view mercurial/cext/base85.c @ 41987:c1d83d916e85

revert: option to choose what to keep, not what to discard

I know the you (the reader) are probably tired of discussing how `hg
revert -i -r .` should behave and so am I. And I know I'm one of the
people who argued that showing the diff from the working copy to the
parent was confusing. I think it is less confusing now that we show
the diff from the parent to the working copy, but I still find it
confusing. I think showing the diff of hunks to keep might make it
easier to understand. So that's what this patch provides an option
for.

One argument doing it this way is that most people seem to find `hg
split` natural. I suspect that is because it shows the forward diff
(from parent commit to the commit) and asks you what to put in the
first commit. I think the new "keep" mode for revert (this patch)
matches that.

In "keep" mode, all the changes are still selected by default. That
means that `hg revert -i` followed by 'A' (keep all) (or 'c' in
curses) will be different from `hg revert -a`. That's mostly because
that was simplest. It can also be argued that it's safest. But it can
also be argued that it should be consistent with `hg revert -a`.

Note that in this mode, you can edit the hunks and it will do what you
expect (e.g. add new lines to your file if you added a new lines when
editing). The test case shows that that works.

Differential Revision: https://phab.mercurial-scm.org/D6125

/*
 base85 codec

 Copyright 2006 Brendan Cully <[e-mail]>

 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)
{
	unsigned 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, PY23("s#|i", "y#|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 = NULL;
	const char *text;
	char *dst;
	Py_ssize_t len, i, j, olen, cap;
	int c;
	unsigned int acc;

	if (!PyArg_ParseTuple(args, PY23("s#", "y#"), &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) {
				PyErr_Format(
				    PyExc_ValueError,
				    "bad base85 character at position %d",
				    (int)i);
				goto bail;
			}
			acc = acc * 85 + c;
		}
		if (i++ < len) {
			c = b85dec[(int)*text++] - 1;
			if (c < 0) {
				PyErr_Format(
				    PyExc_ValueError,
				    "bad base85 character at position %d",
				    (int)i);
				goto bail;
			}
			/* overflow detection: 0xffffffff == "|NsC0",
			 * "|NsC" == 0x03030303 */
			if (acc > 0x03030303 || (acc *= 85) > 0xffffffff - c) {
				PyErr_Format(
				    PyExc_ValueError,
				    "bad base85 sequence at position %d",
				    (int)i);
				goto bail;
			}
			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;
bail:
	Py_XDECREF(out);
	return NULL;
}

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},
};

static const int version = 1;

#ifdef IS_PY3K
static struct PyModuleDef base85_module = {
    PyModuleDef_HEAD_INIT, "base85", base85_doc, -1, methods,
};

PyMODINIT_FUNC PyInit_base85(void)
{
	PyObject *m;
	b85prep();

	m = PyModule_Create(&base85_module);
	PyModule_AddIntConstant(m, "version", version);
	return m;
}
#else
PyMODINIT_FUNC initbase85(void)
{
	PyObject *m;
	m = Py_InitModule3("base85", methods, base85_doc);

	b85prep();
	PyModule_AddIntConstant(m, "version", version);
}
#endif