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/* t1code.c: Copyright 2005 Jörg Lehmann
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307,
* USA.
*/
#define PY_SSIZE_T_CLEAN
#include <Python.h>
#include <stdlib.h>
#include <stdint.h>
#define C1 52845
#define C2 22719
/*
def decoder(code, r, n):
c1 = 52845
c2 = 22719
data = array.array("B")
for x in array.array("B", code):
data.append(x ^ (r >> 8))
r = ((x + r) * c1 + c2) & 0xffff
return data.tobytes()[n:]
*/
static PyObject *py_decoder(PyObject *self, PyObject *args)
{
unsigned char *code;
Py_ssize_t lcode;
int pr, n;
if (PyArg_ParseTuple(args, "y#ii", (char **) &code, &lcode, &pr, &n)) {
unsigned char *data;
Py_ssize_t i;
unsigned char x;
uint16_t r=pr;
PyObject *result;
if (! (data = (unsigned char *) malloc(lcode)) )
return NULL;
for (i=0; i<lcode; i++) {
x = code[i];
data[i] = x ^ ( r >> 8);
r = (x + r) * C1 + C2;
}
/* convert result to string stripping first n chars */
result = PyBytes_FromStringAndSize((const char *)data + n, lcode - n);
free(data);
return result;
}
else return NULL;
}
/*
def encoder(data, r, random):
c1 = 52845
c2 = 22719
code = array.array("B")
for x in array.array("B", random+data):
code.append(x ^ (r >> 8))
r = ((code[-1] + r) * c1 + c2) & 0xffff;
return code.tobytes()
*/
static PyObject *py_encoder(PyObject *self, PyObject *args)
{
unsigned char *data;
unsigned char *random;
Py_ssize_t ldata, lrandom;
int pr;
if (PyArg_ParseTuple(args, "y#iy#", (char **) &data, &ldata, &pr, (char **) &random, &lrandom)) {
unsigned char *code;
Py_ssize_t i;
uint16_t r=pr;
PyObject *result;
if (! (code = (unsigned char *) malloc(ldata + lrandom)) )
return NULL;
for (i=0; i<lrandom; i++) {
code[i] = random[i] ^ ( r >> 8);
r = (code[i] + r) * C1 + C2;
}
for (i=0; i<ldata; i++) {
code[i+lrandom] = data[i] ^ ( r >> 8);
r = (code[i+lrandom] + r) * C1 + C2;
}
result = PyBytes_FromStringAndSize((const char *)code, ldata + lrandom);
free(code);
return result;
}
else return NULL;
}
/* exported methods */
static PyMethodDef t1code_methods[] = {
{"decoder", py_decoder, METH_VARARGS, NULL},
{"encoder", py_encoder, METH_VARARGS, NULL},
{NULL, NULL}
};
static struct PyModuleDef moduledef = {
PyModuleDef_HEAD_INIT,
"_t1code",
NULL,
-1,
t1code_methods,
NULL,
NULL,
NULL,
NULL
};
PyMODINIT_FUNC
PyInit__t1code(void)
{
PyObject *module = PyModule_Create(&moduledef);
return module;
}
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