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Viewing File: buffer.rb
# encoding: ascii-8bit
module Parser
module Source
##
# A buffer with source code. {Buffer} contains the source code itself,
# associated location information (name and first line), and takes care
# of encoding.
#
# A source buffer is immutable once populated.
#
# @!attribute [r] name
# Buffer name. If the buffer was created from a file, the name corresponds
# to relative path to the file.
# @return [String] buffer name
#
# @!attribute [r] first_line
# First line of the buffer, 1 by default.
# @return [Integer] first line
#
# @api public
#
class Buffer
attr_reader :name, :first_line
##
# @api private
#
ENCODING_RE =
/\#.*coding\s*[:=]\s*
(
# Special-case: there's a UTF8-MAC encoding.
(utf8-mac)
|
# Chew the suffix; it's there for emacs compat.
([A-Za-z0-9_-]+?)(-unix|-dos|-mac)
|
([A-Za-z0-9_-]+)
)
/x
##
# Try to recognize encoding of `string` as Ruby would, i.e. by looking for
# magic encoding comment or UTF-8 BOM. `string` can be in any encoding.
#
# @param [String] string
# @return [String|nil] encoding name, if recognized
#
def self.recognize_encoding(string)
return if string.empty?
# extract the first two lines in an efficient way
string =~ /\A(.*)\n?(.*\n)?/
first_line, second_line = $1, $2
if first_line =~ /\A\xef\xbb\xbf/ # BOM
return Encoding::UTF_8
elsif first_line[0, 2] == '#!'.freeze
encoding_line = second_line
else
encoding_line = first_line
end
if (result = ENCODING_RE.match(encoding_line))
Encoding.find(result[2] || result[3] || result[5])
else
nil
end
end
##
# Recognize encoding of `input` and process it so it could be lexed.
#
# * If `input` does not contain BOM or magic encoding comment, it is
# kept in the original encoding.
# * If the detected encoding is binary, `input` is kept in binary.
# * Otherwise, `input` is re-encoded into UTF-8 and returned as a
# new string.
#
# This method mutates the encoding of `input`, but not its content.
#
# @param [String] input
# @return [String]
# @raise [EncodingError]
#
def self.reencode_string(input)
original_encoding = input.encoding
detected_encoding = recognize_encoding(input.force_encoding(Encoding::BINARY))
if detected_encoding.nil?
input.force_encoding(original_encoding)
elsif detected_encoding == Encoding::BINARY
input
else
input.
force_encoding(detected_encoding).
encode(Encoding::UTF_8)
end
end
def initialize(name, first_line = 1)
@name = name
@source = nil
@first_line = first_line
@lines = nil
@line_begins = nil
# UTF-32-reencoded source for O(1) slicing
@slice_source = nil
# Cache for fast lookup
@line_for_position = {}
@column_for_position = {}
end
##
# Populate this buffer from correspondingly named file.
#
# @example
# Parser::Source::Buffer.new('foo/bar.rb').read
#
# @return [Buffer] self
# @raise [ArgumentError] if already populated
#
def read
File.open(@name, 'rb') do |io|
self.source = io.read
end
self
end
##
# Source code contained in this buffer.
#
# @return [String] source code
# @raise [RuntimeError] if buffer is not populated yet
#
def source
if @source.nil?
raise RuntimeError, 'Cannot extract source from uninitialized Source::Buffer'
end
@source
end
##
# Populate this buffer from a string with encoding autodetection.
# `input` is mutated if not frozen.
#
# @param [String] input
# @raise [ArgumentError] if already populated
# @raise [EncodingError] if `input` includes invalid byte sequence for the encoding
# @return [String]
#
def source=(input)
if defined?(Encoding)
input = input.dup if input.frozen?
input = self.class.reencode_string(input)
unless input.valid_encoding?
raise EncodingError, "invalid byte sequence in #{input.encoding.name}"
end
end
self.raw_source = input
end
##
# Populate this buffer from a string without encoding autodetection.
#
# @param [String] input
# @raise [ArgumentError] if already populated
# @return [String]
#
def raw_source=(input)
if @source
raise ArgumentError, 'Source::Buffer is immutable'
end
@source = input.gsub("\r\n".freeze, "\n".freeze).freeze
if defined?(Encoding) &&
!@source.ascii_only? &&
@source.encoding != Encoding::UTF_32LE &&
@source.encoding != Encoding::BINARY
@slice_source = @source.encode(Encoding::UTF_32LE)
end
end
def slice(range)
if @slice_source.nil?
@source[range]
else
@slice_source[range].encode(@source.encoding)
end
end
##
# Convert a character index into the source to a `[line, column]` tuple.
#
# @param [Integer] position
# @return [[Integer, Integer]] `[line, column]`
#
def decompose_position(position)
line_no, line_begin = line_for(position)
[ @first_line + line_no, position - line_begin ]
end
##
# Convert a character index into the source to a line number.
#
# @param [Integer] position
# @return [Integer] line
# @api private
#
def line_for_position(position)
@line_for_position[position] ||= begin
line_no, _ = line_for(position)
@first_line + line_no
end
end
##
# Convert a character index into the source to a column number.
#
# @param [Integer] position
# @return [Integer] column
# @api private
#
def column_for_position(position)
@column_for_position[position] ||= begin
_, line_begin = line_for(position)
position - line_begin
end
end
##
# Return an `Array` of source code lines.
#
# @return [Array<String>]
#
def source_lines
@lines ||= begin
lines = @source.lines.to_a
lines << '' if @source.end_with?("\n".freeze)
lines.each do |line|
line.chomp!("\n".freeze)
line.freeze
end
lines.freeze
end
end
##
# Extract line `lineno` from source, taking `first_line` into account.
#
# @param [Integer] lineno
# @return [String]
# @raise [IndexError] if `lineno` is out of bounds
#
def source_line(lineno)
source_lines.fetch(lineno - @first_line).dup
end
##
# Extract line `lineno` as a new `Range`, taking `first_line` into account.
#
# @param [Integer] lineno
# @return [Range]
# @raise [IndexError] if `lineno` is out of bounds
#
def line_range(lineno)
index = lineno - @first_line + 1
if index <= 0 || index > line_begins.size
raise IndexError, 'Parser::Source::Buffer: range for line ' \
"#{lineno} requested, valid line numbers are #{@first_line}.." \
"#{@first_line + line_begins.size - 1}"
elsif index == line_begins.size
Range.new(self, line_begins[-index][1], @source.size)
else
Range.new(self, line_begins[-index][1], line_begins[-index - 1][1] - 1)
end
end
##
# Number of last line in the buffer
#
# @return [Integer]
#
def last_line
line_begins.size + @first_line - 1
end
private
def line_begins
unless @line_begins
@line_begins, index = [ [ 0, 0 ] ], 0
while index = @source.index("\n".freeze, index)
index += 1
@line_begins.unshift [ @line_begins.length, index ]
end
end
@line_begins
end
if [].respond_to?(:bsearch)
def line_for(position)
# Fast O(log n) variant for Ruby >=2.0.
line_begins.bsearch do |line, line_begin|
line_begin <= position
end
end
else
def line_for(position)
# Slower O(n) variant for Ruby <2.0.
line_begins.find do |line, line_begin|
line_begin <= position
end
end
end
end
end
end