650 lines
29 KiB
Ada
650 lines
29 KiB
Ada
------------------------------------------------------------------------------
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-- --
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-- GNAT LIBRARY COMPONENTS --
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-- --
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-- S Y S T E M . R E G P A T --
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-- --
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-- S p e c --
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-- --
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-- Copyright (C) 1986 by University of Toronto. --
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-- Copyright (C) 1996-2014, AdaCore --
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-- --
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-- GNAT is free software; you can redistribute it and/or modify it under --
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-- terms of the GNU General Public License as published by the Free Soft- --
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-- ware Foundation; either version 3, or (at your option) any later ver- --
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-- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
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-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
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-- or FITNESS FOR A PARTICULAR PURPOSE. --
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-- --
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-- As a special exception under Section 7 of GPL version 3, you are granted --
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-- additional permissions described in the GCC Runtime Library Exception, --
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-- version 3.1, as published by the Free Software Foundation. --
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-- --
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-- You should have received a copy of the GNU General Public License and --
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-- a copy of the GCC Runtime Library Exception along with this program; --
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-- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
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-- <http://www.gnu.org/licenses/>. --
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-- --
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-- GNAT was originally developed by the GNAT team at New York University. --
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-- Extensive contributions were provided by Ada Core Technologies Inc. --
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-- --
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------------------------------------------------------------------------------
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-- This package implements roughly the same set of regular expressions as
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-- are available in the Perl or Python programming languages.
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-- This is an extension of the original V7 style regular expression library
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-- written in C by Henry Spencer. Apart from the translation to Ada, the
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-- interface has been considerably changed to use the Ada String type
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-- instead of C-style nul-terminated strings.
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-- Note: this package is in the System hierarchy so that it can be directly
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-- be used by other predefined packages. User access to this package is via
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-- a renaming of this package in GNAT.Regpat (file g-regpat.ads).
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package System.Regpat is
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pragma Preelaborate;
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-- The grammar is the following:
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-- regexp ::= expr
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-- ::= ^ expr -- anchor at the beginning of string
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-- ::= expr $ -- anchor at the end of string
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-- expr ::= term
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-- ::= term | term -- alternation (term or term ...)
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-- term ::= item
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-- ::= item item ... -- concatenation (item then item)
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-- item ::= elmt -- match elmt
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-- ::= elmt * -- zero or more elmt's
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-- ::= elmt + -- one or more elmt's
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-- ::= elmt ? -- matches elmt or nothing
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-- ::= elmt *? -- zero or more times, minimum number
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-- ::= elmt +? -- one or more times, minimum number
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-- ::= elmt ?? -- zero or one time, minimum number
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-- ::= elmt { num } -- matches elmt exactly num times
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-- ::= elmt { num , } -- matches elmt at least num times
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-- ::= elmt { num , num2 } -- matches between num and num2 times
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-- ::= elmt { num }? -- matches elmt exactly num times
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-- ::= elmt { num , }? -- matches elmt at least num times
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-- non-greedy version
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-- ::= elmt { num , num2 }? -- matches between num and num2 times
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-- non-greedy version
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-- elmt ::= nchr -- matches given character
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-- ::= [range range ...] -- matches any character listed
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-- ::= [^ range range ...] -- matches any character not listed
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-- ::= . -- matches any single character
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-- -- except newlines
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-- ::= ( expr ) -- parenthesis used for grouping
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-- ::= (?: expr ) -- non-capturing parenthesis
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-- ::= \ num -- reference to num-th capturing
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-- parenthesis
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-- range ::= char - char -- matches chars in given range
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-- ::= nchr
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-- ::= [: posix :] -- any character in the POSIX range
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-- ::= [:^ posix :] -- not in the POSIX range
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-- posix ::= alnum -- alphanumeric characters
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-- ::= alpha -- alphabetic characters
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-- ::= ascii -- ascii characters (0 .. 127)
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-- ::= cntrl -- control chars (0..31, 127..159)
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-- ::= digit -- digits ('0' .. '9')
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-- ::= graph -- graphic chars (32..126, 160..255)
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-- ::= lower -- lower case characters
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-- ::= print -- printable characters (32..127)
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-- -- and whitespaces (9 .. 13)
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-- ::= punct -- printable, except alphanumeric
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-- ::= space -- space characters
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-- ::= upper -- upper case characters
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-- ::= word -- alphanumeric characters
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-- ::= xdigit -- hexadecimal chars (0..9, a..f)
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-- char ::= any character, including special characters
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-- ASCII.NUL is not supported.
