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344
lib/impure/re.nim
Executable file
344
lib/impure/re.nim
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#
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#
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# Nimrod's Runtime Library
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# (c) Copyright 2010 Andreas Rumpf
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#
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# See the file "copying.txt", included in this
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# distribution, for details about the copyright.
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#
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## Regular expression support for Nimrod. Consider using the pegs module
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## instead.
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## This module is implemented by providing a wrapper around the
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## `PRCE (Perl-Compatible Regular Expressions) <http://www.pcre.org>`_
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## C library. This means that your application will depend on the PRCE
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## library's licence when using this module, which should not be a problem
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## though.
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## PRCE's licence follows:
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##
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## .. include:: ../doc/regexprs.txt
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##
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import
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pcre, strutils
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const
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MaxSubpatterns* = 10
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## defines the maximum number of subpatterns that can be captured.
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## More subpatterns cannot be captured!
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type
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TRegExFlag* = enum ## options for regular expressions
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reIgnoreCase = 0, ## do caseless matching
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reMultiLine = 1, ## ``^`` and ``$`` match newlines within data
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reDotAll = 2, ## ``.`` matches anything including NL
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reExtended = 3 ## ignore whitespace and ``#`` comments
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TRegExDesc {.pure, final.} = object
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h: PPcre
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TRegEx* = ref TRegExDesc ## a compiled regular expression
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EInvalidRegEx* = object of EInvalidValue
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## is raised if the pattern is no valid regular expression.
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proc rawCompile(pattern: string, flags: cint): PPcre =
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var
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msg: CString
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offset: cint
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com = pcre.Compile(pattern, flags, addr(msg), addr(offset), nil)
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if com == nil:
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var e: ref EInvalidRegEx
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new(e)
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e.msg = $msg & "\n" & pattern & "\n" & repeatChar(offset) & "^\n"
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raise e
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return com
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proc finalizeRegEx(x: TRegEx) =
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# XXX This is a hack, but PCRE does not export it's "free" function properly.
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# Sigh. The hack relies on PCRE's implementation (see ``pcre_get.c``).
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# Fortunately the implementation is unlikely to change.
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pcre.free_substring(cast[cstring](x.h))
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proc re*(s: string, flags = {reExtended}): TRegEx =
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## Constructor of regular expressions. Note that Nimrod's
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## extended raw string literals supports this syntax ``re"[abc]"`` as
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## a short form for ``re(r"[abc]")``.
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new(result, finalizeRegEx)
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result.h = rawCompile(s, cast[cint](flags))
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proc matchOrFind(s: string, pattern: TRegEx, matches: var openarray[string],
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start, flags: cint): cint =
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var
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rawMatches: array[0..maxSubpatterns * 3 - 1, cint]
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res = pcre.Exec(pattern.h, nil, s, len(s), start, flags,
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cast[ptr cint](addr(rawMatches)), maxSubpatterns * 3)
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if res < 0'i32: return res
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for i in 1..int(res)-1:
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var a = rawMatches[i * 2]
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var b = rawMatches[i * 2 + 1]
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if a >= 0'i32: matches[i-1] = copy(s, int(a), int(b)-1)
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else: matches[i-1] = ""
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return rawMatches[1] - rawMatches[0]
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proc matchOrFind(s: string, pattern: TRegEx, start, flags: cint): cint =
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var rawMatches: array [0..maxSubpatterns * 3 - 1, cint]
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result = pcre.Exec(pattern.h, nil, s, len(s), start, flags,
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cast[ptr cint](addr(rawMatches)), maxSubpatterns * 3)
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if result >= 0'i32:
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result = rawMatches[1] - rawMatches[0]
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proc match*(s: string, pattern: TRegEx, matches: var openarray[string],
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start = 0): bool =
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## returns ``true`` if ``s[start..]`` matches the ``pattern`` and
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## the captured substrings in the array ``matches``. If it does not
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## match, nothing is written into ``matches`` and ``false`` is
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## returned.
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return matchOrFind(s, pattern, matches, start,
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pcre.ANCHORED) == cint(s.len - start)
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proc match*(s: string, pattern: TRegEx, start = 0): bool =
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## returns ``true`` if ``s[start..]`` matches the ``pattern``.
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return matchOrFind(s, pattern, start, pcre.ANCHORED) == cint(s.len - start)
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proc matchLen*(s: string, pattern: TRegEx, matches: var openarray[string],
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start = 0): int =
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## the same as ``match``, but it returns the length of the match,
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## if there is no match, -1 is returned. Note that a match length
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## of zero can happen.
