# CSV -- module for generating/parsing CSV data.
# $Id: csv.rb,v 1.1.1.1 2003/10/15 10:11:48 melville Exp $
# This module is copyrighted free software by NAKAMURA, Hiroshi.
# You can redistribute it and/or modify it under the same term as Ruby.
class CSV
public
# DESCRIPTION
# CSV::Cell -- Describes 1 cell of CSV.
#
class Cell
public
# Datum as string.
attr_accessor :data
# Is this datum null?
attr_accessor :is_null
# SYNOPSIS
# cell = CSV::Cell.new(data = '', is_null = true)
#
# ARGS
# data: datum as String
# is_null: is this datum null?
#
# RETURNS
# cell: Created instance.
#
# DESCRIPTION
# Create instance. If is_null is true, datum is stored in the instance
# created but it should be treated as 'NULL'.
#
def initialize(data = '', is_null = true)
@data = data
@is_null = is_null
end
# SYNOPSIS
# CSV::Cell#match(rhs)
#
# ARGS
# rhs: an instance of CSV::Cell to be compared.
#
# RETURNS
# true/false. See the souce if you want to know matching algorithm.
#
# DESCRIPTION
# Compare another cell with me. Bare in mind Null matches with Null
# using this method. Use CSV::Cell#== if you want Null never matches
# with other data including Null.
#
def match(rhs)
if @is_null and rhs.is_null
true
elsif @is_null or rhs.is_null
false
else
@data == rhs.data
end
end
# SYNOPSIS
# CSV::Cell#==(rhs)
#
# ARGS
# rhs: an instance of CSV::Cell to be compared.
#
# RETURNS
# true/false. See the souce if you want to know matching algorithm.
#
# DESCRIPTION
# Compare another cell with me. Bare in mind Null is not match with
# Null using this method. Null never matches with other data including
# Null. Use CSV::Cell#match if you want Null matches with Null.
#
def ==(rhs)
if @is_null or rhs.is_null
false
else
@data == rhs.data
end
end
end
# DESCRIPTION
# CSV::Row -- Describes a row of CSV. Each element must be a CSV::Cell.
#
class Row < Array
public
# SYNOPSIS
# CSV::Row#to_a
#
# RETURNS
# An Array of String.
#
# DESCRIPTION
# Convert CSV::Cell to String. Null is converted to nil.
#
def to_a
self.collect { |cell| cell.is_null ? nil : cell.data }
end
# SYNOPSIS
# CSV::Row#match(rhs)
#
# ARGS
# rhs: an Array of cells. Each cell is a instance of CSV::Cell.
#
# RETURNS
# true/false. See the souce if you want to know matching algorithm.
#
# DESCRIPTION
# Compare another row with me.
#
def match(rhs)
if self.size != rhs.size
return false
end
for idx in 0...(self.size)
unless self[idx].match(rhs[idx])
