在Ruby中以块的形式读取文件

Question

我需要以MB块的形式读取一个文件,有没有更简洁的方法在Ruby中执行此操作:

FILENAME="d:\\tmp\\file.bin"
MEGABYTE = 1024*1024
size = File.size(FILENAME)
open(FILENAME, "rb") do |io| 
  read = 0
  while read < size
    left = (size - read)
    cur = left < MEGABYTE ? left : MEGABYTE
    data = io.read(cur)
    read += data.size
    puts "READ #{cur} bytes" #yield data
  end
end

Answer 1

改编自Ruby Cookbook第204页:

FILENAME = "d:\\tmp\\file.bin"
MEGABYTE = 1024 * 1024

class File
  def each_chunk(chunk_size = MEGABYTE)
    yield read(chunk_size) until eof?
  end
end

open(FILENAME, "rb") do |f|
  f.each_chunk { |chunk| puts chunk }
end

免责声明:我是一个红宝石新手,并没有测试过这个.

Answer 2

或者,如果你不想monkeypatch File:

until my_file.eof?
  do_something_with( my_file.read( bytes ) )
end

例如,将上载的临时文件流式传输到新文件中:

# tempfile is a File instance
File.open( new_file, 'wb' ) do |f|
  # Read in small 65k chunks to limit memory usage
  f.write(tempfile.read(2**16)) until tempfile.eof?
end

Answer 3

您可以使用IO#each(sep, limit), 并设置sep为nil或空字符串，例如：

chunk_size = 1024
File.open('/path/to/file.txt').each(nil, chunk_size) do |chunk|
  puts chunk
end