Pl_RunLength.cc
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#include <qpdf/Pl_RunLength.hh>
#include <qpdf/QUtil.hh>
#include <qpdf/QTC.hh>
Pl_RunLength::Pl_RunLength(char const* identifier, Pipeline* next,
action_e action) :
Pipeline(identifier, next),
action(action),
state(st_top),
length(0)
{
}
Pl_RunLength::~Pl_RunLength()
{
}
void
Pl_RunLength::write(unsigned char* data, size_t len)
{
if (this->action == a_encode)
{
encode(data, len);
}
else
{
decode(data, len);
}
}
void
Pl_RunLength::encode(unsigned char* data, size_t len)
{
for (size_t i = 0; i < len; ++i)
{
if ((this->state == st_top) != (this->length <= 1))
{
throw std::logic_error(
"Pl_RunLength::encode: state/length inconsistency");
}
unsigned char ch = data[i];
if ((this->length > 0) &&
((this->state == st_copying) || (this->length < 128)) &&
(ch == this->buf[this->length-1]))
{
QTC::TC("libtests", "Pl_RunLength: switch to run",
(this->length == 128) ? 0 : 1);
if (this->state == st_copying)
{
--this->length;
flush_encode();
this->buf[0] = ch;
this->length = 1;
}
this->state = st_run;
this->buf[this->length] = ch;
++this->length;
}
else
{
if ((this->length == 128) || (this->state == st_run))
{
flush_encode();
}
else if (this->length > 0)
{
this->state = st_copying;
}
this->buf[this->length] = ch;
++this->length;
}
}
}
void
Pl_RunLength::decode(unsigned char* data, size_t len)
{
for (size_t i = 0; i < len; ++i)
{
unsigned char ch = data[i];
switch (this->state)
{
case st_top:
if (ch < 128)
{
// length represents remaining number of bytes to copy
this->length = 1 + ch;
this->state = st_copying;
}
else if (ch > 128)
{
// length represents number of copies of next byte
this->length = 257 - ch;
this->state = st_run;
}
else // ch == 128
{
// EOD; stay in this state
}
break;
case st_copying:
this->getNext()->write(&ch, 1);
if (--this->length == 0)
{
this->state = st_top;
}
break;
case st_run:
for (unsigned int j = 0; j < this->length; ++j)
{
this->getNext()->write(&ch, 1);
}
this->state = st_top;
break;
}
}
}
void
Pl_RunLength::flush_encode()
{
if (this->length == 128)
{
QTC::TC("libtests", "Pl_RunLength flush full buffer",
(this->state == st_copying ? 0 :
this->state == st_run ? 1 :
-1));
}
if (this->length == 0)
{
QTC::TC("libtests", "Pl_RunLength flush empty buffer");
}
if (this->state == st_run)
{
if ((this->length < 2) || (this->length > 128))
{
throw std::logic_error(
"Pl_RunLength: invalid length in flush_encode for run");
}
unsigned char ch = static_cast<unsigned char>(257 - this->length);
this->getNext()->write(&ch, 1);
this->getNext()->write(&this->buf[0], 1);
}
else if (this->length > 0)
{
unsigned char ch = static_cast<unsigned char>(this->length - 1);
this->getNext()->write(&ch, 1);
this->getNext()->write(this->buf, this->length);
}
this->state = st_top;
this->length = 0;
}
void
Pl_RunLength::finish()
{
// When decoding, we might have read a length byte not followed by
// data, which means the stream was terminated early, but we will
// just ignore this case since this is the only sensible thing to
// do.
if (this->action == a_encode)
{
flush_encode();
unsigned char ch = 128;
this->getNext()->write(&ch, 1);
}
this->getNext()->finish();
}