Class: CSV::StreamBuf

Buffered stream.

EXAMPLE 1 — an IO.

  class MyBuf < StreamBuf
    # Do initialize myself before a super class.  Super class might call my
    # method 'read'. (Could be awful for C++ user. :-)
    def initialize(s)
      @s = s
      super()
    end

    # define my own 'read' method.
    # CAUTION: Returning nil means EnfOfStream.
    def read(size)
      @s.read(size)
    end

    # release buffers. in Ruby which has GC, you do not have to call this...
    def terminate
      @s = nil
      super()
    end
  end

  buf = MyBuf.new(STDIN)
  my_str = ''
  p buf[0, 0]               # => '' (null string)
  p buf[0]                  # => 97 (char code of 'a')
  p buf[0, 1]               # => 'a'
  my_str = buf[0, 5]
  p my_str                  # => 'abcde' (5 chars)
  p buf[0, 6]               # => "abcde\n" (6 chars)
  p buf[0, 7]               # => "abcde\n" (6 chars)
  p buf.drop(3)             # => 3 (dropped chars)
  p buf.get(0, 2)           # => 'de' (2 chars)
  p buf.is_eos?             # => false (is not EOS here)
  p buf.drop(5)             # => 3 (dropped chars)
  p buf.is_eos?             # => true (is EOS here)
  p buf[0]                  # => nil (is EOS here)

EXAMPLE 2 — String.

  This is a conceptual example.  No pros with this.

  class StrBuf < StreamBuf
    def initialize(s)
      @str = s
      @idx = 0
      super()
    end

    def read(size)
      str = @str[@idx, size]
      @idx += str.size
      str
    end
  end

Methods

[] drop get is_eos? new read terminate

Constants

BufSize = 1024 * 8

Public Class methods

new()

WARN: Do not instantiate this class directly. Define your own class which derives this class and define ‘read’ instance method.

[Source]

# File csv.rb, line 888
    def initialize
      @buf_list = []
      @cur_buf = @buf_tail_idx = -1
      @offset = 0
      @is_eos = false
      add_buf
      @cur_buf = @buf_tail_idx
    end

Public Instance methods

[](idx, n = nil)

get a char or a partial string from the stream. idx: index of a string to specify a start point of a string to get. unlike String instance, idx < 0 returns nil. n: size of a string to get. returns char at idx if n == nil. returns a partial string, from idx to (idx + n) if n != nil. at EOF, the string size could not equal to arg n.

[Source]

# File csv.rb, line 803
    def [](idx, n = nil) 
      if idx < 0
        return nil
      end
      if (idx_is_eos?(idx))
        if n and (@offset + idx == buf_size(@cur_buf))
          # Like a String, 'abc'[4, 1] returns nil and
          # 'abc'[3, 1] returns '' not nil.
          return ''
        else
          return nil
        end
      end
      my_buf = @cur_buf
      my_offset = @offset
      next_idx = idx
      while (my_offset + next_idx >= buf_size(my_buf))
        if (my_buf == @buf_tail_idx)
          unless add_buf
            break
          end
        end
        next_idx = my_offset + next_idx - buf_size(my_buf)
        my_buf += 1
        my_offset = 0
      end
      loc = my_offset + next_idx
      if !n
        return @buf_list[my_buf][loc]           # Fixnum of char code.
      elsif (loc + n - 1 < buf_size(my_buf))
        return @buf_list[my_buf][loc, n]        # String.
      else # should do loop insted of (tail) recursive call...
        res = @buf_list[my_buf][loc, BufSize]
        size_added = buf_size(my_buf) - loc
        if size_added > 0
          idx += size_added
          n -= size_added
          ret = self[idx, n]
          if ret
            res << ret
          end
        end
        return res
      end
    end

drop(n)

drop a string from the stream. returns dropped size. at EOF, dropped size might not equals to arg n. Once you drop the head of the stream, access to the dropped part via [] or get returns nil.

[Source]

# File csv.rb, line 854
    def drop(n)
      if is_eos?
        return 0
      end
      size_dropped = 0
      while (n > 0)
        if !@is_eos or (@cur_buf != @buf_tail_idx)
          if (@offset + n < buf_size(@cur_buf))
            size_dropped += n
            @offset += n
            n = 0
          else
            size = buf_size(@cur_buf) - @offset
            size_dropped += size
            n -= size
            @offset = 0
            unless rel_buf
              unless add_buf
                break
              end
              @cur_buf = @buf_tail_idx
            end
          end
        end
      end
      size_dropped
    end

get(idx, n = nil)

Alias for #[]

is_eos?()

[Source]

# File csv.rb, line 882
    def is_eos?
      return idx_is_eos?(0)
    end

Protected Instance methods

read(size)

protected method ‘read’ must be defined in derived classes. CAUTION: Returning a string which size is not equal to ‘size’ means EnfOfStream. When it is not at EOS, you must block the callee, try to read and return the sized string.

[Source]

# File csv.rb, line 907
    def read(size) # raise EOFError
      raise NotImplementedError.new('Method read must be defined in a derived class.')
    end

terminate()

[Source]

# File csv.rb, line 899
    def terminate
      while (rel_buf); end
    end