Copyright | Will Thompson and Iñaki García Etxebarria |
---|---|
License | LGPL-2.1 |
Maintainer | Iñaki García Etxebarria |
Safe Haskell | None |
Language | Haskell2010 |
GI.GLib.Structs.MatchInfo
Description
A GMatchInfo is an opaque struct used to return information about matches.
Synopsis
- newtype MatchInfo = MatchInfo (ManagedPtr MatchInfo)
- matchInfoExpandReferences :: (HasCallStack, MonadIO m) => Maybe MatchInfo -> Text -> m (Maybe Text)
- matchInfoFetch :: (HasCallStack, MonadIO m) => MatchInfo -> Int32 -> m (Maybe Text)
- matchInfoFetchAll :: (HasCallStack, MonadIO m) => MatchInfo -> m [Text]
- matchInfoFetchNamed :: (HasCallStack, MonadIO m) => MatchInfo -> Text -> m (Maybe Text)
- matchInfoFetchNamedPos :: (HasCallStack, MonadIO m) => MatchInfo -> Text -> m (Bool, Int32, Int32)
- matchInfoFetchPos :: (HasCallStack, MonadIO m) => MatchInfo -> Int32 -> m (Bool, Int32, Int32)
- matchInfoFree :: (HasCallStack, MonadIO m) => Maybe MatchInfo -> m ()
- matchInfoGetMatchCount :: (HasCallStack, MonadIO m) => MatchInfo -> m Int32
- matchInfoGetRegex :: (HasCallStack, MonadIO m) => MatchInfo -> m Regex
- matchInfoGetString :: (HasCallStack, MonadIO m) => MatchInfo -> m Text
- matchInfoIsPartialMatch :: (HasCallStack, MonadIO m) => MatchInfo -> m Bool
- matchInfoMatches :: (HasCallStack, MonadIO m) => MatchInfo -> m Bool
- matchInfoNext :: (HasCallStack, MonadIO m) => MatchInfo -> m ()
- matchInfoRef :: (HasCallStack, MonadIO m) => MatchInfo -> m MatchInfo
- matchInfoUnref :: (HasCallStack, MonadIO m) => MatchInfo -> m ()
Exported types
Memory-managed wrapper type.
Constructors
MatchInfo (ManagedPtr MatchInfo) |
Instances
Eq MatchInfo Source # | |
GBoxed MatchInfo Source # | |
Defined in GI.GLib.Structs.MatchInfo | |
ManagedPtrNewtype MatchInfo Source # | |
Defined in GI.GLib.Structs.MatchInfo Methods | |
TypedObject MatchInfo Source # | |
Defined in GI.GLib.Structs.MatchInfo | |
HasParentTypes MatchInfo Source # | |
Defined in GI.GLib.Structs.MatchInfo | |
IsGValue (Maybe MatchInfo) Source # | Convert |
Defined in GI.GLib.Structs.MatchInfo Methods gvalueGType_ :: IO GType # gvalueSet_ :: Ptr GValue -> Maybe MatchInfo -> IO () # gvalueGet_ :: Ptr GValue -> IO (Maybe MatchInfo) # | |
type ParentTypes MatchInfo Source # | |
Defined in GI.GLib.Structs.MatchInfo type ParentTypes MatchInfo = '[] :: [Type] |
Methods
Click to display all available methods, including inherited ones
Methods
expandReferences, fetch, fetchAll, fetchNamed, fetchNamedPos, fetchPos, free, isPartialMatch, matches, next, ref, unref.
Getters
getMatchCount, getRegex, getString.
Setters
None.
expandReferences
matchInfoExpandReferences Source #
Arguments
:: (HasCallStack, MonadIO m) | |
=> Maybe MatchInfo | |
-> Text |
|
-> m (Maybe Text) | Returns: the expanded string, or |
Returns a new string containing the text in stringToExpand
with
references and escape sequences expanded. References refer to the last
match done with string
against regex
and have the same syntax used by
regexReplace
.
The stringToExpand
must be UTF-8 encoded even if RegexCompileFlagsRaw
was
passed to regexNew
.
The backreferences are extracted from the string passed to the match function, so you cannot call this function after freeing the string.
matchInfo
may be Nothing
in which case stringToExpand
must not
contain references. For instance "foo\n" does not refer to an actual
pattern and '\n' merely will be replaced with \n character,
while to expand "\0" (whole match) one needs the result of a match.
Use regexCheckReplacement
to find out whether stringToExpand
contains references.
