Documentation based on man pcreapi, written by Philip Hazel, 2007.
License : BSD3 Maintainer: Don Stewart firstname.lastname@example.org Stability : experimental Portability: CPP, FFI Tested with: GHC 6.8.2
Raw FFI bindings to PCRE functions and constants.
- type PCRE = ()
- data Regex = Regex !(ForeignPtr PCRE) !ByteString
- c_pcre_compile :: CString -> PCREOption -> Ptr CString -> Ptr CInt -> Ptr Word8 -> IO (Ptr PCRE)
- c_pcre_exec :: Ptr PCRE -> Ptr PCREExtra -> Ptr Word8 -> CInt -> CInt -> PCREExecOption -> Ptr CInt -> CInt -> IO CInt
- c_pcre_fullinfo :: Ptr PCRE -> Ptr PCREExtra -> PCREInfo -> Ptr a -> IO CInt
- data PCREOption
- combineOptions :: [PCREOption] -> PCREOption
- anchored :: PCREOption
- auto_callout :: PCREOption
- caseless :: PCREOption
- dollar_endonly :: PCREOption
- dotall :: PCREOption
- dupnames :: PCREOption
- extended :: PCREOption
- extra :: PCREOption
- firstline :: PCREOption
- multiline :: PCREOption
- newline_cr :: PCREOption
- newline_crlf :: PCREOption
- newline_lf :: PCREOption
- no_auto_capture :: PCREOption
- ungreedy :: PCREOption
- utf8 :: PCREOption
- no_utf8_check :: PCREOption
- data PCREExecOption
- combineExecOptions :: [PCREExecOption] -> PCREExecOption
- exec_anchored :: PCREExecOption
- exec_newline_cr :: PCREExecOption
- exec_newline_crlf :: PCREExecOption
- exec_newline_lf :: PCREExecOption
- exec_notbol :: PCREExecOption
- exec_noteol :: PCREExecOption
- exec_notempty :: PCREExecOption
- exec_no_utf8_check :: PCREExecOption
- exec_partial :: PCREExecOption
- type PCREError = CInt
- error_nomatch :: PCREError
- error_null :: PCREError
- error_badoption :: PCREError
- error_badmagic :: PCREError
- error_unknown_node :: PCREError
- error_nomemory :: PCREError
- error_nosubstring :: PCREError
- error_matchlimit :: PCREError
- error_callout :: PCREError
- error_badutf8 :: PCREError
- error_badutf8_offset :: PCREError
- error_partial :: PCREError
- error_badpartial :: PCREError
- error_internal :: PCREError
- error_badcount :: PCREError
- error_dfa_uitem :: PCREError
- error_dfa_ucond :: PCREError
- error_dfa_umlimit :: PCREError
- error_dfa_wssize :: PCREError
- error_dfa_recurse :: PCREError
- error_recursionlimit :: PCREError
- type PCREInfo = CInt
- info_options :: PCREInfo
- info_size :: PCREInfo
- info_capturecount :: PCREInfo
- info_backrefmax :: PCREInfo
- info_firstbyte :: PCREInfo
- info_firstchar :: PCREInfo
- info_firsttable :: PCREInfo
- info_lastliteral :: PCREInfo
- info_nameentrysize :: PCREInfo
- info_namecount :: PCREInfo
- info_nametable :: PCREInfo
- info_studysize :: PCREInfo
- info_default_tables :: PCREInfo
- type PCREConfig = CInt
- config_utf8 :: PCREConfig
- config_newline :: PCREConfig
- config_link_size :: PCREConfig
- config_posix_malloc_threshold :: PCREConfig
- config_match_limit :: PCREConfig
- config_stackrecurse :: PCREConfig
- config_unicode_properties :: PCREConfig
- config_match_limit_recursion :: PCREConfig
- type PCREExtraFlags = CInt
- extra_study_data :: PCREExtraFlags
- extra_match_limit :: PCREExtraFlags
- extra_callout_data :: PCREExtraFlags
- extra_tables :: PCREExtraFlags
- extra_match_limit_recursion :: PCREExtraFlags
- size_of_cint :: Int
A PCRE structure
An abstract pointer to a compiled PCRE Regex structure The structure allocated by the PCRE library will be deallocated automatically by the Haskell storage manager.
