osutil: treat open modes 'w' and 'a' as 'w+' and 'a+' in posixfile

to work around http://support.microsoft.com/kb/899149.

Also, Microsoft's documentation of the CreateFile Windows API says (quote):

  When an application creates a file across a network, it is better to use
  GENERIC_READ | GENERIC_WRITE for dwDesiredAccess than to use
  GENERIC_WRITE alone. The resulting code is faster, because the
  redirector can use the cache manager and send fewer SMBs with more data.
  This combination also avoids an issue where writing to a file across a
  network can occasionally return ERROR_ACCESS_DENIED.

mercurial/osutil.c

@@ -1,559 +1,554
 /*
  osutil.c - native operating system services
 
  Copyright 2007 Matt Mackall and others
 
  This software may be used and distributed according to the terms of
  the GNU General Public License, incorporated herein by reference.
 */
 
 #define _ATFILE_SOURCE
 #include <Python.h>
 #include <fcntl.h>
 #include <stdio.h>
 #include <string.h>
 
 #ifdef _WIN32
 #include <windows.h>
 #include <io.h>
 #else
 #include <dirent.h>
 #include <sys/stat.h>
 #include <sys/types.h>
 #include <unistd.h>
 #endif
 
 #include "util.h"
 
 /* some platforms lack the PATH_MAX definition (eg. GNU/Hurd) */
 #ifndef PATH_MAX
 #define PATH_MAX 4096
 #endif
 
 #ifdef _WIN32
 /*
 stat struct compatible with hg expectations
 Mercurial only uses st_mode, st_size and st_mtime
 the rest is kept to minimize changes between implementations
 */
 struct hg_stat {
 	int st_dev;
 	int st_mode;
 	int st_nlink;
 	__int64 st_size;
 	int st_mtime;
 	int st_ctime;
 };
 struct listdir_stat {
 	PyObject_HEAD
 	struct hg_stat st;
 };
 #else
 struct listdir_stat {
 	PyObject_HEAD
 	struct stat st;
 };
 #endif
 
 #define listdir_slot(name) \
 	static PyObject *listdir_stat_##name(PyObject *self, void *x) \
 	{ \
 		return PyInt_FromLong(((struct listdir_stat *)self)->st.name); \
 	}
 
 listdir_slot(st_dev)
 listdir_slot(st_mode)
 listdir_slot(st_nlink)
 #ifdef _WIN32
 static PyObject *listdir_stat_st_size(PyObject *self, void *x)
 {
 	return PyLong_FromLongLong(
 		(PY_LONG_LONG)((struct listdir_stat *)self)->st.st_size);
 }
 #else
 listdir_slot(st_size)
 #endif
 listdir_slot(st_mtime)
 listdir_slot(st_ctime)
 
 static struct PyGetSetDef listdir_stat_getsets[] = {
 	{"st_dev", listdir_stat_st_dev, 0, 0, 0},
 	{"st_mode", listdir_stat_st_mode, 0, 0, 0},
 	{"st_nlink", listdir_stat_st_nlink, 0, 0, 0},
 	{"st_size", listdir_stat_st_size, 0, 0, 0},
 	{"st_mtime", listdir_stat_st_mtime, 0, 0, 0},
 	{"st_ctime", listdir_stat_st_ctime, 0, 0, 0},
 	{0, 0, 0, 0, 0}
 };
 
 static PyObject *listdir_stat_new(PyTypeObject *t, PyObject *a, PyObject *k)
 {
 	return t->tp_alloc(t, 0);
 }
 
