mercurial/exewrapper.c

templater: add subsetparents(rev, revset) function

Naming suggestions are welcome. And this could be flagged as an (ADVANCED)
function since the primary use case is to draw a graph.

This provides all data needed for drawing revisions graph filtered by revset,
and allows us to implement a GUI graph viewer in some languages better than
Python. A frontend grapher will be quite similar to our graphmod since
subsetparents() just returns parent-child relations in the filtered sub graph.

Frontend example:

  https://hg.sr.ht/~yuja/hgv/browse/default/core/hgchangesetgrapher.cpp

However, the resulting graph will be simpler than the one "hg log -G" would
generate because redundant edges are eliminated. This should be the same graph
rendering strategy as TortoiseHg.

This function could be implemented as a revset predicate, but that would mean
the scanning state couldn't be cached and thus slow.

Test cases are split to new file since test-template-functions.t is quite
big and we'll need a new branchy repository anyway.

/*
 exewrapper.c - wrapper for calling a python script on Windows

 Copyright 2012 Adrian Buehlmann <[e-mail]> and others

 This software may be used and distributed according to the terms of the
 GNU General Public License version 2 or any later version.
*/

#include <Python.h>
#include <stdio.h>
#include <tchar.h>
#include <windows.h>

#include "hgpythonlib.h"

#ifdef __GNUC__
int strcat_s(char *d, size_t n, const char *s)
{
	return !strncat(d, s, n);
}
int strcpy_s(char *d, size_t n, const char *s)
{
	return !strncpy(d, s, n);
}

#define _tcscpy_s strcpy_s
#define _tcscat_s strcat_s
#define _countof(array) (sizeof(array) / sizeof(array[0]))
#endif

static TCHAR pyscript[MAX_PATH + 10];
static TCHAR pyhome[MAX_PATH + 10];
static TCHAR pydllfile[MAX_PATH + 10];

int _tmain(int argc, TCHAR *argv[])
{
	TCHAR *p;
	int ret;
	int i;
	int n;
	TCHAR **pyargv;
	WIN32_FIND_DATA fdata;
	HANDLE hfind;
	const char *err;
	HMODULE pydll;
	void(__cdecl * Py_SetPythonHome)(TCHAR * home);
	int(__cdecl * Py_Main)(int argc, TCHAR *argv[]);

#if PY_MAJOR_VERSION >= 3
	Py_LegacyWindowsStdioFlag = 1;
#endif

	if (GetModuleFileName(NULL, pyscript, _countof(pyscript)) == 0) {
		err = "GetModuleFileName failed";
		goto bail;
	}

	p = _tcsrchr(pyscript, '.');
	if (p == NULL) {
		err = "malformed module filename";
		goto bail;
	}
	*p = 0; /* cut trailing ".exe" */
	_tcscpy_s(pyhome, _countof(pyhome), pyscript);

	hfind = FindFirstFile(pyscript, &fdata);
	if (hfind != INVALID_HANDLE_VALUE) {
		/* pyscript exists, close handle */
		FindClose(hfind);
	} else {
		/* file pyscript isn't there, take <pyscript>exe.py */
		_tcscat_s(pyscript, _countof(pyscript), _T("exe.py"));
	}

	pydll = NULL;

	p = _tcsrchr(pyhome, _T('\\'));
	if (p == NULL) {
		err = "can't find backslash in module filename";
		goto bail;
	}
	*p = 0; /* cut at directory */

	/* check for private Python of HackableMercurial */
	_tcscat_s(pyhome, _countof(pyhome), _T("\\hg-python"));

	hfind = FindFirstFile(pyhome, &fdata);
	if (hfind != INVALID_HANDLE_VALUE) {
		/* Path .\hg-python exists. We are probably in HackableMercurial
		scenario, so let's load python dll from this dir. */
		FindClose(hfind);
		_tcscpy_s(pydllfile, _countof(pydllfile), pyhome);
		_tcscat_s(pydllfile, _countof(pydllfile),
		          _T("\\") _T(HGPYTHONLIB) _T(".dll"));
		pydll = LoadLibrary(pydllfile);
		if (pydll == NULL) {
			err = "failed to load private Python DLL " HGPYTHONLIB
			      ".dll";
			goto bail;
		}
		Py_SetPythonHome =
		    (void *)GetProcAddress(pydll, "Py_SetPythonHome");
		if (Py_SetPythonHome == NULL) {
			err = "failed to get Py_SetPythonHome";
			goto bail;
		}
		Py_SetPythonHome(pyhome);
	}

	if (pydll == NULL) {
		pydll = LoadLibrary(_T(HGPYTHONLIB) _T(".dll"));
		if (pydll == NULL) {
			err = "failed to load Python DLL " HGPYTHONLIB ".dll";
			goto bail;
		}
	}

	Py_Main = (void *)GetProcAddress(pydll, "Py_Main");
	if (Py_Main == NULL) {
		err = "failed to get Py_Main";
		goto bail;
	}

	/*
	Only add the pyscript to the args, if it's not already there. It may
	already be there, if the script spawned a child process of itself, in
	the same way as it got called, that is, with the pyscript already in
	place. So we optionally accept the pyscript as the first argument
	(argv[1]), letting our exe taking the role of the python interpreter.
	*/
	if (argc >= 2 && _tcscmp(argv[1], pyscript) == 0) {
		/*
		pyscript is already in the args, so there is no need to copy
		the args and we can directly call the python interpreter with
		the original args.
		*/
		return Py_Main(argc, argv);
	}

	/*
	Start assembling the args for the Python interpreter call. We put the
	name of our exe (argv[0]) in the position where the python.exe
	canonically is, and insert the pyscript next.
	*/
	pyargv = malloc((argc + 5) * sizeof(TCHAR *));
	if (pyargv == NULL) {
		err = "not enough memory";
		goto bail;
	}
	n = 0;
	pyargv[n++] = argv[0];
	pyargv[n++] = pyscript;

	/* copy remaining args from the command line */
	for (i = 1; i < argc; i++)
		pyargv[n++] = argv[i];
	/* argv[argc] is guaranteed to be NULL, so we forward that guarantee */
	pyargv[n] = NULL;

	ret = Py_Main(n, pyargv); /* The Python interpreter call */

	free(pyargv);
	return ret;

bail:
	fprintf(stderr, "abort: %s\n", err);
	return 255;
}