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f85485df31
The issue was that the has function was generating different results depending on the signedness of char on the host platform. This commit fixes the issue by explicitly using an unsigned char type to prevent sign extension and adds some extra tests. The original commit message was: This patch implements a variant of the DJB hash function which folds the input according to the algorithm in the Dwarf 5 specification (Section 6.1.1.4.5), which in turn references the Unicode Standard (Section 5.18, "Case Mappings"). To achieve this, I have added a llvm::sys::unicode::foldCharSimple function, which performs this mapping. The implementation of this function was generated from the CaseMatching.txt file from the Unicode spec using a python script (which is also included in this patch). The script tries to optimize the function by coalescing adjecant mappings with the same shift and stride (terms I made up). Theoretically, it could be made a bit smarter and merge adjecant blocks that were interrupted by only one or two characters with exceptional mapping, but this would save only a couple of branches, while it would greatly complicate the implementation, so I deemed it was not worth it. Since we assume that the vast majority of the input characters will be US-ASCII, the folding hash function has a fast-path for handling these, and only whips out the full decode+fold+encode logic if we encounter a character outside of this range. It might be possible to implement the folding directly on utf8 sequences, but this would also bring a lot of complexity for the few cases where we will actually need to process non-ascii characters. Reviewers: JDevlieghere, aprantl, probinson, dblaikie Subscribers: mgorny, hintonda, echristo, clayborg, vleschuk, llvm-commits Differential Revision: https://reviews.llvm.org/D42740 llvm-svn: 325732
138 lines
4.4 KiB
Python
Executable File
138 lines
4.4 KiB
Python
Executable File
#!/usr/bin/env python
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"""
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Unicode case folding database conversion utility
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Parses the database and generates a C++ function which implements the case
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folding algorithm. The database entries are of the form:
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<code>; <status>; <mapping>; # <name>
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<status> can be one of four characters:
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C - Common mappings
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S - mappings for Simple case folding
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F - mappings for Full case folding
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T - special case for Turkish I characters
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Right now this generates a function which implements simple case folding (C+S
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entries).
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"""
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import sys
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import re
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import urllib2
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# This variable will body of the mappings function
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body = ""
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# Reads file line-by-line, extracts Common and Simple case fold mappings and
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# returns a (from_char, to_char, from_name) tuple.
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def mappings(f):
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previous_from = -1
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expr = re.compile(r'^(.*); [CS]; (.*); # (.*)')
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for line in f:
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m = expr.match(line)
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if not m: continue
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from_char = int(m.group(1), 16)
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to_char = int(m.group(2), 16)
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from_name = m.group(3)
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if from_char <= previous_from:
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raise Exception("Duplicate or unsorted characters in input")
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yield from_char, to_char, from_name
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previous_from = from_char
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# Computes the shift (to_char - from_char) in a mapping.
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def shift(mapping):
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return mapping[1] - mapping[0]
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# Computes the stride (from_char2 - from_char1) of two mappings.
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def stride2(mapping1, mapping2):
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return mapping2[0] - mapping1[0]
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# Computes the stride of a list of mappings. The list should have at least two
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# mappings. All mappings in the list are assumed to have the same stride.
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def stride(block):
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return stride2(block[0], block[1])
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# b is a list of mappings. All the mappings are assumed to have the same
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# shift and the stride between adjecant mappings (if any) is constant.
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def dump_block(b):
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global body
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if len(b) == 1:
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# Special case for handling blocks of length 1. We don't even need to
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# emit the "if (C < X) return C" check below as all characters in this
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# range will be caught by the "C < X" check emitted by the first
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# non-trivial block.
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body += " // {2}\n if (C == {0:#06x})\n return {1:#06x};\n".format(*b[0])
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return
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first = b[0][0]
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last = first + stride(b) * (len(b)-1)
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modulo = first % stride(b)
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# All characters before this block map to themselves.
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body += " if (C < {0:#06x})\n return C;\n".format(first)
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body += " // {0} characters\n".format(len(b))
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# Generic pattern: check upper bound (lower bound is checked by the "if"
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# above) and modulo of C, return C+shift.
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pattern = " if (C <= {0:#06x} && C % {1} == {2})\n return C + {3};\n"
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if stride(b) == 2 and shift(b[0]) == 1 and modulo == 0:
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# Special case:
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# We can elide the modulo-check because the expression "C|1" will map
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# the intervening characters to themselves.
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pattern = " if (C <= {0:#06x})\n return C | 1;\n"
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elif stride(b) == 1:
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# Another special case: X % 1 is always zero, so don't emit the
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# modulo-check.
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pattern = " if (C <= {0:#06x})\n return C + {3};\n"
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body += pattern.format(last, stride(b), modulo, shift(b[0]))
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current_block = []
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f = urllib2.urlopen(sys.argv[1])
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for m in mappings(f):
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if len(current_block) == 0:
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current_block.append(m)
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continue
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if shift(current_block[0]) != shift(m):
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# Incompatible shift, start a new block.
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dump_block(current_block)
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current_block = [m]
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continue
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if len(current_block) == 1 or stride(current_block) == stride2(current_block[-1], m):
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current_block.append(m)
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continue
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# Incompatible stride, start a new block.
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dump_block(current_block)
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current_block = [m]
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f.close()
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dump_block(current_block)
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print '//===---------- Support/UnicodeCaseFold.cpp -------------------------------===//'
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print '//'
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print '// This file was generated by utils/unicode-case-fold.py from the Unicode'
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print '// case folding database at'
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print '// ', sys.argv[1]
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print '//'
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print '// To regenerate this file, run:'
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print '// utils/unicode-case-fold.py \\'
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print '// "{}" \\'.format(sys.argv[1])
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print '// > lib/Support/UnicodeCaseFold.cpp'
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print '//'
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print '//===----------------------------------------------------------------------===//'
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print ''
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print '#include "llvm/Support/Unicode.h"'
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print ''
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print "int llvm::sys::unicode::foldCharSimple(int C) {"
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print body
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print " return C;"
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print "}"
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