbits | ch >> 6, dcursor, dend); // 6..7 bits -> 0..1 in value
             writeBase64(ch & 0x3F, dcursor, dend); // 0..5 bits -> output
             mNextbits = 0;
             mWrittenPacketsOnThisLine++;
             break;
         default:
             assert(0);
         }
         mStepNo = (mStepNo + 1) % 3;
     }
 
     if (d->outputBufferCursor) {
         flushOutputBuffer(dcursor, dend);
     }
 
     return scursor == send;
 }
 
 bool Rfc2047BEncodingEncoder::encode(const char *&scursor, const char *const send, char *&dcursor, const char *const dend)
 {
     // detect when the caller doesn't adhere to our rules:
     if (mInsideFinishing) {
         return true;
     }
 
     while (scursor != send && dcursor != dend) {
         // properly empty the output buffer before starting something new:
         // ### fixme: we can optimize this away, since the buffer isn't
         // written to anyway (most of the time)
         if (d->outputBufferCursor && !flushOutputBuffer(dcursor, dend)) {
             return scursor == send;
         }
 
         uchar ch = *scursor++;
         // mNextbits   // (part of) value of next sextet
 
         // depending on mStepNo, extract value and mNextbits from the
         // octet stream:
         switch (mStepNo) {
         case 0:
             assert(mNextbits == 0);
             writeBase64(ch >> 2, dcursor, dend); // top-most 6 bits -> output
             mNextbits = (ch & 0x3) << 4; // 0..1 bits -> 4..5 in mNextbits
             break;
         case 1:
             assert((mNextbits & ~0x30) == 0);
             writeBase64(mNextbits | ch >> 4, dcursor, dend); // 4..7 bits -> 0..3 in value
             mNextbits = (ch & 0xf) << 2; // 0..3 bits -> 2..5 in mNextbits
             break;
         case 2:
             assert((mNextbits & ~0x3C) == 0);
             writeBase64(mNextbits | ch >> 6, dcursor, dend); // 6..7 bits -> 0..1 in value
             writeBase64(ch & 0x3F, dcursor, dend); // 0..5 bits -> output
             mNextbits = 0;
             break;
         default:
             assert(0);
         }
         mStepNo = (mStepNo + 1) % 3;
     }
 
     if (d->outputBufferCursor) {
         flushOutputBuffer(dcursor, dend);
     }
 
     return scursor == send;
 }
 
 bool Base64Encoder::finish(char *&dcursor, const char *const dend)
 {
     return generic_finish(dcursor, dend, true);
 }
 
 bool Rfc2047BEncodingEncoder::finish(char *&dcursor, const char *const dend)
 {
     return generic_finish(dcursor, dend, false);
 }
 
 bool Base64Encoder::generic_finish(char *&dcursor, const char *const dend, bool withLFatEnd)
 {
     if (mInsideFinishing) {
         return flushOutputBuffer(dcursor, dend);
     }
 
     if (d->outputBufferCursor && !flushOutputBuffer(dcursor, dend)) {
         return false;
     }
 
     mInsideFinishing = true;
 
     //
     // writing out the last mNextbits...
     //
     switch (mStepNo) {
     case 1: // 2 mNextbits waiting to be written. Needs two padding chars:
     case 2: // 4 or 6 mNextbits waiting to be written. Completes a block
         writeBase64(mNextbits, dcursor, dend);
         mNextbits = 0;
         break;
     case 0: // no padding, nothing to be written, except possibly the CRLF
         assert(mNextbits == 0);
         break;
     default:
         assert(0);
     }
 
     //
     // adding padding...
     //
     switch (mStepNo) {
     case 1:
         write('=', dcursor, dend);
         Q_FALLTHROUGH();
     // fall through:
     case 2:
         write('=', dcursor, dend);
         Q_FALLTHROUGH();
     // fall through:
     case 0: // completed an quartet - add CRLF
         if (withLFatEnd) {
             writeCRLF(dcursor, dend);
         }
         return flushOutputBuffer(dcursor, dend);
     default:
         assert(0);
     }
     return true; // asserts get compiled out
 }
 
 } // namespace KCodecs