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Updated PCRE source to version 8.32 (bug 5593).

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Nicholas Hastings
2013-03-17 11:32:03 -04:00
parent ed6d8521e6
commit 6ce00034a2
340 changed files with 154241 additions and 63858 deletions
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@@ -2,7 +2,9 @@ Technical Notes about PCRE
--------------------------
These are very rough technical notes that record potentially useful information
about PCRE internals.
about PCRE internals. For information about testing PCRE, see the pcretest
documentation and the comment at the head of the RunTest file.
Historical note 1
-----------------
@@ -22,6 +24,7 @@ the one matching the longest subset of the subject string was chosen. This did
not necessarily maximize the individual wild portions of the pattern, as is
expected in Unix and Perl-style regular expressions.
Historical note 2
-----------------
@@ -34,6 +37,7 @@ maximizing (or, optionally, minimizing in Perl) the amount of the subject that
matches individual wild portions of the pattern. This is an "NFA algorithm" in
Friedl's terminology.
OK, here's the real stuff
-------------------------
@@ -44,6 +48,20 @@ in the pattern, to save on compiling time. However, because of the greater
complexity in Perl regular expressions, I couldn't do this. In any case, a
first pass through the pattern is helpful for other reasons.
Support for 16-bit and 32-bit data strings
-------------------------------------------
From release 8.30, PCRE supports 16-bit as well as 8-bit data strings; and from
release 8.32, PCRE supports 32-bit data strings. The library can be compiled
in any combination of 8-bit, 16-bit or 32-bit modes, creating different
libraries. In the description that follows, the word "short" is
used for a 16-bit data quantity, and the word "unit" is used for a quantity
that is a byte in 8-bit mode, a short in 16-bit mode and a 32-bit unsigned
integer in 32-bit mode. However, so as not to over-complicate the text, the
names of PCRE functions are given in 8-bit form only.
Computing the memory requirement: how it was
--------------------------------------------
@@ -54,6 +72,7 @@ idea was that this would turn out faster than the Henry Spencer code because
the first pass is degenerate and the second pass can just store stuff straight
into the vector, which it knows is big enough.
Computing the memory requirement: how it is
-------------------------------------------
@@ -63,26 +82,31 @@ things I did for 6.8 was to fix Yet Another Bug in the memory computation. Then
I had a flash of inspiration as to how I could run the real compile function in
a "fake" mode that enables it to compute how much memory it would need, while
actually only ever using a few hundred bytes of working memory, and without too
many tests of the mode that might slow it down. So I re-factored the compiling
many tests of the mode that might slow it down. So I refactored the compiling
functions to work this way. This got rid of about 600 lines of source. It
should make future maintenance and development easier. As this was such a major
change, I never released 6.8, instead upping the number to 7.0 (other quite
major changes are also present in the 7.0 release).
major changes were also present in the 7.0 release).
A side effect of this work is that the previous limit of 200 on the nesting
A side effect of this work was that the previous limit of 200 on the nesting
depth of parentheses was removed. However, there is a downside: pcre_compile()
runs more slowly than before (30% or more, depending on the pattern) because it
is doing a full analysis of the pattern. My hope is that this is not a big
issue.
is doing a full analysis of the pattern. My hope was that this would not be a
big issue, and in the event, nobody has commented on it.
Traditional matching function
-----------------------------
The "traditional", and original, matching function is called pcre_exec(), and
it implements an NFA algorithm, similar to the original Henry Spencer algorithm
and the way that Perl works. Not surprising, since it is intended to be as
compatible with Perl as possible. This is the function most users of PCRE will
use most of the time.
and the way that Perl works. This is not surprising, since it is intended to be
as compatible with Perl as possible. This is the function most users of PCRE
will use most of the time. From release 8.20, if PCRE is compiled with
just-in-time (JIT) support, and studying a compiled pattern with JIT is
successful, the JIT code is run instead of the normal pcre_exec() code, but the
result is the same.
Supplementary matching function
-------------------------------
@@ -101,28 +125,39 @@ needed at compile time to produce a traditional FSM where only one state is
ever active at once. I believe some other regex matchers work this way.
Changeable options
------------------
The /i, /m, or /s options (PCRE_CASELESS, PCRE_MULTILINE, PCRE_DOTALL) may
change in the middle of patterns. From PCRE 8.13, their processing is handled
entirely at compile time by generating different opcodes for the different
settings. The runtime functions do not need to keep track of an options state
any more.