 static void listdir_stat_dealloc(PyObject *o)
 {
 	o->ob_type->tp_free(o);
 }
 
 static PyTypeObject listdir_stat_type = {
 	PyVarObject_HEAD_INIT(NULL, 0)
 	"osutil.stat",             /*tp_name*/
 	sizeof(struct listdir_stat), /*tp_basicsize*/
 	0,                         /*tp_itemsize*/
 	(destructor)listdir_stat_dealloc, /*tp_dealloc*/
 	0,                         /*tp_print*/
 	0,                         /*tp_getattr*/
 	0,                         /*tp_setattr*/
 	0,                         /*tp_compare*/
 	0,                         /*tp_repr*/
 	0,                         /*tp_as_number*/
 	0,                         /*tp_as_sequence*/
 	0,                         /*tp_as_mapping*/
 	0,                         /*tp_hash */
 	0,                         /*tp_call*/
 	0,                         /*tp_str*/
 	0,                         /*tp_getattro*/
 	0,                         /*tp_setattro*/
 	0,                         /*tp_as_buffer*/
 	Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE, /*tp_flags*/
 	"stat objects",            /* tp_doc */
 	0,                         /* tp_traverse */
 	0,                         /* tp_clear */
 	0,                         /* tp_richcompare */
 	0,                         /* tp_weaklistoffset */
 	0,                         /* tp_iter */
 	0,                         /* tp_iternext */
 	0,                         /* tp_methods */
 	0,                         /* tp_members */
 	listdir_stat_getsets,      /* tp_getset */
 	0,                         /* tp_base */
 	0,                         /* tp_dict */
 	0,                         /* tp_descr_get */
 	0,                         /* tp_descr_set */
 	0,                         /* tp_dictoffset */
 	0,                         /* tp_init */
 	0,                         /* tp_alloc */
 	listdir_stat_new,          /* tp_new */
 };
 
 #ifdef _WIN32
 
 static int to_python_time(const FILETIME *tm)
 {
 	/* number of seconds between epoch and January 1 1601 */
 	const __int64 a0 = (__int64)134774L * (__int64)24L * (__int64)3600L;
 	/* conversion factor from 100ns to 1s */
 	const __int64 a1 = 10000000;
 	/* explicit (int) cast to suspend compiler warnings */
 	return (int)((((__int64)tm->dwHighDateTime << 32)
 			+ tm->dwLowDateTime) / a1 - a0);
 }
 
 static PyObject *make_item(const WIN32_FIND_DATAA *fd, int wantstat)
 {
 	PyObject *py_st;
 	struct hg_stat *stp;
 
 	int kind = (fd->dwFileAttributes & FILE_ATTRIBUTE_DIRECTORY)
 		? _S_IFDIR : _S_IFREG;
 
 	if (!wantstat)
 		return Py_BuildValue("si", fd->cFileName, kind);
 
 	py_st = PyObject_CallObject((PyObject *)&listdir_stat_type, NULL);
 	if (!py_st)
 		return NULL;
 
 	stp = &((struct listdir_stat *)py_st)->st;
 	/*
 	use kind as st_mode
 	rwx bits on Win32 are meaningless
 	and Hg does not use them anyway
 	*/
 	stp->st_mode  = kind;
 	stp->st_mtime = to_python_time(&fd->ftLastWriteTime);
 	stp->st_ctime = to_python_time(&fd->ftCreationTime);
 	if (kind == _S_IFREG)
 		stp->st_size = ((__int64)fd->nFileSizeHigh << 32)
 				+ fd->nFileSizeLow;
 	return Py_BuildValue("siN", fd->cFileName,
 		kind, py_st);
 }
 
 static PyObject *_listdir(char *path, int plen, int wantstat, char *skip)
 {
 	PyObject *rval = NULL; /* initialize - return value */
 	PyObject *list;
 	HANDLE fh;
 	WIN32_FIND_DATAA fd;
 	char *pattern;
 
