Sha256: e33cc0d4d51fe14ecda4175eefcc125e0476e68eb4131cde6bb2b5ca4e5d83fc
Contents?: true
Size: 1.85 KB
Versions: 25
Compression:
Stored size: 1.85 KB
Contents
class FileReverseReader
attr_reader :io, :step
def initialize(io, step = 1024 * 1024 * 1)
@io = io
@step = step
end
def each_line(&block)
#read from the end of file
io.seek(0, IO::SEEK_END)
buf = ""
loop do
if reach_start_of_file?
read_rest(buf, &block)
break
end
read_to_buf_by_step(buf)
#if buffer dose not include multi lines, seek more.
if buf[$/].nil?
next
else
split_only_whole_lines(buf, &block)
buf = ""
end
end
end
def tail(limit = 10)
enum_for(:each_line).first(limit).reverse
end
def binary_file?
sample = io.read(1024) || ""
!sample.force_encoding('utf-8').valid_encoding?
ensure
io.rewind
end
private
def read_rest(buf, &block)
last_pos = io.pos
io.seek(0, IO::SEEK_SET)
buf.insert(0, io.read(last_pos))
split_each_line(buf, &block)
end
def read_to_buf_by_step(buf)
#move up file pointer by one step
io.seek(-1 * step, IO::SEEK_CUR) #point[A]
#read strings by one step from the pointer, and insert to buffer
#(on io.read, file pointer returns down to the point before [A])
buf.insert(0, io.read(step))
#forword file pointer to [A]
io.seek(-1 * step, IO::SEEK_CUR)
end
def split_only_whole_lines(buf, &block)
#if budder includes multi lines,
gap = buf.index($/)
#cut off first line (*first* line because it's seeking from end of file, and first line may be broken-line)
buf.gsub!(/\A.*?\n/, "")
split_each_line(buf, &block)
#move file pointer to the gap(= the end of *first* line)
io.seek(gap, IO::SEEK_CUR)
end
def split_each_line(buf, &block)
return unless buf.force_encoding('utf-8').valid_encoding?
buf.split($/).reverse.each do |line|
block.call(line)
end
end
def reach_start_of_file?
step >= io.pos
end
end
Version data entries
25 entries across 25 versions & 1 rubygems