cpython/Objects/codeobject.c

#include "Python.h"
#include "code.h"
#include "structmember.h"

#define NAME_CHARS \
	"0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ_abcdefghijklmnopqrstuvwxyz"

/* all_name_chars(s): true iff all chars in s are valid NAME_CHARS */

static int
all_name_chars(unsigned char *s)
{
	static char ok_name_char[256];
	static unsigned char *name_chars = (unsigned char *)NAME_CHARS;

	if (ok_name_char[*name_chars] == 0) {
		unsigned char *p;
		for (p = name_chars; *p; p++)
			ok_name_char[*p] = 1;
	}
	while (*s) {
		if (ok_name_char[*s++] == 0)
			return 0;
	}
	return 1;
}

static void
intern_strings(PyObject *tuple)
{
	Py_ssize_t i;

	for (i = PyTuple_GET_SIZE(tuple); --i >= 0; ) {
		PyObject *v = PyTuple_GET_ITEM(tuple, i);
		if (v == NULL || !PyString_CheckExact(v)) {
			Py_FatalError("non-string found in code slot");
		}
		PyString_InternInPlace(&PyTuple_GET_ITEM(tuple, i));
	}
}


PyCodeObject *
PyCode_New(int argcount, int nlocals, int stacksize, int flags,
	   PyObject *code, PyObject *consts, PyObject *names,
	   PyObject *varnames, PyObject *freevars, PyObject *cellvars,
	   PyObject *filename, PyObject *name, int firstlineno,
	   PyObject *lnotab)
{
	PyCodeObject *co;
	Py_ssize_t i;
	/* Check argument types */
	if (argcount < 0 || nlocals < 0 ||
	    code == NULL ||
	    consts == NULL || !PyTuple_Check(consts) ||
	    names == NULL || !PyTuple_Check(names) ||
	    varnames == NULL || !PyTuple_Check(varnames) ||
	    freevars == NULL || !PyTuple_Check(freevars) ||
	    cellvars == NULL || !PyTuple_Check(cellvars) ||
	    name == NULL || !PyString_Check(name) ||
	    filename == NULL || !PyString_Check(filename) ||
	    lnotab == NULL || !PyString_Check(lnotab) ||
	    !PyObject_CheckReadBuffer(code)) {
		PyErr_BadInternalCall();
		return NULL;
	}
	intern_strings(names);
	intern_strings(varnames);
	intern_strings(freevars);
	intern_strings(cellvars);
	/* Intern selected string constants */
	for (i = PyTuple_Size(consts); --i >= 0; ) {
		PyObject *v = PyTuple_GetItem(consts, i);
		if (!PyString_Check(v))
			continue;
		if (!all_name_chars((unsigned char *)PyString_AS_STRING(v)))
			continue;
		PyString_InternInPlace(&PyTuple_GET_ITEM(consts, i));
	}
	co = PyObject_NEW(PyCodeObject, &PyCode_Type);
	if (co != NULL) {
		co->co_argcount = argcount;
		co->co_nlocals = nlocals;
		co->co_stacksize = stacksize;
		co->co_flags = flags;
		Py_INCREF(code);
		co->co_code = code;
		Py_INCREF(consts);
		co->co_consts = consts;
		Py_INCREF(names);
		co->co_names = names;
		Py_INCREF(varnames);
		co->co_varnames = varnames;
		Py_INCREF(freevars);
		co->co_freevars = freevars;
		Py_INCREF(cellvars);
		co->co_cellvars = cellvars;
		Py_INCREF(filename);
		co->co_filename = filename;
		Py_INCREF(name);
		co->co_name = name;
		co->co_firstlineno = firstlineno;
		Py_INCREF(lnotab);
		co->co_lnotab = lnotab;
	}
	return co;
}