Compile a pattern to an internal form. The pattern is a C string terminated by a binary zero. A pointer to a single block of memory that is obtained via pcre_malloc is returned. It is up to the caller to free the memory (via pcre_free) when it is no longer required
The options argument contains various bit settings that affect the compilation. It should be zero if no options are required.
If errptr is NULL, pcre_compile() returns NULL immediately. Otherwise, if compilation of a pattern fails, pcre_compile() returns NULL, and sets the variable pointed to by errptr to point to a textual error message.
The offset from the start of the pattern to the character where the error was discovered is placed in the variable pointed to by erroffset, which must not be NULL.
This function matches a compiled regular expression against a given subject string, using a matching algorithm that is similar to Perl's. It returns offsets to captured substrings.
Its arguments are, in order:
codePoints to the compiled pattern (result of pcre_compile)
extraPoints to an associated pcre_extra structure (result of pcre_study), or is NULL
subjectPoints to the subject string
lengthLength of the subject string, in bytes
startoffsetOffset in bytes in the subject at which to start matching
ovectorPoints to a vector of ints for result substrings
ovecsizeNumber of elements in the vector (a multiple of 3)
Note, subject not required to be null terminated.
Return information about a compiled pattern
PCRE Options, an abstract newtyped Num wrapper over a CInt
A type for PCRE compile-time options. These are newtyped CInts, which can be bitwise-or'd together, using '(Data.Bits..|.)'
Combine a list of options into a single option, using bitwise (.|.)
If this bit is set, the pattern is forced to be anchored, that is, it is constrained to match only at the first matching point in the string that is being searched (the subject string). This effect can also be achieved by appropriate constructs in the pattern itself, which is the only way to do it in Perl.
These options (which are mutually exclusive) control what the \R escape sequence matches. The choice is either to match only CR, LF, or CRLF, or to match any Unicode new- line sequence. The default is specified when PCRE is built. It can be overridden from within the pattern, or by setting an option when a compiled pattern is matched.
bsr_anycrlf :: PCREOption bsr_anycrlf = PCREOption bsr_anycrlf_cint
bsr_unicode :: PCREOption bsr_unicode = PCREOption bsr_unicode_cint
If this bit is set, letters in the pattern match both upper and lower case letters. It is equivalent to Perl's /i option, and it can be changed within a pattern by a (?i) option setting. In UTF-8 mode, PCRE always understands the concept of case for characters whose values are less than 128, so caseless matching is always possible. For characters with higher values, the concept of case is supported if PCRE is compiled with Unicode property sup- port, but not otherwise. If you want to use caseless matching for characters 128 and above, you must ensure that PCRE is compiled with Unicode property support as well as with UTF-8 support.
If this bit is set, a dollar metacharacter in the pattern matches only at
the end of the subject string. Without this option, a dollar also matches
immediately before a newline at the end of the string (but not before any other
dollar_endonly option is ignored if
is set. There is no equivalent to this option in Perl, and no way to set it
within a pattern.
If this bit is set, a dot metacharater in the pattern matches all characters, including those that indicate newline. Without it, a dot does not match when the current position is at a newline. This option is equivalent to Perl's /s option, and it can be changed within a pattern by a (?s) option setting. A negative class such as [^a] always matches newline characters, independent of the setting of this option.
If this bit is set, names used to identify capturing subpatterns need not be unique. This can be helpful for certain types of pattern when it is known that only one instance of the named subpattern can ever be matched. There are more details of named subpatterns in the man pcreapi documentation.
If this bit is set, whitespace data characters in the pattern are totally ignored except when escaped or inside a character class. Whitespace does not include the VT character (code 11). In addition, characters between an unescaped # outside a character class and the next newline, inclusive, are also ignored. This is equivalent to Perl's /x option, and it can be changed within a pattern by a (?x) option setting.
This option makes it possible to include comments inside complicated patterns. Note, however, that this applies only to data characters. Whitespace characters may never appear within special character sequences in a pattern, for example within the sequence (?( which introduces a conditional subpattern.
