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lua-ffi-zlib
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lua-ffi-zlib
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# lua-ffi-zlib A [Lua](http://www.lua.org) module using LuaJIT's [FFI](http://luajit.org/ext_ffi.html) feature to access zlib. Intended primarily for use within [OpenResty](http://openresty.org) to allow manipulation of gzip encoded HTTP responses. # Methods Basic methods allowing for simple compression or decompression of gzip data ## inflateGzip `Syntax: ok, err = inflateGzip(input, output, chunk?, windowBits?)` * `input` should be a function that accepts a chunksize as its only argument and return that many bytes of the gzip stream * `output` will receive a string of decompressed data as its only argument, do with it as you will! * `chunk` is the size of the input and output buffers, optional and defaults to 16KB * `windowBits` is passed to `inflateInit2()`, should be left as default for most cases. See [zlib manual](http://zlib.net/manual.html) for details On error returns `false` and the error message, otherwise `true` and the last status message ## deflateGzip `Syntax: ok, err = deflateGzip(input, output, chunk?, options?)` * `input` should be a function that accepts a chunksize as its only argument and return that many bytes of uncompressed data. * `output` will receive a string of compressed data as its only argument, do with it as you will! * `chunk` is the size of the input and output buffers, optional and defaults to 16KB * `options` is a table of options to pass to `deflateInit2()` Valid options are level, memLevel, strategy and windowBits, see [zlib manual](http://zlib.net/manual.html) for details On error returns `false` and the error message, otherwise `true` and the last status message # Example Reads a file and output the decompressed version. Roughly equivalent to running `gzip -dc file.gz > out_file | tee` ```lua local table_insert = table.insert local table_concat = table.concat local zlib = require('lib.ffi-zlib') local f = io.open(arg[1], "rb") local out_f = io.open(arg[2], "w") local input = function(bufsize) -- Read the next chunk local d = f:read(bufsize) if d == nil then return nil end return d end local output_table = {} local output = function(data) table_insert(output_table, data) local ok, err = out_f:write(data) if not ok then -- abort decompression when error occurs return nil, err end end -- Decompress the data local ok, err = zlib.inflateGzip(input, output) if not ok then print(err) return end local decompressed = table_concat(output_table,'') print(decompressed) ``` # Advanced Usage Several other methods are available for advanced usage. Some of these map directly to functions in the zlib library itself, see the [manual](http://zlib.net/manual.html) for full details. Others are lower level utility functions. ## createStream `Synax: stream, inbuf, outbuf = createStream(bufsize)` Returns a z_stream struct, input buffer and output buffer of length `bufsize` ## initInflate `Syntax: ok = initInflate(stream, windowBits?)` Calls zlib's inflateInit2 with given stream, defaults to automatic header detection. ## initDeflate `Syntax: ok = initDeflate(stream, options?)` Calls zlib's deflateInit2 with the given stream. `options` is an optional table that can set level, memLevel, strategy and windowBits ## deflate `Syntax: ok, err = deflate(input, output, bufsize, stream, inbuf, outbuf)` * `input` is a function that takes a chunk size argument and returns at most that many input bytes * `output` is a function that takes a string argument of output data * `bufsize` is the length of the output buffer * `inbuf` cdata input buffer * `outpuf` ccdata output buffer This function will loop until all input data is consumed (`input` returns nil) or an error occurs. It will then clean up the stream and return an error code ## inflate `Syntax: ok, err = inflate(input, output, bufsize, stream, inbuf, outbuf)` * `input` is a function that takes a chunk size argument and returns at most that many input bytes * `output` is a function that takes a string argument of output data * `bufsize` is the length of the output buffer * `inbuf` cdata input buffer * `outpuf` ccdata output buffer This function will loop until all input data is consumed (`input` returns nil) or an error occurs. It will then clean up the stream and return an error code ## adler `Syntax: chksum = adler(str, chksum?)` Computes an adler32 checksum for a string, updates an existing checksum if provided ## crc `Syntax: chksum = crc(str, chksum?)` Computes an crc32 checksum for a string, updates an existing checksum if provided ## zlib_err `Syntax: err = zlib_err(code)` Returns the string representation of a zlib error code
