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class SourceMap
class ParserError < RuntimeError; end
# Load a SourceMap from a Hash such as might be returned by
# {SourceMap#as_json}.
#
def self.from_json(json)
raise ParserError, "Cannot parse version: #{json['version']} of SourceMap" unless json['version'] == 3
map = new(:file => json['file'],
:source_root => json['sourceRoot'],
:sources => json['sources'],
:names => json['names'])
map.parse_mappings(json['mappings'] || '')
map
end
# Load a SourceMap from a String.
def self.from_s(str)
from_json JSON.parse(str)
end
# Load a SourceMap from a file.
def self.load(filename)
from_s File.read(filename)
end
module Parser
# Parse the mapping string from a SourceMap.
#
# The mappings string contains one comma-separated list of segments per line
# in the output file, these lists are joined by semi-colons.
#
def parse_mappings(string)
@previous = Hash.new{ 0 }
string.split(";").each_with_index do |line, line_idx|
# The generated_col resets to 0 at the start of every line, though
# all the other differences are maintained.
@previous[:generated_col] = 0
line.split(",").each do |segment|
mappings << parse_mapping(segment, line_idx + 1)
end
end
self.mappings = self.mappings.sort_by{ |x| [x[:generated_line], x[:generated_col]] }
end
# All the numbers in SourceMaps are stored as differences from each other,
# so we need to remove the difference every time we read a number.
def undiff(int, type)
@previous[type] += int
end
# Parse an individual mapping.
#
# This is a list of variable-length-quanitity, with 1, 4 or 5 items. See the spec
# https://docs.google.com/document/d/1U1RGAehQwRypUTovF1KRlpiOFze0b-_2gc6fAH0KY0k/edit
# for more details.
def parse_mapping(segment, line_num)
item = VLQ.decode_array(segment)
unless [1, 4, 5].include?(item.size)
raise ParserError, "In map for #{file}:#{line_num}: unparseable item: #{segment}"
end
map = {
:generated_line => line_num,
:generated_col => undiff(item[0], :generated_col),
}
if item.size >= 4
map[:source] = sources[undiff(item[1], :source_id)]
map[:source_line] = undiff(item[2], :source_line) + 1 # line numbers are stored starting from 0
map[:source_col] = undiff(item[3], :source_col)
map[:name] = names[undiff(item[4], :name_id)] if item[4]
end
if map[:generated_col] < 0
raise ParserError, "In map for #{file}:#{line_num}: unexpected generated_col: #{map[:generated_col]}"
elsif map.key?(:source) && (map[:source].nil? || @previous[:source_id] < 0)
raise ParserError, "In map for #{file}:#{line_num}: unknown source id: #{@previous[:source_id]}"
elsif map.key?(:source_line) && map[:source_line] < 1
raise ParserError, "In map for #{file}:#{line_num}: unexpected source_line: #{map[:source_line]}"
elsif map.key?(:source_col) && map[:source_col] < 0
raise ParserError, "In map for #{file}:#{line_num}: unexpected source_col: #{map[:source_col]}"
elsif map.key?(:name) && (map[:name].nil? || @previous[:name_id] < 0)
raise ParserError, "In map for #{file}:#{line_num}: unknown name id: #{@previous[:name_id]}"
else
map
end
end
end
end
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