[catacomb] / math / mpgen

#! @PYTHON@
###
### Generate multiprecision integer representations
###
### (c) 2013 Straylight/Edgeware
###

###----- Licensing notice ---------------------------------------------------
###
### This file is part of Catacomb.
###
### Catacomb is free software; you can redistribute it and/or modify
### it under the terms of the GNU Library General Public License as
### published by the Free Software Foundation; either version 2 of the
### License, or (at your option) any later version.
###
### Catacomb is distributed in the hope that it will be useful,
### but WITHOUT ANY WARRANTY; without even the implied warranty of
### MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
### GNU Library General Public License for more details.
###
### You should have received a copy of the GNU Library General Public
### License along with Catacomb; if not, write to the Free
### Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
### MA 02111-1307, USA.

from __future__ import with_statement

import re as RX
import optparse as OP
import types as TY

from sys import stdout

###--------------------------------------------------------------------------
### Random utilities.

def write_header(mode, name):
  """
  Write a C-language file header.

  The header comment identifies the processing MODE, and the NAME of the
  output file.
  """
  stdout.write("""\
/* -*-c-*- GENERATED by mpgen (%s)
 *
 * %s
 */

""" % (mode, name))

def write_banner(text):
  """Write a separator banner to the output, with header TEXT."""
  stdout.write("/*----- %s %s*/\n" % (text, '-' * (66 - len(text))))

class struct (object):
  """
  A struct object exists so that you can set attributes on it.
  """
  pass

R_IDBAD = RX.compile('[^0-9A-Za-z]')
def fix_name(name):
  """Replace non-alphanumeric characters in NAME with underscores."""
  return R_IDBAD.sub('_', name)

###--------------------------------------------------------------------------
### Determining the appropriate types.

## A dictionary mapping type tags to subclasses of BasicIntType.
TYPEMAP = {}

class IntClass (type):
  """
  The IntClass is a metaclass for integer-type classes.

  It associates the type class with its tag in the `TYPEMAP' dictionary.
  """
  def __new__(cls, name, supers, dict):
    c = type.__new__(cls, name, supers, dict)
    try: TYPEMAP[c.tag] = c
    except AttributeError: pass
    return c

class BasicIntType (object):
  """
  A base class for integer-type classes, providing defaults and protocol.

  Integer-type classes have the following attributes and methods.

  preamble              Some code to be emitted to a header file to make use
                        of the type.  Defaults to the empty string.

  typedef_prefix        A prefix to be written before the type's name in a
                        `typedef' declaration, possibly to muffle warnings.
                        Defaults to the empty string.

  literalfmt            A Python `%' format string for generating literal
                        values of the type; used by the default `literal'
                        method (so if you override it then you don't need to
                        set this).  Defaults to `%su'.

  literal(VALUE, [FMT]) Emit a literal value of the type, encoding VALUE.
                        The default FMT has the form `0x%0Nx', so as to emit
                        in hex with the appropriate number of leading zeros.

  Instances also carry additional attributes.

  bits                  The width of the integer type, in bits.

  rank                  An integer giving the conversion rank of the type.
                        Higher values generally denote wider types.

  litwd                 The width of a literal of the type, in characters.
  """
  __metaclass__ = IntClass
  preamble = ''
  typedef_prefix = ''
  literalfmt = '%su'
  def __init__(me, bits, rank):
    me.bits = bits
    me.rank = rank
    me.litwd = len(me.literal(0))
  def literal(me, value, fmt = None):
    if fmt is None: fmt = '0x%0' + str((me.bits + 3)//4) + 'x'
    return me.literalfmt % (fmt % value)

class UnsignedCharType (BasicIntType):
  tag = 'uchar'
  name = 'unsigned char'

class UnsignedShortType (BasicIntType):
  tag = 'ushort'
  name = 'unsigned short'

class UnsignedIntType (BasicIntType):
  tag = 'uint'
  name = 'unsigned int'

