.. .. NB: This file is machine generated, DO NOT EDIT! .. .. Edit vmod.vcc and run make instead .. .. role:: ref(emphasis) .. _vmod_re2(3): ======== vmod_re2 ======== --------------------------------------------------------------------- Varnish Module for access to the Google RE2 regular expression engine --------------------------------------------------------------------- :Manual section: 3 SYNOPSIS ======== import re2 [from "path"] ; :: # regex object interface new OBJECT = re2.regex(STRING pattern [, ]) BOOL .match(STRING) STRING .backref(INT ref) STRING .namedref(STRING name) STRING .sub(STRING text, STRING rewrite) STRING .suball(STRING text, STRING rewrite) STRING .extract(STRING text, STRING rewrite) # regex function interface BOOL re2.match(STRING pattern, STRING subject [, ]) STRING re2.backref(INT ref) STRING re2.namedref(STRING name) STRING re2.sub(STRING pattern, STRING text, STRING rewrite [, ]) STRING re2.suball(STRING pattern, STRING text, STRING rewrite [, ]) STRING re2.extract(STRING pattern, STRING text, STRING rewrite [, ]) # set object interface new OBJECT = re2.set([ENUM anchor] [, ]) VOID .add(STRING) VOID .compile() BOOL .match(STRING) DESCRIPTION =========== Varnish Module (VMOD) for access to the Google RE2 regular expression engine. Varnish VCL uses the PCRE library (Perl Compatible Regular Expressions) for its native regular expressions, which runs very efficiently for many common uses of pattern matching in VCL, as attested by years of successful use of PCRE with Varnish. But for certain kinds of patterns, the worst-case running time of the PCRE matcher is exponential in the length of the string to be matched. The matcher uses backtracking, implemented with recursive calls to the internal ``match()`` function. In principle there is no upper bound to the possible depth of backtracking and recursion, except as imposed by the ``varnishd`` runtime parameters ``pcre_match_limit`` and ``pcre_match_limit_recursion``; matches fail if either of these limits are met. Stack overflow caused by deep backtracking has occasionally been the subject of ``varnishd`` issues. RE2 differs from PCRE in that it limits the syntax of patterns so that they always specify a regular language in the formally strict sense. Most notably, backreferences within a pattern are not permitted, for example ``(foo|bar)\1`` to match ``foofoo`` and ``barbar``, but not ``foobar`` or ``barfoo``. See the link in ``SEE ALSO`` for the specification of RE2 syntax. This means that an RE2 matcher runs as a finite automaton, which guarantees linear running time in the length of the matched string. There is no backtracking, and hence no risk of deep recursion or stack overflow. The relative advantages and disadvantages of RE2 and PCRE is a broad subject, beyond the scope of this manual. See the references in ``SEE ALSO`` for more in-depth discussion. regex object and function interfaces ------------------------------------ The VMOD provides regular expression operations by way of the ``regex`` object interface and a functional interface. For ``regex`` objects, the pattern is compiled at VCL initialization time, and the compiled pattern is re-used for each invocation of its methods. Compilation failures (due to errors in the pattern) cause failure at initialization time, and the VCL fails to load. The ``.backref()`` and ``.namedref()`` methods refer back to the last invocation of the ``.match()`` method for the same object. The functional interface provides the same set of operations, but the pattern is compiled at runtime on each invocation (and then discarded). Compilation failures are reported as errors in the Varnish log. The ``backref()`` and ``namedref()`` functions refer back to the last invocation of the ``match()`` function, for any pattern. Compiling a pattern at runtime on each invocation is considerably more costly than re-using a compiled pattern. So for patterns that are fixed and known at VCL initialization, the object interface should be used. The functional interface should only be used for patterns