If we want to match greedy or reluctant regular expressions, we have
to make sure that certain threads are split off with a higher priority
than others. We will use the ThreadQueues' natural order as priority
order: high to low.
To support splitting into different-priority threads, let's introduce
a second SPLIT opcode: SPLIT_JMP. The latter prefers to jump while the
former prefers to execute the opcode directly after the SPLIT opcode.
There is a subtle challenge here, though: let's assume that there are
two current threads and the higher-priority one wants to jump where
the lower-priority one is already. In the PikeVM implementation
before this change, queueImmediately() would see that there is
already a thread queued for that program counter and *not* queue the
higher-priority one.
Example: when matching the pattern '(a?)(a??)(a?)' against the string
'aa', after the first character, the first (high priority) thread
will have matched the first group while the second thread matched the
second group. In the following step, therefore, the first thread will
want to SPLIT_JMP to match the final 'a' to the third group but the
second thread already queued that program counter.
The proposed solution is to introduce a third thread queue: 'queued'.
When queuing threads to be executed after reading the next character
from the string to match, they are not directly queued into 'next' but
into 'queued'. Every thread requiring immediate execution (i.e. before
reading the next character) will be queued into 'current'. Whenever
'current' is drained, the next thread from 'queued' that has not been
queued to 'current' yet will be executed.
That way, we can guarantee that 1) no lower-priority thread can override
a higher-priority thread and 2) infinite loop are prevented.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Instead of having an opcode 'CHAR', let's have the opcodes that fall
within the range of a char *be* the opcode 'match this character'.
While at it, break the ranges of the different types of opcodes apart
into ranges so that related operations are clustered.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
We still do not parse the regular expression patterns, but we can at
least test that the hardcoded 'a(bb)+a' works as expected.
This class will be extended as we support more and more features.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Based on the just-implemented PikeVM, let's test it with a specific
regular expression. At this point, no parsing is implemented but instead
an explicit program executing a(bb)?a is hardcoded.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
So far, these are humble beginnings indeed. Based on the descriptions of
http://swtch.com/%7Ersc/regexp/regexp2.html
I started implementing a Thompson NFA / Pike VM.
The idea being that eventually, regular expressions are to be compiled
into special-purpose bytecode for the Pike VM that executes a varying
number of threads in lock-step over each character of the text to match.
The thread count is bounded by the length of the program: two different
threads with identical instruction pointer at the same character-to-match
would yield exactly the same outcome (and therefore, we can execute just
one such thread instead of possibly many).
To allow for matching groups, each thread carries a state with it, saving
the group offsets acquired so far.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
This makes both the Pattern and the Matcher class abstract so that more
specialized patterns than the trivial patterns we support so far can be
implemented as convenient subclasses of the respective abstract base
classes.
To ease development, we work on copies in test/regex/ in the 'regex'
package. That way, it can be developed in Eclipse (because it does not
interfere with Oracle JRE's java.util.regex.* classes).
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
For quick access, the sezpoz library stores lists in
META-INF/annotations/ of classes that have been annotated in a
special way.
To support the use case where the annotations actually changed since
sezpoz stored said lists, sezpoz then creates proxy instances for the
annotations to provide some backwards compatibility: as long as there
are default values for any newly-introduced annotation values,
everything is groovy.
Therefore, let's make sure that proxy instances inherit the
annotations' default values.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
We should pass the method of the original interface to the
InvocationHandler, not the method of the interface.
That way, proxy instances of annotations will have easy access to
the default values.
This happens to be compatible with the way Oracle Java does it, too.
To accomplish our goal, we keep a global map between proxy classes and
Method references and assign the appropriate list to a field of the
Proxy subclass. This means that we now have to call the super-class
constructor in the generated constructor (which is the correct thing to
do anyway... ;-)).
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
This is only a cosmetic change, but we should not call getName()
over and over again ;-)
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Proxies implement interfaces whose methods *must* be public, as per the
specification of the Java language.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Earlier, if the annotations were already up-to-date (but
Annotations.class not), the compilation would fail.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
This developer did not read the specs closely enough and missed that
the length of the byte array needs to be written out first, so that
DataInputStream#readUTF has a chance of reading the string back.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
... for proper statistics (I thought I was #5 contributor at the
time I started the mailmap, but I was only #6).
Unfortunately, I could not find the full name of Stan
<goo.in.my.shoes@gmail.com> for proper credit.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
When the class whose field is to be inspected has no annotations at all,
at least my javac here (1.6.0_51 on MacOSX) does not produce any class
addendum.
Therefore, let's verify that the addendum is not null before proceeding.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