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return matchOrFind(s, pattern, matches, start, pcre.ANCHORED)
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proc matchLen*(s: string, pattern: TRegEx, start = 0): int =
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## the same as ``match``, but it returns the length of the match,
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## if there is no match, -1 is returned. Note that a match length
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## of zero can happen.
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return matchOrFind(s, pattern, start, pcre.ANCHORED)
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proc find*(s: string, pattern: TRegEx, matches: var openarray[string],
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start = 0): int =
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## returns the starting position of ``pattern`` in ``s`` and the captured
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## substrings in the array ``matches``. If it does not match, nothing
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## is written into ``matches`` and -1 is returned.
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var
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rawMatches: array[0..maxSubpatterns * 3 - 1, cint]
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res = pcre.Exec(pattern.h, nil, s, len(s), start, 0'i32,
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cast[ptr cint](addr(rawMatches)), maxSubpatterns * 3)
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if res < 0'i32: return res
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for i in 1..int(res)-1:
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var a = rawMatches[i * 2]
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var b = rawMatches[i * 2 + 1]
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if a >= 0'i32: matches[i-1] = copy(s, int(a), int(b)-1)
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else: matches[i-1] = ""
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return rawMatches[0]
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proc find*(s: string, pattern: TRegEx, start = 0): int =
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## returns the starting position of ``pattern`` in ``s``. If it does not
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## match, -1 is returned.
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var matches: array[0..maxSubpatterns-1, string]
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result = find(s, pattern, matches, start)
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template `=~` *(s: string, pattern: TRegEx): expr =
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## This calls ``match`` with an implicit declared ``matches`` array that
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## can be used in the scope of the ``=~`` call:
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##
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## .. code-block:: nimrod
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##
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## if line =~ re"\s*(\w+)\s*\=\s*(\w+)":
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## # matches a key=value pair:
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## echo("Key: ", matches[0])
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## echo("Value: ", matches[1])
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## elif line =~ re"\s*(\#.*)":
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## # matches a comment
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## # note that the implicit ``matches`` array is different from the
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## # ``matches`` array of the first branch
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## echo("comment: ", matches[0])
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## else:
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## echo("syntax error")
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##
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when not definedInScope(matches):
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var matches: array[0..maxSubPatterns-1, string]
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match(s, pattern, matches)
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# ------------------------- more string handling ------------------------------
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proc contains*(s: string, pattern: TRegEx, start = 0): bool =
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## same as ``find(s, pattern, start) >= 0``
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return find(s, pattern, start) >= 0
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proc contains*(s: string, pattern: TRegEx, matches: var openArray[string],
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start = 0): bool =
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## same as ``find(s, pattern, matches, start) >= 0``
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return find(s, pattern, matches, start) >= 0
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proc startsWith*(s: string, prefix: TRegEx): bool =
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## returns true if `s` starts with the pattern `prefix`
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result = matchLen(s, prefix) >= 0
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proc endsWith*(s: string, suffix: TRegEx): bool =
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## returns true if `s` ends with the pattern `prefix`
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for i in 0 .. s.len-1:
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if matchLen(s, suffix, i) == s.len - i: return true
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proc replace*(s: string, sub: TRegEx, by: string): string =
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## Replaces `sub` in `s` by the string `by`. Captures can be accessed in `by`
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## with the notation ``$i`` and ``$#`` (see strutils.`%`). Examples:
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##
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## .. code-block:: nimrod
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## "var1=key; var2=key2".replace(re"(\w+)'='(\w+)", "$1<-$2$2")
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##
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## Results in:
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##
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## .. code-block:: nimrod
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##
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## "var1<-keykey; val2<-key2key2"
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result = ""
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var i = 0
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var caps: array[0..maxSubpatterns-1, string]
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while i < s.len:
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var x = matchLen(s, sub, caps, i)
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if x <= 0:
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add(result, s[i])
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inc(i)
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else:
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addf(result, by, caps)
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inc(i, x)
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# copy the rest:
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add(result, copy(s, i))
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proc parallelReplace*(s: string, subs: openArray[
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tuple[pattern: TRegEx, repl: string]]): string =
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## Returns a modified copy of `s` with the substitutions in `subs`
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## applied in parallel.
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result = ""
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var i = 0
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var caps: array[0..maxSubpatterns-1, string]
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while i < s.len:
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block searchSubs:
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for j in 0..high(subs):
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var x = matchLen(s, subs[j][0], caps, i)
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if x > 0:
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addf(result, subs[j][1], caps)
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inc(i, x)
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break searchSubs
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add(result, s[i])
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inc(i)
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# copy the rest:
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add(result, copy(s, i))
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proc transformFile*(infile, outfile: string,
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subs: openArray[tuple[pattern: TRegEx, repl: string]]) =
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## reads in the file `infile`, performs a parallel replacement (calls
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## `parallelReplace`) and writes back to `outfile`. Calls ``quit`` if an
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## error occurs. This is supposed to be used for quick scripting.