whose contents are not known until runtime. set object interface -------------------- ``set`` objects provide a shorthand for constructing patterns that consist of an alternation -- a group of patterns combined with ``|`` for "or". For example:: import re2; sub vcl_init { new myset = re2.set(); myset.add("foo"); myset.add("bar"); myset.add("baz"); myset.compile(); } ``myset.match()`` can now be used to match a string against the pattern ``foo|bar|baz``. regex options ------------- Where a pattern is compiled -- in the ``regex`` and ``set`` constructors, and in functions that require compilation -- options may be specified that can affect the interpretation of the pattern or the operation of the matcher. There are default values for each option, and it is only necessary to specify options in VCL that differ from the defaults. Options specified in a ``set`` constructor apply to all of the patterns in the resulting alternation. ``utf8`` If true, characters in a pattern match Unicode code points, and hence may match more than one byte. If false, the pattern and strings to be matched are interpreted as Latin-1 (ISO 8859-1), and a pattern character matches exactly one byte. Default is **false**. Note that this differs from the RE2 default. ``posix_syntax`` If true, patterns are restricted to POSIX (egrep) syntax. Otherwise, the pattern syntax resembles that of PCRE, with some deviations. See the link in ``SEE ALSO`` for the syntax specification. Default is **false**. The options ``perl_classes``, ``word_boundary`` and ``one_line`` are only consulted when this option is true. ``longest_match`` If true, the matcher searches for the longest possible match where alternatives are possible. Otherwise, search for the first match. For example with the pattern ``a(b|bb)`` and the string ``abb``, ``abb`` matches when ``longest_match`` is true, and backref 1 is ``bb``. Otherwise, ``ab`` matches, and backref 1 is ``b``. Default is **false**. ``max_mem`` An upper bound (in bytes) for the size of the compiled pattern. If ``max_mem`` is too small, the matcher may fall back to less efficient algorithms, or the pattern may fail to compile. Default is the RE2 default (8MB), which should suffice for typical patterns. ``literal`` If true, the pattern is interpreted as a literal string, and no regex metacharacters (such as ``*``, ``+``, ``^`` and so forth) have their special meaning. Default is **false**. ``never_nl`` If true, the newline character ``\n`` in a string is never matched, even if it appears in the pattern. Default is **false**. ``dot_nl`` If true, then the dot character ``.`` in a pattern matches everything, including newline. Otherwise, ``.`` never matches newline. Default is **false**. ``never_capture`` If true, parentheses in a pattern are interpreted as non-capturing, and all invocations of the ``backref`` and ``namedref`` methods or functions will fail, including ``backref(0)`` after a successful match. Default is **false**, except for set objects, for which ``never_capture`` is always true (and cannot be changed), since back references are not possible with sets. ``case_sensitive`` If true, matches are case-sensitive. A pattern can override this option with the ``(?i)`` flag, unless ``posix_syntax`` is true. Default is **true**. The following options are only consulted when ``posix_syntax`` is true. If ``posix_syntax`` is false, then these features are always enabled and cannot be turned off. ``perl_classes`` If true, then the perl character classes ``\d``, ``\s``, ``\w``, ``\D``, ``\S`` and ``\W`` are permitted in a pattern. Default is **false**. ``word_boundary`` If true, the perl assertions ``\b`` and ``\B`` (word boundary and not a word boundary) are permitted. Default is **false**. ``one_line`` If true, then ``^`` and ``$`` only match at the beginning and end of the string to be matched, regardless of newlines. Otherwise, ``^`` also matches just after a newline, and ``$`` also matches just before a newline. Default is **false**. CONTENTS ======== * STRING backref(PRIV_TASK, INT, STRING) * STRING