return false
end
end
true
end
end
# SYNOPSIS
# 1. reader = CSV.open(filename, 'r')
#
# 2. CSV.open(filename, 'r') do |row|
# ...
# end
#
# 3. writer = CSV.open(filename, 'w')
#
# 4. CSV.open(filename, 'w') do |writer|
# ...
# end
#
# ARGS
# filename: filename to open.
# mode: 'r' for read (parse)
# 'w' for write (generate)
# row: an Array of cells which is a parsed line.
# writer: Created writer instance. See CSV::Writer#<< and
# CSV::Writer#add_row to know how to generate CSV string.
#
# RETURNS
# reader: Create reader instance. To get parse result, see
# CSV::Reader#each.
# writer: Created writer instance. See CSV::Writer#<< and
# CSV::Writer#add_row to know how to generate CSV string.
#
# DESCRIPTION
# Open a CSV formatted file to read or write.
#
# EXAMPLE 1
# reader = CSV.open('csvfile.csv', 'r')
# row1 = reader.shift
# row2 = reader.shift
# if row2.empty?
# p 'row2 not find.'
# end
# reader.close
#
# EXAMPLE 2
# CSV.open('csvfile.csv', 'r') do |row|
# p row
# end
#
# EXAMPLE 3
# writer = CSV.open('csvfile.csv', 'w')
# writer << ['r1c1', 'r1c2'] << ['r2c1', 'r2c2'] << [nil, nil]
# writer.close
#
# EXAMPLE 4
# CSV.open('csvfile.csv', 'w') do |writer|
# writer << ['r1c1', 'r1c2']
# writer << ['r2c1', 'r2c2']
# writer << [nil, nil]
# end
#
def CSV.open(filename, mode, col_sep = ?,, &block)
if mode == 'r' or mode == 'rb'
open_reader(filename, col_sep, &block)
elsif mode == 'w' or mode == 'wb'
open_writer(filename, col_sep, &block)
else
raise ArgumentError.new("'mode' must be 'r', 'rb', 'w', or 'wb'")
end
end
def CSV.parse(filename, col_sep = ?,, &block)
open_reader(filename, col_sep, &block)
end
def CSV.generate(filename, col_sep = ?,, &block)
open_writer(filename, col_sep, &block)
end
# Private class methods.
class << self
private
def open_reader(filename, col_sep, &block)
file = File.open(filename, 'rb')
if block
begin
CSV::Reader.parse(file, col_sep) do |row|
yield(row)
end
ensure
file.close
end
nil
else
reader = CSV::Reader.create(file, col_sep)
reader.close_on_terminate
reader
end
end
def open_writer(filename, col_sep, &block)
file = File.open(filename, 'wb')
if block
begin
CSV::Writer.generate(file, col_sep) do |writer|
yield(writer)
end
ensure
file.close
end
nil
else
writer = CSV::Writer.create(file, col_sep)
writer.close_on_terminate
writer
end
end
end
# DESCRIPTION
# CSV::Reader -- CSV formatted string/stream reader.
#
# EXAMPLE
# Read CSV lines untill the first column is 'stop'.
#
# CSV::Reader.parse(File.open('bigdata', 'rb')) do |row|
# p row
# break if !row[0].is_null && row[0].data == 'stop'
# end
#
class Reader
include Enumerable
public
# SYNOPSIS
# reader = CSV::Reader.create(str_or_readable)
#
# ARGS
# str_or_readable: a CSV data to be parsed. A String or an IO.
#
# RETURNS
# reader: Created instance.
#
# DESCRIPTION
# Create instance. To get parse result, see CSV::Reader#each.
#
def Reader.create(str_or_readable, col_sep = ?,)
case str_or_readable
when IO
IOReader.new(str_or_readable, col_sep)
when String
StringReader.new(str_or_readable, col_sep)
else
IOReader.new(str_or_readable, col_sep)
end
end
# SYNOPSIS
# CSV::Reader.parse(str_or_readable) do |row|
# ...
# end
#
# ARGS
# str_or_readable: a CSV data to be parsed. A String or an IO.
# row: a CSV::Row; an Array of a CSV::Cell in a line.
#
# RETURNS
# nil
#
# DESCRIPTION
# Parse CSV data and get lines. Caller block is called for each line
# with an argument which is a chunk of cells in a row.
#
# Block value is always nil. Rows are not cached for performance
# reason.
#
def Reader.parse(str_or_readable, col_sep = ?,)
reader = create(str_or_readable, col_sep)
reader.each do |row|
yield(row)
end
reader.close
nil
end
# SYNOPSIS
# CSV::Reader#each do |row|
# ...
# end
#
# ARGS
# row: a CSV::Row; an Array of a CSV::Cell in a line.
#
# RETURNS
# nil
#
# DESCRIPTION
# Caller block is called for each line with an argument which is a chunk
# of cells in a row.
#
# Block value is always nil. Rows are not cached for performance
# reason.
#
def each
while true
row = Row.new
parsed_cells = get_row(row)
if parsed_cells == 0
break
end
yield(row)
end
nil
end
# SYNOPSIS
# cell = CSV::Reader#shift
#
# RETURNS
# cell: a CSV::Row; an Array of a CSV::Cell.
#
# DESCRIPTION
# Extract cells of next line.
#
def shift
row = Row.new
parsed_cells = get_row(row)
row
end
# SYNOPSIS
# CSV::Reader#close
#
# RETURNS
# nil
#
# DESCRIPTION
# Close this reader.
#
def close
terminate
end
private
def initialize(dev)
raise RuntimeError.new('Do not instanciate this class directly.')
