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require 'thread'
require 'sync'
# Gotten from:
# http://path.berkeley.edu/~vjoel/ruby/solaris-bug.rb
# Extensions to the File class for exception-safe file locking in a
# environment with multiple user threads.
# This is here because closing a file on solaris unlocks any locks that
# other threads might have. So we have to make sure that only the last
# reader thread closes the file.
#
# The hash maps inode number to a count of reader threads
$reader_count = Hash.new(0)
class File
# Get an exclusive (i.e., write) lock on the file, and yield to the block.
# If the lock is not available, wait for it without blocking other ruby
# threads.
def lock_exclusive
if Thread.list.size == 1
flock(LOCK_EX)
else
# ugly hack because waiting for a lock in a Ruby thread blocks the
# process
period = 0.001
until flock(LOCK_EX|LOCK_NB)
sleep period
period *= 2 if period < 1
end
end
yield self
ensure
flush
flock(LOCK_UN)
end
# Get a shared (i.e., read) lock on the file, and yield to the block.
# If the lock is not available, wait for it without blocking other ruby
# threads.
def lock_shared
if Thread.list.size == 1
flock(LOCK_SH)
else
# ugly hack because waiting for a lock in a Ruby thread blocks the
# process
period = 0.001
until flock(LOCK_SH|LOCK_NB)
sleep period
period *= 2 if period < 1
end
end
yield self
ensure
Thread.exclusive {flock(LOCK_UN) if $reader_count[self.stat.ino] == 1}
## for solaris, no need to unlock here--closing does it
## but this has no effect on the bug
end
end
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