extract(STRING, STRING, STRING, STRING, BOOL, BOOL, BOOL, INT, BOOL, BOOL, BOOL, BOOL, BOOL, BOOL, BOOL, BOOL) * BOOL match(PRIV_TASK, STRING, STRING, BOOL, BOOL, BOOL, INT, BOOL, BOOL, BOOL, BOOL, BOOL, BOOL, BOOL, BOOL) * STRING namedref(PRIV_TASK, STRING, STRING) * Object regex * STRING regex.backref(INT, STRING) * STRING regex.extract(STRING, STRING, STRING) * BOOL regex.match(STRING) * STRING regex.namedref(STRING, STRING) * STRING regex.sub(STRING, STRING, STRING) * STRING regex.suball(STRING, STRING, STRING) * Object set * VOID set.add(STRING) * VOID set.compile() * BOOL set.match(STRING) * STRING sub(STRING, STRING, STRING, STRING, BOOL, BOOL, BOOL, INT, BOOL, BOOL, BOOL, BOOL, BOOL, BOOL, BOOL, BOOL) * STRING suball(STRING, STRING, STRING, STRING, BOOL, BOOL, BOOL, INT, BOOL, BOOL, BOOL, BOOL, BOOL, BOOL, BOOL, BOOL) * STRING version() .. _obj_regex: Object regex ============ Prototype new OBJECT = re2.regex(STRING pattern [, ]) Description Create a regex object from ``pattern`` and the given options (or option defaults). If the pattern is invalid, then VCL will fail to load and the VCC compiler will emit an error message. Example:: sub vcl_init { new domainmatcher = re2.regex("^www\.([^.]+)\.com$"); new maxagematcher = re2.regex("max-age\s*=\s*(\d+)"); # Group possible subdomains without capturing new submatcher = re2.regex("^www\.(domain1|domain2)\.com$", never_capture=true); } .. _func_regex.match: BOOL regex.match(STRING) ------------------------ Prototype BOOL regex.match(STRING) Description Returns ``true`` if and only if the compiled regex matches the given string; corresponds to VCL's infix operator ``~``. Example:: if (myregex.match(req.http.Host)) { call do_on_match; } .. _func_regex.backref: STRING regex.backref(INT, STRING) --------------------------------- Prototype STRING regex.backref(INT ref, STRING fallback) Description Returns the `nth` captured subexpression from the most recent successful call of the ``.match()`` method for this object in the same client or backend, context, or a fallback string in case the capture fails. Backref 0 indicates the entire matched string. Thus this function behaves like the ``\n`` in the native VCL functions ``regsub`` and ``regsuball``, and the ``$1``, ``$2`` ... variables in Perl. Since Varnish client and backend operations run in different threads, ``.backref()`` can only refer back to a ``.match()`` call in the same thread. Thus a ``.backref()`` call in any of the ``vcl_backend_*`` subroutines -- the backend context -- refers back to a previous ``.match()`` in any of those same subroutines; and a call in any of the other VCL subroutines -- the client context -- refers back to a ``.match()`` in the same client context. After unsuccessful matches, the ``fallback`` string is returned for any call to ``.backref()``. The default value of ``fallback`` is ``"**BACKREF METHOD FAILED**"``. ``.backref()`` always fails after a failed match, even if ``.match()`` had been called successfully before the failure. ``.backref()`` may also return ``fallback`` after a successful match, if no captured group in the matching string corresponds to the backref number. For example, when the pattern ``(a|(b))c`` matches the string ``ac``, there is no backref 2, since nothing matches ``b`` in the string. The VCL infix operators ``~`` and ``!~`` do not affect this method, nor do the functions ``regsub`` or ``regsuball``. Nor is it affected by the matches performed by any other method or function in this VMOD (such as the ``sub()``, ``suball()`` or ``extract()`` methods or functions, or the ``set`` object's ``.match()`` method). ``.backref()`` fails, returning ``fallback`` and writing an error message to the Varnish log with the ``VCL_Error`` tag, under the following conditions (even if a previous match was successful and a substring could have been captured): * The ``fallback`` string is undefined, for example if set from an unset header variable. * The ``never_capture`` option was set to ``true`` for this object. In this case, even ``.backref(0)`` fails