end
def get_row(row)
raise NotImplementedError.new('Method get_row must be defined in a derived class.')
end
def terminate
# Define if needed.
end
end
# DESCRIPTION
# CSV::StringReader -- CSV formatted stream reader.
#
# EXAMPLE
# Read CSV lines untill the first column is 'stop'.
#
# CSV::Reader.parse(File.open('bigdata', 'rb')) do |row|
# p row
# break if !row[0].is_null && row[0].data == 'stop'
# end
#
class StringReader < Reader
public
# SYNOPSIS
# reader = CSV::StringReader.new(string)
#
# ARGS
# string: a CSV String to be parsed.
#
# RETURNS
# reader: Created instance.
#
# DESCRIPTION
# Create instance. To get parse result, see CSV::Reader#each.
#
def initialize(string, col_sep = ?,)
@col_sep = col_sep
@dev = string
@idx = 0
if @dev[0, 3] == "\xef\xbb\xbf"
@idx += 3
end
end
private
def get_row(row)
parsed_cells, next_idx = CSV.parse_row(@dev, @idx, row, @col_sep)
if parsed_cells == 0 && next_idx == 0 && @idx != @dev.size
raise IllegalFormatError.new
end
@idx = next_idx
parsed_cells
end
end
# DESCRIPTION
# CSV::IOReader -- CSV formatted stream reader.
#
# EXAMPLE
# Read CSV lines untill the first column is 'stop'.
#
# CSV::Reader.parse(File.open('bigdata', 'rb')) do |row|
# p row
# break if !row[0].is_null && row[0].data == 'stop'
# end
#
class IOReader < Reader
public
# SYNOPSIS
# reader = CSV::IOReader.new(io)
#
# ARGS
# io: a CSV data to be parsed. Must be an IO. (io#read is called.)
#
# RETURNS
# reader: Created instance.
#
# DESCRIPTION
# Create instance. To get parse result, see CSV::Reader#each.
#
def initialize(io, col_sep = ?,)
@io = io
@col_sep = col_sep
@dev = CSV::IOBuf.new(@io)
@idx = 0
if @dev[0] == 0xef and @dev[1] == 0xbb and @dev[2] == 0xbf
@idx += 3
end
@close_on_terminate = false
end
# SYNOPSIS
# CSV::IOReader#close_on_terminate
#
# RETURNS
# true
#
# DESCRIPTION
# Tell this reader to close the IO when terminated (Triggered by invoking
# CSV::IOReader#close).
#
def close_on_terminate
@close_on_terminate = true
end
private
def get_row(row)
parsed_cells, next_idx = CSV.parse_row(@dev, @idx, row, @col_sep)
if parsed_cells == 0 && next_idx == 0 && !@dev.is_eos?
raise IllegalFormatError.new
end
dropped = @dev.drop(next_idx)
