Move reference material on PyArg_Parse*() out of the Extending & Embedding
document to the C API reference. Move some instructional text from the API
reference to the Extending & Embedding manual.
Fix the descriptions of the es and es# formats for PyArg_Parse*().
This closes SF bug #536516.
diff --git a/Doc/api/utilities.tex b/Doc/api/utilities.tex
index a5ffe3a..96ff816 100644
--- a/Doc/api/utilities.tex
+++ b/Doc/api/utilities.tex
@@ -357,13 +357,291 @@
\citetitle[../ext/ext.html]{Extending and Embedding the Python
Interpreter}.
+The first three of these functions described,
+\cfunction{PyArg_ParseTuple()},
+\cfunction{PyArg_ParseTupleAndKeywords()}, and
+\cfunction{PyArg_Parse()}, all use \emph{format strings} which are
+used to tell the function about the expected arguments. The format
+strings use the same syntax for each of these functions.
+
+A format string consists of zero or more ``format units.'' A format
+unit describes one Python object; it is usually a single character or
+a parenthesized sequence of format units. With a few exceptions, a
+format unit that is not a parenthesized sequence normally corresponds
+to a single address argument to these functions. In the following
+description, the quoted form is the format unit; the entry in (round)
+parentheses is the Python object type that matches the format unit;
+and the entry in [square] brackets is the type of the C variable(s)
+whose address should be passed.
+
+\begin{description}
+ \item[\samp{s} (string or Unicode object) {[char *]}]
+ Convert a Python string or Unicode object to a C pointer to a
+ character string. You must not provide storage for the string
+ itself; a pointer to an existing string is stored into the character
+ pointer variable whose address you pass. The C string is
+ NUL-terminated. The Python string must not contain embedded NUL
+ bytes; if it does, a \exception{TypeError} exception is raised.
+ Unicode objects are converted to C strings using the default
+ encoding. If this conversion fails, a \exception{UnicodeError} is
+ raised.
+
+ \item[\samp{s\#} (string, Unicode or any read buffer compatible object)
+ {[char *, int]}]
+ This variant on \samp{s} stores into two C variables, the first one
+ a pointer to a character string, the second one its length. In this
+ case the Python string may contain embedded null bytes. Unicode
+ objects pass back a pointer to the default encoded string version of
+ the object if such a conversion is possible. All other read-buffer
+ compatible objects pass back a reference to the raw internal data
+ representation.
+
+ \item[\samp{z} (string or \code{None}) {[char *]}]
+ Like \samp{s}, but the Python object may also be \code{None}, in
+ which case the C pointer is set to \NULL.
+
+ \item[\samp{z\#} (string or \code{None} or any read buffer
+ compatible object) {[char *, int]}]
+ This is to \samp{s\#} as \samp{z} is to \samp{s}.
+
+ \item[\samp{u} (Unicode object) {[Py_UNICODE *]}]
+ Convert a Python Unicode object to a C pointer to a NUL-terminated
+ buffer of 16-bit Unicode (UTF-16) data. As with \samp{s}, there is
+ no need to provide storage for the Unicode data buffer; a pointer to
+ the existing Unicode data is stored into the \ctype{Py_UNICODE}
+ pointer variable whose address you pass.
+
+ \item[\samp{u\#} (Unicode object) {[Py_UNICODE *, int]}]
+ This variant on \samp{u} stores into two C variables, the first one
+ a pointer to a Unicode data buffer, the second one its length.
+ Non-Unicode objects are handled by interpreting their read-buffer
+ pointer as pointer to a \ctype{Py_UNICODE} array.
+
+ \item[\samp{es} (string, Unicode object or character buffer
+ compatible object) {[const char *encoding, char **buffer]}]
+ This variant on \samp{s} is used for encoding Unicode and objects
+ convertible to Unicode into a character buffer. It only works for
+ encoded data without embedded NUL bytes.
+
+ This format requires two arguments. The first is only used as
+ input, and must be a \ctype{char*} which points to the name of an
+ encoding as a NUL-terminated string, or \NULL, in which case the
+ default encoding is used. An exception is raised if the named
+ encoding is not known to Python. The second argument must be a
+ \ctype{char**}; the value of the pointer it references will be set
+ to a buffer with the contents of the argument text. The text will
+ be encoded in the encoding specified by the first argument.
