lua-resty-bzlib

luajit ffi bindings for libbzip2 - bzip2 compress library

Lua-Resty-bzlib

中文说明

LuaJIT FFI Bindings for bzlib(libbz2.so) - A Lua Bzip2 Library for OpenResty

Contents

Status

This library is considered experimental.

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Usage

This library implements two sorts of interfaces.

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Simple Interface

    local bzlib = require 'resty.bzlib'
    --[[
        local bz = bzlib:new(
            dest_buff_size  -- Optional, default is 8192.
            -- The libbz2.so will return BZ_OUTBUFF_FULL(-8)
            -- if this buffer size is not enough to storage
            -- the output data.
        )
    ]]--
    local bz = bzlib:new()
    local bin1 = bz:compress('xiaooloong')
    local bin2 = bz:compress('foobar')
    
    local text1 = bz:decompress(bin1)
    local text2 = bz:decompress(bin2)
    
    print(text1, '\n', text2)
    --[[
    [root@localhost ~]# resty a.lua 
    xiaooloong
    foobar
    ]]--

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Streaming Interface

Compress

Initialize:

    local bzlib = require 'resty.bzlib.compress'
    --[[
        local bz = bzlib:new(
            compresslevel,  -- Optional, default is 9.
            workfactor      -- Optional, default is 30.
            -- In fact, these two are parameters 'blockSize100k'
            -- and 'workFactor' of the function 'BZ2_bzCompressInit'
        )
    ]]--
    local bz = bzlib:new()
    
    local name = 'agw.log'
    local fd1 = io.open(name, 'r')
    local fd2 = io.open(name .. '.bz2', 'wb')

Append data:

    while true do
        local ln = fd1:read('*line')
        if not ln then
            break
        end
        --[[
            local part, err = bz:append(text)
            -- Append part of data to this method.
            -- In case of failed to compress, it will return
            -- nil and a string contains error message.
        ]]--
        local part, err = bz:append(ln .. '\n')
        if not part then
            print(err)
            break
        end
        --[[
            The returned string may be '' because libbz2.so may buffer some data.
            In this case, there is no need to write the file.
        ]]--
        if #part > 0 then
            fd2:write(part)
        end
    end
    fd1:close()

Clean up:

    --[[
        Use bz:finish() to tell libbz2.so that compress comes to an end.
        This method will return all remaining data the libbz2.so has buffered.
    ]]--
    local part, err = bz:finish()
    if not part then
        print(err)
    end
    fd2:write(part)
    fd2:close()

Note:

Whatever compress:append() is returned, you must call compress:finish() after bzlib:new()

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Decompress

Initialize:

    local bzlib = require 'resty.bzlib.decompress'
    --[[
        local bz = bzlib:new(
            reducemem   -- Optional. Default is 0.
            -- In fact, this parameters is 'small'
            -- of the function 'BZ2_bzDecompressInit'
        )
    ]]--
    local bz = bzlib:new()
    
    local name = 'agw.log.bz2'
    local fd1 = io.open(name, 'rb')
    local fd2 = io.open(name .. '.txt', 'wb')

Append data:

    while true do
        local bin = fd1:read(4096)
        if not bin then break end
        --[[
            local text, finish, err = bz:append(bin)
            -- Append part of data to this method.
            -- In case of success, 'finish' tells you wheather
            -- the compressed stream comes to an end. That means
            -- you can finish decompress when 'finish' is true.
            -- In case of failed, it will return
            -- nil and a string contains error message.
        ]]--
        local text, finish, err = bz:append(bin)
        if not text then
            print('append no return')
            break
        end
        --[[
            The returned string may be '' because libbz2.so may buffer some data.
            In this case, there is no need to write the file.
        ]]--
        if #text > 0 then
            fd2:write(text)
        end
        if finish then
            print('stream end')
            break
        end
    end
    fd1:close()
    fd2:close()

The bzip2 stream contains header and end-of-stream itself. The decompress:append() will automaticlly do a cleanning up if decompress is failed or over.

Manually stop decompress:

If you want to stop decompress when neither error occurs nor decompress comes to an end, you should call Decompress:finish() manually to deallocate the memory.

    local bzlib = require 'resty.bzlib'
    local bzdec = require 'resty.bzlib.decompress'
    
    local bz = bzlib:new()
    local text = 'xiaooloong'
    local bin = bz:compress(text)
        
    while true do
        local bzd = bzdec:new()
    
        local part, finish, err = bzd:append(bin:sub(1, 10))
        --[[
            Part of bzip2 stream has been append to the method and no error occurs.
            If you want to abandon decompress now you should manually call method finish() 
            as below.
        ]]--
    
        local ok = bzd:finish()
        --[[
            Without this line, memory space will be deallocated by luajit gc.
        ]]--
        
        print(tostring(ok))
    end

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Prerequisites

This library requires LuaJIT and libbz2.so to be installed.

For CentOS users, you can install libbz2.so by the following command:

    yum install -y bzip2-libs

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See Also

  • bzip2 man page: http://www.bzip.org/1.0.5/bzip2-manual-1.0.5.html

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[1]: http://openresty.org/cn/ [2]: http://www.bzip.org/ [3]: http://luajit.org/ext_ffi.html

Authors

xiaooloong

License

mit

Dependencies

luajit

Versions