@idx = next_idx - dropped
parsed_cells
end
def terminate
if @close_on_terminate
@io.close
end
if @dev
@dev.close
end
end
end
# DESCRIPTION
# CSV::Writer -- CSV formatted string/stream writer.
#
# EXAMPLE
# Write rows to 'csvout' file.
#
# outfile = File.open('csvout', 'wb')
# CSV::Writer.generate(outfile) do |csv|
# csv << ['c1', nil, '', '"', "\r\n", 'c2']
# # or
# csv.add_row [
# CSV::Cell.new('c1', false),
# CSV::Cell.new('dummy', true),
# CSV::Cell.new('', false),
# CSV::Cell.new('"', false),
# CSV::Cell.new("\r\n", false)
# CSV::Cell.new('c2', false)
# ]
# ...
# ...
# end
#
# outfile.close
#
class Writer
public
# SYNOPSIS
# writer = CSV::Writer.create(str_or_readable)
#
# ARGS
# str_or_writable: device for generated CSV string. Must respond to
# '<<(string)'.
#
# RETURNS
# writer: Created instance.
#
# DESCRIPTION
# Create instance. To add CSV data to generate CSV string, see
# CSV::Writer#<< or CSV::Writer#add_row.
#
def Writer.create(str_or_readable, col_sep = ?,)
BasicWriter.new(str_or_readable, col_sep)
end
# SYNOPSIS
# CSV::Writer.generate(str_or_writable) do |writer|
# ...
# end
#
# ARGS
# str_or_writable: device for generated CSV string. Must respond to
# '<<(string)'.
# writer: Created writer instance. See CSV::Writer#<< and
# CSV::Writer#add_row to know how to generate CSV string.
#
# RETURNS
# nil
#
# DESCRIPTION
# Create writer instance. Caller block is called with the new instance.
# To add CSV data to generate CSV string, see CSV::Writer#<< or
# CSV::Writer#add_row.
#
def Writer.generate(str_or_writable, col_sep = ?,)
writer = Writer.create(str_or_writable, col_sep)
yield(writer)
writer.close
nil
end
# SYNOPSIS
# CSV::Writer#<<(row)
#
# ARGS
# row: an Array of a String.
#
# RETURNS
# self
#
# DESCRIPTION
# Dump CSV stream to the device. Argument is an array of a String like
# ['c1', 'c2', 'c3'].
#
def <<(ary)
row = ary.collect { |item|
if item.is_a?(Cell)
item
elsif (item.nil?)
Cell.new('', true)
else
Cell.new(item.to_s, false)
end
}
CSV.generate_row(row, row.size, @dev, @col_sep)
self
end
# SYNOPSIS
# CSV::Writer#<<(row)
#
# ARGS
# row: an Array of a CSV::Cell.
#
# RETURNS
# self
#
# DESCRIPTION
# Dump CSV stream to the device. Argument is an array of a CSV::Cell
# like [CSV::Cell.new('c1', false), CSV::Cell.new('dummy', true)].
# (Formar is 'c1' and latter is Null.)
#
def add_row(row)
CSV.generate_row(row, row.size, @dev, @col_sep)
self
end
# SYNOPSIS
# CSV::Writer#close
#
# RETURNS
# nil
#
# DESCRIPTION
# Close this writer.
#
def close
terminate
end
private
def initialize(dev)
raise RuntimeError.new('Do not instanciate this class directly.')
end
def terminate
# Define if needed.
end
end
# DESCRIPTION
# CSV::BasicWriter -- CSV formatted string/stream writer using <<.
#
class BasicWriter < Writer
public
# SYNOPSIS
# writer = CSV::BasicWriter.new(str_or_writable)
#
# ARGS
# str_or_writable: device for generated CSV string. Must respond to
# '<<(string)'.
#
# RETURNS
# writer: Created instance.
#
# DESCRIPTION
# Create instance. To add CSV data to generate CSV string, see
# CSV::Writer#<< or CSV::Writer#add_row.
#
def initialize(str_or_writable, col_sep = ?,)