Since: 2.14
fetch
Arguments
:: (HasCallStack, MonadIO m) | |
=> MatchInfo |
|
-> Int32 |
|
-> m (Maybe Text) | Returns: The matched substring, or |
Retrieves the text matching the matchNum
'th capturing
parentheses. 0 is the full text of the match, 1 is the first paren
set, 2 the second, and so on.
If matchNum
is a valid sub pattern but it didn't match anything
(e.g. sub pattern 1, matching "b" against "(a)?b") then an empty
string is returned.
If the match was obtained using the DFA algorithm, that is using
regexMatchAll
or regexMatchAllFull
, the retrieved
string is not that of a set of parentheses but that of a matched
substring. Substrings are matched in reverse order of length, so
0 is the longest match.
The string is fetched from the string passed to the match function, so you cannot call this function after freeing the string.
Since: 2.14
fetchAll
Arguments
:: (HasCallStack, MonadIO m) | |
=> MatchInfo |
|
-> m [Text] | Returns: a |
Bundles up pointers to each of the matching substrings from a match and stores them in an array of gchar pointers. The first element in the returned array is the match number 0, i.e. the entire matched text.
If a sub pattern didn't match anything (e.g. sub pattern 1, matching "b" against "(a)?b") then an empty string is inserted.
If the last match was obtained using the DFA algorithm, that is using
regexMatchAll
or regexMatchAllFull
, the retrieved
strings are not that matched by sets of parentheses but that of the
matched substring. Substrings are matched in reverse order of length,
so the first one is the longest match.
The strings are fetched from the string passed to the match function, so you cannot call this function after freeing the string.
Since: 2.14
fetchNamed
Arguments
:: (HasCallStack, MonadIO m) | |
=> MatchInfo |
|
-> Text |
|
-> m (Maybe Text) | Returns: The matched substring, or |
Retrieves the text matching the capturing parentheses named name
.
If name
is a valid sub pattern name but it didn't match anything
(e.g. sub pattern "X"
, matching "b"
against "(?P<X>a)?b"
)
then an empty string is returned.
The string is fetched from the string passed to the match function, so you cannot call this function after freeing the string.
Since: 2.14
fetchNamedPos
matchInfoFetchNamedPos Source #
Arguments
:: (HasCallStack, MonadIO m) | |
=> MatchInfo |
|
-> Text |
|
-> m (Bool, Int32, Int32) | Returns: |
Retrieves the position in bytes of the capturing parentheses named name
.
If name
is a valid sub pattern name but it didn't match anything
(e.g. sub pattern "X"
, matching "b"
against "(?P<X>a)?b"
)
then startPos
and endPos
are set to -1 and True
is returned.
As endPos
is set to the byte after the final byte of the match (on success),
the length of the match can be calculated as end_pos - start_pos
.
Since: 2.14
fetchPos
Arguments
:: (HasCallStack, MonadIO m) | |
=> MatchInfo |
|
-> Int32 |
|
-> m (Bool, Int32, Int32) | Returns: True if |
Returns the start and end positions (in bytes) of a successfully matching capture parenthesis.
Valid values for matchNum
are 0
for the full text of the match,
1
for the first paren set, 2
for the second, and so on.
As endPos
is set to the byte after the final byte of the match (on success),
the length of the match can be calculated as end_pos - start_pos
.
As a best practice, initialize startPos
and endPos
to identifiable
values, such as G_MAXINT
, so that you can test if
g_match_info_fetch_pos()
actually changed the value for a given
capture parenthesis.
The parameter matchNum
corresponds to a matched capture parenthesis. The
actual value you use for matchNum
depends on the method used to generate
matchInfo
. The following sections describe those methods.
Methods Using Non-deterministic Finite Automata Matching
The methods regexMatch
and regexMatchFull
return a MatchInfo
using traditional (greedy) pattern
matching, also known as
Non-deterministic Finite Automaton
(NFA) matching. You pass the returned GMatchInfo
from these methods to
g_match_info_fetch_pos()
to determine the start and end positions
of capture parentheses. The values for matchNum
correspond to the capture
parentheses in order, with 0
corresponding to the entire matched string.
matchNum
can refer to a capture parenthesis with no match. For example,
the string b
matches against the pattern (a)?b
, but the capture
parenthesis (a)
has no match. In this case, g_match_info_fetch_pos()
returns true and sets startPos
and endPos
to -1
when called with
match_num
as 1
(for (a)
).
