# frozen_string_literal: true
# rubocop:disable Style/AsciiComments
# Copyright (C) 2004 Mauricio Julio Fernández Pradier
# See LICENSE.txt for additional licensing information.
# rubocop:enable Style/AsciiComments
##
# Class for reading entries out of a tar file
class Gem::Package::TarReader::Entry
##
# Creates a new tar entry for +header+ that will be read from +io+
# If a block is given, the entry is yielded and then closed.
def self.open(header, io, &block)
entry = new header, io
return entry unless block_given?
begin
yield entry
ensure
entry.close
end
end
##
# Header for this tar entry
attr_reader :header
##
# Creates a new tar entry for +header+ that will be read from +io+
def initialize(header, io)
@closed = false
@header = header
@io = io
@orig_pos = @io.pos
@end_pos = @orig_pos + @header.size
@read = 0
end
def check_closed # :nodoc:
raise IOError, "closed #{self.class}" if closed?
end
##
# Number of bytes read out of the tar entry
def bytes_read
@read
end
##
# Closes the tar entry
def close
return if closed?
# Seek to the end of the entry if it wasn't fully read
seek(0, IO::SEEK_END)
# discard trailing zeros
skip = (512 - (@header.size % 512)) % 512
@io.read(skip)
@closed = true
nil
end
##
# Is the tar entry closed?
def closed?
@closed
end
##
# Are we at the end of the tar entry?
def eof?
check_closed
@read >= @header.size
end
##
# Full name of the tar entry
def full_name
if @header.prefix != ""
File.join @header.prefix, @header.name
else
@header.name
end
rescue ArgumentError => e
raise unless e.message == "string contains null byte"
raise Gem::Package::TarInvalidError,
"tar is corrupt, name contains null byte"
end
##
# Read one byte from the tar entry
def getc
return nil if eof?
ret = @io.getc
@read += 1 if ret
ret
end
##
# Is this tar entry a directory?
def directory?
@header.typeflag == "5"
end
##
# Is this tar entry a file?
def file?
@header.typeflag == "0"
end
##
# Is this tar entry a symlink?
def symlink?
@header.typeflag == "2"
end
##
# The position in the tar entry
def pos
check_closed
bytes_read
end
##
# Seek to the position in the tar entry
def pos=(new_pos)
seek(new_pos, IO::SEEK_SET)
end
def size
@header.size
end
alias_method :length, :size
##
# Reads +maxlen+ bytes from the tar file entry, or the rest of the entry if nil
def read(maxlen = nil)
if eof?
return maxlen.to_i.zero? ? "" : nil
end
max_read = [maxlen, @header.size - @read].compact.min
ret = @io.read max_read
if ret.nil?
return maxlen ? nil : "" # IO.read returns nil on EOF with len argument
end
@read += ret.size
ret
end
def readpartial(maxlen, outbuf = "".b)
if eof? && maxlen > 0
raise EOFError, "end of file reached"
end
max_read = [maxlen, @header.size - @read].min
@io.readpartial(max_read, outbuf)
@read += outbuf.size
outbuf
end
##
# Seeks to +offset+ bytes into the tar file entry
# +whence+ can be IO::SEEK_SET, IO::SEEK_CUR, or IO::SEEK_END
def seek(offset, whence = IO::SEEK_SET)
check_closed
new_pos =
case whence
when IO::SEEK_SET then @orig_pos + offset
when IO::SEEK_CUR then @io.pos + offset
when IO::SEEK_END then @end_pos + offset
else
raise ArgumentError, "invalid whence"
end
if new_pos < @orig_pos
new_pos = @orig_pos
elsif new_pos > @end_pos
new_pos = @end_pos
end
pending = new_pos - @io.pos
return 0 if pending == 0
if @io.respond_to?(:seek)
begin
# avoid reading if the @io supports seeking
@io.seek new_pos, IO::SEEK_SET
pending = 0
rescue Errno::EINVAL
end
end
# if seeking isn't supported or failed
# negative seek requires that we rewind and read
if pending < 0
@io.rewind
pending = new_pos
end
while pending > 0 do
size_read = @io.read([pending, 4096].min)&.size
raise(EOFError, "end of file reached") if size_read.nil?
pending -= size_read
end
@read = @io.pos - @orig_pos
0
end
##
# Rewinds to the beginning of the tar file entry
def rewind
check_closed
seek(0, IO::SEEK_SET)
end
end
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