@col_sep = col_sep
@dev = str_or_writable
@close_on_terminate = false
end
# SYNOPSIS
# CSV::BasicWriter#close_on_terminate
#
# RETURNS
# true
#
# DESCRIPTION
# Tell this writer to close the IO when terminated (Triggered by invoking
# CSV::BasicWriter#close).
#
def close_on_terminate
@close_on_terminate = true
end
private
def terminate
if @close_on_terminate
@dev.close
end
end
end
# SYNOPSIS
# cells = CSV.parse_line(src, col_sep = ?,)
#
# ARGS
# src: a CSV String.
# col_sep: Column separator. ?, by default. If you want to separate
# fields with semicolon, give ?; here.
#
# RETURNS
# cells: an Array of parsed cells in first line. Each cell is a String.
#
# DESCRIPTION
# Parse one line from given string. Bare in mind it parses ONE LINE. Rest
# of the string is ignored for example "a,b\r\nc,d" => ['a', 'b'] and the
# second line 'c,d' is ignored.
#
# If you don't know whether a target string to parse is exactly 1 line or
# not, use CSV.parse_row instead of this method.
#
def CSV.parse_line(src, col_sep = ?,)
idx = 0
res_type = :DT_COLSEP
cells = Row.new
begin
while (res_type.equal?(:DT_COLSEP))
cell = Cell.new
res_type, idx = parse_body(src, idx, cell, col_sep)
cells.push(cell.is_null ? nil : cell.data)
end
rescue IllegalFormatError
return Row.new
end
cells
end
# SYNOPSIS
# str = CSV.generate_line(cells, col_sep = ?,)
#
# ARGS
# cells: an Array of cell to be converted to CSV string. Each cell must
# respond to 'to_s'.
# col_sep: Column separator. ?, by default. If you want to separate
# fields with semicolon, give ?; here.
#
# RETURNS
# str: a String of generated CSV string.
#
# DESCRIPTION
# Create a line from cells. Each cell is stringified by to_s.
#
def CSV.generate_line(cells, col_sep = ?,)
if (cells.size == 0)
return ''
end
res_type = :DT_COLSEP
result_str = ''
idx = 0
while true
cell = if (cells[idx].nil?)
Cell.new('', true)
else
Cell.new(cells[idx].to_s, false)
end
generate_body(cell, result_str, col_sep)
idx += 1
if (idx == cells.size)
break
end
generate_separator(:DT_COLSEP, result_str, col_sep)
end
result_str
end
# SYNOPSIS
# parsed_cells, idx = CSV.parse_row(src, idx, out_dev, col_sep = ?,)
#
# ARGS
# src: a CSV data to be parsed. Must respond '[](idx)'.
# src[](idx) must return a char. (Not a string such as 'a', but 97).
# src[](idx_out_of_bounds) must return nil. A String satisfies this
# requirement.
# idx: index of parsing location of 'src'. 0 origin.
# out_dev: buffer for parsed cells. Must respond '<<(CSV::Cell)'.
# col_sep: Column separator. ?, by default. If you want to separate
# fields with semicolon, give ?; here.
#
# RETURNS
# parsed_cells: num of parsed cells.
# idx: index of next parsing location of 'src'.
#
# DESCRIPTION
# Parse a line from string. To parse lines in CSV string, see EXAMPLE
# below.
#
# EXAMPLE
# src = "a,b\r\nc,d\r\ne,f"
# idx = 0
# begin
# parsed = []
# parsed_cells, idx = CSV.parse_row(src, idx, parsed)
# puts "Parsed #{ parsed_cells } cells."
# p parsed
# end while parsed_cells > 0
#
def CSV.parse_row(src, idx, out_dev, col_sep = ?,)
idx_backup = idx
parsed_cells = 0
res_type = :DT_COLSEP
begin
while (!res_type.equal?(:DT_ROWSEP))
cell = Cell.new
res_type, idx = parse_body(src, idx, cell, col_sep)
if res_type.equal?(:DT_EOS)
if idx == idx_backup #((parsed_cells == 0) && (cell.is_null))