class UnsignedLongType (BasicIntType):
  tag = 'ulong'
  name = 'unsigned long'
  literalfmt = '%sul'

class UnsignedLongLongType (BasicIntType):
  tag = 'ullong'
  name = 'unsigned long long'
  preamble = """
#if __GNUC__ > 2 || (__GNUC__ == 2 && __GNUC_MINOR__ >= 91)
#  define CATACOMB_GCC_EXTENSION __extension__
#else
#  define CATACOMB_GCC_EXTENSION
#endif
"""
  typedef_prefix = 'CATACOMB_GCC_EXTENSION '
  literalfmt = 'CATACOMB_GCC_EXTENSION %sull'

class UIntMaxType (BasicIntType):
  tag = 'uintmax'
  name = 'uintmax_t'
  preamble = "\n#include <stdint.h>\n"

class TypeChoice (object):
  """
  A TypeChoice object selects C integer types for multiprecision integers.

  It exports its decisions as attributes:

  mpwbits               The width of an `mpw', in bits.

  mpw                   The integer type for single-precision values.

  mpd                   The integer type for double-precision values.

  ti                    An object bearing raw information about the available
                        integer types, as follows...

    TYPEINFO            A list of items (TAG, BITS) describing the widths of
                        the available types suitable for multiprecision use,
                        in ascending order of rank.

    LIMITS              A list of items (TAG, LO, HI) describing the ranges
                        of integer types, for constructing the `mplimits'
                        files.
  """

  def __init__(me, tifile):
    """
    Read the definitions from TIFILE, and select types appropriately.

    The TIFILE is a tiny fragment of Python code which should set `TYPEINFO'
    and `LIMITS' in its global namespace.
    """

    ## Load the captured type information.
    me.ti = TY.ModuleType('typeinfo')
    execfile(opts.typeinfo, me.ti.__dict__)

    ## Build a map of the available types.
    tymap = {}
    byrank = []
    for tag, bits in me.ti.TYPEINFO:
      rank = len(byrank)
      tymap[tag] = rank
      byrank.append(TYPEMAP[tag](bits, rank))

    ## First pass: determine a suitable word size.  The criteria are (a)
    ## there exists another type at least twice as long (so that we can do a
    ## single x single -> double multiplication), and (b) operations on a
    ## word are efficient (so we'd prefer a plain machine word).  We'll start
    ## at `int' and work down.  Maybe this won't work: there's a plan B.
    mpwbits = 0
    i = tymap['uint']
    while not mpwbits and i >= 0:
      ibits = byrank[i].bits
      for j in xrange(i + 1, len(byrank)):
        if byrank[j].bits >= 2*ibits:
          mpwbits = ibits
          break

    ## If that didn't work, then we'll start with the largest type available
    ## and go with half its size.
    if not mpwbits:
      mpwbits = byrank[-1].bits//2

    ## Make sure we've not ended up somewhere really silly.
    if mpwbits < 16:
      raise Exception, "`mpw' type is too small: your C environment is weird"

    ## Now figure out suitable types for `mpw' and `mpd'.
    def find_type(bits, what):
      for ty in byrank:
        if ty.bits >= bits: return ty
      raise Exception, \
          "failed to find suitable %d-bit type, for %s" % (bits, what)

    ## Store our decisions.
    me.mpwbits = mpwbits
    me.mpw = find_type(mpwbits, 'mpw')
    me.mpd = find_type(mpwbits*2, 'mpd')

###--------------------------------------------------------------------------
### Outputting constant multiprecision integers.

## The margin for outputting MP literals.
MARGIN = 72

def write_preamble():
  """
  Write a preamble for files containing multiprecision literals.

  We define a number of macros for use by the rest of the code:

  ZERO_MP               An `mp' initializer denoting the value zero.

  POS_MP(NAME)          Constructs an `mp' initializer denoting a positive
                        integer whose limbs were emitted with the given
                        NAME.

