/* string_format.h -- implementation of string.format(). It uses the Objects/stringlib conventions, so that it can be compiled for both unicode and string objects. */ /* Defines for more efficiently reallocating the string buffer */ #define INITIAL_SIZE_INCREMENT 100 #define SIZE_MULTIPLIER 2 #define MAX_SIZE_INCREMENT 3200 /************************************************************************/ /*********** Global data structures and forward declarations *********/ /************************************************************************/ /* A SubString consists of the characters between two string or unicode pointers. */ typedef struct { STRINGLIB_CHAR *ptr; STRINGLIB_CHAR *end; } SubString; /* forward declaration for recursion */ static PyObject * build_string(SubString *input, PyObject *args, PyObject *kwargs, int *recursion_level); /************************************************************************/ /************************** Utility functions ************************/ /************************************************************************/ /* fill in a SubString from a pointer and length */ Py_LOCAL_INLINE(void) SubString_init(SubString *str, STRINGLIB_CHAR *p, Py_ssize_t len) { str->ptr = p; if (p == NULL) str->end = NULL; else str->end = str->ptr + len; } Py_LOCAL_INLINE(PyObject *) SubString_new_object(SubString *str) { return STRINGLIB_NEW(str->ptr, str->end - str->ptr); } /************************************************************************/ /*********** Error handling and exception generation **************/ /************************************************************************/ /* Most of our errors are value errors, because to Python, the format string is a "value". Also, it's convenient to return a NULL when we are erroring out. XXX: need better error handling, per PEP 3101. */ static void * SetError(const char *s) { /* PyErr_Format always returns NULL */ return PyErr_Format(PyExc_ValueError, "%s in format string", s); } /************************************************************************/ /*********** Output string management functions ****************/ /************************************************************************/ typedef struct { STRINGLIB_CHAR *ptr; STRINGLIB_CHAR *end; PyObject *obj; Py_ssize_t size_increment; } OutputString; /* initialize an OutputString object, reserving size characters */ static int output_initialize(OutputString *output, Py_ssize_t size) { output->obj = STRINGLIB_NEW(NULL, size); if (output->obj == NULL) return 0; output->ptr = STRINGLIB_STR(output->obj); output->end = STRINGLIB_LEN(output->obj) + output->ptr; output->size_increment = INITIAL_SIZE_INCREMENT; return 1; } /* output_extend reallocates the output string buffer. It returns a status: 0 for a failed reallocation, 1 for success. */ static int output_extend(OutputString *output, Py_ssize_t count) { STRINGLIB_CHAR *startptr = STRINGLIB_STR(output->obj); Py_ssize_t curlen = output->ptr - startptr; Py_ssize_t maxlen = curlen + count + output->size_increment; if (STRINGLIB_RESIZE(&output->obj, maxlen) < 0) return 0; startptr = STRINGLIB_STR(output->obj); output->ptr = startptr + curlen; output->end = startptr + maxlen; if (output->size_increment < MAX_SIZE_INCREMENT) output->size_increment *= SIZE_MULTIPLIER; return 1; } /* output_data dumps characters into our output string buffer. In some cases, it has to reallocate the string. It returns a status: 0 for a failed reallocation, 1 for success. */ static int output_data(OutputString *output, const STRINGLIB_CHAR *s, Py_ssize_t count) { if ((count > output->end - output->ptr) && !output_extend(output, count)) return 0; memcpy(output->ptr, s, count * sizeof(STRINGLIB_CHAR)); output->ptr += count; return 1; } /************************************************************************/ /*********** Format string parsing -- integers and identifiers *********/ /************************************************************************/ static Py_ssize_t get_integer(const SubString *str) { Py_ssize_t accumulator = 0; Py_ssize_t digitval; Py_ssize_t oldaccumulator; STRINGLIB_CHAR *p; /* empty string is an error */ if (str->ptr >= str->end) return -1; for (p = str->ptr; p < str->end; p++) { digitval = STRINGLIB_TODECIMAL(*p); if (digitval < 0) return -1; /* This trick was copied from old Unicode format code. It's