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| 1 | +# frozen_string_literal: true |
| 2 | + |
| 3 | +# Released under the MIT License. |
| 4 | +# Copyright, 2026, by Samuel Williams. |
| 5 | + |
| 6 | +require_relative "../error" |
| 7 | + |
| 8 | +module Protocol |
| 9 | + module HTTP |
| 10 | + module Header |
| 11 | + # Represents a `range` request header. |
| 12 | + class Range |
| 13 | + ParseError = Class.new(Error) |
| 14 | + |
| 15 | + TOKEN = /[!#$%&'*+\-.0-9A-Z^_`a-z|~]+/ |
| 16 | + HEADER = /\A(?<unit>#{TOKEN})=(?<ranges>.*)\z/ |
| 17 | + BYTE_RANGE = /\A(?:(?<first>\d+)-(?<last>\d*)|-(?<suffix>\d+))\z/ |
| 18 | + OTHER_RANGE = /\A[\x21-\x2B\x2D-\x7E]+\z/ |
| 19 | + SEPARATOR = /\s*,\s*/ |
| 20 | + |
| 21 | + # Represents one byte-range-spec or suffix-byte-range-spec. |
| 22 | + ByteRange = Struct.new(:first, :last) do |
| 23 | + # Parse one byte range. |
| 24 | + # @parameter value [String] The byte range to parse. |
| 25 | + # @returns [ByteRange] The parsed byte range. |
| 26 | + def self.parse(value) |
| 27 | + unless match = BYTE_RANGE.match(value) |
| 28 | + raise ParseError, "Invalid byte range: #{value.inspect}" |
| 29 | + end |
| 30 | + |
| 31 | + if suffix = match[:suffix] |
| 32 | + self.new(nil, Integer(suffix)) |
| 33 | + else |
| 34 | + first = Integer(match[:first]) |
| 35 | + last = match[:last] |
| 36 | + last = last.empty? ? nil : Integer(last) |
| 37 | + |
| 38 | + if last && last < first |
| 39 | + raise ParseError, "Invalid byte range: #{value.inspect}" |
| 40 | + end |
| 41 | + |
| 42 | + self.new(first, last) |
| 43 | + end |
| 44 | + end |
| 45 | + |
| 46 | + # Resolve this byte range against the selected representation size. |
| 47 | + # @parameter size [Integer] The size of the selected representation. |
| 48 | + # @returns [::Range | Nil] The resolved range, or `nil` when it is unsatisfiable. |
| 49 | + def resolve(size) |
| 50 | + if first |
| 51 | + return if first >= size |
| 52 | + first..[last || size - 1, size - 1].min |
| 53 | + else |
| 54 | + return if last.zero? || size.zero? |
| 55 | + |
| 56 | + [0, size - last].max..size - 1 |
| 57 | + end |
| 58 | + end |
| 59 | + |
| 60 | + # Convert this byte range to its wire representation. |
| 61 | + # @returns [String] The serialized byte range. |
| 62 | + def to_s |
| 63 | + if first |
| 64 | + "#{first}-#{last}" |
| 65 | + else |
| 66 | + "-#{last}" |
| 67 | + end |
| 68 | + end |
| 69 | + end |
| 70 | + |
| 71 | + # Parse a raw range header value. |
| 72 | + # @parameter value [String] The raw header value. |
| 73 | + # @returns [Range] The parsed range header. |
| 74 | + def self.parse(value) |
| 75 | + unless match = HEADER.match(value) |
| 76 | + raise ParseError, "Invalid range header: #{value.inspect}" |
| 77 | + end |
| 78 | + |
| 79 | + unit = match[:unit].downcase |
| 80 | + ranges = match[:ranges].split(SEPARATOR, -1) |
| 81 | + |
| 82 | + if ranges.empty? || ranges.any?(&:empty?) |
| 83 | + raise ParseError, "Invalid range set: #{match[:ranges].inspect}" |
| 84 | + end |
| 85 | + |
| 86 | + if unit == "bytes" |
| 87 | + ranges.map!{|range| ByteRange.parse(range)} |
| 88 | + elsif ranges.any?{|range| !OTHER_RANGE.match?(range)} |
| 89 | + raise ParseError, "Invalid range set: #{match[:ranges].inspect}" |
| 90 | + end |
| 91 | + |
| 92 | + self.new(unit, ranges) |
| 93 | + end |
| 94 | + |
| 95 | + # Coerce a value into a range header. |
| 96 | + # @parameter value [Object] The value to coerce. |
| 97 | + # @returns [Range] The parsed range header. |
| 98 | + def self.coerce(value) |
| 99 | + self.parse(value.to_s) |
| 100 | + end |
| 101 | + |
| 102 | + # Initialize a range header. |
| 103 | + # @parameter unit [String] The range unit. |
| 104 | + # @parameter ranges [Array] The range specifiers. |
| 105 | + def initialize(unit, ranges) |
| 106 | + @unit = unit |
| 107 | + @ranges = ranges |
| 108 | + end |
| 109 | + |
| 110 | + # @attribute [String] The range unit. |
| 111 | + attr :unit |
| 112 | + |
| 113 | + # @attribute [Array] The range specifiers. |
| 114 | + attr :ranges |
| 115 | + |
| 116 | + # Whether this header contains byte ranges. |
| 117 | + # @returns [Boolean] Whether the range unit is `bytes`. |
| 118 | + def bytes? |
| 119 | + @unit == "bytes" |
| 120 | + end |
| 121 | + |
| 122 | + # Resolve all byte ranges against the selected representation size. |
| 123 | + # @parameter size [Integer] The size of the selected representation. |
| 124 | + # @returns [Array(::Range)] The satisfiable byte ranges. |
| 125 | + def resolve(size) |
| 126 | + unless bytes? |
| 127 | + raise ArgumentError, "Cannot resolve #{@unit.inspect} ranges as byte ranges!" |
| 128 | + end |
| 129 | + |
| 130 | + size = Integer(size) |
| 131 | + raise ArgumentError, "Size must not be negative!" if size < 0 |
| 132 | + |
| 133 | + @ranges.filter_map{|range| range.resolve(size)} |
| 134 | + end |
| 135 | + |
| 136 | + # Combine another raw range header value with this one. |
| 137 | + # @parameter value [String] The raw range header value. |
| 138 | + def <<(value) |
| 139 | + other = self.class.parse(value) |
| 140 | + |
| 141 | + unless other.unit == @unit |
| 142 | + raise ParseError, "Cannot combine range units: #{@unit.inspect} and #{other.unit.inspect}" |
| 143 | + end |
| 144 | + |
| 145 | + @ranges.concat(other.ranges) |
| 146 | + |
| 147 | + return self |
| 148 | + end |
| 149 | + |
| 150 | + # Convert this header to its wire representation. |
| 151 | + # @returns [String] The serialized range header. |
| 152 | + def to_s |
| 153 | + "#{@unit}=#{@ranges.join(",")}" |
| 154 | + end |
| 155 | + |
| 156 | + # Whether this header is acceptable in HTTP trailers. |
| 157 | + # @returns [Boolean] `false`, as range headers apply to a selected representation. |
| 158 | + def self.trailer? |
| 159 | + false |
| 160 | + end |
| 161 | + end |
| 162 | + end |
| 163 | + end |
| 164 | +end |
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