164 lines
6.4 KiB
Groff
164 lines
6.4 KiB
Groff
|
.TH PCRE2CONVERT 3 "12 July 2017" "PCRE2 10.30"
|
||
|
|
.SH NAME
|
||
|
|
PCRE2 - Perl-compatible regular expressions (revised API)
|
||
|
|
.SH "EXPERIMENTAL PATTERN CONVERSION FUNCTIONS"
|
||
|
|
.rs
|
||
|
|
.sp
|
||
|
|
This document describes a set of functions that can be used to convert
|
||
|
|
"foreign" patterns into PCRE2 regular expressions. This facility is currently
|
||
|
|
experimental, and may be changed in future releases. Two kinds of pattern,
|
||
|
|
globs and POSIX patterns, are supported.
|
||
|
|
.
|
||
|
|
.
|
||
|
|
.SH "THE CONVERT CONTEXT"
|
||
|
|
.rs
|
||
|
|
.sp
|
||
|
|
.nf
|
||
|
|
.B pcre2_convert_context *pcre2_convert_context_create(
|
||
|
|
.B " pcre2_general_context *\fIgcontext\fP);"
|
||
|
|
.sp
|
||
|
|
.B pcre2_convert_context *pcre2_convert_context_copy(
|
||
|
|
.B " pcre2_convert_context *\fIcvcontext\fP);"
|
||
|
|
.sp
|
||
|
|
.B void pcre2_convert_context_free(pcre2_convert_context *\fIcvcontext\fP);
|
||
|
|
.sp
|
||
|
|
.B int pcre2_set_glob_escape(pcre2_convert_context *\fIcvcontext\fP,
|
||
|
|
.B " uint32_t \fIescape_char\fP);"
|
||
|
|
.sp
|
||
|
|
.B int pcre2_set_glob_separator(pcre2_convert_context *\fIcvcontext\fP,
|
||
|
|
.B " uint32_t \fIseparator_char\fP);"
|
||
|
|
.fi
|
||
|
|
.sp
|
||
|
|
A convert context is used to hold parameters that affect the way that pattern
|
||
|
|
conversion works. Like all PCRE2 contexts, you need to use a context only if
|
||
|
|
you want to override the defaults. There are the usual create, copy, and free
|
||
|
|
functions. If custom memory management functions are set in a general context
|
||
|
|
that is passed to \fBpcre2_convert_context_create()\fP, they are used for all
|
||
|
|
memory management within the conversion functions.
|
||
|
|
.P
|
||
|
|
There are only two parameters in the convert context at present. Both apply
|
||
|
|
only to glob conversions. The escape character defaults to grave accent under
|
||
|
|
Windows, otherwise backslash. It can be set to zero, meaning no escape
|
||
|
|
character, or to any punctuation character with a code point less than 256.
|
||
|
|
The separator character defaults to backslash under Windows, otherwise forward
|
||
|
|
slash. It can be set to forward slash, backslash, or dot.
|
||
|
|
.P
|
||
|
|
The two setting functions return zero on success, or PCRE2_ERROR_BADDATA if
|
||
|
|
their second argument is invalid.
|
||
|
|
.
|
||
|
|
.
|
||
|
|
.SH "THE CONVERSION FUNCTION"
|
||
|
|
.rs
|
||
|
|
.sp
|
||
|
|
.nf
|
||
|
|
.B int pcre2_pattern_convert(PCRE2_SPTR \fIpattern\fP, PCRE2_SIZE \fIlength\fP,
|
||
|
|
.B " uint32_t \fIoptions\fP, PCRE2_UCHAR **\fIbuffer\fP,"
|
||
|
|
.B " PCRE2_SIZE *\fIblength\fP, pcre2_convert_context *\fIcvcontext\fP);"
|
||
|
|
.sp
|
||
|
|
.B void pcre2_converted_pattern_free(PCRE2_UCHAR *\fIconverted_pattern\fP);
|
||
|
|
.fi
|
||
|
|
.sp
|
||
|
|
The first two arguments of \fBpcre2_pattern_convert()\fP define the foreign
|
||
|
|
pattern that is to be converted. The length may be given as
|
||
|
|
PCRE2_ZERO_TERMINATED. The \fBoptions\fP argument defines how the pattern is to
|
||
|
|
be processed. If the input is UTF, the PCRE2_CONVERT_UTF option should be set.
|
||
|
|
PCRE2_CONVERT_NO_UTF_CHECK may also be set if you are sure the input is valid.
|
||
|
|
One or more of the glob options, or one of the following POSIX options must be
|
||
|
|
set to define the type of conversion that is required:
|
||
|
|
.sp
|
||
|
|
PCRE2_CONVERT_GLOB
|
||
|
|
PCRE2_CONVERT_GLOB_NO_WILD_SEPARATOR
|
||
|
|
PCRE2_CONVERT_GLOB_NO_STARSTAR
|
||
|
|
PCRE2_CONVERT_POSIX_BASIC
|
||
|
|
PCRE2_CONVERT_POSIX_EXTENDED
|
||
|
|
.sp
|
||
|
|
Details of the conversions are given below. The \fBbuffer\fP and \fBblength\fP
|
||
|
|
arguments define how the output is handled:
|
||
|
|
.P
|
||
|
|
If \fBbuffer\fP is NULL, the function just returns the length of the converted
|
||
|
|
pattern via \fBblength\fP. This is one less than the length of buffer needed,
|
||
|
|
because a terminating zero is always added to the output.