Format of compiled patterns
---------------------------
The compiled form of a pattern is a vector of bytes, containing items of
variable length. The first byte in an item is an opcode, and the length of the
item is either implicit in the opcode or contained in the data bytes that
follow it.
The compiled form of a pattern is a vector of units (bytes in 8-bit mode, or
shorts in 16-bit mode, 32-bit unsigned integers in 32-bit mode), containing
items of variable length. The first unit in an item contains an opcode, and
the length of the item is either implicit in the opcode or contained in the
data that follows it.
In many cases below LINK_SIZE data values are specified for offsets within the
compiled pattern. The default value for LINK_SIZE is 2, but PCRE can be
compiled to use 3-byte or 4-byte values for these offsets (impairing the
performance). This is necessary only when patterns whose compiled length is
greater than 64K are going to be processed. In this description, we assume the
"normal" compilation options. Data values that are counts (e.g. for
quantifiers) are always just two bytes long.
A list of the opcodes follows:
In many cases listed below, LINK_SIZE data values are specified for offsets
within the compiled pattern. LINK_SIZE always specifies a number of bytes. The
default value for LINK_SIZE is 2, but PCRE can be compiled to use 3-byte or
4-byte values for these offsets, although this impairs the performance. (3-byte
LINK_SIZE values are available only in 8-bit mode.) Specifing a LINK_SIZE
larger than 2 is necessary only when patterns whose compiled length is greater
than 64K are going to be processed. In this description, we assume the "normal"
compilation options. Data values that are counts (e.g. for quantifiers) are
always just two bytes long (one short in 16-bit mode).
Opcodes with no following data
------------------------------
These items are all just one byte long
These items are all just one unit long
OP_END end of pattern
OP_ANY match any one character other than newline
@@ -131,7 +166,8 @@ These items are all just one byte long
OP_SOD match start of data: \A
OP_SOM, start of match (subject + offset): \G
OP_SET_SOM, set start of match (\K)
OP_CIRC ^ (start of data, or after \n in multiline)
OP_CIRC ^ (start of data)
OP_CIRCM ^ multiline mode (start of data or after newline)
OP_NOT_WORD_BOUNDARY \W
OP_WORD_BOUNDARY \w
OP_NOT_DIGIT \D
@@ -146,48 +182,71 @@ These items are all just one byte long
OP_WORDCHAR \w
OP_EODN match end of data or \n at end: \Z
OP_EOD match end of data: \z
OP_DOLL $ (end of data, or before \n in multiline)
OP_DOLL $ (end of data, or before final newline)
OP_DOLLM $ multiline mode (end of data or before newline)
OP_EXTUNI match an extended Unicode character
OP_ANYNL match any Unicode newline sequence
OP_ACCEPT )
OP_COMMIT )
OP_FAIL ) These are Perl 5.10's "backtracking
OP_PRUNE ) control verbs".
OP_SKIP )
OP_THEN )
OP_ACCEPT ) These are Perl 5.10's "backtracking control
OP_COMMIT ) verbs". If OP_ACCEPT is inside capturing
OP_FAIL ) parentheses, it may be preceded by one or more
OP_PRUNE ) OP_CLOSE, followed by a 2-byte number,
OP_SKIP ) indicating which parentheses must be closed.
Backtracking control verbs with (optional) data
-----------------------------------------------
(*THEN) without an argument generates the opcode OP_THEN and no following data.
OP_MARK is followed by the mark name, preceded by a one-unit length, and
followed by a binary zero. For (*PRUNE), (*SKIP), and (*THEN) with arguments,
the opcodes OP_PRUNE_ARG, OP_SKIP_ARG, and OP_THEN_ARG are used, with the name
following in the same format.
Matching literal characters
---------------------------
The OP_CHAR opcode is followed by a single character that is to be matched
casefully. For caseless matching, OP_CHARI is used. In UTF-8 or UTF-16 modes,
the character may be more than one unit long. In UTF-32 mode, characters
are always exactly one unit long.
