214 Commits (5a833bd982f8f43f8df7234d0f177030db53b053)

Author SHA1 Message Date
David Majda 3981433984 Fix too eager proxy rules removal
Fixes GH-137.
11 years ago
David Majda 549d052710 Make |GrammarError| require work also in the browser version
Fixes a bug from ac179cda7b (a fix for
GH-135).
11 years ago
David Majda 09f3f83e1c Merge pull request #135 from hyperpape/master
PEG.GrammarError is undefined in report-missing-rules and report-left-recursion
11 years ago
David Majda fe1ca481ab Code generator rewrite
This is a complete rewrite of the PEG.js code generator. Its goals are:

  1. Allow optimizing the generated parser code for code size as well as
     for parsing speed.

  2. Prepare ground for future optimizations and big features (like
     incremental parsing).

  2. Replace the old template-based code-generation system with
     something more lightweight and flexible.

  4. General code cleanup (structure, style, variable names, ...).

New Architecture
----------------

The new code generator consists of two steps:

  * Bytecode generator -- produces bytecode for an abstract virtual
    machine

  * JavaScript generator -- produces JavaScript code based on the
    bytecode

The abstract virtual machine is stack-based. Originally I wanted to make
it register-based, but it turned out that all the code related to it
would be more complex and the bytecode itself would be longer (because
of explicit register specifications in instructions). The only downsides
of the stack-based approach seem to be few small inefficiencies (see
e.g. the |NIP| instruction), which seem to be insignificant.

The new generator allows optimizing for parsing speed or code size (you
can choose using the |optimize| option of the |PEG.buildParser| method
or the --optimize/-o option on the command-line).

When optimizing for size, the JavaScript generator emits the bytecode
together with its constant table and a generic bytecode interpreter.
Because the interpreter is small and the bytecode and constant table
grow only slowly with size of the grammar, the resulting parser is also
small.

When optimizing for speed, the JavaScript generator just compiles the
bytecode into JavaScript. The generated code is relatively efficient, so
the resulting parser is fast.

Internal Identifiers
--------------------

As a small bonus, all internal identifiers visible to user code in the
initializer, actions and predicates are prefixed by |peg$|. This lowers
the chance that identifiers in user code will conflict with the ones
from PEG.js. It also makes using any internals in user code ugly, which
is a good thing. This solves GH-92.

Performance
-----------

The new code generator improved parsing speed and parser code size
significantly. The generated parsers are now:

  * 39% faster when optimizing for speed

  * 69% smaller when optimizing for size (without minification)

  * 31% smaller when optimizing for size (with minification)

(Parsing speed was measured using the |benchmark/run| script. Code size
was measured by generating parsers for examples in the |examples|
directory and adding up the file sizes. Minification was done by |uglify
--ascii| in version 1.3.4.)

Final Note
----------

This is just a beginning! The new code generator lays a foundation upon
which many optimizations and improvements can (and will) be made.

Stay tuned :-)
11 years ago
Justin Blank b58533ec2f Merge branch 'master' of https://github.com/dmajda/pegjs 12 years ago
Justin Blank ac179cda7b Fix ReferenceError in compiler passes.
Previously, the report-left-recursion and report-missing-rules passes
used PEG.GrammarError without requiring it, causing a ReferenceError.

Since requiring lib/peg.js would cause circular requirements, this
commit imports lib/grammar-error.js as GrammarError.

The bug was introduced in commit
4cda79951a.

Fixes GH-135.
12 years ago
David Majda bea6b1fde7 Implement the |text| function
When called inside an action, the |text| function returns the text
matched by action's expression. It can be also called inside an
initializer or a predicate where it returns an empty string.

The |text| function will be useful mainly in cases where one needs a
structured representation of the input and simultaneously the raw text.
Until now, the only way to get the raw text in these cases was to
painfully build it from the structured representation.

Fixes GH-131.
12 years ago
David Majda 5e146fce38 Text nodes: Implement text nodes
Implement a new syntax to extract matched strings from expressions. For
example, instead of:

  identifier = first:[a-zA-Z_] rest:[a-zA-Z0-9_]* { return first + rest.join(""); }

you can now just write:

  identifier = $([a-zA-Z_] [a-zA-Z0-9_]*)

This is useful mostly for "lexical" rules at the bottom of many
grammars.

Note that structured match results are still built for the expressions
prefixed by "$", they are just ignored. I plan to optimize this later
(sometime after the code generator rewrite).
12 years ago
David Majda 28860e88df Position tracking: Cache position info computed by |line| and |column|
Cache the last reported position info. If the position advances, the
code uses the cache and only computes the differnece. If the position
goes back, the cache is simply dropped.
12 years ago
David Majda 3333cdd18d Position tracking: Kill the |trackLineAndColumn| option
Getting rid of the |trackLineAndColumn| simplifies the code generator
(by unifying two paths in the code).

The |line| and |column| functions currently always compute all the
position info from scratch, which is horribly ineffective. This will be
improved in later commit(s).
12 years ago
David Majda da8c455640 Position tracking: Make |offset|, |line| and |column| functions
This will allow to compute position data lazily and get rid of the
|trackLineAndColumn| option without affecting performance of generated
parsers that don't use position data.
12 years ago
David Majda 05a6bad989 Kill the |toSource| method, introduce the |output| option
Before this commit, |PEG.buildParser| always returned a parser object.
The only way to get its source code was to call the |toSource| method on
it. While this method worked for parsers produced by |PEG.buildParser|
directly, it didn't work for parsers instantiated by executing their
source code. In other words, it was unreliable.

This commit remvoes the |toSource| method on generated parsers and
introduces a new |output| option to |PEG.buildParser|. It allows callers
to specify whether they want to get back the parser object
(|options.output === "parser"|) or its source code (|options.output ===
"source"|). This is much better and more reliable API.
12 years ago
David Majda 3629d880d3 Make sure the |options| param passed to passes is always an object
Pass code can be simpler as a result.
12 years ago
David Majda 0519d7e3ce Git repo npmization: Make the repo a npm package
Includes:

  * Moving the source code from /src to /lib.
  * Adding an explicit file list to package.json
  * Updating the Makefile.
  * Updating the spec and benchmark suites and their READMEs.

Part of a fix for GH-32.
12 years ago