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.

2 files changed, 415 insertions, 110 deletions

diff --git a/Doc/api/newtypes.tex b/Doc/api/newtypes.tex
index b4f90e5..49c3dad 100644
--- a/Doc/api/newtypes.tex
+++ b/Doc/api/newtypes.tex
@@ -1,4 +1,8 @@
-\chapter{Defining New Object Types \label{newTypes}}
+\chapter{Object Implementation Support \label{newTypes}}
+
+
+This chapter describes the functions, types, and macros used when
+defining new object types.
 
 
 \section{Allocating Objects on the Heap
@@ -388,6 +392,12 @@ which do not store references to other objects, or which only store
 references to atomic types (such as numbers or strings), do not need
 to provide any explicit support for garbage collection.
 
+An example showing the use of these interfaces can be found in
+``\ulink{Supporting the Cycle
+Collector}{../ext/example-cycle-support.html}'' in
+\citetitle[../ext/ext.html]{Extending and Embedding the Python
+Interpreter}.
+
 To create a container type, the \member{tp_flags} field of the type
 object must include the \constant{Py_TPFLAGS_HAVE_GC} and provide an
 implementation of the \member{tp_traverse} handler.  If instances of the
@@ -504,103 +514,3 @@ The \member{tp_clear} handler must be of the \ctype{inquiry} type, or
   this method if it detects that this object is involved in a
   reference cycle.
 \end{ctypedesc}
-
-
-\subsection{Example Cycle Collector Support
-            \label{example-cycle-support}}
-
-This example shows only enough of the implementation of an extension
-type to show how the garbage collector support needs to be added.  It
-shows the definition of the object structure, the
-\member{tp_traverse}, \member{tp_clear} and \member{tp_dealloc}
-implementations, the type structure, and a constructor --- the module
-initialization needed to export the constructor to Python is not shown
-as there are no special considerations there for the collector.  To
-make this interesting, assume that the module exposes ways for the
-\member{container} field of the object to be modified.  Note that
-since no checks are made on the type of the object used to initialize
-\member{container}, we have to assume that it may be a container.
-
-\begin{verbatim}
-#include "Python.h"
-
-typedef struct {
-    PyObject_HEAD
-    PyObject *container;
-} MyObject;
-
-static int
-my_traverse(MyObject *self, visitproc visit, void *arg)
-{
-    if (self->container != NULL)
-        return visit(self->container, arg);
-    else
-        return 0;
-}
-
-static int
-my_clear(MyObject *self)
-{
-    Py_XDECREF(self->container);
-    self->container = NULL;
-
-    return 0;
-}
-
-static void
-my_dealloc(MyObject *self)
-{
-    PyObject_GC_UnTrack((PyObject *) self);
-    Py_XDECREF(self->container);
-    PyObject_GC_Del(self);
-}
-\end{verbatim}
-
-\begin{verbatim}
-statichere PyTypeObject
-MyObject_Type = {
-    PyObject_HEAD_INIT(NULL)
-    0,
-    "MyObject",
-    sizeof(MyObject),
-    0,
-    (destructor)my_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_HAVE_GC,
-    0,                          /* tp_doc */
-    (traverseproc)my_traverse,  /* tp_traverse */
-    (inquiry)my_clear,          /* tp_clear */
-    0,                          /* tp_richcompare */
-    0,                          /* tp_weaklistoffset */
-};
-
-/* This constructor should be made accessible from Python. */
-static PyObject *
-new_object(PyObject *unused, PyObject *args)
-{
-    PyObject *container = NULL;
-    MyObject *result = NULL;
-
-    if (PyArg_ParseTuple(args, "|O:new_object", &container)) {
-        result = PyObject_GC_New(MyObject, &MyObject_Type);
-        if (result != NULL) {
-            result->container = container;
-            PyObject_GC_Track(result);
-        }
-    }
-    return (PyObject *) result;
-}
-\end{verbatim}
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 @@ and methods.  Additional information and examples are available in
 \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 @@ Interpreter}.
   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 @@ PyArg_ParseTuple(args, "O|O:ref", &object, &callback)
   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}