Implemented thread-local data as proposed on python-dev:

http://mail.python.org/pipermail/python-dev/2004-June/045785.html

Modules/threadmodule.c

@@ -158,6 +158,259 @@ static PyTypeObject Locktype = {
 	0,				/*tp_repr*/
 };
 
+/* Thread-local objects */
+
+#include "structmember.h"
+
+typedef struct {
+    PyObject_HEAD
+    PyObject *key;
+    PyObject *args;
+    PyObject *kw;
+    PyObject *dict;
+} localobject;
+
+static PyTypeObject localtype;
+
+static PyObject *
+local_new(PyTypeObject *type, PyObject *args, PyObject *kw)
+{
+    	localobject *self;
+        PyObject *tdict;
+
+        if (type->tp_init == PyBaseObject_Type.tp_init
+            && ((args && PyObject_IsTrue(args))
+                ||
+                (kw && PyObject_IsTrue(kw))
+                )
+            ) {
+          	PyErr_SetString(PyExc_TypeError,
+                          "Initialization arguments are not supported");
+                return NULL;
+        }
+
+    	self = (localobject *)type->tp_alloc(type, 0);
+        if (self == NULL)
+          return NULL;
+
+        Py_XINCREF(args);
+        self->args = args;
+        Py_XINCREF(kw);
+        self->kw = kw;
+        self->dict = NULL;      /* making sure */
+        self->key = PyString_FromFormat("thread.local.%p", self);
+        if (self->key == NULL) 
+                goto err;
+
+        self->dict = PyDict_New();
+        if (self->dict == NULL)
+                goto err;
+
+        tdict = PyThreadState_GetDict();
+        if (tdict == NULL) {
+                PyErr_SetString(PyExc_SystemError,
+                                "Couldn't get thread-state dictionary");
+                goto err;
+        }
+
+        if (PyDict_SetItem(tdict, self->key, self->dict) < 0)
+                goto err;
+       
+    	return (PyObject *)self;
+
+ err:
+        Py_DECREF(self);
+        return NULL;
+}
+
+static int
+local_traverse(localobject *self, visitproc visit, void *arg)
+{
+        Py_VISIT(self->args);
+        Py_VISIT(self->kw);
+        Py_VISIT(self->dict);
+	return 0;
+}
+
+static int
+local_clear(localobject *self)
+{
+  	Py_CLEAR(self->key);
+        Py_CLEAR(self->args);
+        Py_CLEAR(self->kw);
+        Py_CLEAR(self->dict);
+        return 0;
+}
+
+static void
+local_dealloc(localobject *self)
+{
+        PyThreadState *tstate;
+        if (self->key
+            && (tstate = PyThreadState_Get())
+            && tstate->interp) {
+                for(tstate = PyInterpreterState_ThreadHead(tstate->interp);
+                    tstate;
+                    tstate = PyThreadState_Next(tstate)
+                    ) 
+                        if (tstate->dict &&
+                            PyDict_GetItem(tstate->dict, self->key))
+                                PyDict_DelItem(tstate->dict, self->key);
+        }
+
+  	local_clear(self);
+        self->ob_type->tp_free((PyObject*)self);
+}
+
+static PyObject *
+_ldict(localobject *self)
+{
+	PyObject *tdict, *ldict;
+
+	tdict = PyThreadState_GetDict();
+        if (tdict == NULL) {
+        	PyErr_SetString(PyExc_SystemError,
+                                "Couldn't get thread-state dictionary");
+                return NULL;
+        }
+
+        ldict = PyDict_GetItem(tdict, self->key);
+        if (ldict == NULL) {
+        	ldict = PyDict_New(); /* we own ldict */
+
+                if (ldict == NULL)
+                	return NULL;
+                else {
+                        int i = PyDict_SetItem(tdict, self->key, ldict);
+                        Py_DECREF(ldict); /* now ldict is borowed */
+                        if (i < 0) 
+                                return NULL;
+                }
+
+                Py_CLEAR(self->dict);
+                Py_INCREF(ldict);
+                self->dict = ldict; /* still borrowed */
+
+                if (self->ob_type->tp_init != PyBaseObject_Type.tp_init &&
+                    self->ob_type->tp_init((PyObject*)self, 
+                                           self->args, self->kw) < 0
+                    ) {
+                        /* we need to get rid of ldict from thread so
+                           we create a new one the next time we do an attr
+                           acces */
