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# Licensed to the Apache Software Foundation (ASF) under one
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# to you under the Apache License, Version 2.0 (the
# "License"); you may not use this file except in compliance
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# 
#   http://www.apache.org/licenses/LICENSE-2.0
# 
# Unless required by applicable law or agreed to in writing,
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module Thrift
  class BufferedTransport < BaseTransport
    DEFAULT_BUFFER = 4096
    
    def initialize(transport)
      @transport = transport
      @wbuf = Bytes.empty_byte_buffer
      @rbuf = Bytes.empty_byte_buffer
      @index = 0
    end

    def open?
      return @transport.open?
    end

    def open
      @transport.open
    end

    def close
      flush
      @transport.close
    end

    def read(sz)
      @index += sz
      ret = @rbuf.slice(@index - sz, sz) || Bytes.empty_byte_buffer

      if ret.length == 0
        @rbuf = @transport.read([sz, DEFAULT_BUFFER].max)
        @index = sz
        ret = @rbuf.slice(0, sz) || Bytes.empty_byte_buffer
      end

      ret
    end

    def read_byte
      # If the read buffer is exhausted, try to read up to DEFAULT_BUFFER more bytes into it.
      if @index >= @rbuf.size
        @rbuf = @transport.read(DEFAULT_BUFFER)
        @index = 0
      end

      # The read buffer has some data now, read a single byte. Using get_string_byte() avoids
      # allocating a temp string of size 1 unnecessarily.
      @index += 1
      return Bytes.get_string_byte(@rbuf, @index - 1)
    end

    # Reads a number of bytes from the transport into the buffer passed.
    #
    # buffer - The String (byte buffer) to write data to; this is assumed to have a BINARY encoding.
    # size   - The number of bytes to read from the transport and write to the buffer.
    #
    # Returns the number of bytes read.
    def read_into_buffer(buffer, size)
      i = 0
      while i < size
        # If the read buffer is exhausted, try to read up to DEFAULT_BUFFER more bytes into it.
        if @index >= @rbuf.size
          @rbuf = @transport.read(DEFAULT_BUFFER)
          @index = 0
        end

        # The read buffer has some data now, so copy bytes over to the output buffer.
        byte = Bytes.get_string_byte(@rbuf, @index)
        Bytes.set_string_byte(buffer, i, byte)
        @index += 1
        i += 1
      end
      i
    end

    def write(buf)
      @wbuf << Bytes.force_binary_encoding(buf)
    end

    def flush
      unless @wbuf.empty?
        @transport.write(@wbuf)
        @wbuf = Bytes.empty_byte_buffer
      end
      
      @transport.flush
    end
  end

  class BufferedTransportFactory < BaseTransportFactory
    def get_transport(transport)
      return BufferedTransport.new(transport)
    end
  end
end