+
+ \cfunction{PyArg_ParseTuple()} will allocate a buffer of the needed
+ size, copy the encoded data into this buffer and adjust
+ \var{*buffer} to reference the newly allocated storage. The caller
+ is responsible for calling \cfunction{PyMem_Free()} to free the
+ allocated buffer after use.
+
+ \item[\samp{et} (string, Unicode object or character buffer
+ compatible object) {[const char *encoding, char **buffer]}]
+ Same as \samp{es} except that 8-bit string objects are passed
+ through without recoding them. Instead, the implementation assumes
+ that the string object uses the encoding passed in as parameter.
+
+ \item[\samp{es\#} (string, Unicode object or character buffer compatible
+ object) {[const char *encoding, char **buffer, int *buffer_length]}]
+ This variant on \samp{s\#} is used for encoding Unicode and objects
+ convertible to Unicode into a character buffer. Unlike the
+ \samp{es} format, this variant allows input data which contains NUL
+ characters.
+
+ It requires three arguments. The first is only used as input, and
+ must be a \ctype{char*} which points to the name of an encoding as a
+ NUL-terminated string, or \NULL, in which case the default encoding
+ is used. An exception is raised if the named encoding is not known
+ to Python. The second argument must be a \ctype{char**}; the value
+ of the pointer it references will be set to a buffer with the
+ contents of the argument text. The text will be encoded in the
+ encoding specified by the first argument. The third argument must
+ be a pointer to an integer; the referenced integer will be set to
+ the number of bytes in the output buffer.
+
+ There are two modes of operation:
+
+ If \var{*buffer} points a \NULL{} pointer, the function will
+ allocate a buffer of the needed size, copy the encoded data into
+ this buffer and set \var{*buffer} to reference the newly allocated
+ storage. The caller is responsible for calling
+ \cfunction{PyMem_Free()} to free the allocated buffer after usage.
+
+ If \var{*buffer} points to a non-\NULL{} pointer (an already
+ allocated buffer), \cfunction{PyArg_ParseTuple()} will use this
+ location as the buffer and interpret the initial value of
+ \var{*buffer_length} as the buffer size. It will then copy the
+ encoded data into the buffer and NUL-terminate it. If the buffer
+ is not large enough, a \exception{ValueError} will be set.
+
+ In both cases, \var{*buffer_length} is set to the length of the
+ encoded data without the trailing NUL byte.
+
+ \item[\samp{et\#} (string, Unicode object or character buffer compatible
+ object) {[const char *encoding, char **buffer]}]
+ Same as \samp{es\#} except that string objects are passed through
+ without recoding them. Instead, the implementation assumes that the
+ string object uses the encoding passed in as parameter.
+
+ \item[\samp{b} (integer) {[char]}]
+ Convert a Python integer to a tiny int, stored in a C \ctype{char}.
+
+ \item[\samp{h} (integer) {[short int]}]
+ Convert a Python integer to a C \ctype{short int}.
+
+ \item[\samp{i} (integer) {[int]}]
+ Convert a Python integer to a plain C \ctype{int}.
+
+ \item[\samp{l} (integer) {[long int]}]
+ Convert a Python integer to a C \ctype{long int}.
+
+ \item[\samp{L} (integer) {[LONG_LONG]}]
+ Convert a Python integer to a C \ctype{long long}. This format is
+ only available on platforms that support \ctype{long long} (or
+ \ctype{_int64} on Windows).
+
+ \item[\samp{c} (string of length 1) {[char]}]
+ Convert a Python character, represented as a string of length 1, to
+ a C \ctype{char}.
+
+ \item[\samp{f} (float) {[float]}]
+ Convert a Python floating point number to a C \ctype{float}.
+
+ \item[\samp{d} (float) {[double]}]
+ Convert a Python floating point number to a C \ctype{double}.
+
+ \item[\samp{D} (complex) {[Py_complex]}]
+ Convert a Python complex number to a C \ctype{Py_complex} structure.