after a successful match (otherwise, backref 0 always returns the full matched string). * ``ref`` (the backref number) is out of range, i.e. it is larger than the highest number for a capturing group in the pattern. * ``.match()`` was never called for this object prior to calling ``.backref()``. * There is insufficient workspace for the string to be returned. Example:: if (domainmatcher.match(req.http.Host)) { set req.http.X-Domain = domainmatcher.backref(1); } .. _func_regex.namedref: STRING regex.namedref(STRING, STRING) ------------------------------------- Prototype STRING regex.namedref(STRING name, STRING fallback) Description Returns the captured subexpression designated by ``name`` from the most recent successful call to ``.match()`` in the current context (client or backend), or ``fallback`` in case of failure. Named capturing groups are written in RE2 as: ``(?Pre)``. (Note that this syntax with ``P``, inspired by Python, differs from the notation for named capturing groups in PCRE.) Thus when ``(?P.+)bar$`` matches ``bazbar``, then ``.namedref("foo")`` returns ``baz``. Note that a named capturing group can also be referenced as a numbered group. So in the previous example, ``.backref(1)`` also returns ``baz``. ``fallback`` is returned when ``.namedref()`` is called after an unsuccessful match. The default fallback is ``"**NAMEDREF METHOD FAILED**"``. Like ``.backref()``, ``.namedref()`` is not affected by native VCL regex operations, nor by any other matches performed by methods or functions of the VMOD, except for a prior ``.match()`` for the same object. ``.namedref()`` fails, returning ``fallback`` and logging a ``VCL_Error`` message, if: * The ``fallback`` string is undefined. * ``name`` is undefined or the empty string. * The ``never_capture`` option was set to ``true``. * There is no such named group. * ``.match()`` was not called for this object. * There is insufficient workspace for the string to be returned. Example:: sub vcl_init { new domainmatcher = re2.regex("^www\.(?P[^.]+)\.com$"); } sub vcl_recv { if (domainmatcher.match(req.http.Host)) { set req.http.X-Domain = domainmatcher.namedref("domain"); } } .. _func_regex.sub: STRING regex.sub(STRING, STRING, STRING) ---------------------------------------- Prototype STRING regex.sub(STRING text, STRING rewrite, STRING fallback) Description If the compiled pattern for this regex object matches ``text``, then return the result of replacing the first match in ``text`` with ``rewrite``. Within ``rewrite``, ``\1`` through ``\9`` can be used to insert the the numbered capturing group from the pattern, and ``\0`` to insert the entire matching text. This method corresponds to the VCL native function ``regsub()``. ``fallback`` is returned if the pattern does not match ``text``. The default fallback is ``"**SUB METHOD FAILED**"``. ``.sub()`` fails, returning ``fallback`` and logging a ``VCL_Error`` message, if: * Any of ``text``, ``rewrite`` or ``fallback`` are undefined. * There is insufficient workspace for the rewritten string. Example:: sub vcl_init { new bmatcher = re2.regex("b+"); } sub vcl_recv { # If Host contains "www.yabba.dabba.doo.com", then this will # set X-Yada to "www.yada.dabba.doo.com". set req.http.X-Yada = bmatcher.sub(req.http.Host, "d"); } .. _func_regex.suball: STRING regex.suball(STRING, STRING, STRING) ------------------------------------------- Prototype STRING regex.suball(STRING text, STRING rewrite, STRING fallback) Description Like ``.sub()``, except that all successive non-overlapping matches in ``text`` are replaced with ``rewrite``. This method corresponds to VCL native ``regsuball()``. The default fallback is ``"**SUBALL METHOD FAILED**"``. ``.suball()`` fails under the same conditions as ``.sub()``. Since only non-overlapping matches are substituted, replacing ``"ana"`` within ``"banana"`` only results in one substitution, not two. Example:: sub vcl_init { new bmatcher = re2.regex("b+"); } sub vcl_recv { # If Host contains "www.yabba.dabba.doo.com", then set X-Yada to # "www.yada.dada.doo.com". set