cute, but would really suck on an old machine with a slow divide implementation. Fortunately, in the normal case we do not expect too many digits. */ oldaccumulator = accumulator; accumulator *= 10; if ((accumulator+10)/10 != oldaccumulator+1) { PyErr_Format(PyExc_ValueError, "Too many decimal digits in format string"); return -1; } accumulator += digitval; } return accumulator; } /************************************************************************/ /******** Functions to get field objects and specification strings ******/ /************************************************************************/ /* do the equivalent of obj.name */ static PyObject * getattr(PyObject *obj, SubString *name) { PyObject *newobj; PyObject *str = STRINGLIB_NEW(name->ptr, name->end - name->ptr); if (str == NULL) return NULL; newobj = PyObject_GetAttr(obj, str); Py_DECREF(str); return newobj; } /* do the equivalent of obj[idx], where obj is a sequence */ static PyObject * getitem_sequence(PyObject *obj, Py_ssize_t idx) { return PySequence_GetItem(obj, idx); } /* do the equivalent of obj[idx], where obj is not a sequence */ static PyObject * getitem_idx(PyObject *obj, Py_ssize_t idx) { PyObject *newobj; PyObject *idx_obj = PyInt_FromSsize_t(idx); if (idx_obj == NULL) return NULL; newobj = PyObject_GetItem(obj, idx_obj); Py_DECREF(idx_obj); return newobj; } /* do the equivalent of obj[name] */ static PyObject * getitem_str(PyObject *obj, SubString *name) { PyObject *newobj; PyObject *str = STRINGLIB_NEW(name->ptr, name->end - name->ptr); if (str == NULL) return NULL; newobj = PyObject_GetItem(obj, str); Py_DECREF(str); return newobj; } typedef struct { /* the entire string we're parsing. we assume that someone else is managing its lifetime, and that it will exist for the lifetime of the iterator. can be empty */ SubString str; /* pointer to where we are inside field_name */ STRINGLIB_CHAR *ptr; } FieldNameIterator; static int FieldNameIterator_init(FieldNameIterator *self, STRINGLIB_CHAR *ptr, Py_ssize_t len) { SubString_init(&self->str, ptr, len); self->ptr = self->str.ptr; return 1; } static int _FieldNameIterator_attr(FieldNameIterator *self, SubString *name) { STRINGLIB_CHAR c; name->ptr = self->ptr; /* return everything until '.' or '[' */ while (self->ptr < self->str.end) { switch (c = *self->ptr++) { case '[': case '.': /* backup so that we this character will be seen next time */ self->ptr--; break; default: continue; } break; } /* end of string is okay */ name->end = self->ptr; return 1; } static int _FieldNameIterator_item(FieldNameIterator *self, SubString *name) { STRINGLIB_CHAR c; name->ptr = self->ptr; /* return everything until ']' */ while (self->ptr < self->str.end) { switch (c = *self->ptr++) { case ']': break; default: continue; } break; } /* end of string is okay */ /* don't include the ']' */ name->end = self->ptr-1; return 1; } /* returns 0 on error, 1 on non-error termination, and 2 if it returns a value */ static int FieldNameIterator_next(FieldNameIterator *self, int *is_attribute, Py_ssize_t *name_idx, SubString *name) { /* check at end of input */ if (self->ptr >= self->str.end) return 1; switch (*self->ptr++) { case '.': *is_attribute = 1; if (_FieldNameIterator_attr(self, name) == 0) { return 0; } *name_idx = -1; break; case '[': *is_attribute = 0; if (_FieldNameIterator_item(self, name) == 0) { return 0; } *name_idx = get_integer(name); break; default: /* interal error, can't get here */ assert(0); return 0; } /* empty string is an error */ if (name->ptr == name->end) { PyErr_SetString(PyExc_ValueError, "Empty attribute in format string"); return 0; } return 2; } /* input: field_name output: 'first' points to the part before the first '[' or '.' 