+
+ \item[\samp{O} (object) {[PyObject *]}]
+ Store a Python object (without any conversion) in a C object
+ pointer. The C program thus receives the actual object that was
+ passed. The object's reference count is not increased. The pointer
+ stored is not \NULL.
+
+ \item[\samp{O!} (object) {[\var{typeobject}, PyObject *]}]
+ Store a Python object in a C object pointer. This is similar to
+ \samp{O}, but takes two C arguments: the first is the address of a
+ Python type object, the second is the address of the C variable (of
+ type \ctype{PyObject*}) into which the object pointer is stored. If
+ the Python object does not have the required type,
+ \exception{TypeError} is raised.
+
+ \item[\samp{O\&} (object) {[\var{converter}, \var{anything}]}]
+ Convert a Python object to a C variable through a \var{converter}
+ function. This takes two arguments: the first is a function, the
+ second is the address of a C variable (of arbitrary type), converted
+ to \ctype{void *}. The \var{converter} function in turn is called
+ as follows:
+
+ \var{status}\code{ = }\var{converter}\code{(}\var{object},
+ \var{address}\code{);}
+
+ where \var{object} is the Python object to be converted and
+ \var{address} is the \ctype{void*} argument that was passed to the
+ \cfunction{PyArg_Parse*()} function. The returned \var{status}
+ should be \code{1} for a successful conversion and \code{0} if the
+ conversion has failed. When the conversion fails, the
+ \var{converter} function should raise an exception.
+
+ \item[\samp{S} (string) {[PyStringObject *]}]
+ Like \samp{O} but requires that the Python object is a string
+ object. Raises \exception{TypeError} if the object is not a string
+ object. The C variable may also be declared as \ctype{PyObject*}.
+
+ \item[\samp{U} (Unicode string) {[PyUnicodeObject *]}]
+ Like \samp{O} but requires that the Python object is a Unicode
+ object. Raises \exception{TypeError} if the object is not a Unicode
+ object. The C variable may also be declared as \ctype{PyObject*}.
+
+ \item[\samp{t\#} (read-only character buffer) {[char *, int]}]
+ Like \samp{s\#}, but accepts any object which implements the
+ read-only buffer interface. The \ctype{char*} variable is set to
+ point to the first byte of the buffer, and the \ctype{int} is set to
+ the length of the buffer. Only single-segment buffer objects are
+ accepted; \exception{TypeError} is raised for all others.
+
+ \item[\samp{w} (read-write character buffer) {[char *]}]
+ Similar to \samp{s}, but accepts any object which implements the
+ read-write buffer interface. The caller must determine the length
+ of the buffer by other means, or use \samp{w\#} instead. Only
+ single-segment buffer objects are accepted; \exception{TypeError} is
+ raised for all others.
+
+ \item[\samp{w\#} (read-write character buffer) {[char *, int]}]
+ Like \samp{s\#}, but accepts any object which implements the
+ read-write buffer interface. The \ctype{char *} variable is set to
+ point to the first byte of the buffer, and the \ctype{int} is set to
+ the length of the buffer. Only single-segment buffer objects are
+ accepted; \exception{TypeError} is raised for all others.
+
+ \item[\samp{(\var{items})} (tuple) {[\var{matching-items}]}]
+ The object must be a Python sequence whose length is the number of
+ format units in \var{items}. The C arguments must correspond to the
+ individual format units in \var{items}. Format units for sequences
+ may be nested.
+
+ \note{Prior to Python version 1.5.2, this format specifier only
+ accepted a tuple containing the individual parameters, not an
+ arbitrary sequence. Code which previously caused
+ \exception{TypeError} to be raised here may now proceed without an
+ exception. This is not expected to be a problem for existing code.}
+\end{description}
+
+It is possible to pass Python long integers where integers are
+requested; however no proper range checking is done --- the most
+significant bits are silently truncated when the receiving field is
+too small to receive the value (actually, the semantics are inherited
+from downcasts in C --- your mileage may vary).