For an expanded example, a regex pattern is (a)?(.*?)the (.*)
,
and a candidate string is glib regexes are the best
. In this scenario
there are four capture parentheses numbered 0–3: an implicit one
for the entire string, and three explicitly declared in the regex pattern.
Given this example, the following table describes the return values
from g_match_info_fetch_pos()
for various values of matchNum
.
match_num
| Contents | Return value | Returned start_pos
| Returned end_pos
----------- | -------- | ------------ | -------------------- | ------------------
0 | Matches entire string | True | 0 | 25
1 | Does not match first character | True | -1 | -1
2 | All text before the
| True | 0 | 17
3 | All text after the
| True | 21 | 25
4 | Capture paren out of range | False | Unchanged | Unchanged
The following code sample and output implements this example.
{ .c } code
#include <glib.h> int main (int argc, char *argv[]) { g_autoptr(GError) local_error = NULL; const char *regex_pattern = "(a)?(.*?)the (.*)"; const char *test_string = "glib regexes are the best"; g_autoptr(GRegex) regex = NULL; regex = g_regex_new (regex_pattern, G_REGEX_DEFAULT, G_REGEX_MATCH_DEFAULT, &local_error); if (regex == NULL) { g_printerr ("Error creating regex: %s\n", local_error->message); return 1; } g_autoptr(GMatchInfo) match_info = NULL; g_regex_match (regex, test_string, G_REGEX_MATCH_DEFAULT, &match_info); int n_matched_strings = g_match_info_get_match_count (match_info); // Print header line g_print ("match_num Contents Return value returned start_pos returned end_pos\n"); // Iterate over each capture paren, including one that is out of range as a demonstration. for (int match_num = 0; match_num <= n_matched_strings; match_num++) { gboolean found_match; g_autofree char *paren_string = NULL; int start_pos = G_MAXINT; int end_pos = G_MAXINT; found_match = g_match_info_fetch_pos (match_info, match_num, &start_pos, &end_pos); // If no match, display N/A as the found string. if (start_pos == G_MAXINT || start_pos == -1) paren_string = g_strdup ("N/A"); else paren_string = g_strndup (test_string + start_pos, end_pos - start_pos); g_print ("%-9d %-25s %-12d %-18d %d\n", match_num, paren_string, found_match, start_pos, end_pos); } return 0; }
match_num Contents Return value returned start_pos returned end_pos 0 glib regexes are the best 1 0 25 1 N/A 1 -1 -1 2 glib regexes are 1 0 17 3 best 1 21 25 4 N/A 0 2147483647 2147483647
Methods Using Deterministic Finite Automata Matching
The methods regexMatchAll
and
regexMatchAllFull
return a GMatchInfo
using
Deterministic Finite Automaton
(DFA) pattern matching. This algorithm detects overlapping matches. You pass
the returned GMatchInfo
from these methods to g_match_info_fetch_pos()
to determine the start and end positions of each overlapping match. Use the
method matchInfoGetMatchCount
to determine the number
of overlapping matches.
For example, a regex pattern is <.*>
, and a candidate string is
<a> <b> <c>
. In this scenario there are three implicit capture
parentheses: one for the entire string, one for <a> <b>
, and one for <a>
.
Given this example, the following table describes the return values from
g_match_info_fetch_pos()
for various values of matchNum
.
match_num
| Contents | Return value | Returned start_pos
| Returned end_pos
----------- | -------- | ------------ | -------------------- | ------------------
0 | Matches entire string | True | 0 | 11
1 | Matches <a> <b>
| True | 0 | 7
2 | Matches <a>
| True | 0 | 3
3 | Capture paren out of range | False | Unchanged | Unchanged
The following code sample and output implements this example.
