Class: Hyperion::H2Codec::Decoder

Inherits:

Object

• Object
• Hyperion::H2Codec::Decoder

Defined in:

lib/hyperion/h2_codec.rb

Overview

Ruby-friendly decoder wrapper. ‘#decode(bytes)` → array of

name, value

byte pairs.

Class Method Summary

• .finalizer(ptr) ⇒ Object

Instance Method Summary

• #decode(bytes) ⇒ Object
• #initialize ⇒ Decoder constructor

  A new instance of Decoder.

Constructor Details

#initialize ⇒ Decoder

Returns a new instance of Decoder.

# File 'lib/hyperion/h2_codec.rb', line 248

def initialize
  raise 'H2Codec native library unavailable' unless H2Codec.available?

  @ptr = H2Codec.decoder_new
  ObjectSpace.define_finalizer(self, self.class.finalizer(@ptr))
  # 2.4-A — per-decoder reusable scratch buffer for the v3 path.
  @scratch_out = String.new(capacity: DECODER_SCRATCH_DEFAULT, encoding: Encoding::ASCII_8BIT)
  @scratch_out_capacity = DECODER_SCRATCH_DEFAULT
end

Class Method Details

.finalizer(ptr) ⇒ Object

# File 'lib/hyperion/h2_codec.rb', line 258

def self.finalizer(ptr)
  proc { H2Codec.decoder_free(ptr) if H2Codec.available? && ptr }
end

Instance Method Details

#decode(bytes) ⇒ Object

# File 'lib/hyperion/h2_codec.rb', line 262

def decode(bytes)
  bytes = bytes.to_s.b
  return [] if bytes.empty?

  # Decoded pairs can be ~larger than the wire because Huffman
  # decoding inflates. 8x is a generous upper bound for RFC 7541
  # — a single-bit Huffman input can decode to 8 bits but
  # adding the framing bytes per pair makes 8x conservative.
  capacity = (bytes.bytesize * 8) + 4096

  # 2.4-A — fast path: reuse a per-decoder scratch and dispatch
  # through the C glue. The Rust ABI writes `[u32 name_len][name]
  # [u32 val_len][val]` repeated; we unpack that in Ruby.
  if H2Codec.cglue_available?
    if capacity > @scratch_out_capacity
      new_cap = @scratch_out_capacity
      new_cap *= 2 while new_cap < capacity
      @scratch_out = String.new(capacity: new_cap, encoding: Encoding::ASCII_8BIT)
      @scratch_out_capacity = new_cap
    end
    # Pad the scratch to its full capacity so RSTRING_LEN ==
    # @scratch_out_capacity inside the C ext (the ext reads
    # RSTRING_LEN to know the writable region size).
    if @scratch_out.bytesize < @scratch_out_capacity
      @scratch_out << ("\x00".b * (@scratch_out_capacity - @scratch_out.bytesize))
    end
    written = H2Codec::CGlue.decoder_decode_v3(@ptr.to_i, bytes, @scratch_out)
    return [] if written.zero?

    return unpack_headers(@scratch_out.byteslice(0, written))
  end

  out = (+'').b
  out.force_encoding(Encoding::ASCII_8BIT)
  out << ("\x00".b * capacity)

  written = H2Codec.decoder_decode(@ptr, bytes, bytes.bytesize, out, capacity)
  raise "H2Codec decoder failed (rc=#{written})" if written.negative?

  unpack_headers(out.byteslice(0, written))
end