  NEG_MP(NAME)          Constructs an `mp' initializer denoting a negative
                        integer whose limbs were emitted with the given
                        NAME.
  """
  stdout.write("""
#include <mLib/macros.h>
#define MP_(name, flags) \\
  { (/*unconst*/ mpw *)name##__mpw, \\
    (/*unconst*/ mpw *)name##__mpw + N(name##__mpw), \\
    N(name##__mpw), 0, MP_CONST | flags, 0 }
#define ZERO_MP { 0, 0, 0, 0, MP_CONST, 0 }
#define POS_MP(name) MP_(name, 0)
#define NEG_MP(name) MP_(name, MP_NEG)
""")

def write_limbs(name, x):
  """
  Write the limbs of the value X, with the given NAME.
  """

  ## We don't need to do anything special for zero.
  if not x: return

  ## Start on the limb vector.  No delimiter needed, and we shall need to
  ## start a new line before any actual output.  We want to write the
  ## absolute value here, because we use a signed-magnitude representation.
  stdout.write("\nstatic const mpw %s__mpw[] = {" % name)
  sep = ''
  pos = MARGIN
  if x < 0: x = -x
  mask = (1 << TC.mpwbits) - 1

  ## We work from the little-end up, picking off `mpwbits' at a time.  Start
  ## a new line if we can't fit the value on the current one.
  while x > 0:
    w, x = x & mask, x >> TC.mpwbits
    f = TC.mpw.literal(w)
    if pos + 2 + len(f) <= MARGIN:
      stdout.write(sep + ' ' + f)
    else:
      pos = 2
      stdout.write(sep + '\n  ' + f)
    pos += len(f) + 2
    sep = ','

  ## We're done.  Finish off the initializer.
  stdout.write("\n};\n")

def mp_body(name, x):
  """
  Write the body of an `mp' object, for the value NAME.
  """
  return "%s_MP(%s)" % (x >= 0 and "POS" or "NEG", name)

###--------------------------------------------------------------------------
### Mode definition machinery.

## A dictionary mapping mode names to their handler functions.
MODEMAP = {}

def defmode(func):
  """
  Function decorator: associate the function with the name of a mode.

  The mode name is taken from the function's name: a leading `m_' is stripped
  off, if there is one.  Mode functions are invoked with the positional
  arguments from the command and are expected to write their output to
  stdout.
  """
  name = func.func_name
  if name.startswith('m_'): name = name[2:]
  MODEMAP[name] = func
  return func

###--------------------------------------------------------------------------
### The basic types header.

@defmode
def m_mptypes():
  """
  Write the `mptypes.h' header.

  This establishes the following types.

  mpw                   An integer type for single-precision values.

  mpd                   An integer type for double-precision values.

  And, for t being each of `w' or `d', the following constants:

  MPt_BITS              The width of the type, in bits.

  MPt_P2                The smallest integer k such that 2^k is not less than
                        MPt_BITS.  (This is used for binary searches.)

  MPt_MAX               The largest value which may be stored in an object of
                        the type.
  """

  ## Write the preamble.
  write_header("mptypes", "mptypes.h")
  stdout.write("""\
#ifndef CATACOMB_MPTYPES_H
#define CATACOMB_MPTYPES_H
""")

  ## Write any additional premable for the types we've selected.
  have = set([TC.mpw, TC.mpd])
  for t in have:
    stdout.write(t.preamble)

  ## Emit the types and constants.
  for label, t, bits in [('mpw', TC.mpw, TC.mpwbits),
                         ('mpd', TC.mpd, TC.mpwbits*2)]:
    LABEL = label.upper()
    stdout.write("\n%stypedef %s %s;\n" % (t.typedef_prefix, t.name, label))
    stdout.write("#define %s_BITS %d\n" % (LABEL, bits))
    i = 1
    while 2*i < bits: i *= 2
    stdout.write("#define %s_P2 %d\n" % (LABEL, i))
    stdout.write("#define %s_MAX %s\n" % (LABEL,
                                          t.literal((1 << bits) - 1, "%d")))

  ## Done.
  stdout.write("\n#endif\n")

###--------------------------------------------------------------------------
### Constant tables.