Repeating single characters
---------------------------
The common repeats (*, +, ?) when applied to a single character use the
following opcodes:
The common repeats (*, +, ?), when applied to a single character, use the
following opcodes, which come in caseful and caseless versions:
OP_STAR
OP_MINSTAR
OP_POSSTAR
OP_PLUS
OP_MINPLUS
OP_POSPLUS
OP_QUERY
OP_MINQUERY
OP_POSQUERY
Caseful Caseless
OP_STAR OP_STARI
OP_MINSTAR OP_MINSTARI
OP_POSSTAR OP_POSSTARI
OP_PLUS OP_PLUSI
OP_MINPLUS OP_MINPLUSI
OP_POSPLUS OP_POSPLUSI
OP_QUERY OP_QUERYI
OP_MINQUERY OP_MINQUERYI
OP_POSQUERY OP_POSQUERYI
In ASCII mode, these are two-byte items; in UTF-8 mode, the length is variable.
Those with "MIN" in their name are the minimizing versions. Those with "POS" in
their names are possessive versions. Each is followed by the character that is
to be repeated. Other repeats make use of
Each opcode is followed by the character that is to be repeated. In ASCII mode,
these are two-unit items; in UTF-8 or UTF-16 modes, the length is variable; in
UTF-32 mode these are one-unit items.
Those with "MIN" in their names are the minimizing versions. Those with "POS"
in their names are possessive versions. Other repeats make use of these
opcodes:
OP_UPTO
OP_MINUPTO
OP_POSUPTO
OP_EXACT
Caseful Caseless
OP_UPTO OP_UPTOI
OP_MINUPTO OP_MINUPTOI
OP_POSUPTO OP_POSUPTOI
OP_EXACT OP_EXACTI
which are followed by a two-byte count (most significant first) and the
repeated character. OP_UPTO matches from 0 to the given number. A repeat with a
non-zero minimum and a fixed maximum is coded as an OP_EXACT followed by an
OP_UPTO (or OP_MINUPTO or OPT_POSUPTO).
Each of these is followed by a two-byte (one short) count (most significant
byte first in 8-bit mode) and then the repeated character. OP_UPTO matches from
0 to the given number. A repeat with a non-zero minimum and a fixed maximum is
coded as an OP_EXACT followed by an OP_UPTO (or OP_MINUPTO or OPT_POSUPTO).
Repeating character types
@@ -195,7 +254,7 @@ Repeating character types
Repeats of things like \d are done exactly as for single characters, except
that instead of a character, the opcode for the type is stored in the data
byte. The opcodes are:
unit. The opcodes are:
OP_TYPESTAR
OP_TYPEMINSTAR
@@ -217,65 +276,58 @@ Match by Unicode property
OP_PROP and OP_NOTPROP are used for positive and negative matches of a
character by testing its Unicode property (the \p and \P escape sequences).
Each is followed by two bytes that encode the desired property as a type and a
Each is followed by two units that encode the desired property as a type and a
value.
Repeats of these items use the OP_TYPESTAR etc. set of opcodes, followed by
three bytes: OP_PROP or OP_NOTPROP and then the desired property type and
Repeats of these items use the OP_TYPESTAR etc. set of opcodes, followed by
three units: OP_PROP or OP_NOTPROP, and then the desired property type and
value.
Matching literal characters
---------------------------
The OP_CHAR opcode is followed by a single character that is to be matched
casefully. For caseless matching, OP_CHARNC is used. In UTF-8 mode, the
character may be more than one byte long. (Earlier versions of PCRE used
multi-character strings, but this was changed to allow some new features to be
added.)
Character classes
-----------------
If there is only one character, OP_CHAR or OP_CHARNC is used for a positive
class, and OP_NOT for a negative one (that is, for something like [^a]).
However, in UTF-8 mode, the use of OP_NOT applies only to characters with
values < 128, because OP_NOT is confined to single bytes.
If there is only one character in the class, OP_CHAR or OP_CHARI is used for a
positive class, and OP_NOT or OP_NOTI for a negative one (that is, for
something like [^a]).
Another set of repeating opcodes (OP_NOTSTAR etc.) are used for a repeated,
negated, single-character class. The normal ones (OP_STAR etc.) are used for a
repeated positive single-character class.
Another set of 13 repeating opcodes (called OP_NOTSTAR etc.) are used for
repeated, negated, single-character classes. The normal single-character
opcodes (OP_STAR, etc.) are used for repeated positive single-character
classes.
When there's more than one character in a class and all the characters are less
than 256, OP_CLASS is used for a positive class, and OP_NCLASS for a negative
one. In either case, the opcode is followed by a 32-byte bit map containing a 1
bit for every character that is acceptable. The bits are counted from the least
significant end of each byte.
