pyx/font/_t1code.c

   1 /*  t1code.c: Copyright 2005 Jörg Lehmann
   2  *  This program is distributed in the hope that it will be useful,
   3  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
   4  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   5  *  GNU General Public License for more details.
   6  *
   7  *  You should have received a copy of the GNU General Public License
   8  *  along with this program; if not, write to the Free Software
   9  *  Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307,
  10  *  USA.
  11  */
  12
  13 #include <Python.h>
  14 #include <stdlib.h>
  15
  16 #define C1 52845
  17 #define C2 22719
  18
  19 /*
  20 def decoder(code, r, n):
  21     c1 = 52845
  22     c2 = 22719
  23     data = array.array("B")
  24     for x in array.array("B", code):
  25         data.append(x ^ (r >> 8))
  26         r = ((x + r) * c1 + c2) & 0xffff
  27     return data.tostring()[n:]
  28
  29 */
  30
  31 static PyObject *py_decoder(PyObject *self, PyObject *args)
  32 {
  33     unsigned char *code;
  34     int lcode, n;
  35     unsigned int r;
  36
  37     /* XXX: should we use U (unsigned int) for argument r */
  38     if (PyArg_ParseTuple(args, "s#ii", (char **) &code, &lcode, (int *) &r, &n)) {
  39       unsigned char *data;
  40       int i;
  41       unsigned char x;
  42       PyObject *result;
  43
  44       if (! (data = (unsigned char *) malloc(lcode)) )
  45           return NULL;
  46
  47       for (i=0; i<lcode; i++) {
  48         x = code[i];
  49         data[i] = x ^ ( r >> 8);
  50         r = (x + r) * C1 + C2;
  51       }
  52
  53       /* convert result to string stripping first n chars */
  54       result = PyString_FromStringAndSize((const char *)data + n, lcode - n);
  55       free(data);
  56       return result;
  57     }
  58     else return NULL;
  59
  60 }
  61
  62 /*
  63 def encoder(data, r, random):
  64     c1 = 52845
  65     c2 = 22719
  66     code = array.array("B")
  67     for x in array.array("B", random+data):
  68         code.append(x ^ (r >> 8))
  69         r = ((code[-1] + r) * c1 + c2) & 0xffff;
  70     return code.tostring()
  71 */
  72
  73 static PyObject *py_encoder(PyObject *self, PyObject *args)
  74 {
  75     unsigned char *data;
  76     unsigned char *random;
  77     int ldata, lrandom;
  78     unsigned int r;
  79
  80     /* XXX: should we use U (unsigned int) for argument r */
  81     if (PyArg_ParseTuple(args, "s#is#", (char **) &data, &ldata, (int *) &r, (char **) &random, &lrandom)) {
  82       unsigned char *code;
  83       int i;
  84       PyObject *result;
  85
  86       if (! (code = (unsigned char *) malloc(ldata + lrandom)) )
  87           return NULL;
  88
  89       for (i=0; i<lrandom; i++) {
  90         code[i] = random[i] ^ ( r >> 8);
  91         r = (code[i] + r) * C1 + C2;
  92       }
  93
  94       for (i=0; i<ldata; i++) {
  95         code[i+lrandom] = data[i] ^ ( r >> 8);
  96         r = (code[i+lrandom] + r) * C1 + C2;
  97       }
  98
  99       result = PyString_FromStringAndSize((const char *)code, ldata + lrandom);
 100       free(code);
 101       return result;
 102     }
 103     else return NULL;
 104
 105 }
 106
 107
 108
 109 /* exported methods */
 110
 111 static PyMethodDef t1code_methods[] = {
 112     {"decoder", py_decoder,  METH_VARARGS},
 113     {"encoder", py_encoder,  METH_VARARGS},
 114     {NULL, NULL}
 115 };
 116
 117 void init_t1code(void) {
 118     (void) Py_InitModule("_t1code", t1code_methods);
 119 }