#define OFF(x) offsetof(PyCodeObject, x)

static PyMemberDef code_memberlist[] = {
	{"co_argcount",	T_INT,		OFF(co_argcount),	READONLY},
	{"co_nlocals",	T_INT,		OFF(co_nlocals),	READONLY},
	{"co_stacksize",T_INT,		OFF(co_stacksize),	READONLY},
	{"co_flags",	T_INT,		OFF(co_flags),		READONLY},
	{"co_code",	T_OBJECT,	OFF(co_code),		READONLY},
	{"co_consts",	T_OBJECT,	OFF(co_consts),		READONLY},
	{"co_names",	T_OBJECT,	OFF(co_names),		READONLY},
	{"co_varnames",	T_OBJECT,	OFF(co_varnames),	READONLY},
	{"co_freevars",	T_OBJECT,	OFF(co_freevars),	READONLY},
	{"co_cellvars",	T_OBJECT,	OFF(co_cellvars),	READONLY},
	{"co_filename",	T_OBJECT,	OFF(co_filename),	READONLY},
	{"co_name",	T_OBJECT,	OFF(co_name),		READONLY},
	{"co_firstlineno", T_INT,	OFF(co_firstlineno),	READONLY},
	{"co_lnotab",	T_OBJECT,	OFF(co_lnotab),		READONLY},
	{NULL}	/* Sentinel */
};

/* Helper for code_new: return a shallow copy of a tuple that is
   guaranteed to contain exact strings, by converting string subclasses
   to exact strings and complaining if a non-string is found. */
static PyObject*
validate_and_copy_tuple(PyObject *tup)
{
	PyObject *newtuple;
	PyObject *item;
	Py_ssize_t i, len;

	len = PyTuple_GET_SIZE(tup);
	newtuple = PyTuple_New(len);
	if (newtuple == NULL)
		return NULL;

	for (i = 0; i < len; i++) {
		item = PyTuple_GET_ITEM(tup, i);
		if (PyString_CheckExact(item)) {
			Py_INCREF(item);
		}
		else if (!PyString_Check(item)) {
			PyErr_Format(
				PyExc_TypeError,
				"name tuples must contain only "
				"strings, not '%.500s'",
				item->ob_type->tp_name);
			Py_DECREF(newtuple);
			return NULL;
		}
		else {
			item = PyString_FromStringAndSize(
				PyString_AS_STRING(item),
				PyString_GET_SIZE(item));
			if (item == NULL) {
				Py_DECREF(newtuple);
				return NULL;
			}
		}
		PyTuple_SET_ITEM(newtuple, i, item);
	}

	return newtuple;
}

PyDoc_STRVAR(code_doc,
"code(argcount, nlocals, stacksize, flags, codestring, constants, names,\n\
      varnames, filename, name, firstlineno, lnotab[, freevars[, cellvars]])\n\
\n\
Create a code object.  Not for the faint of heart.");

static PyObject *
code_new(PyTypeObject *type, PyObject *args, PyObject *kw)
{
	int argcount;
	int nlocals;
	int stacksize;
	int flags;
	PyObject *co = NULL;
	PyObject *code;
	PyObject *consts;
	PyObject *names, *ournames = NULL;
	PyObject *varnames, *ourvarnames = NULL;
	PyObject *freevars = NULL, *ourfreevars = NULL;
	PyObject *cellvars = NULL, *ourcellvars = NULL;
	PyObject *filename;
	PyObject *name;
	int firstlineno;
	PyObject *lnotab;

	if (!PyArg_ParseTuple(args, "iiiiSO!O!O!SSiS|O!O!:code",
			      &argcount, &nlocals, &stacksize, &flags,
			      &code,
			      &PyTuple_Type, &consts,
			      &PyTuple_Type, &names,
			      &PyTuple_Type, &varnames,
			      &filename, &name,
			      &firstlineno, &lnotab,
			      &PyTuple_Type, &freevars,
			      &PyTuple_Type, &cellvars))
		return NULL;

	if (argcount < 0) {
		PyErr_SetString(
			PyExc_ValueError,
			"code: argcount must not be negative");
		goto cleanup;
	}

	if (nlocals < 0) {
		PyErr_SetString(
			PyExc_ValueError,
			"code: nlocals must not be negative");
		goto cleanup;
	}