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-- nchr ::= any character except \()[].*+?^ or \char to match char
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-- \n means a newline (ASCII.LF)
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-- \t means a tab (ASCII.HT)
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-- \r means a return (ASCII.CR)
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-- \b matches the empty string at the beginning or end of a
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-- word. A word is defined as a set of alphanumerical
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-- characters (see \w below).
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-- \B matches the empty string only when *not* at the
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-- beginning or end of a word.
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-- \d matches any digit character ([0-9])
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-- \D matches any non digit character ([^0-9])
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-- \s matches any white space character. This is equivalent
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-- to [ \t\n\r\f\v] (tab, form-feed, vertical-tab,...
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-- \S matches any non-white space character.
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-- \w matches any alphanumeric character or underscore.
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-- This include accented letters, as defined in the
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-- package Ada.Characters.Handling.
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-- \W matches any non-alphanumeric character.
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-- \A match the empty string only at the beginning of the
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-- string, whatever flags are used for Compile (the
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-- behavior of ^ can change, see Regexp_Flags below).
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-- \G match the empty string only at the end of the
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-- string, whatever flags are used for Compile (the
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-- behavior of $ can change, see Regexp_Flags below).
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-- ... ::= is used to indication repetition (one or more terms)
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-- Embedded newlines are not matched by the ^ operator.
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-- It is possible to retrieve the substring matched a parenthesis
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-- expression. Although the depth of parenthesis is not limited in the
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-- regexp, only the first 9 substrings can be retrieved.
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-- The highest value possible for the arguments to the curly operator ({})
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-- are given by the constant Max_Curly_Repeat below.
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-- The operators '*', '+', '?' and '{}' always match the longest possible
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-- substring. They all have a non-greedy version (with an extra ? after the
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-- operator), which matches the shortest possible substring.
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-- For instance:
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-- regexp="<.*>" string="<h1>title</h1>" matches="<h1>title</h1>"
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-- regexp="<.*?>" string="<h1>title</h1>" matches="<h1>"
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--
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-- '{' and '}' are only considered as special characters if they appear
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-- in a substring that looks exactly like '{n}', '{n,m}' or '{n,}', where
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-- n and m are digits. No space is allowed. In other contexts, the curly
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-- braces will simply be treated as normal characters.
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-- Compiling Regular Expressions
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-- =============================
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-- To use this package, you first need to compile the regular expression
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-- (a string) into a byte-code program, in a Pattern_Matcher structure.
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-- This first step checks that the regexp is valid, and optimizes the
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-- matching algorithms of the second step.
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-- Two versions of the Compile subprogram are given: one in which this
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-- package will compute itself the best possible size to allocate for the
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-- byte code; the other where you must allocate enough memory yourself. An
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-- exception is raised if there is not enough memory.
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-- declare
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-- Regexp : String := "a|b";
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-- Matcher : Pattern_Matcher := Compile (Regexp);
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-- -- The size for matcher is automatically allocated
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-- Matcher2 : Pattern_Matcher (1000);
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-- -- Some space is allocated directly.
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-- begin
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-- Compile (Matcher2, Regexp);
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-- ...
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-- end;
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-- Note that the second version is significantly faster, since with the
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-- first version the regular expression has in fact to be compiled twice
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-- (first to compute the size, then to generate the byte code).
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-- Note also that you cannot use the function version of Compile if you
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-- specify the size of the Pattern_Matcher, since the discriminants will
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-- most probably be different and you will get a Constraint_Error
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-- Matching Strings
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-- ================
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-- Once the regular expression has been compiled, you can use it as often
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-- as needed to match strings.
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-- Several versions of the Match subprogram are provided, with different
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-- parameters and return results.
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-- See the description under each of these subprograms
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-- Here is a short example showing how to get the substring matched by
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-- the first parenthesis pair.
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-- declare
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-- Matches : Match_Array (0 .. 1);
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-- Regexp : String := "a(b|c)d";
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-- Str : String := "gacdg";
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-- begin
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-- Match (Compile (Regexp), Str, Matches);
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-- return Str (Matches (1).First .. Matches (1).Last);
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-- -- returns 'c'
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-- end;
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-- Finding all occurrences
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-- =======================
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-- Finding all the occurrences of a regular expression in a string cannot
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-- be done by simply passing a slice of the string. This wouldn't work for
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-- anchored regular expressions (the ones starting with "^" or ending with
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-- "$").
