Mercurial > hg
view mercurial/base85.c @ 3283:1f2c3983a6c5
Add a base85 codec
author | Brendan Cully <brendan@kublai.com> |
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date | Fri, 06 Oct 2006 13:01:54 -0700 |
parents | |
children | e93c926e069e |
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/* base85 codec Copyright 2006 Brendan Cully <brendan@kublai.com> This software may be used and distributed according to the terms of the GNU General Public License, incorporated herein by reference. Largely based on git's implementation */ #include <Python.h> static const char b85chars[] = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ" "abcdefghijklmnopqrstuvwxyz!#$%&()*+-;<=>?@^_`{|}~"; static char b85dec[256]; static void b85prep(void) { int i; memset(b85dec, 0, sizeof(b85dec)); for (i = 0; i < sizeof(b85chars); i++) b85dec[(int)(b85chars[i])] = i + 1; } static PyObject * b85encode(PyObject *self, PyObject *args) { const unsigned char *text; PyObject *out; char *dst; int len, olen, i; unsigned int acc, val, ch; if (!PyArg_ParseTuple(args, "s#", &text, &len)) return NULL; olen = (len + 3) / 4 * 5; if (!(out = PyString_FromStringAndSize(NULL, olen))) return NULL; dst = PyString_AS_STRING(out); while (len) { acc = 0; for (i = 24; i >= 0; i -= 8) { ch = *text++; acc |= ch << i; if (--len == 0) break; } for (i = 4; i >= 0; i--) { val = acc % 85; acc /= 85; dst[i] = b85chars[val]; } dst += 5; } return out; } static PyObject * b85decode(PyObject *self, PyObject *args) { PyObject *out; const char *text; char *dst; int len, i, j, olen, c; unsigned int acc; if (!PyArg_ParseTuple(args, "s#", &text, &len)) return NULL; olen = (len + 4) / 5 * 4; if (!(out = PyString_FromStringAndSize(NULL, olen))) return NULL; dst = PyString_AS_STRING(out); for (i = 1; len; i++) { acc = 0; for (j = 0; j < 4 && --len; j++) { c = b85dec[(int)*text++] - 1; if (c < 0) return PyErr_Format(PyExc_ValueError, "Bad base85 character at position %d", i); acc = acc * 85 + c; } if (len--) { c = b85dec[(int)*text++] - 1; if (c < 0) return PyErr_Format(PyExc_ValueError, "Bad base85 character at position %d", i); } else c = 0; /* overflow detection: 0xffffffff == "|NsC0", * "|NsC" == 0x03030303 */ if (acc > 0x03030303 || (acc *= 85) > 0xffffffff - c) return PyErr_Format(PyExc_ValueError, "Bad base85 sequence at position %d", i); acc += c; for (j = 0; j < 4; j++) { acc = (acc << 8) | (acc >> 24); *dst++ = (char)acc; } } return out; } static char base85_doc[] = "Base85 Data Encoding"; static PyMethodDef methods[] = { {"b85encode", b85encode, METH_VARARGS, "encode text in base85\n"}, {"b85decode", b85decode, METH_VARARGS, "decode base85 text\n"}, {NULL, NULL} }; PyMODINIT_FUNC initbase85(void) { Py_InitModule3("base85", methods, base85_doc); b85prep(); }