When there is more than one character in a class and all the characters are
less than 256, OP_CLASS is used for a positive class, and OP_NCLASS for a
negative one. In either case, the opcode is followed by a 32-byte (16-short)
bit map containing a 1 bit for every character that is acceptable. The bits are
counted from the least significant end of each unit. In caseless mode, bits for
both cases are set.
The reason for having both OP_CLASS and OP_NCLASS is so that, in UTF-8 mode,
subject characters with values greater than 256 can be handled correctly. For
OP_CLASS they don't match, whereas for OP_NCLASS they do.
The reason for having both OP_CLASS and OP_NCLASS is so that, in UTF-8/16/32 mode,
subject characters with values greater than 255 can be handled correctly. For
OP_CLASS they do not match, whereas for OP_NCLASS they do.
For classes containing characters with values > 255, OP_XCLASS is used. It
optionally uses a bit map (if any characters lie within it), followed by a list
of pairs and single characters. There is a flag character than indicates
whether it's a positive or a negative class.
For classes containing characters with values greater than 255, OP_XCLASS is
used. It optionally uses a bit map (if any characters lie within it), followed
by a list of pairs (for a range) and single characters. In caseless mode, both
cases are explicitly listed. There is a flag character than indicates whether
it is a positive or a negative class.
Back references
---------------
OP_REF is followed by two bytes containing the reference number.
OP_REF (caseful) or OP_REFI (caseless) is followed by two bytes (one short)
containing the reference number.
Repeating character classes and back references
-----------------------------------------------
Single-character classes are handled specially (see above). This section
applies to OP_CLASS and OP_REF. In both cases, the repeat information follows
the base item. The matching code looks at the following opcode to see if it is
one of
applies to OP_CLASS and OP_REF[I]. In both cases, the repeat information
follows the base item. The matching code looks at the following opcode to see
if it is one of
OP_CRSTAR
OP_CRMINSTAR
@@ -286,10 +338,10 @@ one of
OP_CRRANGE
OP_CRMINRANGE
All but the last two are just single-byte items. The others are followed by
four bytes of data, comprising the minimum and maximum repeat counts. There are
no special possessive opcodes for these repeats; a possessive repeat is
compiled into an atomic group.
All but the last two are just single-unit items. The others are followed by
four bytes (two shorts) of data, comprising the minimum and maximum repeat
counts. There are no special possessive opcodes for these repeats; a possessive
repeat is compiled into an atomic group.
Brackets and alternation
@@ -299,7 +351,8 @@ A pair of non-capturing (round) brackets is wrapped round each expression at
compile time, so alternation always happens in the context of brackets.
[Note for North Americans: "bracket" to some English speakers, including
myself, can be round, square, curly, or pointy. Hence this usage.]
myself, can be round, square, curly, or pointy. Hence this usage rather than
"parentheses".]
Non-capturing brackets use the opcode OP_BRA. Originally PCRE was limited to 99
capturing brackets and it used a different opcode for each one. From release
@@ -311,16 +364,17 @@ A bracket opcode is followed by LINK_SIZE bytes which give the offset to the
next alternative OP_ALT or, if there aren't any branches, to the matching
OP_KET opcode. Each OP_ALT is followed by LINK_SIZE bytes giving the offset to
the next one, or to the OP_KET opcode. For capturing brackets, the bracket
number immediately follows the offset, always as a 2-byte item.
number immediately follows the offset, always as a 2-byte (one short) item.
OP_KET is used for subpatterns that do not repeat indefinitely, while
OP_KET is used for subpatterns that do not repeat indefinitely, and
OP_KETRMIN and OP_KETRMAX are used for indefinite repetitions, minimally or
maximally respectively. All three are followed by LINK_SIZE bytes giving (as a
positive number) the offset back to the matching bracket opcode.
maximally respectively (see below for possessive repetitions). All three are
followed by LINK_SIZE bytes giving (as a positive number) the offset back to
the matching bracket opcode.
