| /* |
| 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 |
| */ |
| |
| #define PY_SSIZE_T_CLEAN |
| #include <Python.h> |
| |
| #include "util.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; |
| Py_ssize_t len, olen, i; |
| unsigned int acc, val, ch; |
| int pad = 0; |
| |
| if (!PyArg_ParseTuple(args, "s#|i", &text, &len, &pad)) |
| return NULL; |
| |
| if (pad) |
| olen = ((len + 3) / 4 * 5) - 3; |
| else { |
| olen = len % 4; |
| if (olen) |
| olen++; |
| olen += len / 4 * 5; |
| } |
| if (!(out = PyBytes_FromStringAndSize(NULL, olen + 3))) |
| return NULL; |
| |
| dst = PyBytes_AsString(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; |
| } |
| |
| if (!pad) |
| _PyBytes_Resize(&out, olen); |
| |
| return out; |
| } |
| |
| static PyObject * |
| b85decode(PyObject *self, PyObject *args) |
| { |
| PyObject *out; |
| const char *text; |
| char *dst; |
| Py_ssize_t len, i, j, olen, cap; |
| int c; |
| unsigned int acc; |
| |
| if (!PyArg_ParseTuple(args, "s#", &text, &len)) |
| return NULL; |
| |
| olen = len / 5 * 4; |
| i = len % 5; |
| if (i) |
| olen += i - 1; |
| if (!(out = PyBytes_FromStringAndSize(NULL, olen))) |
| return NULL; |
| |
| dst = PyBytes_AsString(out); |
| |
| i = 0; |
| while (i < len) |
| { |
| acc = 0; |
| cap = len - i - 1; |
| if (cap > 4) |
| cap = 4; |
| for (j = 0; j < cap; i++, j++) |
| { |
| c = b85dec[(int)*text++] - 1; |
| if (c < 0) |
| return PyErr_Format( |
| PyExc_ValueError, |
| "bad base85 character at position %d", |
| (int)i); |
| acc = acc * 85 + c; |
| } |
| if (i++ < len) |
| { |
| c = b85dec[(int)*text++] - 1; |
| if (c < 0) |
| return PyErr_Format( |
| PyExc_ValueError, |
| "bad base85 character at position %d", |
| (int)i); |
| /* overflow detection: 0xffffffff == "|NsC0", |
| * "|NsC" == 0x03030303 */ |
| if (acc > 0x03030303 || (acc *= 85) > 0xffffffff - c) |
| return PyErr_Format( |
| PyExc_ValueError, |
| "bad base85 sequence at position %d", |
| (int)i); |
| acc += c; |
| } |
| |
| cap = olen < 4 ? olen : 4; |
| olen -= cap; |
| for (j = 0; j < 4 - cap; j++) |
| acc *= 85; |
| if (cap && cap < 4) |
| acc += 0xffffff >> (cap - 1) * 8; |
| for (j = 0; j < cap; j++) |
| { |
| acc = (acc << 8) | (acc >> 24); |
| *dst++ = acc; |
| } |
| } |
| |
| return out; |
| } |
| |
| static char base85_doc[] = "Base85 Data Encoding"; |
| |
| static PyMethodDef methods[] = { |
| {"b85encode", b85encode, METH_VARARGS, |
| "Encode text in base85.\n\n" |
| "If the second parameter is true, pad the result to a multiple of " |
| "five characters.\n"}, |
| {"b85decode", b85decode, METH_VARARGS, "Decode base85 text.\n"}, |
| {NULL, NULL} |
| }; |
| |
| #ifdef IS_PY3K |
| static struct PyModuleDef base85_module = { |
| PyModuleDef_HEAD_INIT, |
| "base85", |
| base85_doc, |
| -1, |
| methods |
| }; |
| |
| PyMODINIT_FUNC PyInit_base85(void) |
| { |
| b85prep(); |
| |
| return PyModule_Create(&base85_module); |
| } |
| #else |
| PyMODINIT_FUNC initbase85(void) |
| { |
| Py_InitModule3("base85", methods, base85_doc); |
| |
| b85prep(); |
| } |
| #endif |