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-- Instead, you need to use the last parameter to Match (Data_First), as in
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-- the following loop:
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-- declare
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-- Str : String :=
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-- "-- first line" & ASCII.LF & "-- second line";
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-- Matches : Match_Array (0 .. 0);
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-- Regexp : Pattern_Matcher := Compile ("^--", Multiple_Lines);
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-- Current : Natural := Str'First;
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-- begin
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-- loop
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-- Match (Regexp, Str, Matches, Current);
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-- exit when Matches (0) = No_Match;
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--
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-- -- Process the match at position Matches (0).First
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--
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-- Current := Matches (0).Last + 1;
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-- end loop;
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-- end;
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-- String Substitution
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-- ===================
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-- No subprogram is currently provided for string substitution.
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-- However, this is easy to simulate with the parenthesis groups, as
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-- shown below.
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-- This example swaps the first two words of the string:
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-- declare
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-- Regexp : String := "([a-z]+) +([a-z]+)";
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-- Str : String := " first second third ";
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-- Matches : Match_Array (0 .. 2);
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-- begin
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-- Match (Compile (Regexp), Str, Matches);
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-- return Str (Str'First .. Matches (1).First - 1)
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-- & Str (Matches (2).First .. Matches (2).Last)
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-- & " "
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-- & Str (Matches (1).First .. Matches (1).Last)
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-- & Str (Matches (2).Last + 1 .. Str'Last);
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-- -- returns " second first third "
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-- end;
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---------------
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-- Constants --
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---------------
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Expression_Error : exception;
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-- This exception is raised when trying to compile an invalid regular
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-- expression. All subprograms taking an expression as parameter may raise
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-- Expression_Error.
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Max_Paren_Count : constant := 255;
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-- Maximum number of parenthesis in a regular expression. This is limited
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-- by the size of a Character, as found in the byte-compiled version of
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-- regular expressions.
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Max_Curly_Repeat : constant := 32767;
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-- Maximum number of repetition for the curly operator. The digits in the
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-- {n}, {n,} and {n,m } operators cannot be higher than this constant,
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-- since they have to fit on two characters in the byte-compiled version of
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-- regular expressions.
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Max_Program_Size : constant := 2**15 - 1;
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-- Maximum size that can be allocated for a program
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type Program_Size is range 0 .. Max_Program_Size;
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for Program_Size'Size use 16;
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-- Number of bytes allocated for the byte-compiled version of a regular
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-- expression. The size required depends on the complexity of the regular
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-- expression in a complex manner that is undocumented (other than in the
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-- body of the Compile procedure). Normally the size is automatically set
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-- and the programmer need not be concerned about it. There are two
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-- exceptions to this. First in the calls to Match, it is possible to
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-- specify a non-zero size that is known to be large enough. This can
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-- slightly increase the efficiency by avoiding a copy. Second, in the case
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-- of calling compile, it is possible using the procedural form of Compile
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-- to use a single Pattern_Matcher variable for several different
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-- expressions by setting its size sufficiently large.
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Auto_Size : constant := 0;
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-- Used in calls to Match to indicate that the Size should be set to
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-- a value appropriate to the expression being used automatically.
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type Regexp_Flags is mod 256;
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for Regexp_Flags'Size use 8;
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-- Flags that can be given at compile time to specify default
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-- properties for the regular expression.
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No_Flags : constant Regexp_Flags;
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Case_Insensitive : constant Regexp_Flags;
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-- The automaton is optimized so that the matching is done in a case
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-- insensitive manner (upper case characters and lower case characters
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-- are all treated the same way).
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Single_Line : constant Regexp_Flags;
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-- Treat the Data we are matching as a single line. This means that
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-- ^ and $ will ignore \n (unless Multiple_Lines is also specified),
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-- and that '.' will match \n.
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Multiple_Lines : constant Regexp_Flags;
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-- Treat the Data as multiple lines. This means that ^ and $ will also
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-- match on internal newlines (ASCII.LF), in addition to the beginning
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-- and end of the string.
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--
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-- This can be combined with Single_Line.