+
+A few other characters have a meaning in a format string. These may
+not occur inside nested parentheses. They are:
+
+\begin{description}
+ \item[\samp{|}]
+ Indicates that the remaining arguments in the Python argument list
+ are optional. The C variables corresponding to optional arguments
+ should be initialized to their default value --- when an optional
+ argument is not specified, \cfunction{PyArg_ParseTuple()} does not
+ touch the contents of the corresponding C variable(s).
+
+ \item[\samp{:}]
+ The list of format units ends here; the string after the colon is
+ used as the function name in error messages (the ``associated
+ value'' of the exception that \cfunction{PyArg_ParseTuple()}
+ raises).
+
+ \item[\samp{;}]
+ The list of format units ends here; the string after the semicolon
+ is used as the error message \emph{instead} of the default error
+ message. Clearly, \samp{:} and \samp{;} mutually exclude each
+ other.
+\end{description}
+
+Note that any Python object references which are provided to the
+caller are \emph{borrowed} references; do not decrement their
+reference count!
+
+Additional arguments passed to these functions must be addresses of
+variables whose type is determined by the format string; these are
+used to store values from the input tuple. There are a few cases, as
+described in the list of format units above, where these parameters
+are used as input values; they should match what is specified for the
+corresponding format unit in that case.
+
+For the conversion to succeed, the \var{arg} object must match the
+format and the format must be exhausted. On success, the
+\cfunction{PyArg_Parse*()} functions return true, otherwise they
+return false and raise an appropriate exception.
+
\begin{cfuncdesc}{int}{PyArg_ParseTuple}{PyObject *args, char *format,
\moreargs}
Parse the parameters of a function that takes only positional
parameters into local variables. Returns true on success; on
- failure, it returns false and raises the appropriate exception. See
- \citetitle[../ext/parseTuple.html]{Extending and Embedding the
- Python Interpreter} for more information.
+ failure, it returns false and raises the appropriate exception.
\end{cfuncdesc}
\begin{cfuncdesc}{int}{PyArg_ParseTupleAndKeywords}{PyObject *args,
@@ -372,8 +650,6 @@
Parse the parameters of a function that takes both positional and
keyword parameters into local variables. Returns true on success;
on failure, it returns false and raises the appropriate exception.
- See \citetitle[../ext/parseTupleAndKeywords.html]{Extending and
- Embedding the Python Interpreter} for more information.
\end{cfuncdesc}
\begin{cfuncdesc}{int}{PyArg_Parse}{PyObject *args, char *format,
@@ -440,8 +716,127 @@
Create a new value based on a format string similar to those
accepted by the \cfunction{PyArg_Parse*()} family of functions and a
sequence of values. Returns the value or \NULL{} in the case of an
- error; an exception will be raised if \NULL{} is returned. For more
- information on the format string and additional parameters, see
- \citetitle[../ext/buildValue.html]{Extending and Embedding the
- Python Interpreter}.
+ error; an exception will be raised if \NULL{} is returned.
+
+ \cfunction{Py_BuildValue()} does not always build a tuple. It
+ builds a tuple only if its format string contains two or more format
+ units. If the format string is empty, it returns \code{None}; if it
+ contains exactly one format unit, it returns whatever object is
+ described by that format unit. To force it to return a tuple of
+ size 0 or one, parenthesize the format string.
+
+ When memory buffers are passed as parameters to supply data to build
+ objects, as for the \samp{s} and \samp{s\#} formats, the required
+ data is copied. Buffers provided by the caller are never referenced
+ by the objects created by \cfunction{Py_BuildValue()}. In other
+ words, if your code invokes \cfunction{malloc()} and passes the
+ allocated memory to \cfunction{Py_BuildValue()}, your code is
+ responsible for calling \cfunction{free()} for that memory once
+ \cfunction{Py_BuildValue()} returns.
+
+ In the following description, the quoted form is the format unit;
+ the entry in (round) parentheses is the Python object type that the
+ format unit will return; and the entry in [square] brackets is the
+ type of the C value(s) to be passed.
+
+ The characters space, tab, colon and comma are ignored in format
+ strings (but not within format units such as \samp{s\#}). This can
+ be used to make long format strings a tad more readable.