return 0, 0
end
res_type = :DT_ROWSEP
end
parsed_cells += 1
out_dev << cell
end
rescue IllegalFormatError
return 0, 0
end
return parsed_cells, idx
end
# SYNOPSIS
# parsed_cells = CSV.generate_row(src, cells, out_dev, col_sep = ?,)
#
# ARGS
# src: an Array of CSV::Cell to be converted to CSV string. Must respond to
# 'size' and '[](idx)'. src[idx] must return CSV::Cell.
# cells: num of cells in a line.
# out_dev: buffer for generated CSV string. Must respond to '<<(string)'.
# col_sep: Column separator. ?, by default. If you want to separate
# fields with semicolon, give ?; here.
#
# RETURNS
# parsed_cells: num of converted cells.
#
# DESCRIPTION
# Convert a line from cells data to string. To generate multi-row CSV
# string, See EXAMPLE below.
#
# EXAMPLE
# def d(str)
# CSV::Cell.new(str, false)
# end
#
# row1 = [d('a'), d('b')]
# row2 = [d('c'), d('d')]
# row3 = [d('e'), d('f')]
# src = [row1, row2, row3]
# buf = ''
# src.each do |row|
# parsed_cells = CSV.generate_row(row, 2, buf)
# puts "Created #{ parsed_cells } cells."
# end
# p buf
#
def CSV.generate_row(src, cells, out_dev, col_sep = ?,)
src_size = src.size
if (src_size == 0)
if cells == 0
generate_separator(:DT_ROWSEP, out_dev, col_sep)
end
return 0
end
res_type = :DT_COLSEP
parsed_cells = 0
generate_body(src[parsed_cells], out_dev, col_sep)
parsed_cells += 1
while ((parsed_cells < cells) && (parsed_cells != src_size))
generate_separator(:DT_COLSEP, out_dev, col_sep)
generate_body(src[parsed_cells], out_dev, col_sep)
parsed_cells += 1
end
if (parsed_cells == cells)
generate_separator(:DT_ROWSEP, out_dev, col_sep)
else
generate_separator(:DT_COLSEP, out_dev, col_sep)
end
parsed_cells
end
private
class IllegalFormatError < RuntimeError; end
# Private class methods.
class << self
private
def parse_body(src, idx, cell, col_sep)
cell.is_null = false
state = :ST_START
quoted = false
cr = false
c = nil
while (c = src[idx])
idx += 1
result_state = :DT_UNKNOWN
if (c == col_sep)
if state.equal?(:ST_DATA)
if cr
raise IllegalFormatError.new
end
if (!quoted)
state = :ST_END
result_state = :DT_COLSEP
else
cell.data << c.chr
end
elsif state.equal?(:ST_QUOTE)
if cr
raise IllegalFormatError.new
end
state = :ST_END
result_state = :DT_COLSEP
else # :ST_START
cell.is_null = true
state = :ST_END
result_state = :DT_COLSEP
end
elsif (c == ?") # " for vim syntax hilighting.
if state.equal?(:ST_DATA)
if cr
raise IllegalFormatError.new
end
if quoted
quoted = false
state = :ST_QUOTE
else
raise IllegalFormatError.new
end
elsif state.equal?(:ST_QUOTE)
cell.data << c.chr
quoted = true
state = :ST_DATA
else # :ST_START
quoted = true
state = :ST_DATA
end
elsif (c == ?\r)
if cr
raise IllegalFormatError.new
end
if quoted
cell.data << c.chr
state = :ST_DATA
else
cr = true
end
elsif (c == ?\n)
if state.equal?(:ST_DATA)
if cr
state = :ST_END
result_state = :DT_ROWSEP
cr = false
else
if quoted
cell.data << c.chr
state = :ST_DATA
else
state = :ST_END
result_state = :DT_ROWSEP
end
end
elsif state.equal?(:ST_QUOTE)
state = :ST_END
result_state = :DT_ROWSEP
if cr
cr = false
end
else # :ST_START
cell.is_null = true
state = :ST_END
result_state = :DT_ROWSEP
end
else
if state.equal?(:ST_DATA) || state.equal?(:ST_START)
if cr
raise IllegalFormatError.new
end
cell.data << c.chr
state = :ST_DATA
else # :ST_QUOTE
raise IllegalFormatError.new
end
end
if state.equal?(:ST_END)
return result_state, idx;
end
end
if state.equal?(:ST_START)
cell.is_null = true
elsif state.equal?(:ST_QUOTE)
true # dummy for coverate; only a data
elsif quoted
raise IllegalFormatError.new
elsif cr
raise IllegalFormatError.new
end
return :DT_EOS, idx
end
def generate_body(cells, out_dev, col_sep)
row_data = cells.data.dup
if (!cells.is_null)
if (row_data.gsub!('"', '""') ||
row_data.include?(col_sep) ||
(/[\r\n]/ =~ row_data) || (cells.data.empty?))