	ournames = validate_and_copy_tuple(names);
	if (ournames == NULL)
		goto cleanup;
	ourvarnames = validate_and_copy_tuple(varnames);
	if (ourvarnames == NULL)
		goto cleanup;
	if (freevars)
		ourfreevars = validate_and_copy_tuple(freevars);
	else
		ourfreevars = PyTuple_New(0);
	if (ourfreevars == NULL)
		goto cleanup;
	if (cellvars)
		ourcellvars = validate_and_copy_tuple(cellvars);
	else
		ourcellvars = PyTuple_New(0);
	if (ourcellvars == NULL)
		goto cleanup;

	co = (PyObject *)PyCode_New(argcount, nlocals, stacksize, flags,
				    code, consts, ournames, ourvarnames,
				    ourfreevars, ourcellvars, filename,
				    name, firstlineno, lnotab);
  cleanup:
	Py_XDECREF(ournames);
	Py_XDECREF(ourvarnames);
	Py_XDECREF(ourfreevars);
	Py_XDECREF(ourcellvars);
	return co;
}

static void
code_dealloc(PyCodeObject *co)
{
	Py_XDECREF(co->co_code);
	Py_XDECREF(co->co_consts);
	Py_XDECREF(co->co_names);
	Py_XDECREF(co->co_varnames);
	Py_XDECREF(co->co_freevars);
	Py_XDECREF(co->co_cellvars);
	Py_XDECREF(co->co_filename);
	Py_XDECREF(co->co_name);
	Py_XDECREF(co->co_lnotab);
	PyObject_DEL(co);
}

static PyObject *
code_repr(PyCodeObject *co)
{
	char buf[500];
	int lineno = -1;
	char *filename = "???";
	char *name = "???";

	if (co->co_firstlineno != 0)
		lineno = co->co_firstlineno;
	if (co->co_filename && PyString_Check(co->co_filename))
		filename = PyString_AS_STRING(co->co_filename);
	if (co->co_name && PyString_Check(co->co_name))
		name = PyString_AS_STRING(co->co_name);
	PyOS_snprintf(buf, sizeof(buf),
		      "<code object %.100s at %p, file \"%.300s\", line %d>",
		      name, co, filename, lineno);
	return PyString_FromString(buf);
}

static int
code_compare(PyCodeObject *co, PyCodeObject *cp)
{
	int cmp;
	cmp = PyObject_Compare(co->co_name, cp->co_name);
	if (cmp) return cmp;
	cmp = co->co_argcount - cp->co_argcount;
	if (cmp) goto normalize;
	cmp = co->co_nlocals - cp->co_nlocals;
	if (cmp) goto normalize;
	cmp = co->co_flags - cp->co_flags;
	if (cmp) goto normalize;
	cmp = co->co_firstlineno - cp->co_firstlineno;
	if (cmp) goto normalize;
	cmp = PyObject_Compare(co->co_code, cp->co_code);
	if (cmp) return cmp;
	cmp = PyObject_Compare(co->co_consts, cp->co_consts);
	if (cmp) return cmp;
	cmp = PyObject_Compare(co->co_names, cp->co_names);
	if (cmp) return cmp;
	cmp = PyObject_Compare(co->co_varnames, cp->co_varnames);
	if (cmp) return cmp;
	cmp = PyObject_Compare(co->co_freevars, cp->co_freevars);
	if (cmp) return cmp;
	cmp = PyObject_Compare(co->co_cellvars, cp->co_cellvars);
	return cmp;

 normalize:
	if (cmp > 0)
		return 1;
	else if (cmp < 0)
		return -1;
	else
		return 0;
}

