Module: ResponseBank::BrotliSpliceSlot

Defined in:
lib/response_bank/brotli_splice_slot.rb

Defined Under Namespace

Classes: EncodedBody

Constant Summary collapse

INJECTOR_ENV_KEY = 
'response_bank.html_metadata_injector'
METADATA_KEY = 
'brotli_splice'
METADATA_VERSION = 
1
CONTEXT_SUFFIX_LENGTH =

BrotliSplice reserves the last 2 bytes of every slot as a fixed "\r\n" context suffix, so a slot must be longer than that to hold any replaceable content -- BrotliSplice.encode raises unless the slot length exceeds it.

2

Class Method Summary collapse

Class Method Details

.encode_body(env, body, headers, compression_level:) ⇒ Object 



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# File 'lib/response_bank/brotli_splice_slot.rb', line 16

def encode_body(env, body, headers, compression_level:)
  injector = env[INJECTOR_ENV_KEY]
  return unless injector
  return unless body && body != ''

  prepared = injector.prepare_response_bank_brotli_splice(body, headers)
  return unless prepared

  prepared_body = hash_fetch(prepared, :body)
  slots = hash_fetch(prepared, :slots)
  return unless prepared_body && slots && slots.length == 1

  slot = slots.first
  slot_name = hash_fetch(slot, :name).to_s
  html_offset = integer_value(hash_fetch(slot, :offset))
  html_length = integer_value(hash_fetch(slot, :length))
  return unless valid_html_slot?(prepared_body, html_offset, html_length)

  # Load the native gem only once we have real splice work to do. Keeping this
  # outside the begin/rescue below is deliberate: the rescue clause references
  # BrotliSplice::Error, so if the gem is missing, evaluating that clause would
  # raise NameError and mask the LoadError we want the caller to see.
  ensure_brotli_splice_loaded!

  begin
    result = BrotliSplice.encode(prepared_body, html_offset, html_length, quality: compression_level)

    EncodedBody.new(
      body: prepared_body,
      compressed_body: result[:data],
      metadata: metadata_for(
        name: slot_name,
        compressed_offset: result[:secret_offset],
        replacement_length: result[:secret_length],
        html_placeholder_offset: html_offset,
        html_placeholder_length: html_length,
        context_suffix: result[:context_suffix],
      ),
    )
  rescue BrotliSplice::Error, ArgumentError => error
    ResponseBank.log("BrotliSplice encode skipped: #{error.class}")
    nil
  end
end

.metadata_for(name:, compressed_offset:, replacement_length:, html_placeholder_offset:, html_placeholder_length:, context_suffix:) ⇒ Object 



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# File 'lib/response_bank/brotli_splice_slot.rb', line 61

def metadata_for(
  name:,
  compressed_offset:,
  replacement_length:,
  html_placeholder_offset:,
  html_placeholder_length:,
  context_suffix:
)
  {
    METADATA_KEY => {
      'version' => METADATA_VERSION,
      'slots' => [{
        'name' => name.to_s,
        'compressed_offset' => compressed_offset,
        'replacement_length' => replacement_length,
        'html_placeholder_offset' => html_placeholder_offset,
        'html_placeholder_length' => html_placeholder_length,
        'context_suffix' => context_suffix,
      }],
    },
  }
end

.metadata_slots(metadata) ⇒ Object 



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# File 'lib/response_bank/brotli_splice_slot.rb', line 133

def metadata_slots(metadata)
  return unless metadata

  brotli_splice = metadata[METADATA_KEY]
  return unless brotli_splice && brotli_splice['version'] == METADATA_VERSION

  brotli_splice['slots']
end

.replace_compressed_secret(env, body, metadata) ⇒ Object 



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# File 'lib/response_bank/brotli_splice_slot.rb', line 84

def replace_compressed_secret(env, body, metadata)
  injector = env[INJECTOR_ENV_KEY]
  slots = metadata_slots(metadata)
  return body unless injector && slots && body && body != ''

  # See encode_body: load outside the begin/rescue so a missing gem surfaces as
  # LoadError rather than a masked NameError from the BrotliSplice::Error clause.
  ensure_brotli_splice_loaded!

  begin
    slots.reduce(body) do |current_body, slot|
      replacement = replacement_for_slot(injector, slot)

      unless valid_replacement?(replacement, slot)
        got = replacement ? replacement.bytesize : 'nil'
        ResponseBank.log(
          'BrotliSplice replace skipped: replacement length mismatch ' \
          "(got #{got}, want #{slot['replacement_length']})",
        )
        next current_body
      end

      offset = integer_value(slot['compressed_offset'])
      length = integer_value(slot['replacement_length'])

      unless valid_compressed_slot?(current_body, offset, length)
        ResponseBank.log('BrotliSplice replace skipped: compressed slot out of bounds')
        next current_body
      end

      BrotliSplice.replace(current_body, replacement, offset, length)
    end
  rescue BrotliSplice::Error, ArgumentError => error
    ResponseBank.log("BrotliSplice replace skipped: #{error.class}")
    body
  end
end

.replace_plain_body(env, body, metadata) ⇒ Object 



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# File 'lib/response_bank/brotli_splice_slot.rb', line 122

def replace_plain_body(env, body, metadata)
  injector = env[INJECTOR_ENV_KEY]
  slots = metadata_slots(metadata)
  return body unless injector && slots && body && body != ''

  injector.replace_response_bank_brotli_splice_placeholders(body, slots)
rescue ArgumentError => error
  ResponseBank.log("BrotliSplice plain replacement skipped: #{error.class}")
  body
end