/************************************************* * Perl-Compatible Regular Expressions * *************************************************/ /* PCRE is a library of functions to support regular expressions whose syntax and semantics are as close as possible to those of the Perl 5 language. Written by Philip Hazel Original API code Copyright (c) 1997-2012 University of Cambridge New API code Copyright (c) 2016-2023 University of Cambridge ----------------------------------------------------------------------------- Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met: * Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer. * Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution. * Neither the name of the University of Cambridge nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission. THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. ----------------------------------------------------------------------------- */ /* This module contains the external function pcre2_dfa_match(), which is an alternative matching function that uses a sort of DFA algorithm (not a true FSM). This is NOT Perl-compatible, but it has advantages in certain applications. */ /* NOTE ABOUT PERFORMANCE: A user of this function sent some code that improved the performance of his patterns greatly. I could not use it as it stood, as it was not thread safe, and made assumptions about pattern sizes. Also, it caused test 7 to loop, and test 9 to crash with a segfault. The issue is the check for duplicate states, which is done by a simple linear search up the state list. (Grep for "duplicate" below to find the code.) For many patterns, there will never be many states active at one time, so a simple linear search is fine. In patterns that have many active states, it might be a bottleneck. The suggested code used an indexing scheme to remember which states had previously been used for each character, and avoided the linear search when it knew there was no chance of a duplicate. This was implemented when adding states to the state lists. I wrote some thread-safe, not-limited code to try something similar at the time of checking for duplicates (instead of when adding states), using index vectors on the stack. It did give a 13% improvement with one specially constructed pattern for certain subject strings, but on other strings and on many of the simpler patterns in the test suite it did worse. The major problem, I think, was the extra time to initialize the index. This had to be done for each call of internal_dfa_match(). (The supplied patch used a static vector, initialized only once - I suspect this was the cause of the problems with the tests.) Overall, I concluded that the gains in some cases did not outweigh the losses in others, so I abandoned this code. */ #ifdef HAVE_CONFIG_H #include "config.h" #endif #define NLBLOCK … #define PSSTART … #define PSEND … #include "pcre2_internal.h" #define PUBLIC_DFA_MATCH_OPTIONS … /************************************************* * Code parameters and static tables * *************************************************/ /* These are offsets that are used to turn the OP_TYPESTAR and friends opcodes into others, under special conditions. A gap of 20 between the blocks should be enough. The resulting opcodes don't have to be less than 256 because they are never stored, so we push them well clear of the normal opcodes. */ #define OP_PROP_EXTRA … #define OP_EXTUNI_EXTRA … #define OP_ANYNL_EXTRA … #define OP_HSPACE_EXTRA … #define OP_VSPACE_EXTRA … /* This table identifies those opcodes that are followed immediately by a character that is to be tested in some way. This makes it possible to centralize the loading of these characters. In the case of Type * etc, the "character" is the opcode for \D, \d, \S, \s, \W, or \w, which will always be a small value. Non-zero values in the table are the offsets from the opcode where the character is to be found. ***NOTE*** If the start of this table is modified, the three tables that follow must also be modified. */ static const uint8_t coptable[] = …; /* This table identifies those opcodes that inspect a character. It is used to remember the fact that a character could have been inspected when the end of the subject is reached. ***NOTE*** If the start of this table is modified, the two tables that follow must also be modified. */ static const uint8_t poptable[] = …; /* These 2 tables allow for compact code for testing for \D, \d, \S, \s, \W, and \w */ static const uint8_t toptable1[] = …; static const uint8_t toptable2[] = …; /* Structure for holding data about a particular state, which is in effect the current data for an active path through the match tree. It must consist entirely of ints because the working vector we are passed, and which we put these structures in, is a vector of ints. */ stateblock; #define INTS_PER_STATEBLOCK … /* Before version 10.32 the recursive calls of internal_dfa_match() were passed local working space and output vectors that