{ .c } code
#include <glib.h> int main (int argc, char *argv[]) { g_autoptr(GError) local_error = NULL; const char *regex_pattern = "<.*>"; const char *test_string = "<a> <b> <c>"; g_autoptr(GRegex) regex = NULL; regex = g_regex_new (regex_pattern, G_REGEX_DEFAULT, G_REGEX_MATCH_DEFAULT, &local_error); if (regex == NULL) { g_printerr ("Error creating regex: %s\n", local_error->message); return -1; } g_autoptr(GMatchInfo) match_info = NULL; g_regex_match_all (regex, test_string, G_REGEX_MATCH_DEFAULT, &match_info); int n_matched_strings = g_match_info_get_match_count (match_info); // Print header line g_print ("match_num Contents Return value returned start_pos returned end_pos\n"); // Iterate over each capture paren, including one that is out of range as a demonstration. for (int match_num = 0; match_num <= n_matched_strings; match_num++) { gboolean found_match; g_autofree char *paren_string = NULL; int start_pos = G_MAXINT; int end_pos = G_MAXINT; found_match = g_match_info_fetch_pos (match_info, match_num, &start_pos, &end_pos); // If no match, display N/A as the found string. if (start_pos == G_MAXINT || start_pos == -1) paren_string = g_strdup ("N/A"); else paren_string = g_strndup (test_string + start_pos, end_pos - start_pos); g_print ("%-9d %-25s %-12d %-18d %d\n", match_num, paren_string, found_match, start_pos, end_pos); } return 0; }
match_num Contents Return value returned start_pos returned end_pos 0 <a> <b> <c> 1 0 11 1 <a> <b> 1 0 7 2 <a> 1 0 3 3 N/A 0 2147483647 2147483647
Since: 2.14
free
If matchInfo
is not Nothing
, calls matchInfoUnref
; otherwise does
nothing.
Since: 2.14
getMatchCount
matchInfoGetMatchCount Source #
Arguments
:: (HasCallStack, MonadIO m) | |
=> MatchInfo |
|
-> m Int32 | Returns: Number of matched substrings, or -1 if an error occurred |
Retrieves the number of matched substrings (including substring 0, that is the whole matched text), so 1 is returned if the pattern has no substrings in it and 0 is returned if the match failed.
If the last match was obtained using the DFA algorithm, that is
using regexMatchAll
or regexMatchAllFull
, the retrieved
count is not that of the number of capturing parentheses but that of
the number of matched substrings.
Since: 2.14
getRegex
getString
Arguments
:: (HasCallStack, MonadIO m) | |
=> MatchInfo |
|
-> m Text | Returns: the string searched with |
Returns the string searched with matchInfo
. This is the
string passed to regexMatch
or regexReplace
so
you may not free it before calling this function.
Since: 2.14
isPartialMatch
matchInfoIsPartialMatch Source #
Usually if the string passed to g_regex_match*() matches as far as
it goes, but is too short to match the entire pattern, False
is
returned. There are circumstances where it might be helpful to
distinguish this case from other cases in which there is no match.
Consider, for example, an application where a human is required to type in data for a field with specific formatting requirements. An example might be a date in the form ddmmmyy, defined by the pattern "^\d?\d(jan|feb|mar|apr|may|jun|jul|aug|sep|oct|nov|dec)\d\d$". If the application sees the user’s keystrokes one by one, and can check that what has been typed so far is potentially valid, it is able to raise an error as soon as a mistake is made.
GRegex supports the concept of partial matching by means of the
RegexMatchFlagsPartialSoft
and RegexMatchFlagsPartialHard
flags.
When they are used, the return code for
regexMatch
or regexMatchFull
is, as usual, True
for a complete match, False
otherwise. But, when these functions
return False
, you can check if the match was partial calling
matchInfoIsPartialMatch
.
The difference between RegexMatchFlagsPartialSoft
and
RegexMatchFlagsPartialHard
is that when a partial match is encountered
with RegexMatchFlagsPartialSoft
, matching continues to search for a
possible complete match, while with RegexMatchFlagsPartialHard
matching
stops at the partial match.
When both RegexMatchFlagsPartialSoft
and RegexMatchFlagsPartialHard
are set, the latter takes precedence.
There were formerly some restrictions on the pattern for partial matching. The restrictions no longer apply.
See pcrepartial(3) for more information on partial matching.
Since: 2.14
matches
Arguments
:: (HasCallStack, MonadIO m) | |
=> MatchInfo |
|
-> m Bool | Returns: |
Returns whether the previous match operation succeeded.
Since: 2.14
next
Arguments
:: (HasCallStack, MonadIO m) | |
=> MatchInfo |
|
-> m () | (Can throw |
Scans for the next match using the same parameters of the previous
call to regexMatchFull
or regexMatch
that returned
matchInfo
.
The match is done on the string passed to the match function, so you cannot free it before calling this function.
Since: 2.14
ref
Arguments
:: (HasCallStack, MonadIO m) | |
=> MatchInfo |
|
-> m MatchInfo | Returns: |
Increases reference count of matchInfo
by 1.
Since: 2.30
unref
Decreases reference count of matchInfo
by 1. When reference count drops
to zero, it frees all the memory associated with the match_info structure.
Since: 2.30