@defmode
def m_mplimits_c():
  """
  Write the `mplimits.c' source file.

  This contains `mp' constants corresponding to the various integer types'
  upper and lower bounds.  The output is a vector `mp_limits' consisting of
  the distinct nonzero bounds, in order of their first occurrence in the
  `ti.LIMITS' list.
  """

  ## Write the preamble.
  write_header("mplimits_c", "mplimits.c")
  stdout.write('#include "mplimits.h"\n')
  write_preamble()

  ## Write out limbs for limits as we come across them.
  seen = {}
  v = []
  def write(x):
    if not x or x in seen: return
    seen[x] = 1
    write_limbs('limits_%d' % len(v), x)
    v.append(x)
  for tag, lo, hi in TC.ti.LIMITS:
    write(lo)
    write(hi)

  ## Write the main vector.
  stdout.write("\nmp mp_limits[] = {")
  i = 0
  sep = "\n  "
  for x in v:
    stdout.write("%s%s_MP(limits_%d)" % (sep, x < 0 and "NEG" or "POS", i))
    i += 1
    sep = ",\n  "
  stdout.write("\n};\n");

@defmode
def m_mplimits_h():
  """
  Write the `mplimits.h' source file.

  For each type TAG, this defines constants MP_TAG_MIN and MP_TAG_MAX
  representing the lower and upper bounds of the type.
  """

  ## Write the preamble.
  write_header("mplimits_h", "mplimits.h")
  stdout.write("""\
#ifndef CATACOMB_MPLIMITS_H
#define CATACOMB_MPLIMITS_H

#ifndef CATACOMB_MP_H
#  include "mp.h"
#endif

extern mp mp_limits[];

""")

  ## Now define constants for the bounds.  Things which are zero can go to
  ## our existing `MP_ZERO'; otherwise we index the `mp_limits' vector.
  seen = { 0: "MP_ZERO" }
  slot = [0]
  def find(x):
    try:
      r = seen[x]
    except KeyError:
      r = seen[x] = '(&mp_limits[%d])' % slot[0]
      slot[0] += 1
    return r
  for tag, lo, hi in TC.ti.LIMITS:
    stdout.write("#define MP_%s_MIN %s\n" % (tag, find(lo)))
    stdout.write("#define MP_%s_MAX %s\n" % (tag, find(hi)))

  ## All done.
  stdout.write("\n#endif\n")

###--------------------------------------------------------------------------
### Group tables.

class GroupTableClass (type):
  """
  Metaclass for group tables, which registers them in the `MODEMAP'.

  Such a class must define an attribute `mode' giving the mode name, and a
  class method `run' which writes the necessary output.
  """
  def __new__(cls, name, supers, dict):
    c = type.__new__(cls, name, supers, dict)
    try: mode = c.mode
    except AttributeError: pass
    else: MODEMAP[c.mode] = c.run
    return c

class GroupTable (object):
  """
  Base class for group tables objects.

  A `group table' is a table of constants, typically defining a cyclic group
  or something similar.  We read the values from an input file, and write
  them out as C definitions.  These have a somewhat stereotyped format, so we
  can mostly handle them uniformly.

  Specifically, input files consist of lines which are split into
  whitespace-separated words.  Blank lines, and lines beginning with `#', are
  ignored.  The remaining lines are gathered together into stanzas of the
  form

  KEYWORD NAME [HEAD-VALUE ...]
        SLOT VALUE
        ...

  (Indentation is shown for clarity only.)  Such a stanza describes a group
  NAME; some slots are assigned values from the headline, and others from
  their own individual lines.