+
+ \begin{description}
+ \item[\samp{s} (string) {[char *]}]
+ Convert a null-terminated C string to a Python object. If the C
+ string pointer is \NULL, \code{None} is used.
+
+ \item[\samp{s\#} (string) {[char *, int]}]
+ Convert a C string and its length to a Python object. If the C
+ string pointer is \NULL, the length is ignored and \code{None} is
+ returned.
+
+ \item[\samp{z} (string or \code{None}) {[char *]}]
+ Same as \samp{s}.
+
+ \item[\samp{z\#} (string or \code{None}) {[char *, int]}]
+ Same as \samp{s\#}.
+
+ \item[\samp{u} (Unicode string) {[Py_UNICODE *]}]
+ Convert a null-terminated buffer of Unicode (UCS-2) data to a
+ Python Unicode object. If the Unicode buffer pointer is \NULL,
+ \code{None} is returned.
+
+ \item[\samp{u\#} (Unicode string) {[Py_UNICODE *, int]}]
+ Convert a Unicode (UCS-2) data buffer and its length to a Python
+ Unicode object. If the Unicode buffer pointer is \NULL, the
+ length is ignored and \code{None} is returned.
+
+ \item[\samp{i} (integer) {[int]}]
+ Convert a plain C \ctype{int} to a Python integer object.
+
+ \item[\samp{b} (integer) {[char]}]
+ Same as \samp{i}.
+
+ \item[\samp{h} (integer) {[short int]}]
+ Same as \samp{i}.
+
+ \item[\samp{l} (integer) {[long int]}]
+ Convert a C \ctype{long int} to a Python integer object.
+
+ \item[\samp{c} (string of length 1) {[char]}]
+ Convert a C \ctype{int} representing a character to a Python
+ string of length 1.
+
+ \item[\samp{d} (float) {[double]}]
+ Convert a C \ctype{double} to a Python floating point number.
+
+ \item[\samp{f} (float) {[float]}]
+ Same as \samp{d}.
+
+ \item[\samp{D} (complex) {[Py_complex *]}]
+ Convert a C \ctype{Py_complex} structure to a Python complex
+ number.
+
+ \item[\samp{O} (object) {[PyObject *]}]
+ Pass a Python object untouched (except for its reference count,
+ which is incremented by one). If the object passed in is a
+ \NULL{} pointer, it is assumed that this was caused because the
+ call producing the argument found an error and set an exception.
+ Therefore, \cfunction{Py_BuildValue()} will return \NULL{} but
+ won't raise an exception. If no exception has been raised yet,
+ \exception{SystemError} is set.
+
+ \item[\samp{S} (object) {[PyObject *]}]
+ Same as \samp{O}.
+
+ \item[\samp{U} (object) {[PyObject *]}]
+ Same as \samp{O}.
+
+ \item[\samp{N} (object) {[PyObject *]}]
+ Same as \samp{O}, except it doesn't increment the reference count
+ on the object. Useful when the object is created by a call to an
+ object constructor in the argument list.
+
+ \item[\samp{O\&} (object) {[\var{converter}, \var{anything}]}]
+ Convert \var{anything} to a Python object through a
+ \var{converter} function. The function is called with
+ \var{anything} (which should be compatible with \ctype{void *}) as
+ its argument and should return a ``new'' Python object, or \NULL{}
+ if an error occurred.
+
+ \item[\samp{(\var{items})} (tuple) {[\var{matching-items}]}]
+ Convert a sequence of C values to a Python tuple with the same
+ number of items.
+
+ \item[\samp{[\var{items}]} (list) {[\var{matching-items}]}]
+ Convert a sequence of C values to a Python list with the same
+ number of items.
+
+ \item[\samp{\{\var{items}\}} (dictionary) {[\var{matching-items}]}]
+ Convert a sequence of C values to a Python dictionary. Each pair
+ of consecutive C values adds one item to the dictionary, serving
+ as key and value, respectively.
+
+ \end{description}
+
+ If there is an error in the format string, the
+ \exception{SystemError} exception is set and \NULL{} returned.
\end{cfuncdesc}