This option was invented in order to turn on additional functionality of PCRE that is incompatible with Perl, but it is currently of very little use. When set, any backslash in a pattern that is followed by a letter that has no special meaning causes an error, thus reserving these combinations for future expansion. By default, as in Perl, a backslash followed by a letter with no special meaning is treated as a literal. (Perl can, however, be persuaded to give a warning for this.) There are at present no other features controlled by this option. It can also be set by a (?X) option setting within a pattern.
If this option is set, an unanchored pattern is required to match before or at the first newline in the subject string, though the matched text may continue over the newline.
By default, PCRE treats the subject string as consisting of a single line
of characters (even if it actually contains newlines). The start of line
metacharacter (^) matches only at the start of the string, while the end of line
metacharacter ($) matches only at the end of the string, or before a
terminating newline (unless
dollar_endonly is set). This is the same
multiline it is set, the start of line and end of line
constructs match immediately following or immediately before internal newlines
in the subject string, respectively, as well as at the very start and end. This
is equivalent to Perl's /m option, and it can be changed within a pattern by a
(?m) option setting. If there are no newlines in a subject string, or no occur-
rences of ^ or $ in a pattern, setting PCRE_MULTILINE has no effect.
These options override the default newline definition that
was chosen when PCRE was built. Setting the first or the
second specifies that a newline is indicated by a single
character (CR or LF, respectively). Setting
that a newline is indicated by the two-character CRLF sequence.
specifies that any of the three preceding sequences should
be recognized. Setting
newline_any specifies that any
Unicode newline sequence should be recognized. The Unicode
newline sequences are the three just mentioned, plus the
single characters VT (vertical tab, U+000B), FF (formfeed,
U+000C), NEL (next line, U+0085), LS (line separator,
U+2028), and PS (paragraph separator, U+2029). The last
two are recognized only in UTF-8 mode.
The newline setting in the options word uses three bits
that are treated as a number, giving eight possibilities.
Currently only six are used (default plus the five values
above). This means that if you set more than one newline
option, the combination may or may not be sensible. For
newline_lf is equivalent to
newline_crlf, but other combinations may yield unused numbers and
cause an error.
The only time that a line break is specially recognized
when compiling a pattern is if
extended is set, and
an unescaped # outside a character class is encountered.
This indicates a comment that lasts until after the next
line break sequence. In other circumstances, line break
sequences are treated as literal data, except that in
extended mode, both CR and LF are treated as whitespace characters
and are therefore ignored. --
The newline option that is set at compile time becomes the
default that is used for
exec but it can be overridden.
newline_any :: PCREOption newline_any = PCREOption newline_any_cint
newline_anycrlf :: PCREOption
newline_anycrlf = PCREOption newline_anycrlf_cint
If this option is set, it disables the use of numbered capturing parentheses in the pattern. Any opening paren- thesis that is not followed by ? behaves as if it were followed by ?: but named parentheses can still be used for capturing (and they acquire numbers in the usual way). There is no equivalent of this option in Perl.
This option inverts the greediness of the quantifiers so that they are not greedy by default, but become greedy if followed by ?. It is not compatible with Perl. It can also be set by a (?U) option setting within the pattern.
This option causes PCRE to regard both the pattern and the subject as strings of UTF-8 characters instead of single-byte character strings. However, it is available only when PCRE is built to include UTF-8 support. If not, the use of this option provokes an error. Details of how this option changes the behaviour of PCRE are given in the section on UTF-8 support in the main pcre page.
When PCRE_UTF8 is set, the validity of the pattern as a
UTF-8 string is automatically checked. There is a discussion
about the validity of UTF-8 strings in the main pcre
page. If an invalid UTF-8 sequence of bytes is found,
compile() returns an error. If you already know that
your pattern is valid, and you want to skip this check for
performance reasons, you can set the
option. When it is set, the effect of passing an invalid
UTF-8 string as a pattern is undefined. It may cause your
program to crash. Note that this option can also be passed
exec, to suppress the UTF-8 validity checking of subject strings.
