author | Matt Mackall <mpm@selenic.com> |
Mon, 09 Oct 2006 21:27:04 -0500 | |
changeset 3305 | e7abcf3a7c5f |
parent 3287 | e93c926e069e |
child 3330 | a5209a1e53d8 |
permissions | -rw-r--r-- |
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/* |
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base85 codec |
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Copyright 2006 Brendan Cully <brendan@kublai.com> |
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This software may be used and distributed according to the terms of |
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the GNU General Public License, incorporated herein by reference. |
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Largely based on git's implementation |
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*/ |
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#include <Python.h> |
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static const char b85chars[] = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ" |
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"abcdefghijklmnopqrstuvwxyz!#$%&()*+-;<=>?@^_`{|}~"; |
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static char b85dec[256]; |
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static void |
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b85prep(void) |
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{ |
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int i; |
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memset(b85dec, 0, sizeof(b85dec)); |
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for (i = 0; i < sizeof(b85chars); i++) |
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b85dec[(int)(b85chars[i])] = i + 1; |
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} |
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static PyObject * |
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b85encode(PyObject *self, PyObject *args) |
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{ |
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const unsigned char *text; |
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PyObject *out; |
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char *dst; |
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int len, olen, i; |
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unsigned int acc, val, ch; |
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int pad = 0; |
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if (!PyArg_ParseTuple(args, "s#|i", &text, &len, &pad)) |
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return NULL; |
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if (pad) |
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olen = ((len + 3) / 4 * 5) - 3; |
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else { |
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olen = len % 4; |
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if (olen) |
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olen++; |
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olen += len / 4 * 5; |
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} |
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if (!(out = PyString_FromStringAndSize(NULL, olen + 3))) |
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return NULL; |
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dst = PyString_AS_STRING(out); |
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while (len) { |
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acc = 0; |
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for (i = 24; i >= 0; i -= 8) { |
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ch = *text++; |
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acc |= ch << i; |
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if (--len == 0) |
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break; |
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} |
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for (i = 4; i >= 0; i--) { |
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val = acc % 85; |
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acc /= 85; |
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dst[i] = b85chars[val]; |
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} |
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dst += 5; |
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} |
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if (!pad) |
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_PyString_Resize(&out, olen); |
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return out; |
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} |
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static PyObject * |
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b85decode(PyObject *self, PyObject *args) |
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{ |
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PyObject *out; |
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const char *text; |
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char *dst; |
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int len, i, j, olen, c, cap; |
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unsigned int acc; |
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if (!PyArg_ParseTuple(args, "s#", &text, &len)) |
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return NULL; |
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olen = len / 5 * 4; |
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i = len % 5; |
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if (i) |
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olen += i - 1; |
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if (!(out = PyString_FromStringAndSize(NULL, olen))) |
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return NULL; |
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dst = PyString_AS_STRING(out); |
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i = 0; |
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while (i < len) |
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{ |
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acc = 0; |
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cap = len - i - 1; |
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if (cap > 4) |
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cap = 4; |
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for (j = 0; j < cap; i++, j++) |
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{ |
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c = b85dec[(int)*text++] - 1; |
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if (c < 0) |
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return PyErr_Format(PyExc_ValueError, "Bad base85 character at position %d", i); |
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acc = acc * 85 + c; |
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} |
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if (i++ < len) |
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{ |
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c = b85dec[(int)*text++] - 1; |
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if (c < 0) |
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return PyErr_Format(PyExc_ValueError, "Bad base85 character at position %d", i); |
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/* overflow detection: 0xffffffff == "|NsC0", |
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* "|NsC" == 0x03030303 */ |
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if (acc > 0x03030303 || (acc *= 85) > 0xffffffff - c) |
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return PyErr_Format(PyExc_ValueError, "Bad base85 sequence at position %d", i); |
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acc += c; |
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} |
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cap = olen < 4 ? olen : 4; |
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olen -= cap; |
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for (j = 0; j < 4 - cap; j++) |
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acc *= 85; |
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if (cap && cap < 4) |
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acc += 0xffffff >> (cap - 1) * 8; |
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for (j = 0; j < cap; j++) |
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{ |
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acc = (acc << 8) | (acc >> 24); |
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*dst++ = acc; |
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} |
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} |
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return out; |
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} |
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static char base85_doc[] = "Base85 Data Encoding"; |
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static PyMethodDef methods[] = { |
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{"b85encode", b85encode, METH_VARARGS, |
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"Encode text in base85.\n\n" |
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"If the second parameter is true, pad the result to a multiple of " |
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"five characters.\n"}, |
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{"b85decode", b85decode, METH_VARARGS, "Decode base85 text.\n"}, |
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{NULL, NULL} |
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}; |
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PyMODINIT_FUNC initbase85(void) |
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{ |
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Py_InitModule3("base85", methods, base85_doc); |
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b85prep(); |
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} |