qpdf/libqpdf/Pl_ASCII85Decoder.cc

#include <qpdf/Pl_ASCII85Decoder.hh>

#include <qpdf/QTC.hh>
#include <stdexcept>
#include <string.h>

Pl_ASCII85Decoder::Pl_ASCII85Decoder(char const* identifier, Pipeline* next) :
    Pipeline(identifier, next),
    pos(0),
    eod(0)
{
    memset(this->inbuf, 117, 5);
}

Pl_ASCII85Decoder::~Pl_ASCII85Decoder()
{
}

void
Pl_ASCII85Decoder::write(unsigned char* buf, size_t len)
{
    if (eod > 1)
    {
        return;
    }
    for (size_t i = 0; i < len; ++i)
    {
        if (eod > 1)
        {
            break;
        }
        else if (eod == 1)
        {
            if (buf[i] == '>')
            {
                flush();
                eod = 2;
            }
            else
            {
                throw std::runtime_error(
                    "broken end-of-data sequence in base 85 data");
            }
        }
        else
        {
            switch (buf[i])
            {
              case ' ':
              case '\f':
              case '\v':
              case '\t':
              case '\r':
              case '\n':
                QTC::TC("libtests", "Pl_ASCII85Decoder ignore space");
                // ignore whitespace
                break;

              case '~':
                eod = 1;
                break;

              case 'z':
                if (pos != 0)
                {
                    throw std::runtime_error(
                        "unexpected z during base 85 decode");
                }
                else
                {
                    QTC::TC("libtests", "Pl_ASCII85Decoder read z");
                    unsigned char zeroes[4];
                    memset(zeroes, '\0', 4);
                    getNext()->write(zeroes, 4);
                }
                break;

              default:
                if ((buf[i] < 33) || (buf[i] > 117))
                {
                    throw std::runtime_error(
                        "character out of range during base 85 decode");
                }
                else
                {
                    this->inbuf[this->pos++] = buf[i];
                    if (pos == 5)
                    {
                        flush();
                    }
                }
                break;
            }
        }
    }
}

void
Pl_ASCII85Decoder::flush()
{
    if (this->pos == 0)
    {
        QTC::TC("libtests", "Pl_ASCII85Decoder no-op flush");
        return;
    }
    unsigned long lval = 0;
    for (int i = 0; i < 5; ++i)
    {
        lval *= 85;
        lval += (this->inbuf[i] - 33U);
    }

    unsigned char outbuf[4];
    memset(outbuf, 0, 4);
    for (int i = 3; i >= 0; --i)
    {
        outbuf[i] = lval & 0xff;
        lval >>= 8;
    }

    QTC::TC("libtests", "Pl_ASCII85Decoder partial flush",
            (this->pos == 5) ? 0 : 1);
    // Reset before calling getNext()->write in case that throws an
    // exception.
    auto t = this->pos - 1;
    this->pos = 0;
    memset(this->inbuf, 117, 5);

    getNext()->write(outbuf, t);
}

void
Pl_ASCII85Decoder::finish()
{
    flush();
    getNext()->finish();
}