 	/* build the path + \* pattern string */
 	pattern = malloc(plen + 3); /* path + \* + \0 */
 	if (!pattern) {
 		PyErr_NoMemory();
 		goto error_nomem;
 	}
 	strcpy(pattern, path);
 
 	if (plen > 0) {
 		char c = path[plen-1];
 		if (c != ':' && c != '/' && c != '\\')
 			pattern[plen++] = '\\';
 	}
 	strcpy(pattern + plen, "*");
 
 	fh = FindFirstFileA(pattern, &fd);
 	if (fh == INVALID_HANDLE_VALUE) {
 		PyErr_SetFromWindowsErrWithFilename(GetLastError(), path);
 		goto error_file;
 	}
 
 	list = PyList_New(0);
 	if (!list)
 		goto error_list;
 
 	do {
 		PyObject *item;
 
 		if (fd.dwFileAttributes & FILE_ATTRIBUTE_DIRECTORY) {
 			if (!strcmp(fd.cFileName, ".")
 			|| !strcmp(fd.cFileName, ".."))
 				continue;
 
 			if (skip && !strcmp(fd.cFileName, skip)) {
 				rval = PyList_New(0);
 				goto error;
 			}
 		}
 
 		item = make_item(&fd, wantstat);
 		if (!item)
 			goto error;
 
 		if (PyList_Append(list, item)) {
 			Py_XDECREF(item);
 			goto error;
 		}
 
 		Py_XDECREF(item);
 	} while (FindNextFileA(fh, &fd));
 
 	if (GetLastError() != ERROR_NO_MORE_FILES) {
 		PyErr_SetFromWindowsErrWithFilename(GetLastError(), path);
 		goto error;
 	}
 
 	rval = list;
 	Py_XINCREF(rval);
 error:
 	Py_XDECREF(list);
 error_list:
 	FindClose(fh);
 error_file:
 	free(pattern);
 error_nomem:
 	return rval;
 }
 
 #else
 
 int entkind(struct dirent *ent)
 {
 #ifdef DT_REG
 	switch (ent->d_type) {
 	case DT_REG: return S_IFREG;
 	case DT_DIR: return S_IFDIR;
 	case DT_LNK: return S_IFLNK;
 	case DT_BLK: return S_IFBLK;
 	case DT_CHR: return S_IFCHR;
 	case DT_FIFO: return S_IFIFO;
 	case DT_SOCK: return S_IFSOCK;
 	}
 #endif
 	return -1;
 }
 
 static PyObject *_listdir(char *path, int pathlen, int keepstat, char *skip)
 {
 	PyObject *list, *elem, *stat, *ret = NULL;
 	char fullpath[PATH_MAX + 10];
 	int kind, err;
 	struct stat st;
 	struct dirent *ent;
 	DIR *dir;
 #ifdef AT_SYMLINK_NOFOLLOW
 	int dfd = -1;
 #endif
 
 	if (pathlen >= PATH_MAX) {
 		PyErr_SetString(PyExc_ValueError, "path too long");
 		goto error_value;
 	}
 	strncpy(fullpath, path, PATH_MAX);
 	fullpath[pathlen] = '/';
 
 #ifdef AT_SYMLINK_NOFOLLOW
 	dfd = open(path, O_RDONLY);
 	if (dfd == -1) {
 		PyErr_SetFromErrnoWithFilename(PyExc_OSError, path);
 		goto error_value;
 	}
 	dir = fdopendir(dfd);
 #else
 	dir = opendir(path);
 #endif
 	if (!dir) {
 		PyErr_SetFromErrnoWithFilename(PyExc_OSError, path);
 		goto error_dir;
  	}
 
 	list = PyList_New(0);
 	if (!list)
 		goto error_list;
 
 	while ((ent = readdir(dir))) {
 		if (!strcmp(ent->d_name, ".") || !strcmp(ent->d_name, ".."))
 			continue;
 
 		kind = entkind(ent);
 		if (kind == -1 || keepstat) {
 #ifdef AT_SYMLINK_NOFOLLOW
 			err = fstatat(dfd, ent->d_name, &st,
 				      AT_SYMLINK_NOFOLLOW);
 #else
 			strncpy(fullpath + pathlen + 1, ent->d_name,
 				PATH_MAX - pathlen);
 			fullpath[PATH_MAX] = 0;
 			err = lstat(fullpath, &st);
 #endif
 			if (err == -1) {
 				strncpy(fullpath + pathlen + 1, ent->d_name,
 					PATH_MAX - pathlen);
 				fullpath[PATH_MAX] = 0;
 				PyErr_SetFromErrnoWithFilename(PyExc_OSError,
 							       fullpath);
 				goto error;
 			}
 			kind = st.st_mode & S_IFMT;
 		}
 