PCRE exec-time options, an abstract, newtyped Num wrapper over CInt
Combine a list of exec options into a single option, using bitwise (.|.)
These options override the newline definition that was
chosen or defaulted when the pattern was compiled. For
details, see the description of
compile above. Dur-
ing matching, the newline choice affects the behaviour of
the dot, circumflex, and dollar metacharacters. It may
also alter the way the match position is advanced after a
match failure for an unanchored pattern.
is set, and a match attempt for an unanchored
pattern fails when the current position is at a CRLF
sequence, and the pattern contains no explicit matches for
CR or LF characters, the match position is advanced by two
characters instead of one, in other words, to after the
The above rule is a compromise that makes the most common
cases work as expected. For example, if the pattern is .+A
dotall option is not set), it does not match
the string \\r\\nA because, after failing at the start, it
skips both the CR and the LF before retrying. However, the
pattern [\\r\\n]A does match that string, because it contains
an explicit CR or LF reference, and so advances only
by one character after the first failure.
An explicit match for CR of LF is either a literal appear- ance of one of those characters, or one of the \r or \n escape sequences. Implicit matches such as [^X] do not count, nor does \s (which includes CR and LF in the char- acters that it matches).
Notwithstanding the above, anomalous effects may still occur when CRLF is a valid newline sequence and explicit \r or \n escapes appear in the pattern.
exec_newline_any :: PCREExecOption exec_newline_any = PCREExecOption exec_newline_any_cint
exec_newline_anycrlf :: PCREExecOption
exec_newline_anycrlf = PCREExecOption exec_newline_anycrlf_cint
This option specifies that first character of the subject
string is not the beginning of a line, so the circumflex
metacharacter should not match before it. Setting this
multiline (at compile time) causes circumflex
never to match. This option affects only the behaviour of
the circumflex metacharacter. It does not affect \A.
This option specifies that the end of the subject string
is not the end of a line, so the dollar metacharacter
should not match it nor (except in multiline mode) a newline
immediately before it. Setting this without
(at compile time) causes dollar never to match.
This option affects only the behaviour of the dollar
metacharacter. It does not affect \Z or \z.
An empty string is not considered to be a valid match if this option is set. If there are alternatives in the pattern, they are tried. If all the alternatives match the empty string, the entire match fails. For example, if the pattern
is applied to a string not beginning with a or b, it
matches the empty string at the start of the subject. With
notempty set, this match is not valid, so 'PCRE
searches further into the string for occurrences of a or
Perl has no direct equivalent of
notempty, but it
does make a special case of a pattern match of the empty
string within its split() function, and when using the /g
modifier. It is possible to emulate Perl's behaviour after
matching a null string by first trying the match again at
the same offset with PCRE_NOTEMPTY and PCRE_ANCHORED, and
then if that fails by advancing the starting offset (see
below) and trying an ordinary match again. There is some
code that demonstrates how to do this in the pcredemo.c
utf8 is set at compile time, the validity of the
subject as a UTF-8 string is automatically checked when
exec() is subsequently called. The value of
startoffset is also checked to ensure that it points to
the start of a UTF-8 character. There is a discussion
about the validity of UTF-8 strings in the section on
UTF-8 support in the main pcre page. If an invalid UTF-8
sequence of bytes is found, exec() returns the error
error_badutf8. If startoffset contains an invalid
error_badutf8_offset is returned.
If you already know that your subject is valid, and you
want to skip these checks for performance reasons, you can
no_utf8_check option when calling
exec. You might want to do this for the second and
subsequent calls to exec() if you are making repeated
calls to find all the matches in a single subject string.
However, you should be sure that the value of startoffset
points to the start of a UTF-8 character. When
no_utf8_check is set, the effect of passing an
invalid UTF-8 string as a subject, or a value of startoff-
set that does not point to the start of a UTF-8 character,
is undefined. Your program may crash.
This option turns on the partial matching feature. If the
subject string fails to match the pattern, but at some
point during the matching process the end of the subject
was reached (that is, the subject partially matches the
pattern and the failure to match occurred only because
there were not enough subject characters),
error_partial instead of
partial is used, there are restrictions on what
may appear in the pattern. These are discussed in the