req.http.X-Yada = bmatcher.suball(req.http.Host, "d"); } .. _func_regex.extract: STRING regex.extract(STRING, STRING, STRING) -------------------------------------------- Prototype STRING regex.extract(STRING text, STRING rewrite, STRING fallback) Description If the compiled pattern for this regex object matches ``text``, then return ``rewrite`` with substitutions from the matching portions of ``text``. Non-matching substrings of ``text`` are ignored. The default fallback is ``"**EXTRACT METHOD FAILED**"``. Like ``.sub()`` and ``.suball()``, ``.extract()`` fails if: * Any of ``text``, ``rewrite`` or ``fallback`` are undefined. * There is insufficient workspace for the rewritten string. Example:: sub vcl_init { new email = re2.regex("(.*)@([^.]*)"); } sub vcl_deliver { # Sets X-UUCP to "kremvax!boris" set resp.http.X-UUCP = email.extract("boris@kremvax.ru", "\2!\1"); } regex functional interface ========================== .. _func_match: BOOL match(PRIV_TASK, STRING, STRING, BOOL, BOOL, BOOL, INT, BOOL, BOOL, BOOL, BOOL, BOOL, BOOL, BOOL, BOOL) ------------------------------------------------------------------------------------------------------------ Prototype BOOL match(PRIV_TASK, STRING pattern, STRING subject, BOOL utf8, BOOL posix_syntax, BOOL longest_match, INT max_mem, BOOL literal, BOOL never_nl, BOOL dot_nl, BOOL never_capture, BOOL case_sensitive, BOOL perl_classes, BOOL word_boundary, BOOL one_line) Description Like the ``regex.match()`` method, return ``true`` if ``pattern`` matches ``subject``, where ``pattern`` is compiled with the given options (or default options) on each invocation. If ``pattern`` fails to compile, then an error message is logged with the ``VCL_Error`` tag, and ``false`` is returned. Example:: # Match the bereq Host header against a backend response header if (re2.match(pattern=bereq.http.Host, subject=beresp.http.X-Host)) { call do_on_match; } .. _func_backref: STRING backref(PRIV_TASK, INT, STRING) -------------------------------------- Prototype STRING backref(PRIV_TASK, INT ref, STRING fallback) Description Returns the `nth` captured subexpression from the most recent successful call of the ``match()`` function in the current client or backend context, or a fallback string if the capture fails. The default ``fallback`` is ``"**BACKREF FUNCTION FAILED**"``. Similarly to the ``regex.backref()`` method, ``fallback`` is returned after any failed invocation of the ``match()`` function, or if there is no captured group corresponding to the backref number. The function is not affected by native VCL regex operations, or any other method or function of the VMOD except for the ``match()`` function. The function fails, returning ``fallback`` and logging a ``VCL_Error`` message, under the same conditions as the corresponding method: * ``fallback`` is undefined. * ``never_capture`` was true in the previous invocation of the ``match()`` function. * ``ref`` is out of range. * The ``match()`` function was never called in this context. * The pattern failed to compile for the previous ``match()`` call. * There is insufficient workspace for the captured subexpression. Example:: # Match against a pattern provided in a beresp header, and capture # subexpression 1. if (re2.match(pattern=beresp.http.X-Pattern, bereq.http.X-Foo)) { set beresp.http.X-Capture = re2.backref(1); } .. _func_namedref: STRING namedref(PRIV_TASK, STRING, STRING) ------------------------------------------ Prototype STRING namedref(PRIV_TASK, STRING name, STRING fallback) Description Returns the captured subexpression designated by ``name`` from the most recent successful call to the ``match()`` function in the current context, or ``fallback`` in case of failure. The default fallback is ``"**NAMEDREF FUNCTION FAILED**"``. The function returns ``fallback`` when the previous invocation of the ``match()`` function failed, and is only affected by use of the ``match()`` function. The function fails, returning ``fallback`` and logging a ``VCL_Error`` message, under the same conditions as the corresponding method: * ``fallback`` is undefined. * ``name`` is undefined or the empty string. * The ``never_capture`` option was set to ``true``. * There is no such named group. * ``match()`` was not called in this context. * The pattern failed to compile for the previous ``match()`` call. * There is insufficient workspace for the captured expression. Example:: if (re2.match(beresp.http.X-Pattern-With-Names, bereq.http.X-Foo)) { set beresp.http.X-Capture = re2.namedref("foo"); } .. _func_sub: STRING sub(STRING, STRING, STRING, STRING, BOOL, BOOL, BOOL, INT, BOOL, BOOL, BOOL, BOOL, BOOL, BOOL, BOOL, BOOL) ----------------------------------------------------------------------------------------------------------------- Prototype STRING sub(STRING pattern, STRING text, STRING rewrite, STRING fallback, BOOL utf8, BOOL posix_syntax, BOOL longest_match, INT max_mem, BOOL literal, BOOL never_nl, BOOL dot_nl, BOOL never_capture, BOOL case_sensitive, BOOL perl_classes, BOOL word_boundary, BOOL one_line) Description Compiles ``pattern`` with the given options, and if it matches ``text``, then return the result of replacing the first match in ``text`` with ``rewrite``. As with the ``regex.sub()`` method, ``\0`` through ``\9`` may be used in ``rewrite`` to substitute captured groups from the pattern. ``fallback`` is returned if the pattern does not match ``text``. The default fallback is ``"**SUB FUNCTION FAILED**"``. ``sub()`` fails, returning ``fallback`` and logging a ``VCL_Error`` message, if: * ``pattern`` cannot be compiled. * Any of ``text``, ``rewrite`` or ``fallback`` are undefined. * There is insufficient workspace for the rewritten string. Example:: # If the beresp header X-Sub-Letters contains "b+", and Host contains # "www.yabba.dabba.doo.com", then set X-Yada to # "www.yada.dabba.doo.com". set beresp.http.X-Yada = re2.sub(beresp.http.X-Sub-Letters, bereq.http.Host, "d"); .. _func_suball: STRING suball(STRING, STRING, STRING, STRING, BOOL, BOOL, BOOL, INT, BOOL, BOOL, BOOL, BOOL, BOOL, BOOL, BOOL, BOOL) -------------------------------------------------------------------------------------------------------------------- Prototype STRING suball(STRING pattern, STRING text, STRING rewrite, STRING fallback, BOOL utf8, BOOL posix_syntax, BOOL longest_match, INT max_mem, BOOL literal, BOOL never_nl, BOOL dot_nl, BOOL never_capture, BOOL case_sensitive, BOOL perl_classes, BOOL word_boundary, BOOL one_line) Description Like the ``sub()`` function, except that all successive non-overlapping matches in ``text`` are replace with ``rewrite``. The default fallback is ``"**SUBALL FUNCTION FAILED**"``. The ``suball()`` function fails under the same conditions as ``sub()``. Example:: # If the beresp header X-Sub-Letters contains "b+", and Host contains # "www.yabba.dabba.doo.com", then set X-Yada to # "www.yada.dada.doo.com". set beresp.http.X-Yada = re2.suball(beresp.http.X-Sub-Letters, bereq.http.Host, "d"); .. _func_extract: STRING extract(STRING, STRING, STRING, STRING, BOOL, BOOL, BOOL, INT, BOOL, BOOL, BOOL, BOOL, BOOL, BOOL, BOOL, BOOL) --------------------------------------------------------------------------------------------------------------------- Prototype STRING extract(STRING pattern, STRING text, STRING rewrite, STRING fallback, BOOL utf8, BOOL posix_syntax, BOOL longest_match, INT max_mem, BOOL literal, BOOL never_nl, BOOL dot_nl, BOOL never_capture, BOOL case_sensitive, BOOL perl_classes, BOOL word_boundary, BOOL one_line) Description Compiles ``pattern`` with the given options, and if it matches ``text``, then return ``rewrite`` with substitutions from the matching portions of ``text``, ignoring the non-matching portions. The default fallback is ``"**EXTRACT FUNCTION FAILED**"``. The ``extract()`` function fails under the same conditions as ``sub()`` and ``suball()``. Example:: # If beresp header X-Params contains "(foo|bar)=(baz|quux)", and the # URL contains "bar=quux", then set X-Query to "bar:quux". set beresp.http.X-Query = re2.extract(beresp.http.X-Params, bereq.url, "\1:\2"); .. _obj_set: Object set ========== Prototype new OBJECT = re2.set([ENUM anchor] [, ]) Description Initialize a set object that represents several patterns combined by alternation -- ``|`` for "or". Optional parameters control the interpretation of the resulting composed pattern. The ``anchor`` parameter is an enum that can have the values ``none``, ``start`` or ``both``, where ``none`` is the default. ``start`` means that each pattern is matched as if it begins with ``^`` for start-of-text, and ``both`` means that each pattern is anchored with both ``^`` at the beginning and ``$`` for end-of-text at the end. ``none`` means that each pattern is interpreted as a partial match (although individual patterns within the set may have either of ``^`` of ``$``). For example, if a set is initialized with ``anchor=both``, and the patterns ``foo`` and ``bar`` are added, then matches against the set match a string against ``^foo$|^bar$``, or equivalently ``^(foo|bar)$``. The usual regex options can be set, which then control matching against the resulting composed pattern. However, the ``never_capture`` option cannot be set, and is always implicitly true, since backrefs and namedrefs are not possible with sets. Example:: sub vcl_init { # Initialize a regex set for partial matches # with default options new foo = re2.set(); # Initialize a regex set for case insensitive matches # with anchors on both ends (^ and $). new bar = re2.set(anchor=both, case_sensitive=false); # Initialize a regex set using POSIX syntax, but allowing # Perl character classes, and anchoring at the left (^). new baz = re2.set(anchor=start, posix_syntax=true, perl_classes=true); } .. _func_set.add: VOID set.add(STRING) -------------------- Prototype VOID set.add(STRING) Description Add the given pattern to the set. If the pattern is invalid, ``.add()`` fails, and the VCL will fail to load, with an error message describing the problem. ``.add()`` MUST be called in ``vcl_init``, and MAY NOT be called after ``.compile()``. If ``.add()`` is called in any other subroutine, an error message with ``VCL_Error`` is logged, and the call has no effect. If it is called in ``vcl_init`` after ``.compile()``, then the VCL load will fail with an error message. In other words, add all patterns to the set in ``vcl_init``, and finally call ``.compile()`` when you're done. Example:: sub vcl_init { # literal=true means that the dots are interpreted as literal # dots, not "match any character". new hostmatcher = re2.set(anchor=both, case_sensitive=false, literal=true); hostmatcher.add("www.domain1.com"); hostmatcher.add("www.domain2.com"); hostmatcher.add("www.domain3.com"); hostmatcher.compile(); } .. _func_set.compile: VOID set.compile() ------------------ Prototype VOID set.compile() Description Compile the compound pattern represented by the set -- an alternation of all patterns added by ``.add()``. ``.compile()`` may fail if the ``max_mem`` setting is not large enough for the composed pattern. In that case, the VCL load will fail with an error message (then consider a larger value for ``max_mem`` in the set constructor). ``.compile()`` MUST be called in ``vcl_init``, and MAY NOT be called more than once for a set object. If it is called in any other subroutine, a ``VCL_Error`` message is logged, and the call has no effect. If it is called a second time in ``vcl_init``, the VCL load will fail. See above for examples. .. _func_set.match: BOOL set.match(STRING) ---------------------- Prototype BOOL set.match(STRING) Description Returns ``true`` if the given string matches the compound pattern represented by the set, i.e. if it matches any of the patterns that were added to the set. ``.match()`` MUST be called after ``.compile()``; otherwise the match always fails. Example:: if (hostmatcher.match(req.http.Host)) { call do_when_a_host_matched; } .. _func_version: STRING version() ---------------- Prototype STRING version() Description Return the version string for this VMOD. Example:: std.log("Using VMOD re2 version: " + re2.version()); REQUIREMENTS ============ The VMOD requires Varnish 