 		/* quit early? */
 		if (skip && kind == S_IFDIR && !strcmp(ent->d_name, skip)) {
 			ret = PyList_New(0);
 			goto error;
 		}
 
 		if (keepstat) {
 			stat = PyObject_CallObject((PyObject *)&listdir_stat_type, NULL);
 			if (!stat)
 				goto error;
 			memcpy(&((struct listdir_stat *)stat)->st, &st, sizeof(st));
 			elem = Py_BuildValue("siN", ent->d_name, kind, stat);
 		} else
 			elem = Py_BuildValue("si", ent->d_name, kind);
 		if (!elem)
 			goto error;
 
 		PyList_Append(list, elem);
 		Py_DECREF(elem);
 	}
 
 	ret = list;
 	Py_INCREF(ret);
 
 error:
 	Py_DECREF(list);
 error_list:
 	closedir(dir);
 error_dir:
 #ifdef AT_SYMLINK_NOFOLLOW
 	close(dfd);
 #endif
 error_value:
 	return ret;
 }
 
 #endif /* ndef _WIN32 */
 
 static PyObject *listdir(PyObject *self, PyObject *args, PyObject *kwargs)
 {
 	PyObject *statobj = NULL; /* initialize - optional arg */
 	PyObject *skipobj = NULL; /* initialize - optional arg */
 	char *path, *skip = NULL;
 	int wantstat, plen;
 
 	static char *kwlist[] = {"path", "stat", "skip", NULL};
 
 	if (!PyArg_ParseTupleAndKeywords(args, kwargs, "s#|OO:listdir",
 			kwlist, &path, &plen, &statobj, &skipobj))
 		return NULL;
 
 	wantstat = statobj && PyObject_IsTrue(statobj);
 
 	if (skipobj && skipobj != Py_None) {
 		skip = PyBytes_AsString(skipobj);
 		if (!skip)
 			return NULL;
 	}
 
 	return _listdir(path, plen, wantstat, skip);
 }
 
 #ifdef _WIN32
 static PyObject *posixfile(PyObject *self, PyObject *args, PyObject *kwds)
 {
 	static char *kwlist[] = {"name", "mode", "buffering", NULL};
 	PyObject *file_obj = NULL;
 	char *name = NULL;
 	char *mode = "rb";
 	DWORD access = 0;
 	DWORD creation;
 	HANDLE handle;
 	int fd, flags = 0;
 	int bufsize = -1;
 	char m0, m1, m2;
 	char fpmode[4];
 	int fppos = 0;
 	int plus;
 	FILE *fp;
 
 	if (!PyArg_ParseTupleAndKeywords(args, kwds, "et|si:posixfile", kwlist,
 					 Py_FileSystemDefaultEncoding,
 					 &name, &mode, &bufsize))
 		return NULL;
 
 	m0 = mode[0];
 	m1 = m0 ? mode[1] : '\0';
 	m2 = m1 ? mode[2] : '\0';
 	plus = m1 == '+' || m2 == '+';
 
 	fpmode[fppos++] = m0;
 	if (m1 == 'b' || m2 == 'b') {
 		flags = _O_BINARY;
 		fpmode[fppos++] = 'b';
 	}
 	else
 		flags = _O_TEXT;
-	if (plus) {
+	if (m0 == 'r' && !plus) {
+		flags |= _O_RDONLY;
+		access = GENERIC_READ;
+	} else {
+		/*
+		work around http://support.microsoft.com/kb/899149 and
+		set _O_RDWR for 'w' and 'a', even if mode has no '+'
+		*/
 		flags |= _O_RDWR;
 		access = GENERIC_READ | GENERIC_WRITE;
 		fpmode[fppos++] = '+';
 	}
 	fpmode[fppos++] = '\0';
 
