gistfile1.lua

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-- JsonStorageEngine.lua
--
-- Store lua tables as json documents
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local JsonStorageEngine = {}

JsonStorageEngine.DOCUMENTS_DIR = MOAIEnvironment.documentDirectory or 'docs'


JsonStorageEngine.md5   = 'md5'
JsonStorageEngine.sha1  = 'sha1'
JsonStorageEngine.sha256 = 'sha256'
JsonStorageEngine.sha512 = 'sha512'


local hashFuncNames = {
    ['md5']     = 'openMD5',
    ['sha1']    = 'openSHA1',
    ['sha256']  = 'openSHA256',
    ['sha512']  = 'openSHA512',
}

local function getHash(str, algorythm)
    local hashWriter = MOAIHashWriter.new()
    local func = hashFuncNames[algorythm]
    assert(func, "Unknow hash algorythm: " .. algorythm)
    hashWriter[func](hashWriter)
    hashWriter:write(str)
    return hashWriter:getHashHex()
end


local digestLengths = {
    ['md5']     = #getHash('hello', JsonStorageEngine.md5),
    ['sha1']    = #getHash('hello', JsonStorageEngine.sha1),
    ['sha256']  = #getHash('hello', JsonStorageEngine.sha256),
    ['sha512']  = #getHash('hello', JsonStorageEngine.sha512),
}


---
-- Retrieve table from storage
-- @param name      storage name. Table is parsed form json file: <documents_directory>/[name].json
-- @param secret    (optional) string. If set, then hash protection will be applied using secret
-- @param algorythm hashing algorythm. Default is 'sha256'
-- @return table, valid     returns loaded table (or nil if error occurs)
--                          valid is a boolean flag indicating if hash check succeeded
function JsonStorageEngine.load(name, secret, algorythm)
    algorythm = algorythm or JsonStorageEngine.sha256
    local path = string.pathJoin(JsonStorageEngine.DOCUMENTS_DIR, name)

    if secret then
        return JsonStorageEngine.parseFileSecure(path, secret, algorythm)
    else
        return JsonStorageEngine.parseFile(path)
    end
end


---
-- Save table to json file
-- @param t         table to save
-- @param name      name of output file
-- @param secret    (optional) string for hash protection of contents
-- @return success  bool
function JsonStorageEngine.save(t, name, secret, algorythm)
    algorythm = algorythm or JsonStorageEngine.sha256
    local path = string.pathJoin(JsonStorageEngine.DOCUMENTS_DIR, name)

    if secret then
        return JsonStorageEngine.dumpFileSecure(t, path, secret, algorythm)
    else
        return JsonStorageEngine.dumpFile(t, path)
    end
end


---
-- some internalls

function JsonStorageEngine.parseFile(path)
    local dataBuffer = MOAIDataBuffer.new()
    local output

    if dataBuffer:load(path) then
        output = MOAIJsonParser.decode(dataBuffer:getString())
    end
    return output
end


function JsonStorageEngine.parseFileSecure(path, secret, algorythm)
    local dataBuffer = MOAIDataBuffer.new()
    local valid, output

    if dataBuffer:load(path) then
        local all = dataBuffer:getString()
        local hash = string.sub(all, 1, digestLengths[algorythm])
        local payload = string.sub(all, 1 + digestLengths[algorythm])

        valid = (hash == getHash(payload .. secret, algorythm))
        output = MOAIDataBuffer.inflate(payload)
        if output then
            output = MOAIJsonParser.decode(output)
        end
    end

    return output, valid
end


function JsonStorageEngine.dumpFile(t, path)
    local success = false
    local json = MOAIJsonParser.encode(t)
    if json then
        local dataBuffer = MOAIDataBuffer.new()
        dataBuffer:setString(json)
        success = dataBuffer:save(path)
    end

    return success
end


function JsonStorageEngine.dumpFileSecure(t, path, secret, algorythm)
    local success = false
    local json = MOAIJsonParser.encode(t)

    if json then
        local payload = MOAIDataBuffer.deflate(json)
        if payload then
            local dataBuffer = MOAIDataBuffer.new()
            local hash = getHash(payload .. secret, algorythm)
            dataBuffer:setString(hash .. payload)
            success = dataBuffer:save(path)
        end
    end

    return success
end


return JsonStorageEngine