4.1.2 through 4.1.6. It requires the RE2 library, and has been tested against RE2 versions 2015-05-01 through 2017-06-01. INSTALLATION ============ The VMOD is built against a Varnish installation, and the autotools use ``pkg-config(1)`` to locate the necessary header files and other resources for both Varnish and RE2. This sequence will install the VMOD:: > ./autogen.sh # for builds from the git repo > ./configure > make > make check # to run unit tests in src/tests/*.vtc > make distcheck # run check and prepare a distribution tarball > sudo make install If you have installed Varnish and/or RE2 in non-standard directories, call ``autogen.sh`` and ``configure`` with the ``PKG_CONFIG_PATH`` environment variable set to include the paths where the ``.pc`` files can be located for ``varnishapi`` and ``re2``. For example, when varnishd configure was called with ``--prefix=$PREFIX``, use:: > PKG_CONFIG_PATH=${PREFIX}/lib/pkgconfig > export PKG_CONFIG_PATH By default, the vmod ``configure`` script installs the vmod in the same directory as Varnish, determined via ``pkg-config(1)``. The vmod installation directory can be overridden by passing the ``VMOD_DIR`` variable to ``configure``. Other files such as this man-page are installed in the locations determined by ``configure``, which inherits its default ``--prefix`` setting from Varnish. For developers -------------- The VMOD source code is in C and C++, since the RE2 API is C++. Compilation has been tested with gcc/g++ and clang. The build specifies C99 conformance for C sources (``-std=c99``), and C++11 for C++ (``-std=c++11``). For both, all compiler warnings are turned on, and all warnings are considered errors (``-Werror -Wall``). The code should always build without warnings or errors under these constraints. By default, ``CFLAGS`` and ``CXXFLAGS`` are set to ``-g -O2``, so that symbols are included in the shared library, and optimization is at level ``O2``. To change or disable these options, set ``CFLAGS`` and/or ``CXXFLAGS`` explicitly before calling ``configure`` (they may be set to the empty string). For development/debugging cycles, the ``configure`` option ``--enable-debugging`` is recommended (off by default). This will turn off optimizations and function inlining, so that a debugger will step through the code as expected. By default, the VMOD is built with the stack protector enabled (compile option ``-fstack-protector``), but it can be disabled with the ``configure`` option ``--disable-stack-protector``. LIMITATIONS =========== The VMOD allocates Varnish workspace for captured groups and rewritten strings. If operations fail with "insufficient workspace" error messages in the Varnish log (with the ``VCL_Error`` tag), increase the varnishd runtime parameters ``workspace_client`` and/or ``workspace_backend``. The RE2 documentation states that successful matches are slowed quite a bit when they also capture substrings. There is also additional overhead from the VMOD, unless the ``never_capture`` flag is true, to manage data about captured groups in the workspace. This overhead is incurred even if there are no capturing expressions in a pattern, since it is always possible to call ``backref(0)`` to obtain the matched portion of a string. So if you are using a pattern only to match against strings, and never to capture subexpressions, consider setting the ``never_capture`` option to true, to eliminate the extra work for both RE2 and the VMOD. AUTHOR ====== * Geoffrey Simmons UPLEX Nils Goroll Systemoptimierung HISTORY ======= * version 0.1: initial version SEE ALSO ======== * varnishd(1) * vcl(7) * RE2 git repo: https://github.com/google/re2 * RE2 syntax: https://github.com/google/re2/wiki/Syntax * "Implementing Regular Expressions": https://swtch.com/~rsc/regexp/ * Series of articles motivating the design of RE2, with discussion of how RE2 compares with PCRE COPYRIGHT ========= This document is licensed under the same conditions as the libvmod-re2 project. See LICENSE for details. * Copyright (c) 2016 UPLEX Nils Goroll Systemoptimierung