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-----------------
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-- Match_Array --
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-----------------
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subtype Match_Count is Natural range 0 .. Max_Paren_Count;
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type Match_Location is record
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First : Natural := 0;
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Last : Natural := 0;
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end record;
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type Match_Array is array (Match_Count range <>) of Match_Location;
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-- Used for regular expressions that can contain parenthesized
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-- subexpressions. Certain Match subprograms below produce Matches of type
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-- Match_Array. Each component of Matches is set to the subrange of the
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-- matches substring, or to No_Match if no match. Matches (N) is for the
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-- N'th parenthesized subexpressions; Matches (0) is for the whole
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-- expression.
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--
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-- Non-capturing parenthesis (introduced with (?:...)) can not be
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-- retrieved and do not count in the match array index.
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--
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-- For instance, if your regular expression is: "a((b*)c+)(d+)", then
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-- 12 3
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-- Matches (0) is for "a((b*)c+)(d+)" (the entire expression)
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-- Matches (1) is for "(b*)c+"
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-- Matches (2) is for "b*"
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-- Matches (3) is for "d+"
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--
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-- The number of parenthesis groups that can be retrieved is limited only
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-- by Max_Paren_Count.
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--
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-- Normally, the bounds of the Matches actual parameter will be
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-- 0 .. Paren_Count (Regexp), to get all the matches. However, it is fine
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-- if Matches is shorter than that on either end; missing components will
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-- be ignored. Thus, in the above example, you could use 2 .. 2 if all you
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-- care about it the second parenthesis pair "b*". Likewise, if
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-- Matches'Last > Paren_Count (Regexp), the extra components will be set to
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-- No_Match.
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No_Match : constant Match_Location := (First => 0, Last => 0);
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-- The No_Match constant is (0, 0) to differentiate between matching a null
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-- string at position 1, which uses (1, 0) and no match at all.
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---------------------------------
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-- Pattern_Matcher Compilation --
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---------------------------------
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-- The subprograms here are used to precompile regular expressions for use
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-- in subsequent Match calls. Precompilation improves efficiency if the
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-- same regular expression is to be used in more than one Match call.
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type Pattern_Matcher (Size : Program_Size) is private;
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-- Type used to represent a regular expression compiled into byte code
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Never_Match : constant Pattern_Matcher;
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-- A regular expression that never matches anything
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function Compile
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(Expression : String;
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Flags : Regexp_Flags := No_Flags) return Pattern_Matcher;
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-- Compile a regular expression into internal code
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--
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-- Raises Expression_Error if Expression is not a legal regular expression
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--
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-- The appropriate size is calculated automatically to correspond to the
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-- provided expression. This is the normal default method of compilation.
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-- Note that it is generally not possible to assign the result of two
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-- different calls to this Compile function to the same Pattern_Matcher
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-- variable, since the sizes will differ.
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--
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-- Flags is the default value to use to set properties for Expression
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-- (e.g. case sensitivity,...).
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procedure Compile
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(Matcher : out Pattern_Matcher;
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Expression : String;
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Final_Code_Size : out Program_Size;
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Flags : Regexp_Flags := No_Flags);
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-- Compile a regular expression into internal code
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-- This procedure is significantly faster than the Compile function since
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-- it avoids the extra step of precomputing the required size.
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--
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-- However, it requires the user to provide a Pattern_Matcher variable
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-- whose size is preset to a large enough value. One advantage of this
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-- approach, in addition to the improved efficiency, is that the same
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-- Pattern_Matcher variable can be used to hold the compiled code for
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-- several different regular expressions by setting a size that is large
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-- enough to accommodate all possibilities.
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--
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-- In this version of the procedure call, the actual required code size is
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-- returned. Also if Matcher.Size is zero on entry, then the resulting code
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-- is not stored. A call with Matcher.Size set to Auto_Size can thus be
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-- used to determine the space required for compiling the given regular
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-- expression.
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--
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-- This function raises Storage_Error if Matcher is too small to hold
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-- the resulting code (i.e. Matcher.Size has too small a value).
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--
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-- Expression_Error is raised if the string Expression does not contain
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-- a valid regular expression.
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--
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-- Flags is the default value to use to set properties for Expression (case
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-- sensitivity,...).
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procedure Compile
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(Matcher : out Pattern_Matcher;
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Expression : String;
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Flags : Regexp_Flags := No_Flags);
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-- Same procedure as above, expect it does not return the final
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-- program size, and Matcher.Size cannot be Auto_Size.