out_dev << '"' << row_data << '"'
else
out_dev << row_data
end
end
end
def generate_separator(type, out_dev, col_sep)
case type
when :DT_COLSEP
out_dev << col_sep.chr
when :DT_ROWSEP
out_dev << "\r\n"
end
end
end
# DESCRIPTION
# CSV::StreamBuf -- a class for a bufferd 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
#
class StreamBuf # pure virtual. (do not instanciate it directly)
public
# SYNOPSIS
# char/str = CSV::StreamBuf#get(idx, n = nil)
# char/str = CSV::StreamBuf#[idx, n = nil]
#
# ARGS
# 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: if n == nil. A char at idx.
# str: if n != nil. A partial string, from idx to (idx + size). At
# EOF, the string size could not equal to arg n.
#
# DESCRIPTION
# Get a char or a partial string from the stream.
#
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
alias get []
# SYNOPSIS
# size_dropped = CSV::StreamBuf#drop(n)
#
# ARGS
# n: drop size
#
# RETURNS
# size_dropped: droped size. At EOF, dropped size might not equals to arg n.
# 0 if n <= 0.
#
# DESCRIPTION
# Drop a string from the stream. Once you drop the head of the stream,
# access to the dropped part via [] or get returns nil.
#
def drop(n)
if is_eos?
return 0
end
size_dropped = 0
while (n > 0)
if (!@is_eos || (@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
# SYNOPSIS
# is_eos = CSV::StreamBuf#is_eos?
#
# RETURNS
# is_eos: true if end of the stream or false.
#
# DESCRIPTION
# Check EOF or not.
#
def is_eos?
return idx_is_eos?(0)
end
# SYNOPSIS
# N/A
#
# DESCRIPTION
# Do not instanciate this class directly. Define your own class which
# derives this class and define 'read' instance method.
#
def initialize
@buf_list = []
@cur_buf = @buf_tail_idx = -1
@offset = 0
@is_eos = false
add_buf
@cur_buf = @buf_tail_idx
end
protected
def terminate
while (rel_buf); end
end
# 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.
def read(size) # raise EOFError
raise NotImplementedError.new('Method read must be defined in a derived class.')
end
private
def buf_size(idx)
@buf_list[idx].size
end
def add_buf
if @is_eos
return false
end
begin
str_read = read(BufSize)
rescue EOFError
str_read = nil
rescue
terminate
raise
end
if str_read.nil?
@is_eos = true
@buf_list.push('')
@buf_tail_idx += 1
false
else
@buf_list.push(str_read)
@buf_tail_idx += 1
true
end
end
def rel_buf
if (@cur_buf < 0)
return false
end
@buf_list[@cur_buf] = nil
if (@cur_buf == @buf_tail_idx)
@cur_buf = -1
return false
else
@cur_buf += 1
return true
end
end
def idx_is_eos?(idx)
(@is_eos && ((@cur_buf < 0) || (@cur_buf == @buf_tail_idx)))
end
BufSize = 1024 * 8
end
# DESCRIPTION
# CSV::IOBuf -- a class for a bufferd IO.
#
# EXAMPLE
# # File 'bigdata' could be a giga-byte size one!
# buf = CSV::IOBuf.new(File.open('bigdata', 'rb'))
# CSV::Reader.new(buf).each do |row|
# p row
# break if row[0].data == 'admin'
# end
#
class IOBuf < StreamBuf
public
def initialize(s)
@s = s
super()
end
def close
terminate
end
private
def read(size)
@s.read(size)
end
def terminate
super()
end
end
end