utils/unicode-case-fold.py

   1 #!/usr/bin/env python
   2 """
   3 Unicode case folding database conversion utility
   4
   5 Parses the database and generates a C++ function which implements the case
   6 folding algorithm. The database entries are of the form:
   7
   8   <code>; <status>; <mapping>; # <name>
   9
  10 <status> can be one of four characters:
  11   C - Common mappings
  12   S - mappings for Simple case folding
  13   F - mappings for Full case folding
  14   T - special case for Turkish I characters
  15
  16 Right now this generates a function which implements simple case folding (C+S
  17 entries).
  18 """
  19
  20 import sys
  21 import re
  22 import urllib2
  23
  24 # This variable will body of the mappings function
  25 body = ""
  26
  27 # Reads file line-by-line, extracts Common and Simple case fold mappings and
  28 # returns a (from_char, to_char, from_name) tuple.
  29 def mappings(f):
  30     previous_from = -1
  31     expr = re.compile(r'^(.*); [CS]; (.*); # (.*)')
  32     for line in f:
  33         m = expr.match(line)
  34         if not m: continue
  35         from_char = int(m.group(1), 16)
  36         to_char = int(m.group(2), 16)
  37         from_name = m.group(3)
  38
  39         if from_char <= previous_from:
  40             raise Exception("Duplicate or unsorted characters in input")
  41         yield from_char, to_char, from_name
  42         previous_from = from_char
  43
  44 # Computes the shift (to_char - from_char) in a mapping.
  45 def shift(mapping):
  46     return mapping[1] - mapping[0]
  47
  48 # Computes the stride (from_char2 - from_char1) of two mappings.
  49 def stride2(mapping1, mapping2):
  50     return mapping2[0] - mapping1[0]
  51
  52 # Computes the stride of a list of mappings. The list should have at least two
  53 # mappings. All mappings in the list are assumed to have the same stride.
  54 def stride(block):
  55     return stride2(block[0], block[1])
  56
  57
  58 # b is a list of mappings. All the mappings are assumed to have the same
  59 # shift and the stride between adjecant mappings (if any) is constant.
  60 def dump_block(b):
  61     global body
  62
  63     if len(b) == 1:
  64         # Special case for handling blocks of length 1. We don't even need to
  65         # emit the "if (C < X) return C" check below as all characters in this
  66         # range will be caught by the "C < X" check emitted by the first
  67         # non-trivial block.
  68         body  += "  // {2}\n  if (C == {0:#06x})\n    return {1:#06x};\n".format(*b[0])
  69         return
  70
  71     first = b[0][0]
  72     last = first + stride(b) * (len(b)-1)
  73     modulo = first % stride(b)
  74
  75     # All characters before this block map to themselves.
  76     body += "  if (C < {0:#06x})\n    return C;\n".format(first)
  77     body += "  // {0} characters\n".format(len(b))
  78
  79     # Generic pattern: check upper bound (lower bound is checked by the "if"
  80     # above) and modulo of C, return C+shift.
  81     pattern = "  if (C <= {0:#06x} && C % {1} == {2})\n    return C + {3};\n"
  82
  83     if stride(b) == 2 and shift(b[0]) == 1 and modulo == 0:
  84         # Special case:
  85         # We can elide the modulo-check because the expression "C|1" will map
  86         # the intervening characters to themselves.
  87         pattern = "  if (C <= {0:#06x})\n    return C | 1;\n"
  88     elif stride(b) == 1:
  89         # Another special case: X % 1 is always zero, so don't emit the
  90         # modulo-check.
  91         pattern = "  if (C <= {0:#06x})\n    return C + {3};\n"
  92
  93     body += pattern.format(last, stride(b), modulo, shift(b[0]))
  94
  95 current_block = []
  96 f = urllib2.urlopen(sys.argv[1])
  97 for m in mappings(f):
  98     if len(current_block) == 0:
  99         current_block.append(m)
 100         continue
 101
 102     if shift(current_block[0]) != shift(m):
 103         # Incompatible shift, start a new block.
 104         dump_block(current_block)
 105         current_block = [m]
 106         continue
 107
 108     if len(current_block) == 1 or stride(current_block) == stride2(current_block[-1], m):
 109         current_block.append(m)
 110         continue
 111
 112     # Incompatible stride, start a new block.
 113     dump_block(current_block)
 114     current_block = [m]
 115 f.close()
 116
 117 dump_block(current_block)
 118
 119 print '//===---------- Support/UnicodeCaseFold.cpp -------------------------------===//'
 120 print '//'
 121 print '// This file was generated by utils/unicode-case-fold.py from the Unicode'
 122 print '// case folding database at'
 123 print '//   ', sys.argv[1]
 124 print '//'
 125 print '// To regenerate this file, run:'
 126 print '//   utils/unicode-case-fold.py \\'
 127 print '//     "{}" \\'.format(sys.argv[1])
 128 print '//     > lib/Support/UnicodeCaseFold.cpp'
 129 print '//'
 130 print '//===----------------------------------------------------------------------===//'
 131 print ''
 132 print '#include "llvm/Support/Unicode.h"'
 133 print ''
 134 print "int llvm::sys::unicode::foldCharSimple(int C) {"
 135 print body
 136 print "  return C;"
 137 print "}"