'first_idx' is -1 if 'first' is not an integer, otherwise it's the value of first converted to an integer 'rest' is an iterator to return the rest */ static int field_name_split(STRINGLIB_CHAR *ptr, Py_ssize_t len, SubString *first, Py_ssize_t *first_idx, FieldNameIterator *rest) { STRINGLIB_CHAR c; STRINGLIB_CHAR *p = ptr; STRINGLIB_CHAR *end = ptr + len; /* find the part up until the first '.' or '[' */ while (p < end) { switch (c = *p++) { case '[': case '.': /* backup so that we this character is available to the "rest" iterator */ p--; break; default: continue; } break; } /* set up the return values */ SubString_init(first, ptr, p - ptr); FieldNameIterator_init(rest, p, end - p); /* see if "first" is an integer, in which case it's used as an index */ *first_idx = get_integer(first); /* zero length string is an error */ if (first->ptr >= first->end) { PyErr_SetString(PyExc_ValueError, "empty field name"); goto error; } return 1; error: return 0; } /* get_field_object returns the object inside {}, before the format_spec. It handles getindex and getattr lookups and consumes the entire input string. */ static PyObject * get_field_object(SubString *input, PyObject *args, PyObject *kwargs) { PyObject *obj = NULL; int ok; int is_attribute; SubString name; SubString first; Py_ssize_t index; FieldNameIterator rest; if (!field_name_split(input->ptr, input->end - input->ptr, &first, &index, &rest)) { goto error; } if (index == -1) { /* look up in kwargs */ PyObject *key = STRINGLIB_NEW(first.ptr, first.end - first.ptr); if (key == NULL) goto error; if ((kwargs == NULL) || (obj = PyDict_GetItem(kwargs, key)) == NULL) { PyErr_SetString(PyExc_ValueError, "Keyword argument not found " "in format string"); Py_DECREF(key); goto error; } Py_DECREF(key); Py_INCREF(obj); } else { /* look up in args */ obj = PySequence_GetItem(args, index); if (obj == NULL) { /* translate IndexError to a ValueError */ PyErr_SetString(PyExc_ValueError, "Not enough positional arguments " "in format string"); goto error; } } /* iterate over the rest of the field_name */ while ((ok = FieldNameIterator_next(&rest, &is_attribute, &index, &name)) == 2) { PyObject *tmp; if (is_attribute) /* getattr lookup "." */ tmp = getattr(obj, &name); else /* getitem lookup "[]" */ if (index == -1) tmp = getitem_str(obj, &name); else if (PySequence_Check(obj)) tmp = getitem_sequence(obj, index); else /* not a sequence */ tmp = getitem_idx(obj, index); if (tmp == NULL) goto error; /* assign to obj */ Py_DECREF(obj); obj = tmp; } /* end of iterator, this is the non-error case */ if (ok == 1) return obj; error: Py_XDECREF(obj); return NULL; } /************************************************************************/ /***************** Field rendering functions **************************/ /************************************************************************/ /* render_field() is the main function in this section. It takes the field object and field specification string generated by get_field_and_spec, and renders the field into the output string. format() does the actual calling of the objects __format__ method. */ /* returns fieldobj.__format__(format_spec) */ static PyObject * format(PyObject *fieldobj, SubString *format_spec) { static PyObject *format_str = NULL; PyObject *meth; PyObject *spec = NULL; PyObject *result = NULL; /* Initialize cached value */ if (format_str == NULL) { /* Initialize static variable needed by _PyType_Lookup */ format_str = PyUnicode_FromString("__format__"); if (format_str == NULL) return NULL; } /* Make sure the type is initialized. float gets initialized late */ if (Py_Type(fieldobj)->tp_dict == NULL) if (PyType_Ready(Py_Type(fieldobj)) < 0) return NULL; /* we need to create an object out of the pointers we have */ spec = SubString_new_object(format_spec); if (spec == NULL) goto done; /* Find the (unbound!) __format__ method (a borrowed reference) */ meth = _PyType_Lookup(Py_Type(fieldobj), format_str); if (meth == NULL) { PyErr_Format(PyExc_TypeError, "Type %.100s doesn't define __format__", Py_Type(fieldobj)->tp_name); goto done; } /* And call it, binding it to the value */ result = PyObject_CallFunctionObjArgs(meth, fieldobj, spec, NULL); if (result == NULL) goto done; if (!STRINGLIB_CHECK(result)) { PyErr_SetString(PyExc_TypeError, "__format__ method did not return " STRINGLIB_TYPE_NAME); Py_DECREF(result); result = NULL; goto done; } done: Py_XDECREF(spec); return result; } /* render_field calls fieldobj.