 	switch (m0) {
 	case 'r':
 		creation = OPEN_EXISTING;
-		if (!plus) {
-			flags |= _O_RDONLY;
-			access = GENERIC_READ;
-		}
 		break;
 	case 'w':
 		creation = CREATE_ALWAYS;
-		if (!plus) {
-			access = GENERIC_WRITE;
-			flags |= _O_WRONLY;
-		}
 		break;
 	case 'a':
 		creation = OPEN_ALWAYS;
 		flags |= _O_APPEND;
-		if (!plus) {
-			flags |= _O_WRONLY;
-			access = GENERIC_WRITE;
-		}
 		break;
 	default:
 		PyErr_Format(PyExc_ValueError,
 			     "mode string must begin with one of 'r', 'w', "
 			     "or 'a', not '%c'", m0);
 		goto bail;
 	}
 
 	handle = CreateFile(name, access,
 			    FILE_SHARE_READ | FILE_SHARE_WRITE |
 			    FILE_SHARE_DELETE,
 			    NULL,
 			    creation,
 			    FILE_ATTRIBUTE_NORMAL,
 			    0);
 
 	if (handle == INVALID_HANDLE_VALUE) {
 		PyErr_SetFromWindowsErrWithFilename(GetLastError(), name);
 		goto bail;
 	}
 
 	fd = _open_osfhandle((intptr_t)handle, flags);
 
 	if (fd == -1) {
 		CloseHandle(handle);
 		PyErr_SetFromErrnoWithFilename(PyExc_IOError, name);
 		goto bail;
 	}
 #ifndef IS_PY3K
 	fp = _fdopen(fd, fpmode);
 	if (fp == NULL) {
 		_close(fd);
 		PyErr_SetFromErrnoWithFilename(PyExc_IOError, name);
 		goto bail;
 	}
 
 	file_obj = PyFile_FromFile(fp, name, mode, fclose);
 	if (file_obj == NULL) {
 		fclose(fp);
 		goto bail;
 	}
 
 	PyFile_SetBufSize(file_obj, bufsize);
 #else
 	file_obj = PyFile_FromFd(fd, name, mode, bufsize, NULL, NULL, NULL, 1);
 	if (file_obj == NULL)
 		goto bail;
 #endif
 bail:
 	PyMem_Free(name);
 	return file_obj;
 }
 #endif
 
 static char osutil_doc[] = "Native operating system services.";
 
 static PyMethodDef methods[] = {
 	{"listdir", (PyCFunction)listdir, METH_VARARGS | METH_KEYWORDS,
 	 "list a directory\n"},
 #ifdef _WIN32
 	{"posixfile", (PyCFunction)posixfile, METH_VARARGS | METH_KEYWORDS,
 	 "Open a file with POSIX-like semantics.\n"
 "On error, this function may raise either a WindowsError or an IOError."},
 #endif
 	{NULL, NULL}
 };
 
 #ifdef IS_PY3K
 static struct PyModuleDef osutil_module = {
 	PyModuleDef_HEAD_INIT,
 	"osutil",
 	osutil_doc,
 	-1,
 	methods
 };
 
 PyMODINIT_FUNC PyInit_osutil(void)
 {
 	if (PyType_Ready(&listdir_stat_type) < 0)
 		return NULL;
 
 	return PyModule_Create(&osutil_module);
 }
 #else
 PyMODINIT_FUNC initosutil(void)
 {
 	if (PyType_Ready(&listdir_stat_type) == -1)
 		return;
 
 	Py_InitModule3("osutil", methods, osutil_doc);
 }
 #endif