Module: SourceMap::VLQ
- Defined in:
- opal/stdlib/source_map/vlq.rb
Overview
Public: Base64 VLQ encoding
Adopted from ConradIrwin/ruby-source_map https://github.com/ConradIrwin/ruby-source_map/blob/master/lib/source_map/vlq.rb
Resources
http://en.wikipedia.org/wiki/Variable-length_quantity https://docs.google.com/document/d/1U1RGAehQwRypUTovF1KRlpiOFze0b-_2gc6fAH0KY0k/edit https://github.com/mozilla/source-map/blob/master/lib/source-map/base64-vlq.js
Constant Summary
- VLQ_BASE_SHIFT =
5- VLQ_BASE =
1 << VLQ_BASE_SHIFT
- VLQ_BASE_MASK =
VLQ_BASE - 1
- VLQ_CONTINUATION_BIT =
VLQ_BASE- BASE64_DIGITS =
'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/'.split('')
- BASE64_VALUES =
(0...64).inject({}) { |h, i| h[BASE64_DIGITS [i]] = i; h }
Class Method Summary collapse
-
.decode(str) ⇒ Object
Public: Decode a VLQ string.
-
.decode_mappings(str) ⇒ Object
Public: Decode a VLQ string into mapping numbers.
-
.encode(ary) ⇒ Object
Public: Encode a list of numbers into a compact VLQ string.
-
.encode_mappings(ary) ⇒ Object
Public: Encode a mapping array into a compact VLQ string.
Class Method Details
.decode(str) ⇒ Object
Public: Decode a VLQ string.
str - VLQ encoded String
Returns an Array of Integers.
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# File 'opal/stdlib/source_map/vlq.rb', line 46 def self.decode(str) result = [] chars = str.split('') while chars.any? vlq = 0 shift = 0 continuation = true while continuation char = chars.shift raise ArgumentError unless char digit = BASE64_VALUES [char] continuation = false if (digit & VLQ_CONTINUATION_BIT ) == 0 digit &= VLQ_BASE_MASK vlq += digit << shift shift += VLQ_BASE_SHIFT end result << (vlq & 1 == 1 ? -(vlq >> 1) : vlq >> 1) end result end
.decode_mappings(str) ⇒ Object
Public: Decode a VLQ string into mapping numbers.
str - VLQ encoded String
Returns an two dimensional Array of Integers.
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# File 'opal/stdlib/source_map/vlq.rb', line 85 def self.decode_mappings(str) mappings = [] str.split(';').each_with_index do |group, index| mappings[index] = [] group.split(',').each do |segment| mappings[index] << decode(segment) end end mappings end
.encode(ary) ⇒ Object
Public: Encode a list of numbers into a compact VLQ string.
ary - An Array of Integers
Returns a VLQ String.
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# File 'opal/stdlib/source_map/vlq.rb', line 27 def self.encode(ary) result = [] ary.each do |n| vlq = n < 0 ? ((-n) << 1) + 1 : n << 1 begin digit = vlq & VLQ_BASE_MASK vlq >>= VLQ_BASE_SHIFT digit |= VLQ_CONTINUATION_BIT if vlq > 0 result << BASE64_DIGITS [digit] end while vlq > 0 end result.join end
.encode_mappings(ary) ⇒ Object
Public: Encode a mapping array into a compact VLQ string.
ary - Two dimensional Array of Integers.
Returns a VLQ encoded String seperated by , and ;.
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# File 'opal/stdlib/source_map/vlq.rb', line 72 def self.encode_mappings(ary) ary.map { |group| group.map { |segment| encode(segment) }.join(',') }.join(';') end