SourcePro® 2024.1 |
SourcePro® API Reference Guide |
Deprecated. Provides extended regular expression matching similar to that found in lex and awk. More...
#include <rw/re.h>
Inherits RWREBaseClass.
Public Member Functions | |
RWTRegularExpression () | |
RWTRegularExpression (const charT *pat) | |
RWTRegularExpression (const RWTRegularExpression< charT > &other) | |
RWTRegularExpression (const stringT &pat) | |
virtual | ~RWTRegularExpression () |
size_t | index (const stringT &str, size_t *len=NULL, size_t start=0) |
RWTRegularExpression< charT > & | operator= (const RWTRegularExpression< charT > &other) |
statusType | status () const |
RWTRegularExpression< charT > & | operator= (const charT *pat) |
RWTRegularExpression< charT > & | operator= (const stringT &pat) |
Related Symbols | |
(Note that these are not member symbols.) | |
typedef RWTRegularExpression< char > | RWCRExpr |
Class RWTRegularExpression represents an extended regular expression such as those found in lex
and awk
. The constructor "compiles" the expression into a form that can be used more efficiently. The results can then be used for string searches using class RWCString. Regular expressions can be of arbitrary size, limited by memory. The extended regular expression features found here are a subset of those found in the POSIX.2 standard (ANSI/IEEE Std 1003.2, ISO/IEC 9945-2).
The regular expression (RE) is constructed as follows:
The following rules determine one-character REs that match a single character:
Any character that is not a special character (to be defined) matches itself.
\
) followed by any special character matches the literal character itself; that is, its use "escapes" the special character. For example, \*
matches "*" without applying the syntax of the *
special character.
[
]) is a one-character RE that matches any of the characters in that set. This means that
[akm] matches either an "a", "k", or "m". A range of characters can be indicated with a dash, as in
[a-z], which matches any lower-case letter. However, if the first character of the set is the caret (^
), then the RE matches any character except those in the set. It does not match the empty string. For example:
[^akm] matches any character except "a", "k", or "m". The caret loses its special meaning if it is not the first character of the set.The following rules can be used to build a multicharacter RE:
*
) matches zero or more occurrences of the RE. Hence,
[a-z]* matches zero+
) matches one or more occurrences of the RE. Hence,
[a-z]+ matches one or more
?) is an optional element. The preceding RE can occur zero or once in the string – no more. For example,
[A-Z][a-z]* matches
| ) allows a choice between two regular expressions. For example, jell(y|ies) matches either "jelly"{
}
) are reserved for future use.All or part of the regular expression can be "anchored" to either the beginning or end of the string being searched:
^
) is at the beginning of the (sub)expression, then the matched string must be at the beginning of the string$
) is at the end of the (sub)expression, then the matched string must be at the end of the string being searched.The most frequent problem with use of this class is in being able to specify a backslash character to be parsed. If you are attempting to parse a regular expression that contains backslashes, you must be aware that the C++ compiler and the regular expression constructor will both assume that any backslashes they see are intended to escape the following character. Thus, to specify a regular expression that exactly matches "a\a"
, you would have to create the regular expression using four backslashes as follows: the regular expression needs to see "a\\a"
, and for that to happen, the compiler would have to see "a\\\\a"
.
The backslashes marked with a ^
are an escape for the compiler, and the ones marked with | will thus be seen by the regular expression parser. At that point, the backslash marked
1
is an escape, and the one marked 2
will actually be put into the regular expression.
Similarly, if you really need to escape a character, such as a '
.', you will have to pass two backslashes to the compiler:
Once again, the backslash marked ^
is an escape for the compiler, and the one marked with | will be seen by the regular expression constructor as an escape for the following
'
.'.
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inline |
Default constructor. You must assign a pattern to the regular expression before you use it.
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inline |
Construct a regular expression from the pattern given by pat. The status of the results can be found by using member function status().
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inline |
Construct a regular expression from the pattern given by pat. The status of the results can be found by using member function status().
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inline |
Copy constructor. Uses value semantics – self will be a copy of other.
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inlinevirtual |
Destructor. Releases any allocated memory.
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inline |
Returns the index of the first instance in the string str that matches the regular expression compiled in self, or RW_NPOS if there is no such match. The search starts at index start. The length of the matching pattern is returned in the variable pointed to by len. If an invalid regular expression is used for the search, an exception of type RWInternalErr will be thrown. Note that this member function is relatively clumsy to use – class RWCString offers a better interface to regular expression searches.
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inline |
Recompiles self to the pattern given by pat. The status of the results can be found by using member function status().
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inline |
Recompiles self to pattern found in other.
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inline |
Recompiles self to the pattern given by pat. The status of the results can be found by using member function status().
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inline |
Returns the status of the regular expression:
statusType | Meaning |
RWTRegularExpression::OK | No errors |
RWTRegularExpression::NOT_SUPPORTED | POSIX.2 feature not yet supported. |
RWTRegularExpression::NO_MATCH | Tried to find a match but failed |
RWTRegularExpression::BAD_PATTERN | Pattern was illegal |
RWTRegularExpression::BAD_COLLATING_ELEMENT | Invalid collating element referenced |
RWTRegularExpression::BAD_CHAR_CLASS_TYPE | Invalid character class type referenced |
RWTRegularExpression::TRAILING_BACKSLASH | Trailing \ in pattern |
RWTRegularExpression::UNMATCHED_BRACKET | [] imbalance |
RWTRegularExpression::UNMATCHED_PARENTHESIS | () imbalance |
RWTRegularExpression::UNMATCHED_BRACE | {} imbalance |
RWTRegularExpression::BAD_BRACE | Content of {} invalid. |
RWTRegularExpression::BAD_CHAR_RANGE | Invalid endpoint in [a-z] expression |
RWTRegularExpression::OUT_OF_MEMORY | Out of memory |
RWTRegularExpression::BAD_REPEAT | ?,* or + not preceded by valid regular expression |
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