61 lines
1.9 KiB
Lua
61 lines
1.9 KiB
Lua
-- primitive for reading files from a file system (or, later, network)
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-- returns an object or nil on error
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-- read lines from the object using .read() with args similar to file:read()
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-- read() will indicate end of file by returning nil.
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function start_reading(fs, filename)
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local infile = io.open(filename)
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if infile == nil then return nil end
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return {
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read = coroutine.wrap(function(format)
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while true do
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if format == nil then format = '*l' end
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format = coroutine.yield(infile:read(format))
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end
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end),
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}
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end
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-- primitive for writing files to a file system (or, later, network)
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-- returns an object or nil on error
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-- write to the object using .write()
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-- indicate you're done writing by calling .close()
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-- file will not be externally visible until .close()
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function start_writing(fs, filename)
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if filename == nil then
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error('start_writing requires two arguments: a file-system (nil for real disk) and a filename')
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end
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local initial_filename = temporary_filename_in_same_volume(filename)
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local outfile = io.open(initial_filename, 'w')
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if outfile == nil then return nil end
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return {
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write = coroutine.wrap(function(x)
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while true do
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x = coroutine.yield(outfile:write(x))
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end
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end),
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close = function()
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outfile:close()
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os.rename(initial_filename, filename)
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end,
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}
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end
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function temporary_filename_in_same_volume(filename)
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-- opening in same directory will hopefully keep it on the same volume,
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-- so that a future rename works
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local i = 1
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while true do
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temporary_filename = 'teliva_tmp_'..filename..'_'..i
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if io.open(temporary_filename) == nil then
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-- file doesn't exist yet; create a placeholder and return it
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local handle = io.open(temporary_filename, 'w')
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if handle == nil then
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error("this is unexpected; I can't create temporary files..")
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end
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handle:close()
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return temporary_filename
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end
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i = i+1
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end
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end
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