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var x = readFile(infile)
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if not isNil(x):
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var f: TFile
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if open(f, outfile, fmWrite):
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write(f, x.parallelReplace(subs))
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close(f)
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else:
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quit("cannot open for writing: " & outfile)
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else:
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quit("cannot open for reading: " & infile)
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iterator split*(s: string, sep: TRegEx): string =
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## Splits the string `s` into substrings.
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##
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## Substrings are separated by the regular expression `sep`.
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## Examples:
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##
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## .. code-block:: nimrod
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## for word in split("00232this02939is39an22example111", re"\d+"):
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## writeln(stdout, word)
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##
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## Results in:
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##
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## .. code-block:: nimrod
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## "this"
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## "is"
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## "an"
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## "example"
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##
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var
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first = 0
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last = 0
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while last < len(s):
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var x = matchLen(s, sep, last)
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if x > 0: inc(last, x)
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first = last
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while last < len(s):
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inc(last)
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x = matchLen(s, sep, last)
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if x > 0: break
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if first < last:
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yield copy(s, first, last-1)
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proc split*(s: string, sep: TRegEx): seq[string] =
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## Splits the string `s` into substrings.
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accumulateResult(split(s, sep))
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proc escapeRe*(s: string): string =
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## escapes `s` so that it is matched verbatim when used as a regular
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## expression.
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result = ""
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for c in items(s):
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case c
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of 'a'..'z', 'A'..'Z', '0'..'9', '_':
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result.add(c)
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else:
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result.add("\\x")
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result.add(toHex(ord(c), 2))
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const ## common regular expressions
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reIdentifier* = r"\b[a-zA-Z_]+[a-zA-Z_0-9]*\b" ## describes an identifier
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reNatural* = r"\b\d+\b" ## describes a natural number
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reInteger* = r"\b[-+]?\d+\b" ## describes an integer
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reHex* = r"\b0[xX][0-9a-fA-F]+\b" ## describes a hexadecimal number
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reBinary* = r"\b0[bB][01]+\b" ## describes a binary number (example: 0b11101)
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reOctal* = r"\b0[oO][0-7]+\b" ## describes an octal number (example: 0o777)
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reFloat* = r"\b[-+]?[0-9]*\.?[0-9]+([eE][-+]?[0-9]+)?\b"
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## describes a floating point number
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reEmail* = r"\b[a-zA-Z0-9!#$%&'*+/=?^_`{|}~\-]+(?:\. &" &
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r"[a-zA-Z0-9!#$%&'*+/=?^_`{|}~-]+)" &
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r"*@(?:[a-zA-Z0-9](?:[a-zA-Z0-9-]*[a-zA-Z0-9])?\.)+" &
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r"(?:[a-zA-Z]{2}|com|org|" &
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r"net|gov|mil|biz|info|mobi|name|aero|jobs|museum)\b"
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## describes a common email address
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reURL* = r"\b(http(s)?|ftp|gopher|telnet|file|notes|ms\-help):" &
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r"((//)|(\\\\))+[\w\d:#@%/;$()~_?\+\-\=\\\.\&]*\b"
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## describes an URL
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when isMainModule:
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assert match("(a b c)", re"\( .* \)")
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assert match("WHiLe", re("while", {reIgnoreCase}))
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assert "0158787".match(re"\d+")
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assert "ABC 0232".match(re"\w+\s+\d+")
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assert "ABC".match(re"\d+ | \w+")
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assert matchLen("key", re(reIdentifier)) == 3
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var pattern = re"[a-z0-9]+\s*=\s*[a-z0-9]+"
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assert matchLen("key1= cal9", pattern) == 11
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assert find("_____abc_______", re"abc") == 5
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var matches: array[0..5, string]
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if match("abcdefg", re"c(d)ef(g)", matches, 2):
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assert matches[0] == "d"
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assert matches[1] == "g"
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else:
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assert false
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if "abc" =~ re"(a)bcxyz|(\w+)":
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assert matches[1] == "abc"
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else:
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assert false
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assert "var1=key; var2=key2".endsWith(re"\w+=\w+")
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assert("var1=key; var2=key2".replace(re"(\w+)=(\w+)", "$1<-$2$2") ==
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"var1<-keykey; var2<-key2key2")
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for word in split("00232this02939is39an22example111", re"\d+"):
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writeln(stdout, word)
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