91 lines
2.6 KiB
Ruby
91 lines
2.6 KiB
Ruby
|
module Parslet::Atoms
|
||
|
|
# Helper class that implements a transient cache that maps position and
|
||
|
|
# parslet object to results. This is used for memoization in the packrat
|
||
|
|
# style.
|
||
|
|
#
|
||
|
|
# Also, error reporter is stored here and error reporting happens through
|
||
|
|
# this class. This makes the reporting pluggable.
|
||
|
|
#
|
||
|
|
class Context
|
||
|
|
# @param reporter [#err, #err_at] Error reporter (leave empty for default
|
||
|
|
# reporter)
|
||
|
|
def initialize(reporter=Parslet::ErrorReporter::Tree.new)
|
||
|
|
@cache = Hash.new { |h, k| h[k] = {} }
|
||
|
|
@reporter = reporter
|
||
|
|
@captures = Parslet::Scope.new
|
||
|
|
end
|
||
|
|
|
||
|
|
# Caches a parse answer for obj at source.pos. Applying the same parslet
|
||
|
|
# at one position of input always yields the same result, unless the input
|
||
|
|
# has changed.
|
||
|
|
#
|
||
|
|
# We need the entire source here so we can ask for how many characters
|
||
|
|
# were consumed by a successful parse. Imitation of such a parse must
|
||
|
|
# advance the input pos by the same amount of bytes.
|
||
|
|
#
|
||
|
|
def try_with_cache(obj, source, consume_all)
|
||
|
|
beg = source.pos
|
||
|
|
|
||
|
|
# Not in cache yet? Return early.
|
||
|
|
unless entry = lookup(obj, beg)
|
||
|
|
result = obj.try(source, self, consume_all)
|
||
|
|
|
||
|
|
if obj.cached?
|
||
|
|
set obj, beg, [result, source.pos-beg]
|
||
|
|
end
|
||
|
|
|
||
|
|
return result
|
||
|
|
end
|
||
|
|
|
||
|
|
# the condition in unless has returned true, so entry is not nil.
|
||
|
|
result, advance = entry
|
||
|
|
|
||
|
|
# The data we're skipping here has been read before. (since it is in
|
||
|
|
# the cache) PLUS the actual contents are not interesting anymore since
|
||
|
|
# we know obj matches at beg. So skip reading.
|
||
|
|
source.pos = beg + advance
|
||
|
|
return result
|
||
|
|
end
|
||
|
|
|
||
|
|
# Report an error at a given position.
|
||
|
|
# @see ErrorReporter
|
||
|
|
#
|
||
|
|
def err_at(*args)
|
||
|
|
return [false, @reporter.err_at(*args)] if @reporter
|
||
|
|
return [false, nil]
|
||
|
|
end
|
||
|
|
|
||
|
|
# Report an error.
|
||
|
|
# @see ErrorReporter
|
||
|
|
#
|
||
|
|
def err(*args)
|
||
|
|
return [false, @reporter.err(*args)] if @reporter
|
||
|
|
return [false, nil]
|
||
|
|
end
|
||
|
|
|
||
|
|
# Returns the current captures made on the input (see
|
||
|
|
# Parslet::Atoms::Base#capture). Use as follows:
|
||
|
|
#
|
||
|
|
# context.captures[:foobar] # => returns capture :foobar
|
||
|
|
#
|
||
|
|
attr_reader :captures
|
||
|
|
|
||
|
|
# Starts a new scope. Use the #scope method of Parslet::Atoms::DSL
|
||
|
|
# to call this.
|
||
|
|
#
|
||
|
|
def scope
|
||
|
|
captures.push
|
||
|
|
yield
|
||
|
|
ensure
|
||
|
|
captures.pop
|
||
|
|
end
|
||
|
|
|
||
|
|
private
|
||
|
|
def lookup(obj, pos)
|
||
|
|
@cache[pos][obj]
|
||
|
|
end
|
||
|
|
def set(obj, pos, val)
|
||
|
|
@cache[pos][obj] = val
|
||
|
|
end
|
||
|
|
end
|
||
|
|
end
|