  Subclasses must define the following attributes.

  data_t                The name of the type for describing a particular
                        group.

  entry_t               The name of the type which associates a name with
                        some group data; this will be defined as

                                typedef struct ENTRY_T {
                                  const char *name;
                                  DATA_T *data;
                                } ENTRY_T;

                        or similar.

  filename              The filename, typically `SOMETHING.c', to put in the
                        output header.

  header                The header file to include, so as to establish the
                        necessary types and other definitions.

  keyword               The keyword beginning a new definition in the input
                        file.  The default is `group'.

  mode                  The mode name, used to invoke this kind of table
                        operation (used by GroupTableClass).

  slots                 A vector of slot objects (see BaseSlot for the
                        protocol) describing the structure of this particular
                        kind of group, in the order they should be written in
                        an initializer.

  Instances carry an `st' attribute, which contains a `struct' object in
  which slots can maintain some state.  This object carries the following
  attributes maintained by this class.

  d                     A dictionary mapping slots (not their names!) to
                        values assigned in the current stanza.  This is reset
                        at the start of each stanza.  Slot implementations
                        a free to use this or not, and the representation is
                        internal to the specific slot class.

  mpmap                 A dictionary mapping values (integers, or `None') to
                        C initializers (typically, actually, macro
                        invocations).

  name                  The name of the group currently being parsed.

  nextmp                Index for the next `mp' object to be written.
  """

  ## Additional attributes, for internal use:
  ##
  ## _defs              A set of known names for groups.
  ##
  ## _headslots         A list of slots filled in from the headline.
  ##
  ## _names             A list of pairs (ALIAS, DATA) mapping alias names to
  ##                    the actual group data.
  ##
  ## _slotmap           A dictionary mapping slot names to their
  ##                    descriptions.

  __metaclass__ = GroupTableClass

  ## Default values.
  keyword = 'group'
  slots = []

  def __init__(me):
    """
    Initialize a group table object.
    """

    me.st = st = struct()
    st.nextmp = 0
    st.mpmap = { None: 'NO_MP', 0: 'ZERO_MP' }
    st.d = {}
    st.name = None
    me._names = []
    me._defs = set()
    me._slotmap = dict([(s.name, s) for s in me.slots])
    me._headslots = [s for s in me.slots if s.headline]

  def _flush(me):
    """
    Write out the data for a group once we've detected the end of its stanza.
    """

    ## If there's no current stanza, then do nothing.
    if me.st.name is None: return

    ## Start emitting the object.
    stdout.write("/* --- %s --- */\n" % me.st.name)

    ## Get the various slots to compute themselves.
    for s in me.slots: s.setup(me.st)

    ## Write the initializer.
    stdout.write("\nstatic %s c_%s = {" % (me.data_t, fix_name(me.st.name)))
    sep = "\n  "
    for s in me.slots:
      stdout.write(sep)
      s.write(me.st)
      sep = ",\n  "
    stdout.write("\n};\n\n")

    ## Clear the state for the next stanza.
    me.st.d = {}
    me.st.name = None

  @classmethod
  def run(cls, input):
    """
    Main output for a group table.  Reads the file INPUT.
    """

    ## Make an object for us to work on.
    me = cls()

    ## Write the output preamble.
    write_header(me.mode, me.filename)
    stdout.write('#include "%s"\n' % me.header)
    write_preamble()
    stdout.write("#define NO_MP { 0, 0, 0, 0, 0, 0 }\n\n")

    ## The main group data.  This will contain a `data_t' object for each
    ## group we read.  We'll also build the name to data map as we go.
    write_banner("Group data")
    stdout.write('\n')
    with open(input) as file:
      for line in file:

        ## Parse the line into fields.
        ff = line.split()
        if not ff or ff[0].startswith('#'): continue

        if ff[0] == 'alias':
          ## An alias.  Just remember this.
          if len(ff) != 3: raise Exception, "wrong number of alias arguments"
          me._flush()
          me._names.append((ff[1], ff[2]))

        elif ff[0] == me.keyword:
          ## A headline for a new group.