static long
code_hash(PyCodeObject *co)
{
	long h, h0, h1, h2, h3, h4, h5, h6;
	h0 = PyObject_Hash(co->co_name);
	if (h0 == -1) return -1;
	h1 = PyObject_Hash(co->co_code);
	if (h1 == -1) return -1;
	h2 = PyObject_Hash(co->co_consts);
	if (h2 == -1) return -1;
	h3 = PyObject_Hash(co->co_names);
	if (h3 == -1) return -1;
	h4 = PyObject_Hash(co->co_varnames);
	if (h4 == -1) return -1;
	h5 = PyObject_Hash(co->co_freevars);
	if (h5 == -1) return -1;
	h6 = PyObject_Hash(co->co_cellvars);
	if (h6 == -1) return -1;
	h = h0 ^ h1 ^ h2 ^ h3 ^ h4 ^ h5 ^ h6 ^
		co->co_argcount ^ co->co_nlocals ^ co->co_flags;
	if (h == -1) h = -2;
	return h;
}

/* XXX code objects need to participate in GC? */

PyTypeObject PyCode_Type = {
	PyObject_HEAD_INIT(&PyType_Type)
	0,
	"code",
	sizeof(PyCodeObject),
	0,
	(destructor)code_dealloc, 	/* tp_dealloc */
	0,				/* tp_print */
	0, 				/* tp_getattr */
	0,				/* tp_setattr */
	(cmpfunc)code_compare, 		/* tp_compare */
	(reprfunc)code_repr,		/* tp_repr */
	0,				/* tp_as_number */
	0,				/* tp_as_sequence */
	0,				/* tp_as_mapping */
	(hashfunc)code_hash, 		/* tp_hash */
	0,				/* tp_call */
	0,				/* tp_str */
	PyObject_GenericGetAttr,	/* tp_getattro */
	0,				/* tp_setattro */
	0,				/* tp_as_buffer */
	Py_TPFLAGS_DEFAULT,		/* tp_flags */
	code_doc,			/* tp_doc */
	0,				/* tp_traverse */
	0,				/* tp_clear */
	0,				/* tp_richcompare */
	0,				/* tp_weaklistoffset */
	0,				/* tp_iter */
	0,				/* tp_iternext */
	0,				/* tp_methods */
	code_memberlist,		/* tp_members */
	0,				/* 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 */
	code_new,			/* tp_new */
};

/* All about c_lnotab.

c_lnotab is an array of unsigned bytes disguised as a Python string.  In -O
mode, SET_LINENO opcodes aren't generated, and bytecode offsets are mapped
to source code line #s (when needed for tracebacks) via c_lnotab instead.
The array is conceptually a list of
    (bytecode offset increment, line number increment)
pairs.  The details are important and delicate, best illustrated by example:

    byte code offset    source code line number
        0		    1
        6		    2
       50		    7
      350                 307
      361                 308

The first trick is that these numbers aren't stored, only the increments
from one row to the next (this doesn't really work, but it's a start):

    0, 1,  6, 1,  44, 5,  300, 300,  11, 1

The second trick is that an unsigned byte can't hold negative values, or
values larger than 255, so (a) there's a deep assumption that byte code
offsets and their corresponding line #s both increase monotonically, and (b)
if at least one column jumps by more than 255 from one row to the next, more
than one pair is written to the table. In case #b, there's no way to know
from looking at the table later how many were written.  That's the delicate
part.  A user of c_lnotab desiring to find the source line number
corresponding to a bytecode address A should do something like this

    lineno = addr = 0
    for addr_incr, line_incr in c_lnotab:
        addr += addr_incr
        if addr > A:
            return lineno
        lineno += line_incr

In order for this to work, when the addr field increments by more than 255,
the line # increment in each pair generated must be 0 until the remaining addr
increment is < 256.  So, in the example above, com_set_lineno should not (as
was actually done until 2.2) expand 300, 300 to 255, 255,  45, 45, but to
255, 0,  45, 255,  0, 45.
*/

int
PyCode_Addr2Line(PyCodeObject *co, int addrq)
{
	int size = PyString_Size(co->co_lnotab) / 2;
	unsigned char *p = (unsigned char*)PyString_AsString(co->co_lnotab);
	int line = co->co_firstlineno;
	int addr = 0;
	while (--size >= 0) {
		addr += *p++;
		if (addr > addrq)
			break;
		line += *p++;
	}
	return line;
}