|
||
|
|
.P
|
||
|
|
If \fBbuffer\fP points to a NULL pointer, an output buffer is obtained using
|
||
|
|
the allocator in the context or \fBmalloc()\fP if no context is supplied. A
|
||
|
|
pointer to this buffer is placed in the variable to which \fBbuffer\fP points.
|
||
|
|
When no longer needed the output buffer must be freed by calling
|
||
|
|
\fBpcre2_converted_pattern_free()\fP.
|
||
|
|
.P
|
||
|
|
If \fBbuffer\fP points to a non-NULL pointer, \fBblength\fP must be set to the
|
||
|
|
actual length of the buffer provided (in code units).
|
||
|
|
.P
|
||
|
|
In all cases, after successful conversion, the variable pointed to by
|
||
|
|
\fBblength\fP is updated to the length actually used (in code units), excluding
|
||
|
|
the terminating zero that is always added.
|
||
|
|
.P
|
||
|
|
If an error occurs, the length (via \fBblength\fP) is set to the offset
|
||
|
|
within the input pattern where the error was detected. Only gross syntax errors
|
||
|
|
are caught; there are plenty of errors that will get passed on for
|
||
|
|
\fBpcre2_compile()\fP to discover.
|
||
|
|
.P
|
||
|
|
The return from \fBpcre2_pattern_convert()\fP is zero on success or a non-zero
|
||
|
|
PCRE2 error code. Note that PCRE2 error codes may be positive or negative:
|
||
|
|
\fBpcre2_compile()\fP uses mostly positive codes and \fBpcre2_match()\fP
|
||
|
|
negative ones; \fBpcre2_convert()\fP uses existing codes of both kinds. A
|
||
|
|
textual error message can be obtained by calling
|
||
|
|
\fBpcre2_get_error_message()\fP.
|
||
|
|
.
|
||
|
|
.
|
||
|
|
.SH "CONVERTING GLOBS"
|
||
|
|
.rs
|
||
|
|
.sp
|
||
|
|
Globs are used to match file names, and consequently have the concept of a
|
||
|
|
"path separator", which defaults to backslash under Windows and forward slash
|
||
|
|
otherwise. If PCRE2_CONVERT_GLOB is set, the wildcards * and ? are not
|
||
|
|
permitted to match separator characters, but the double-star (**) feature
|
||
|
|
(which does match separators) is supported.
|
||
|
|
.P
|
||
|
|
PCRE2_CONVERT_GLOB_NO_WILD_SEPARATOR matches globs with wildcards allowed to
|
||
|
|
match separator characters. PCRE2_GLOB_NO_STARSTAR matches globs with the
|
||
|
|
double-star feature disabled. These options may be given together.
|
||
|
|
.
|
||
|
|
.
|
||
|
|
.SH "CONVERTING POSIX PATTERNS"
|
||
|
|
.rs
|
||
|
|
.sp
|
||
|
|
POSIX defines two kinds of regular expression pattern: basic and extended.
|
||
|
|
These can be processed by setting PCRE2_CONVERT_POSIX_BASIC or
|
||
|
|
PCRE2_CONVERT_POSIX_EXTENDED, respectively.
|
||
|
|
.P
|
||
|
|
In POSIX patterns, backslash is not special in a character class. Unmatched
|
||
|
|
closing parentheses are treated as literals.
|
||
|
|
.P
|
||
|
|
In basic patterns, ? + | {} and () must be escaped to be recognized
|
||
|
|
as metacharacters outside a character class. If the first character in the
|
||
|
|
pattern is * it is treated as a literal. ^ is a metacharacter only at the start
|
||
|
|
of a branch.
|
||
|
|
.P
|
||
|
|
In extended patterns, a backslash not in a character class always
|
||
|
|
makes the next character literal, whatever it is. There are no backreferences.
|
||
|
|
.P
|
||
|
|
Note: POSIX mandates that the longest possible match at the first matching
|
||
|
|
position must be found. This is not what \fBpcre2_match()\fP does; it yields
|
||
|
|
the first match that is found. An application can use \fBpcre2_dfa_match()\fP
|
||
|
|
to find the longest match, but that does not support backreferences (but then
|
||
|
|
neither do POSIX extended patterns).
|
||
|
|
.
|
||
|
|
.
|
||
|
|
.SH AUTHOR
|
||
|
|
.rs
|
||
|
|
.sp
|
||
|
|
.nf
|
||
|
|
Philip Hazel
|
||
|
|
University Computing Service
|
||
|
|
Cambridge, England.
|
||
|
|
.fi
|
||
|
|
.
|
||
|
|
.
|
||
|
|
.SH REVISION
|
||
|
|
.rs
|
||
|
|
.sp
|
||
|
|
.nf
|
||
|
|
Last updated: 12 July 2017
|
||
|
|
Copyright (c) 1997-2017 University of Cambridge.
|
||
|
|
.fi
|