__format__(format_spec) method, and appends to the output. */ static int render_field(PyObject *fieldobj, SubString *format_spec, OutputString *output) { int ok = 0; PyObject *result = format(fieldobj, format_spec); if (result == NULL) goto done; ok = output_data(output, STRINGLIB_STR(result), STRINGLIB_LEN(result)); done: Py_XDECREF(result); return ok; } static int parse_field(SubString *str, SubString *field_name, SubString *format_spec, STRINGLIB_CHAR *conversion) { STRINGLIB_CHAR c = 0; /* initialize these, as they may be empty */ *conversion = '\0'; SubString_init(format_spec, NULL, 0); /* search for the field name. it's terminated by the end of the string, or a ':' or '!' */ field_name->ptr = str->ptr; while (str->ptr < str->end) { switch (c = *(str->ptr++)) { case ':': case '!': break; default: continue; } break; } if (c == '!' || c == ':') { /* we have a format specifier and/or a conversion */ /* don't include the last character */ field_name->end = str->ptr-1; /* the format specifier is the rest of the string */ format_spec->ptr = str->ptr; format_spec->end = str->end; /* see if there's a conversion specifier */ if (c == '!') { /* there must be another character present */ if (format_spec->ptr >= format_spec->end) { PyErr_SetString(PyExc_ValueError, "end of format while looking for conversion " "specifier"); return 0; } *conversion = *(format_spec->ptr++); /* if there is another character, it must be a colon */ if (format_spec->ptr < format_spec->end) { c = *(format_spec->ptr++); if (c != ':') { PyErr_SetString(PyExc_ValueError, "expected ':' after format specifier"); return 0; } } } return 1; } else { /* end of string, there's no format_spec or conversion */ field_name->end = str->ptr; return 1; } } /************************************************************************/ /******* Output string allocation and escape-to-markup processing ******/ /************************************************************************/ /* MarkupIterator breaks the string into pieces of either literal text, or things inside {} that need to be marked up. it is designed to make it easy to wrap a Python iterator around it, for use with the Formatter class */ typedef struct { SubString str; int in_markup; } MarkupIterator; static int MarkupIterator_init(MarkupIterator *self, STRINGLIB_CHAR *ptr, Py_ssize_t len) { SubString_init(&self->str, ptr, len); self->in_markup = 0; return 1; } /* returns 0 on error, 1 on non-error termination, and 2 if it got a string (or something to be expanded) */ static int MarkupIterator_next(MarkupIterator *self, int *is_markup, SubString *literal, SubString *field_name, SubString *format_spec, STRINGLIB_CHAR *conversion, int *format_spec_needs_expanding) { int at_end; STRINGLIB_CHAR c = 0; STRINGLIB_CHAR *start; int count; Py_ssize_t len; *format_spec_needs_expanding = 0; /* no more input, end of iterator */ if (self->str.ptr >= self->str.end) return 1; *is_markup = self->in_markup; start = self->str.ptr; if (self->in_markup) { /* prepare for next iteration */ self->in_markup = 0; /* this is markup, find the end of the string by counting nested braces. note that this prohibits escaped braces, so that format_specs cannot have braces in them. */ count = 1; /* we know we can't have a zero length string, so don't worry about that case */ while (self->str.ptr < self->str.end) { switch (c = *(self->str.ptr++)) { case '{': /* the format spec needs to be recursively expanded. this is an optimization, and not strictly needed */ *format_spec_needs_expanding = 1; count++; break; case '}': count--; if (count <= 0) { /* we're done. parse and get out */ literal->ptr = start; literal->end = self->str.ptr-1; if (parse_field(literal, field_name, format_spec, conversion) == 0) return 0; /* success */ return 2; } break; } } /* end of string while searching for matching '}' */ PyErr_SetString(PyExc_ValueError, "unmatched '{' in format"); return 0; } else { /* literal text, read until the end of string, an escaped { or }, or an unescaped { */ while (self->str.ptr < self->str.end) { switch (c = *(self->str.ptr++)) { case '{': case '}': self->in_markup = 1; break; default: continue; } break; } at_end = self->str.ptr >= self->str.end; len = self->str.ptr - start; if ((c == '}') && (at_end || (c != *self->str.ptr))) { SetError("Single } encountered"); return 0; } if (at_end && c == '{') { SetError("Single { encountered"); return 0; } if (!at_end) { if (c == *self->str.ptr) { /* escaped } or {, skip it in the input */ self->str.ptr++; self->in_markup = 0; } else len--; } /* this is just plain text, return it */ literal->ptr = start; literal->end = start + len; return 2; } } /* do the !r or !s conversion on obj */ static PyObject * do_conversion(PyObject *obj, STRINGLIB_CHAR conversion) { /* XXX in pre-3.0, do we need to convert this to unicode, since it might have returned a string? */ switch (conversion) { case 