3283
|
1 /*
|
|
2 base85 codec
|
|
3
|
|
4 Copyright 2006 Brendan Cully <brendan@kublai.com>
|
|
5
|
|
6 This software may be used and distributed according to the terms of
|
|
7 the GNU General Public License, incorporated herein by reference.
|
|
8
|
|
9 Largely based on git's implementation
|
|
10 */
|
|
11
|
|
12 #include <Python.h>
|
|
13
|
|
14 static const char b85chars[] = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ"
|
|
15 "abcdefghijklmnopqrstuvwxyz!#$%&()*+-;<=>?@^_`{|}~";
|
|
16 static char b85dec[256];
|
|
17
|
|
18 static void
|
|
19 b85prep(void)
|
|
20 {
|
|
21 int i;
|
|
22
|
|
23 memset(b85dec, 0, sizeof(b85dec));
|
|
24 for (i = 0; i < sizeof(b85chars); i++)
|
|
25 b85dec[(int)(b85chars[i])] = i + 1;
|
|
26 }
|
|
27
|
|
28 static PyObject *
|
|
29 b85encode(PyObject *self, PyObject *args)
|
|
30 {
|
|
31 const unsigned char *text;
|
|
32 PyObject *out;
|
|
33 char *dst;
|
|
34 int len, olen, i;
|
|
35 unsigned int acc, val, ch;
|
|
36
|
|
37 if (!PyArg_ParseTuple(args, "s#", &text, &len))
|
|
38 return NULL;
|
|
39
|
|
40 olen = (len + 3) / 4 * 5;
|
|
41 if (!(out = PyString_FromStringAndSize(NULL, olen)))
|
|
42 return NULL;
|
|
43
|
|
44 dst = PyString_AS_STRING(out);
|
|
45
|
|
46 while (len)
|
|
47 {
|
|
48 acc = 0;
|
|
49 for (i = 24; i >= 0; i -= 8) {
|
|
50 ch = *text++;
|
|
51 acc |= ch << i;
|
|
52 if (--len == 0)
|
|
53 break;
|
|
54 }
|
|
55 for (i = 4; i >= 0; i--) {
|
|
56 val = acc % 85;
|
|
57 acc /= 85;
|
|
58 dst[i] = b85chars[val];
|
|
59 }
|
|
60 dst += 5;
|
|
61 }
|
|
62
|
|
63 return out;
|
|
64 }
|
|
65
|
|
66 static PyObject *
|
|
67 b85decode(PyObject *self, PyObject *args)
|
|
68 {
|
|
69 PyObject *out;
|
|
70 const char *text;
|
|
71 char *dst;
|
|
72 int len, i, j, olen, c;
|
|
73 unsigned int acc;
|
|
74
|
|
75 if (!PyArg_ParseTuple(args, "s#", &text, &len))
|
|
76 return NULL;
|
|
77
|
|
78 olen = (len + 4) / 5 * 4;
|
|
79 if (!(out = PyString_FromStringAndSize(NULL, olen)))
|
|
80 return NULL;
|
|
81
|
|
82 dst = PyString_AS_STRING(out);
|
|
83
|
|
84 for (i = 1; len; i++)
|
|
85 {
|
|
86 acc = 0;
|
|
87 for (j = 0; j < 4 && --len; j++)
|
|
88 {
|
|
89 c = b85dec[(int)*text++] - 1;
|
|
90 if (c < 0)
|
|
91 return PyErr_Format(PyExc_ValueError, "Bad base85 character at position %d", i);
|
|
92 acc = acc * 85 + c;
|
|
93 }
|
|
94 if (len--)
|
|
95 {
|
|
96 c = b85dec[(int)*text++] - 1;
|
|
97 if (c < 0)
|
|
98 return PyErr_Format(PyExc_ValueError, "Bad base85 character at position %d", i);
|
|
99 }
|
|
100 else
|
|
101 c = 0;
|
|
102 /* overflow detection: 0xffffffff == "|NsC0",
|
|
103 * "|NsC" == 0x03030303 */
|
|
104 if (acc > 0x03030303 || (acc *= 85) > 0xffffffff - c)
|
|
105 return PyErr_Format(PyExc_ValueError, "Bad base85 sequence at position %d", i);
|
|
106
|
|
107 acc += c;
|
|
108
|
|
109 for (j = 0; j < 4; j++)
|
|
110 {
|
|
111 acc = (acc << 8) | (acc >> 24);
|
|
112 *dst++ = (char)acc;
|
|
113 }
|
|
114 }
|
|
115
|
|
116 return out;
|
|
117 }
|
|
118
|
|
119 static char base85_doc[] = "Base85 Data Encoding";
|
|
120
|
|
121 static PyMethodDef methods[] = {
|
|
122 {"b85encode", b85encode, METH_VARARGS, "encode text in base85\n"},
|
|
123 {"b85decode", b85decode, METH_VARARGS, "decode base85 text\n"},
|
|
124 {NULL, NULL}
|
|
125 };
|
|
126
|
|
127 PyMODINIT_FUNC initbase85(void)
|
|
128 {
|
|
129 Py_InitModule3("base85", methods, base85_doc);
|
|
130
|
|
131 b85prep();
|
|
132 }
|