176 OWA_PATTERN

Using OWA_PATTERN

• Types

• Operational Notes

Types

You can use a pattern as both an input and output parameter. Thus, you can pass the same regular expression to OWA_PATTERN function calls, and it only has to be parsed once.

• OWA_PATTERN.PATTERN

Operational Notes

The OWA_PATTERN subprograms are overloaded. Specifically, there are six versions of MATCH, and four each of AMATCH and CHANGE. The subprograms use the following parameters:

• line - This is the target to be examined for a match. It can be more than one line of text or a owa_text.multi_line data type.

• pat - This is the pattern that the subprograms attempt to locate in line. The pattern can contain regular expressions. In the owa_pattern.change function and procedure, this parameter is called from_str.

• flags - This specifies whether the search is case-sensitive or if substitutions are done globally.

Use regular expressions with the subprograms in this package. You Specify a regular expression by creating the string you want to match interspersed with various wildcard tokens and quantifiers.

• Wildcards

• Quantifiers

• Flags

Wildcards

Wildcard tokens match something other than themselves:

Quantifiers

Any tokens except & can have their meaning extended by any of the following quantifiers. You can also apply these quantifiers to literals:

Flags

In addition to targets and regular expressions, the OWA_PATTERN functions and procedures use flags to affect how they are interpreted.

Summary of OWA_PATTERN Subprograms

AMATCH Function

This function specifies if a pattern occurs in a particular location in a string. There are four versions to this function:

• The first and second versions of the function do not save the matched tokens (these are saved in the backrefs parameters in the third and fourth versions). The difference between the first and second versions is the pat parameter, which can be a VARCHAR2 or a pattern data type.

• The third and fourth versions of the function save the matched tokens in the backrefs parameter. The difference between the third and fourth versions is the pat parameter, which can be a VARCHAR2 or a pattern data type.

  Note:

  If multiple overlapping strings match the regular expression, this function takes the longest match.

Syntax

OWA_PATTERN.AMATCH(
   line           IN       VARCHAR2,
   from_loc       IN       INTEGER,
   pat            IN       VARCHAR2,
   flags          IN       VARCHAR2   DEFAULT NULL)
 RETURN INTEGER;

OWA_PATTERN.AMATCH(
   line           IN       VARCHAR2,
   from_loc       IN       INTEGER,
   pat            IN OUT   PATTERN,
   flags          IN       VARCHAR2   DEFAULT NULL)
 RETURN INTEGER;

OWA_PATTERN.AMATCH(
   line           IN       VARCHAR2
   from_loc       IN       INTEGER
   pat            in       varchar2
   backrefs       OUT      owa_text.vc_arr
   flags          IN       VARCHAR2   DEFAULT NULL)
 RETURN INTEGER;

OWA_PATTERN.AMATCH(
   line           IN       VARCHAR2
   from_loc       IN       INTEGER
   pat            IN OUT   PATTERN
   backrefs       OUT      owa_text.vc_arr
   flags          IN       VARCHAR2   DEFAULT NULL)
 RETURN INTEGER;

Parameters

Return Values

The index of the character after the end of the match, counting from the beginning of line. If there was no match, the function returns 0.

CHANGE Functions and Procedures

This function or procedure searches and replaces a string or multi_line data type. If multiple overlapping strings match the regular expression, this subprogram takes the longest match.

Syntax

OWA_PATTERN.CHANGE(
   line           IN OUT    VARCHAR2,
   from_str       IN        VARCHAR2,
   to_str         IN        VARCHAR2,
   flags          IN        VARCHAR2   DEFAULT NULL)
 RETURN INTEGER;

OWA_PATTERN.CHANGE(
   line           IN OUT   VARCHAR2,
   from_str       IN       VARCHAR2,
   to_str         IN       VARCHAR2,
   flags          IN       VARCHAR2   DEFAULT NULL);

owa_pattern.change(
   mline          IN OUT   owa_text.multi_line,
   from_str       IN       VARCHAR2,
   to_str         IN       VARCHAR2,
   flags          IN       VARCHAR2   DEFAULT NULL)
 RETURN INTEGER;

OWA_PATTERN.CHANGE(
   mline          IN OUT   owa_text.multi_line,
   from_str       IN       VARCHAR2,
   to_str         IN       VARCHAR2,
   flags          IN       VARCHAR2   DEFAULT NULL);

Parameters

Return Values

As a function, it returns the number of substitutions made. If the flag "g" is not used, this number can only be 0 or 1 and only the first match is replaced. The flag "g" specifies to replace all matches with the regular expression.

