Extended maintenance of Ruby versions 1.8.7 and 1.9.2 ended on July 31, 2014. Read more

In Files

  • csv.rb

Parent

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

Constants

BufSize

Public Class Methods

new() click to toggle source

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

 
               # 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) click to toggle source

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.

 
               # 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
            
Also aliased as: get
drop(n) click to toggle source

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.

 
               # 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) click to toggle source
Alias for: []
is_eos?() click to toggle source
 
               # File csv.rb, line 882
def is_eos?
  return idx_is_eos?(0)
end
            

Protected Instance Methods

read(size) click to toggle source

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.

 
               # File csv.rb, line 907
def read(size) # raise EOFError
  raise NotImplementedError.new('Method read must be defined in a derived class.')
end
            
terminate() click to toggle source
 
               # File csv.rb, line 899
def terminate
  while (rel_buf); end
end
            

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