          ## Check the headline syntax.  Headline slots may be set here, or
          ## later by name.
          if len(ff) < 2 or len(ff) > 2 + len(me._headslots):
            raise Exception, "bad number of headline arguments"

          ## Flush out the previous stanza.
          me._flush()

          ## Remember the new stanza's name, and add it to the list.
          me.st.name = name = ff[1]
          me._defs.add(name)
          me._names.append((name, name))

          ## Set headline slots from the remaining headline words.
          for f, s in zip(ff[2:], me._headslots): s.set(me.st, f)

        elif ff[0] in me._slotmap:
          ## A slot assignment.  Get the slot to store a value.
          if me.st.name is None:
            raise Exception, "no group currently being defined"
          if len(ff) != 2:
            raise Exception, "bad number of values for slot `%s'" % ff[0]
          me._slotmap[ff[0]].set(me.st, ff[1])

        else:
          ## Something incomprehensible.
          raise Exception, "unknown keyword `%s'" % ff[0]

    ## End of the input.  Write out the final stanza.
    me._flush()

    ## Now for the name-to-data mapping.
    write_banner("Main table")
    stdout.write("\nconst %s %s[] = {\n" % (me.entry_t, me.tabname))
    for a, n in me._names:
      if n not in me._defs:
        raise Exception, "alias `%s' refers to unknown group `%s'" % (a, n)
      stdout.write('  { "%s", &c_%s },\n' % (a, fix_name(n)))
    stdout.write("  { 0, 0 }\n};\n\n")

    ## We're done.
    write_banner("That's all, folks")

class BaseSlot (object):
  """
  Base class for slot types.

  The slot protocol works as follows.  Throughout, ST is a state object as
  maintained by a GroupTable.

  __init__(NAME, [HEADLINE], [OMITP], [ALLOWP], ...)
                        Initialize the slot.  The NAME identifies the slot,
                        and the keyword used to set it in input files.  If
                        HEADLINE is true then the slot can be set from the
                        stanza headline.  OMITP and ALLOWP are optional
                        functions: if OMITP(ST) returns true then the slot
                        may be omitted; conversely, if ALLOWP(ST, VALUE)
                        returns false then the slot cannot be assigned the
                        given VALUE.  Other arguments may be allowed by
                        specific slot types.

  set(ST, VALUE)        Set the slot to the given VALUE, typically by setting
                        ST.d[me].  The default just stores the VALUE without
                        interpreting it.

  setup(ST)             Prepare the slot for output.  The default method just
                        checks that ST.d contains a mapping for the slot.
                        All of the stanza's slots are set up before starting
                        on the initializer for the group data, so slots can
                        use this opportunity to emit preparatory definitions.

  write(ST)             Write an initializer for the slot to standard
                        output.  There is no default.

  The following attributes are exported.

  headline              A flag: can the slot be initialized from the stanza
                        headline?

  name                  The slot's name.
  """

  def __init__(me, name, headline = False, omitp = None, allowp = None):
    """
    Initialize a new slot object, setting the necessary attributes.
    """
    me.name = name
    me.headline = headline
    me._omitp = omitp
    me._allowp = allowp

  def set(me, st, value):
    """
    Store a VALUE for the slot.
    """
    if me._allowp and not me._allowp(st, value):
      raise Exception, "slot `%s' not allowed here" % me.name
    st.d[me] = value

  def setup(me, st):
    """
    Prepare the slot for output, checking its value and so on.
    """
    if me not in st.d and (not me._omitp or not me._omitp(st)):
      raise Exception, "missing slot `%s'" % me.name

class EnumSlot (BaseSlot):
  """
  An EnumSlot object represents a slot which can contain one of a number of
  named values.

  An omitted value is written as a literal `0'.
  """

  def __init__(me, name, prefix, values, **kw):
    """
    Initialize an EnumSlot object.