Examples

OWA_PATTERN.CHANGE('Cats in pajamas', 'C.+in', '& red ')

The regular expression matches the substring "Cats in". It then replaces this string with "& red". The ampersand character "&" indicates "Cats in" because that is what matched the regular expression. Thus, this procedure replaces the string "Cats in pajamas" with "Cats in red" If you call this as a function instead of a procedure, the value returned is 1, indicating that a single substitution has been made.

Example 2:

CREATE OR REPLACE PROCEDURE test_pattern as theline VARCHAR2(256);
num_found     INTEGER;
   BEGIN
       theline := 'what is the goal?';
       num_found := OWA_PATTERN.CHANGE(theline, 'goal', 'idea', 'g');
       HTP.PRINT(num_found); -- num_found is 1
       HTP.PRINT(theline); -- theline is 'what is the idea?'
   END;
/
SHOW ERRORS

GETPAT Procedure

This procedure converts a VARCHAR2 string into an OWA_PATTERN.PATTERN DATA TYPE.

Syntax

OWA_PATTERN.GETPAT(
   arg      IN          VARCHAR2, 
   pat      IN OUT      pattern);

Parameters

MATCH Function

This function determines if a string contains the specified pattern. The pattern can contain regular expressions. If multiple overlapping strings can match the regular expression, this function takes the longest match.

Syntax

owa_pattern.match(
   line           IN       VARCHAR2,
   pat            IN       VARCHAR2,
   flags          IN       VARCHAR2   DEFAULT NULL)
 RETURN BOOLEAN;

owa_pattern.match(
   line           IN       VARCHAR2,
   pat            IN OUT   PATTERN,
   flags          IN       VARCHAR2   DEFAULT NULL)
 RETURN BOOLEAN;

owa_pattern.match(
   line           IN       VARCHAR2,
   pat            IN       VARCHAR2,
   backrefs       OUT      owa_text.vc_arr,
   flags          IN       VARCHAR2   DEFAULT NULL)
 RETURN BOOLEAN;

OWA_PATTERN.MATCH(
   line           IN       VARCHAR2,
   pat            IN OUT   PATTERN,
   backrefs       OUT      owa_text.vc_arr,
   flags          IN       VARCHAR2   DEFAULT NULL)
 RETURN BOOLEAN;

owa_pattern.match(
   mline          IN       owa_text.multi_line,
   pat            IN       VARCHAR2,
   rlist          OUT      owa_text.row_list,
   flags          IN       VARCHAR2   DEFAULT NULL)
 RETURN BOOLEAN;

OWA_PATTERN.MATCH(
   mline          IN       owa_text.multi_line,
   pat            IN OUT   pattern,
   rlist          OUT      owa_text.row_list,
   flags          IN       VARCHAR2   DEFAULT NULL)
 RETURN BOOLEAN;

Parameters

Return Values

TRUE if a match was found, FALSE otherwise.

Examples

KAZOO is the target where it is searching for the zoo.* regular expression. The period indicates any character other than newline, and the asterisk matches 0 or more of the preceding characters. In this case, it matches any character other than the newline.

Therefore, this regular expression specifies that a matching target consists of zoo, followed by any set of characters neither ending in nor including a newline (which does not match the period). The i flag indicates to ignore case in the search. In this case, the function returns TRUE, which indicates that a match had been found.

boolean foundMatch;
foundMatch := owa_pattern.match('KAZOO', 'zoo.*', 'i');

The following example searches for the string "goal" followed by any number of characters in sometext. If found,

sometext  VARCHAR2(256);
pat       VARCHAR2(256);

sometext    := 'what is the goal?'
pat         := 'goal.*';
IF OWA_PATTERN.MATCH(sometext, pat) 
   THEN
      HTP.PRINT('Match found');
   ELSE
     HTP.PRINT('Match not found');
END IF;

Operational Notes

• The regular expression in this function can be either a VARCHAR2 or an OWA_PATTERN.PATTERN DATA TYPE. Create AN OWA_PATTERN.PATTERN DATA TYPE from a string using the OWA_PATTERN.GETPAT procedure.

• Create a MULTI_LINE DATA TYPE from a long string using the OWA_TEXT.STREAM2MULTI procedure. If a multi_line is used, the rlist parameter specifies a list of chunks where matches were found.

• If the line is a string and not a multi_line, you can add an optional output parameter called backrefs. This parameter is a row_list that holds each string in the target that was matched by a sequence of tokens in the regular expression.