 | pcre-light-0.4: A small, efficient and portable regex library for Perl 5 compatible regular expressions | Source code | Contents | Index |
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Text.Regex.PCRE.Light.Base |
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Description |
Documentation based on man pcreapi, written by Philip Hazel, 2007.
License : BSD3
Maintainer: Don Stewart dons@galois.com
Stability : experimental
Portability: CPP, FFI
Tested with: GHC 6.8.2
Raw FFI bindings to PCRE functions and constants.
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Synopsis |
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A PCRE structure
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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.
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C exports
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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.
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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:
- code Points to the compiled pattern (result of pcre_compile)
- extra Points to an associated pcre_extra structure (result of pcre_study), or is NULL
- subject Points to the subject string
- length Length of the subject string, in bytes
- startoffset Offset in bytes in the subject at which to start matching
- options Option bits
- ovector Points to a vector of ints for result substrings
- ovecsize Number of elements in the vector (a multiple of 3)
Note, subject not required to be null terminated.
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Return information about a compiled pattern
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PCRE Options, an abstract newtyped Num wrapper over a CInt
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A type for PCRE compile-time options. These are newtyped CInts,
which can be bitwise-or'd together, using '(Data.Bits..|.)'
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Combine a list of options into a single option, using bitwise (.|.)
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anchored
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.
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auto_callout
If this bit is set, compile automatically inserts callout
items, all with number 255, before each pattern item. For discussion
of the callout facility, see the man pcrecallout documentation
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bsr_anycrlf and bsr_unicode
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. See bse_anycrlf
bsr_unicode :: PCREOption
bsr_unicode = PCREOption bsr_unicode_cint
caseless
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.
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dollar_endonly
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
newlines). The dollar_endonly option is ignored if multiline
is set. There is no equivalent to this option in Perl, and no way to set it
within a pattern.
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dotall
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.
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dupnames
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.
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extended
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.
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extra
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.
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firstline
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.
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multiline
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
as Perl.
When 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.
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newline_cr', newline_lf, newline_crlf,
newline_anycrlf, newline_any
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 newline_crlf specifies
that a newline is indicated by the two-character CRLF sequence.
Setting newline_anycrlf
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
example, newline_cr with 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, see newline_any
newline_anycrlf :: PCREOption
newline_anycrlf = PCREOption newline_anycrlf_cint
newline_cr, see newline_any
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newline_crlf, see newline_any
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newline_lf, see newline_any
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no_auto_capture
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.
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ungreedy
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.
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utf8
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.
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no_utf8_check
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 no_utf8_check
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
to exec, to suppress the UTF-8 validity checking of subject strings.
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PCRE exec-time options, an abstract, newtyped Num wrapper over CInt
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Combine a list of exec options into a single option, using bitwise (.|.)
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anchored.
The anchored option limits exec to matching at
the first matching position. If a pattern was compiled
with anchored, or turned out to be anchored by virtue
of its contents, it cannot be made unachored at matching
time.
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newline_cr, newline_lf,
newline_crlf, newline_anycrlf, newline_any
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.
When newline_crlf, newline_anycrlf, or newline_any
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
CRLF.
The above rule is a compromise that makes the most common
cases work as expected. For example, if the pattern is .+A
(and the 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, see exec_newline_any
exec_newline_anycrlf :: PCREExecOption
exec_newline_anycrlf = PCREExecOption exec_newline_anycrlf_cint
exec_newline_cr, see exec_newline_any
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exec_newline_crlf, see exec_newline_any
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exec_newline_lf, see exec_newline_any
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PCRE_NOTBOL
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
without multiline (at compile time) causes circumflex
never to match. This option affects only the behaviour of
the circumflex metacharacter. It does not affect \A.
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noteol
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 multiline
(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.
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PCRE_NOTEMPTY
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
a?b?
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
b.
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
sample program.
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no_utf8_check
When 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
value, 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
set the 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.
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partial
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), exec
returns error_partial instead of error_nomatch.
When partial is used, there are restrictions on what
may appear in the pattern. These are discussed in the
pcrepartial documentation.
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PCRE Errors
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A type for PCRE Errors: exec-time error codes.
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PCRE Info
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PCRE Info requests -- provides information about the compiled pattern.
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Request types for config()
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PCRE Configuration
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PCRE Extra
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PCREExtraFlags. bit flags for extra structure.
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Get sizeof CInt from hsc2hs
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Produced by Haddock version 2.4.2 |