'r': return PyObject_Repr(obj); case 's': return PyObject_Unicode(obj); default: PyErr_Format(PyExc_ValueError, "Unknown converion specifier %c", conversion); return NULL; } } /* given: {field_name!conversion:format_spec} compute the result and write it to output. format_spec_needs_expanding is an optimization. if it's false, just output the string directly, otherwise recursively expand the format_spec string. */ static int output_markup(SubString *field_name, SubString *format_spec, int format_spec_needs_expanding, STRINGLIB_CHAR conversion, OutputString *output, PyObject *args, PyObject *kwargs, int *recursion_level) { PyObject *tmp = NULL; PyObject *fieldobj = NULL; SubString expanded_format_spec; SubString *actual_format_spec; int result = 0; /* convert field_name to an object */ fieldobj = get_field_object(field_name, args, kwargs); if (fieldobj == NULL) goto done; if (conversion != '\0') { tmp = do_conversion(fieldobj, conversion); if (tmp == NULL) goto done; /* do the assignment, transferring ownership: fieldobj = tmp */ Py_DECREF(fieldobj); fieldobj = tmp; tmp = NULL; } /* if needed, recurively compute the format_spec */ if (format_spec_needs_expanding) { tmp = build_string(format_spec, args, kwargs, recursion_level); if (tmp == NULL) goto done; /* note that in the case we're expanding the format string, tmp must be kept around until after the call to render_field. */ SubString_init(&expanded_format_spec, STRINGLIB_STR(tmp), STRINGLIB_LEN(tmp)); actual_format_spec = &expanded_format_spec; } else actual_format_spec = format_spec; if (render_field(fieldobj, actual_format_spec, output) == 0) goto done; result = 1; done: Py_XDECREF(fieldobj); Py_XDECREF(tmp); return result; } /* do_markup is the top-level loop for the format() function. It searches through the format string for escapes to markup codes, and calls other functions to move non-markup text to the output, and to perform the markup to the output. */ static int do_markup(SubString *input, PyObject *args, PyObject *kwargs, OutputString *output, int *recursion_level) { MarkupIterator iter; int is_markup; int format_spec_needs_expanding; int result; SubString str; SubString field_name; SubString format_spec; STRINGLIB_CHAR conversion; MarkupIterator_init(&iter, input->ptr, input->end - input->ptr); while ((result = MarkupIterator_next(&iter, &is_markup, &str, &field_name, &format_spec, &conversion, &format_spec_needs_expanding)) == 2) { if (is_markup) { if (!output_markup(&field_name, &format_spec, format_spec_needs_expanding, conversion, output, args, kwargs, recursion_level)) return 0; } else { if (!output_data(output, str.ptr, str.end-str.ptr)) return 0; } } return result; } /* build_string allocates the output string and then calls do_markup to do the heavy lifting. */ static PyObject * build_string(SubString *input, PyObject *args, PyObject *kwargs, int *recursion_level) { OutputString output; PyObject *result = NULL; Py_ssize_t count; output.obj = NULL; /* needed so cleanup code always works */ /* check the recursion level */ (*recursion_level)--; if (*recursion_level < 0) { PyErr_SetString(PyExc_ValueError, "Max string recursion exceeded"); goto done; } /* initial size is the length of the format string, plus the size increment. seems like a reasonable default */ if (!output_initialize(&output, input->end - input->ptr + INITIAL_SIZE_INCREMENT)) goto done; if (!do_markup(input, args, kwargs, &output, recursion_level)) { goto done; } count = output.ptr - STRINGLIB_STR(output.obj); if (STRINGLIB_RESIZE(&output.obj, count) < 0) { goto done; } /* transfer ownership to result */ result = output.obj; output.obj = NULL; done: (*recursion_level)++; Py_XDECREF(output.obj); return result; } /************************************************************************/ /*********** main routine ***********************************************/ /************************************************************************/ /* this is the main entry point */ static PyObject * do_string_format(PyObject *self, PyObject *args, PyObject *kwargs) { SubString input; /* PEP 3101 says only 2 levels, so that "{0:{1}}".format('abc', 's') # works "{0:{1:{2}}}".format('abc', 's', '') # fails */ int recursion_level = 2; SubString_init(&input, STRINGLIB_STR(self), STRINGLIB_LEN(self)); return build_string(&input, args, kwargs, &recursion_level); }