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function Paren_Count (Regexp : Pattern_Matcher) return Match_Count;
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pragma Inline (Paren_Count);
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-- Return the number of parenthesis pairs in Regexp.
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--
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-- This is the maximum index that will be filled if a Match_Array is
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-- used as an argument to Match.
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--
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-- Thus, if you want to be sure to get all the parenthesis, you should
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-- do something like:
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--
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-- declare
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-- Regexp : Pattern_Matcher := Compile ("a(b*)(c+)");
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-- Matched : Match_Array (0 .. Paren_Count (Regexp));
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-- begin
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-- Match (Regexp, "a string", Matched);
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-- end;
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-------------
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-- Quoting --
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-------------
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function Quote (Str : String) return String;
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-- Return a version of Str so that every special character is quoted.
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-- The resulting string can be used in a regular expression to match
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-- exactly Str, whatever character was present in Str.
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--------------
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-- Matching --
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--------------
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-- The Match subprograms are given a regular expression in string
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-- form, and perform the corresponding match. The following parameters
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-- are present in all forms of the Match call.
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-- Expression contains the regular expression to be matched as a string
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-- Data contains the string to be matched
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-- Data_First is the lower bound for the match, i.e. Data (Data_First)
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-- will be the first character to be examined. If Data_First is set to
|
|
-- the special value of -1 (the default), then the first character to
|
|
-- be examined is Data (Data_First). However, the regular expression
|
|
-- character ^ (start of string) still refers to the first character
|
|
-- of the full string (Data (Data'First)), which is why there is a
|
|
-- separate mechanism for specifying Data_First.
|
|
|
|
-- Data_Last is the upper bound for the match, i.e. Data (Data_Last)
|
|
-- will be the last character to be examined. If Data_Last is set to
|
|
-- the special value of Positive'Last (the default), then the last
|
|
-- character to be examined is Data (Data_Last). However, the regular
|
|
-- expression character $ (end of string) still refers to the last
|
|
-- character of the full string (Data (Data'Last)), which is why there
|
|
-- is a separate mechanism for specifying Data_Last.
|
|
|
|
-- Note: the use of Data_First and Data_Last is not equivalent to
|
|
-- simply passing a slice as Expression because of the handling of
|
|
-- regular expression characters ^ and $.
|
|
|
|
-- Size is the size allocated for the compiled byte code. Normally
|
|
-- this is defaulted to Auto_Size which means that the appropriate
|
|
-- size is allocated automatically. It is possible to specify an
|
|
-- explicit size, which must be sufficiently large. This slightly
|
|
-- increases the efficiency by avoiding the extra step of computing
|
|
-- the appropriate size.
|
|
|
|
-- The following exceptions can be raised in calls to Match
|
|
--
|
|
-- Storage_Error is raised if a non-zero value is given for Size
|
|
-- and it is too small to hold the compiled byte code.
|
|
--
|
|
-- Expression_Error is raised if the given expression is not a legal
|
|
-- regular expression.
|
|
|
|
procedure Match
|
|
(Expression : String;
|
|
Data : String;
|
|
Matches : out Match_Array;
|
|
Size : Program_Size := Auto_Size;
|
|
Data_First : Integer := -1;
|
|
Data_Last : Positive := Positive'Last);
|
|
-- This version returns the result of the match stored in Match_Array;
|
|
-- see comments under Match_Array above for details.
|
|
|
|
function Match
|
|
(Expression : String;
|
|
Data : String;
|
|
Size : Program_Size := Auto_Size;
|
|
Data_First : Integer := -1;
|
|
Data_Last : Positive := Positive'Last) return Natural;
|
|
-- This version returns the position where Data matches, or if there is
|
|
-- no match, then the value Data'First - 1.
|
|
|
|
function Match
|
|
(Expression : String;
|
|
Data : String;
|
|
Size : Program_Size := Auto_Size;
|
|
Data_First : Integer := -1;
|
|
Data_Last : Positive := Positive'Last) return Boolean;
|
|
-- This version returns True if the match succeeds, False otherwise
|
|
|
|
------------------------------------------------
|
|
-- Matching a Pre-Compiled Regular Expression --
|
|
------------------------------------------------
|
|
|
|
-- The following functions are significantly faster if you need to reuse
|
|
-- the same regular expression multiple times, since you only have to
|
|
-- compile it once. For these functions you must first compile the
|
|
-- expression with a call to Compile as previously described.
