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module Gitlab
module Ci
# This was inspired from: http://stackoverflow.com/a/10219411/1520132
class TraceReader
BUFFER_SIZE = 4096
attr_accessor :path, :buffer_size
def initialize(new_path, buffer_size: BUFFER_SIZE)
self.path = new_path
self.buffer_size = Integer(buffer_size)
end
def read(last_lines: nil)
if last_lines
read_last_lines(last_lines)
else
File.read(path)
end
end
def read_last_lines(max_lines)
File.open(path) do |file|
chunks = []
pos = lines = 0
max = file.size
# We want an extra line to make sure fist line has full contents
while lines <= max_lines && pos < max
pos += buffer_size
buf = if pos <= max
file.seek(-pos, IO::SEEK_END)
file.read(buffer_size)
else # Reached the head, read only left
file.seek(0)
file.read(buffer_size - (pos - max))
end
lines += buf.count("\n")
chunks.unshift(buf)
end
chunks.join.lines.last(max_lines).join
.force_encoding(Encoding.default_external)
end
end
end
end
end
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