+                        PyDict_DelItem(tdict, self->key);
+                        return NULL;
+                }
+                
+        }
+        else if (self->dict != ldict) {
+                Py_CLEAR(self->dict);
+                Py_INCREF(ldict);
+                self->dict = ldict;
+        }
+
+  return ldict;
+}
+
+static PyObject *
+local_getattro(localobject *self, PyObject *name)
+{
+	PyObject *ldict, *value;
+
+        ldict = _ldict(self);
+        if (ldict == NULL) 
+        	return NULL;
+
+        if (self->ob_type != &localtype)
+                /* use generic lookup for subtypes */
+                return PyObject_GenericGetAttr((PyObject *)self, name);
+
+        /* Optimization: just look in dict ourselves */
+        value = PyDict_GetItem(ldict, name);
+        if (value == NULL) 
+                /* Fall back on generic to get __class__ and __dict__ */
+                return PyObject_GenericGetAttr((PyObject *)self, name);
+
+        Py_INCREF(value);
+        return value;
+}
+
+static int
+local_setattro(localobject *self, PyObject *name, PyObject *v)
+{
+	PyObject *ldict;
+        
+        ldict = _ldict(self);
+        if (ldict == NULL) 
+          	return -1;
+
+        return PyObject_GenericSetAttr((PyObject *)self, name, v);
+}
+
+static PyObject *
+local_getdict(localobject *self, void *closure)
+{
+        if (self->dict == NULL) {
+                PyErr_SetString(PyExc_AttributeError, "__dict__");
+                return NULL;
+        }
+
+    	Py_INCREF(self->dict);
+        return self->dict;
+}
+
+static PyGetSetDef local_getset[] = {
+    {"__dict__", 
+     (getter)local_getdict, (setter)0,
+     "Local-data dictionary",
+     NULL},
+    {NULL}  /* Sentinel */
+};
+
+static PyTypeObject localtype = {
+	PyObject_HEAD_INIT(NULL)
+	/* ob_size           */ 0,
+	/* tp_name           */ "thread._local",
+	/* tp_basicsize      */ sizeof(localobject),
+	/* tp_itemsize       */ 0,
+	/* tp_dealloc        */ (destructor)local_dealloc,
+	/* tp_print          */ (printfunc)0,
+	/* tp_getattr        */ (getattrfunc)0,
+	/* tp_setattr        */ (setattrfunc)0,
+	/* tp_compare        */ (cmpfunc)0,
+	/* tp_repr           */ (reprfunc)0,
+	/* tp_as_number      */ 0,
+	/* tp_as_sequence    */ 0,
+	/* tp_as_mapping     */ 0,
+	/* tp_hash           */ (hashfunc)0,
+	/* tp_call           */ (ternaryfunc)0,
+	/* tp_str            */ (reprfunc)0,
+        /* tp_getattro       */ (getattrofunc)local_getattro,
+        /* tp_setattro       */ (setattrofunc)local_setattro,
+        /* tp_as_buffer      */ 0,
+        /* tp_flags          */ Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE,
+	/* tp_doc            */ "Thread-local data",
+        /* tp_traverse       */ (traverseproc)local_traverse,
+        /* tp_clear          */ (inquiry)local_clear,
+        /* tp_richcompare    */ (richcmpfunc)0,
+        /* tp_weaklistoffset */ (long)0,
+        /* tp_iter           */ (getiterfunc)0,
+        /* tp_iternext       */ (iternextfunc)0,
+        /* tp_methods        */ 0,
+        /* tp_members        */ 0,
+        /* tp_getset         */ local_getset,
+        /* tp_base           */ 0,
+        /* tp_dict           */ 0, /* internal use */
+        /* tp_descr_get      */ (descrgetfunc)0,
+        /* tp_descr_set      */ (descrsetfunc)0,
+        /* tp_dictoffset     */ offsetof(localobject, dict),
+        /* tp_init           */ (initproc)0,
+        /* tp_alloc          */ (allocfunc)0,
+        /* tp_new            */ (newfunc)local_new,
+	/* tp_free           */ 0, /* Low-level free-mem routine */
+	/* tp_is_gc          */ (inquiry)0, /* For PyObject_IS_GC */
+};
+
 
 /* Module functions */
 
@@ -389,6 +642,10 @@ PyMODINIT_FUNC
 initthread(void)
 {
 	PyObject *m, *d;
+        
+        /* Initialize types: */
+        if (PyType_Ready(&localtype) < 0)
+        	return;
 
 	/* Create the module and add the functions */
 	m = Py_InitModule3("thread", thread_methods, thread_doc);
@@ -401,6 +658,9 @@ initthread(void)
 	Py_INCREF(&Locktype);
 	PyDict_SetItemString(d, "LockType", (PyObject *)&Locktype);
 
+        if (PyModule_AddObject(m, "_local", (PyObject *)&localtype) < 0)
+        	return;
+
 	/* Initialize the C thread library */
 	PyThread_init_thread();
 }