|
|
|
|
-- The parameters Data, Data_First and Data_Last are as described
|
|
-- in the previous section.
|
|
|
|
function Match
|
|
(Self : Pattern_Matcher;
|
|
Data : String;
|
|
Data_First : Integer := -1;
|
|
Data_Last : Positive := Positive'Last) return Natural;
|
|
-- Match Data using the given pattern matcher. Returns the position
|
|
-- where Data matches, or (Data'First - 1) if there is no match.
|
|
|
|
function Match
|
|
(Self : Pattern_Matcher;
|
|
Data : String;
|
|
Data_First : Integer := -1;
|
|
Data_Last : Positive := Positive'Last) return Boolean;
|
|
-- Return True if Data matches using the given pattern matcher
|
|
|
|
pragma Inline (Match);
|
|
-- All except the last one below
|
|
|
|
procedure Match
|
|
(Self : Pattern_Matcher;
|
|
Data : String;
|
|
Matches : out Match_Array;
|
|
Data_First : Integer := -1;
|
|
Data_Last : Positive := Positive'Last);
|
|
-- Match Data using the given pattern matcher and store result in Matches;
|
|
-- see comments under Match_Array above for details.
|
|
|
|
-----------
|
|
-- Debug --
|
|
-----------
|
|
|
|
procedure Dump (Self : Pattern_Matcher);
|
|
-- Dump the compiled version of the regular expression matched by Self
|
|
|
|
--------------------------
|
|
-- Private Declarations --
|
|
--------------------------
|
|
|
|
private
|
|
|
|
subtype Pointer is Program_Size;
|
|
-- The Pointer type is used to point into Program_Data
|
|
|
|
-- Note that the pointer type is not necessarily 2 bytes
|
|
-- although it is stored in the program using 2 bytes
|
|
|
|
type Program_Data is array (Pointer range <>) of Character;
|
|
|
|
Program_First : constant := 1;
|
|
|
|
-- The "internal use only" fields in regexp are present to pass info from
|
|
-- compile to execute that permits the execute phase to run lots faster on
|
|
-- simple cases. They are:
|
|
|
|
-- First character that must begin a match or ASCII.NUL
|
|
-- Anchored true iff match must start at beginning of line
|
|
-- Must_Have pointer to string that match must include or null
|
|
-- Must_Have_Length length of Must_Have string
|
|
|
|
-- First and Anchored permit very fast decisions on suitable starting
|
|
-- points for a match, cutting down the work a lot. Must_Have permits fast
|
|
-- rejection of lines that cannot possibly match.
|
|
|
|
-- The Must_Have tests are costly enough that Optimize supplies a Must_Have
|
|
-- only if the r.e. contains something potentially expensive (at present,
|
|
-- the only such thing detected is * or at the start of the r.e., which can
|
|
-- involve a lot of backup). The length is supplied because the test in
|
|
-- Execute needs it and Optimize is computing it anyway.
|
|
|
|
-- The initialization is meant to fail-safe in case the user of this
|
|
-- package tries to use an uninitialized matcher. This takes advantage
|
|
-- of the knowledge that ASCII.NUL translates to the end-of-program (EOP)
|
|
-- instruction code of the state machine.
|
|
|
|
No_Flags : constant Regexp_Flags := 0;
|
|
Case_Insensitive : constant Regexp_Flags := 1;
|
|
Single_Line : constant Regexp_Flags := 2;
|
|
Multiple_Lines : constant Regexp_Flags := 4;
|
|
|
|
type Pattern_Matcher (Size : Pointer) is record
|
|
First : Character := ASCII.NUL; -- internal use only
|
|
Anchored : Boolean := False; -- internal use only
|
|
Must_Have : Pointer := 0; -- internal use only
|
|
Must_Have_Length : Natural := 0; -- internal use only
|
|
Paren_Count : Natural := 0; -- # paren groups
|
|
Flags : Regexp_Flags := No_Flags;
|
|
Program : Program_Data (Program_First .. Size) :=
|
|
(others => ASCII.NUL);
|
|
end record;
|
|
|
|
Never_Match : constant Pattern_Matcher :=
|
|
(0, ASCII.NUL, False, 0, 0, 0, No_Flags, (others => ASCII.NUL));
|
|
|
|
end System.Regpat;
|