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# frozen_string_literal: true
# Released under the MIT License.
# Copyright, 2025, by Samuel Williams.
require_relative "split"
require_relative "../quoted_string"
require_relative "../error"
module Protocol
module HTTP
module Header
# The `digest` header provides a digest of the message body for integrity verification.
#
# This header allows servers to send cryptographic hashes of the response body, enabling clients to verify data integrity. Multiple digest algorithms can be specified, and the header is particularly useful as a trailer since the digest can only be computed after the entire message body is available.
#
# ## Examples
#
# ```ruby
# digest = Digest.new("sha-256=X48E9qOokqqrvdts8nOJRJN3OWDUoyWxBf7kbu9DBPE=")
# digest << "md5=9bb58f26192e4ba00f01e2e7b136bbd8"
# puts digest.to_s
# # => "sha-256=X48E9qOokqqrvdts8nOJRJN3OWDUoyWxBf7kbu9DBPE=, md5=9bb58f26192e4ba00f01e2e7b136bbd8"
# ```
class Digest < Split
ParseError = Class.new(Error)
# https://tools.ietf.org/html/rfc3230#section-4.3.2
ENTRY = /\A(?<algorithm>[a-zA-Z0-9][a-zA-Z0-9\-]*)\s*=\s*(?<value>.*)\z/
# A single digest entry in the Digest header.
Entry = Struct.new(:algorithm, :value) do
# Create a new digest entry.
#
# @parameter algorithm [String] the digest algorithm (e.g., "sha-256", "md5").
# @parameter value [String] the base64-encoded or hex-encoded digest value.
def initialize(algorithm, value)
super(algorithm.downcase, value)
end
# Convert the entry to its string representation.
#
# @returns [String] the formatted digest string.
def to_s
"#{algorithm}=#{value}"
end
end
# Parse the `digest` header value into a list of digest entries.
#
# @returns [Array(Entry)] the list of digest entries with their algorithms and values.
def entries
self.map do |value|
if match = value.match(ENTRY)
Entry.new(match[:algorithm], match[:value])
else
raise ParseError.new("Could not parse digest value: #{value.inspect}")
end
end
end
# Whether this header is acceptable in HTTP trailers.
# @returns [Boolean] `true`, as digest headers contain integrity hashes that can only be calculated after the entire message body is available.
def self.trailer?
true
end
end
end
end
end
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