    The VALUES are a set of value names.  On output, a value is converted to
    uppercase, and prefixed by the PREFIX and an underscore.
    """
    super(EnumSlot, me).__init__(name, **kw)
    me._values = set(values)
    me._prefix = prefix

  def set(me, st, value):
    """
    Check that the VALUE is one of the ones we know.
    """
    if value not in me._values:
      raise Exception, "invalid %s value `%s'" % (me.name, value)
    super(EnumSlot, me).set(st, value)

  def write(me, st):
    """
    Convert the slot value to the C constant name.
    """
    try: stdout.write('%s_%s' % (me._prefix, st.d[me].upper()))
    except KeyError: stdout.write('0')

class MPSlot (BaseSlot):
  """
  An MPSlot object represents a slot which can contain a multiprecision
  integer.

  An omitted value is written as a invalid `mp' object.
  """

  def set(me, st, value):
    """
    Set a value; convert it to a Python integer.
    """
    super(MPSlot, me).set(st, long(value, 0))

  def setup(me, st):
    """
    Prepare to write the slot.

    If this is a new integer, then write out a limb vector.  Names for the
    limbs are generated unimaginitively, using a counter.
    """
    super(MPSlot, me).setup(st)
    v = st.d.get(me)
    if v not in st.mpmap:
      write_limbs('v%d' % st.nextmp, v)
      st.mpmap[v] = mp_body('v%d' % st.nextmp, v)
      st.nextmp += 1

  def write(me, st):
    """
    Write out an `mp' initializer for the slot.
    """
    stdout.write(st.mpmap[st.d.get(me)])

class BinaryGroupTable (GroupTable):
  mode = 'bintab'
  filename = 'bintab.c'
  header = 'bintab.h'
  data_t = 'bindata'
  entry_t = 'binentry'
  tabname = 'bintab'
  slots = [MPSlot('p'), MPSlot('q'), MPSlot('g')]

class EllipticCurveTable (GroupTable):
  mode = 'ectab'
  filename = 'ectab.c'
  header = 'ectab.h'
  keyword = 'curve'
  data_t = 'ecdata'
  entry_t = 'ecentry'
  tabname = 'ectab'
  _typeslot = EnumSlot('type', 'FTAG',
                       ['prime', 'niceprime', 'binpoly', 'binnorm'],
                       headline = True)
  slots = [_typeslot,
           MPSlot('p'),
           MPSlot('beta',
                  allowp = lambda st, _:
                    st.d[EllipticCurveTable._typeslot] == 'binnorm',
                  omitp = lambda st:
                    st.d[EllipticCurveTable._typeslot] != 'binnorm'),
           MPSlot('a'), MPSlot('b'), MPSlot('r'), MPSlot('h'),
           MPSlot('gx'), MPSlot('gy')]

class PrimeGroupTable (GroupTable):
  mode = 'ptab'
  filename = 'ptab.c'
  header = 'ptab.h'
  data_t = 'pdata'
  entry_t = 'pentry'
  tabname = 'ptab'
  slots = [MPSlot('p'), MPSlot('q'), MPSlot('g')]

###--------------------------------------------------------------------------
### Main program.

op = OP.OptionParser(
  description = 'Generate multiprecision integer representations',
  usage = 'usage: %prog [-t TYPEINFO] MODE [ARGS ...]',
  version = 'Catacomb, version @VERSION@')
for shortopt, longopt, kw in [
  ('-t', '--typeinfo', dict(
      action = 'store', metavar = 'PATH', dest = 'typeinfo',
      help = 'alternative typeinfo file'))]:
  op.add_option(shortopt, longopt, **kw)
op.set_defaults(typeinfo = './typeinfo.py')
opts, args = op.parse_args()

## Parse the positional arguments.
if len(args) < 1: op.error('missing MODE')
mode = args[0]

## Establish the choice of low-level C types.
TC = TypeChoice(opts.typeinfo)

## Find the selected mode, and invoke the appropriate handler.
try: modefunc = MODEMAP[mode]
except KeyError: op.error("unknown mode `%s'" % mode)
modefunc(*args[1:])

###----- That's all, folks --------------------------------------------------