were created on the stack. This has caused issues for some patterns, especially in small-stack environments such as Windows. A new scheme is now in use which sets up a vector on the stack, but if this is too small, heap memory is used, up to the heap_limit. The main parameters are all numbers of ints because the workspace is a vector of ints. The size of the starting stack vector, DFA_START_RWS_SIZE, is in bytes, and is defined in pcre2_internal.h so as to be available to pcre2test when it is finding the minimum heap requirement for a match. */ #define OVEC_UNIT … #define RWS_BASE_SIZE … #define RWS_RSIZE … #define RWS_OVEC_RSIZE … #define RWS_OVEC_OSIZE … /* This structure is at the start of each workspace block. */ RWS_anchor; #define RWS_ANCHOR_SIZE … /************************************************* * Process a callout * *************************************************/ /* This function is called to perform a callout. Arguments: code current code pointer offsets points to current capture offsets current_subject start of current subject match ptr current position in subject mb the match block extracode extra code offset when called from condition lengthptr where to return the callout length Returns: the return from the callout */ static int do_callout_dfa(PCRE2_SPTR code, PCRE2_SIZE *offsets, PCRE2_SPTR current_subject, PCRE2_SPTR ptr, dfa_match_block *mb, PCRE2_SIZE extracode, PCRE2_SIZE *lengthptr) { … } /************************************************* * Expand local workspace memory * *************************************************/ /* This function is called when internal_dfa_match() is about to be called recursively and there is insufficient working space left in the current workspace block. If there's an existing next block, use it; otherwise get a new block unless the heap limit is reached. Arguments: rwsptr pointer to block pointer (updated) ovecsize space needed for an ovector mb the match block Returns: 0 rwsptr has been updated !0 an error code */ static int more_workspace(RWS_anchor **rwsptr, unsigned int ovecsize, dfa_match_block *mb) { … } /************************************************* * Match a Regular Expression - DFA engine * *************************************************/ /* This internal function applies a compiled pattern to a subject string, starting at a given point, using a DFA engine. This function is called from the external one, possibly multiple times if the pattern is not anchored. The function calls itself recursively for some kinds of subpattern. Arguments: mb the match_data block with fixed information this_start_code the opening bracket of this subexpression's code current_subject where we currently are in the subject string start_offset start offset in the subject string offsets vector to contain the matching string offsets offsetcount size of same workspace vector of workspace wscount size of same rlevel function call recursion level Returns: > 0 => number of match offset pairs placed in offsets = 0 => offsets overflowed; longest matches are present -1 => failed to match < -1 => some kind of unexpected problem The following macros are used for adding states to the two state vectors (one for the current character, one for the following character). */ #define ADD_ACTIVE(x,y) … #define ADD_ACTIVE_DATA(x,y,z) … #define ADD_NEW(x,y) … #define ADD_NEW_DATA(x,y,z) … /* And now, here is the code */ static int internal_dfa_match( dfa_match_block *mb, PCRE2_SPTR this_start_code, PCRE2_SPTR current_subject, PCRE2_SIZE start_offset, PCRE2_SIZE *offsets, uint32_t offsetcount, int *workspace, int wscount, uint32_t rlevel, int *RWS) { … } /************************************************* * Match a pattern using the DFA algorithm * *************************************************/ /* This function matches a compiled pattern to a subject string, using the alternate matching algorithm that finds all matches at once. Arguments: code points to the compiled pattern subject subject string length length of subject string startoffset where to start matching in the subject options option bits match_data points to a match data structure gcontext points to a match context workspace pointer to workspace wscount size of workspace Returns: > 0 => number of match offset pairs placed in offsets = 0 => offsets overflowed; longest matches are present -1 => failed to match < -1 => some kind of unexpected problem */ PCRE2_EXP_DEFN int PCRE2_CALL_CONVENTION pcre2_dfa_match(const pcre2_code *code, PCRE2_SPTR subject, PCRE2_SIZE length, PCRE2_SIZE start_offset, uint32_t options, pcre2_match_data *match_data, pcre2_match_context *mcontext, int *workspace, PCRE2_SIZE wscount) { … } /* These #undefs are here to enable unity builds with CMake. */ #undef NLBLOCK /* Block containing newline information */ #undef PSSTART /* Field containing processed string start */ #undef PSEND /* Field containing processed string end */ /* End of pcre2_dfa_match.c */
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