If a subpattern is quantified such that it is permitted to match zero times, it
is preceded by one of OP_BRAZERO, OP_BRAMINZERO, or OP_SKIPZERO. These are
single-byte opcodes that tell the matcher that skipping the following
single-unit opcodes that tell the matcher that skipping the following
subpattern entirely is a valid branch. In the case of the first two, not
skipping the pattern is also valid (greedy and non-greedy). The third is used
when a pattern has the quantifier {0,0}. It cannot be entirely discarded,
@@ -343,6 +397,15 @@ final replication is changed to OP_SBRA or OP_SCBRA. This tells the matcher
that it needs to check for matching an empty string when it hits OP_KETRMIN or
OP_KETRMAX, and if so, to break the loop.
Possessive brackets
-------------------
When a repeated group (capturing or non-capturing) is marked as possessive by
the "+" notation, e.g. (abc)++, different opcodes are used. Their names all
have POS on the end, e.g. OP_BRAPOS instead of OP_BRA and OP_SCPBRPOS instead
of OP_SCBRA. The end of such a group is marked by OP_KETRPOS. If the minimum
repetition is zero, the group is preceded by OP_BRAPOSZERO.
Assertions
----------
@@ -350,11 +413,12 @@ Assertions
Forward assertions are just like other subpatterns, but starting with one of
the opcodes OP_ASSERT or OP_ASSERT_NOT. Backward assertions use the opcodes
OP_ASSERTBACK and OP_ASSERTBACK_NOT, and the first opcode inside the assertion
is OP_REVERSE, followed by a two byte count of the number of characters to move
back the pointer in the subject string. When operating in UTF-8 mode, the count
is a character count rather than a byte count. A separate count is present in
each alternative of a lookbehind assertion, allowing them to have different
fixed lengths.
is OP_REVERSE, followed by a two byte (one short) count of the number of
characters to move back the pointer in the subject string. In ASCII mode, the
count is a number of units, but in UTF-8/16 mode each character may occupy more
than one unit; in UTF-32 mode each character occupies exactly one unit.
A separate count is present in each alternative of a lookbehind
assertion, allowing them to have different fixed lengths.
Once-only (atomic) subpatterns
@@ -371,13 +435,17 @@ Conditional subpatterns
These are like other subpatterns, but they start with the opcode OP_COND, or
OP_SCOND for one that might match an empty string in an unbounded repeat. If
the condition is a back reference, this is stored at the start of the
subpattern using the opcode OP_CREF followed by two bytes containing the
reference number. If the condition is "in recursion" (coded as "(?(R)"), or "in
recursion of group x" (coded as "(?(Rx)"), the group number is stored at the
start of the subpattern using the opcode OP_RREF, and a value of zero for "the
whole pattern". For a DEFINE condition, just the single byte OP_DEF is used (it
has no associated data). Otherwise, a conditional subpattern always starts with
one of the assertions.
subpattern using the opcode OP_CREF followed by two bytes (one short)
containing the reference number. OP_NCREF is used instead if the reference was
generated by name (so that the runtime code knows to check for duplicate
names).
If the condition is "in recursion" (coded as "(?(R)"), or "in recursion of
group x" (coded as "(?(Rx)"), the group number is stored at the start of the
subpattern using the opcode OP_RREF or OP_NRREF (cf OP_NCREF), and a value of
zero for "the whole pattern". For a DEFINE condition, just the single unit
OP_DEF is used (it has no associated data). Otherwise, a conditional subpattern
always starts with one of the assertions.
Recursion
@@ -394,25 +462,12 @@ are not strictly a recursion.
Callout
-------
OP_CALLOUT is followed by one byte of data that holds a callout number in the
OP_CALLOUT is followed by one unit of data that holds a callout number in the
range 0 to 254 for manual callouts, or 255 for an automatic callout. In both
cases there follows a two-byte value giving the offset in the pattern to the
start of the following item, and another two-byte item giving the length of the
next item.
cases there follows a two-byte (one short) value giving the offset in the
pattern to the start of the following item, and another two-byte (one short)
item giving the length of the next item.
Changing options
----------------
If any of the /i, /m, or /s options are changed within a pattern, an OP_OPT
opcode is compiled, followed by one byte containing the new settings of these
flags. If there are several alternatives, there is an occurrence of OP_OPT at
the start of all those following the first options change, to set appropriate
options for the start of the alternative. Immediately after the end of the
group there is another such item to reset the flags to their previous values. A
change of flag right at the very start of the pattern can be handled entirely
at compile time, and so does not cause anything to be put into the compiled
data.
Philip Hazel
April 2008
February 2012