AstrolabeQH/DongleStub.lua

   1 --[[------------------------------------------------------------------
   2 --  $Id: DongleStub.lua 466 2007-06-23 19:17:46Z jnwhiteh $
   3 --
   4 --  DongleStub is a simple versioning stub that allows different
   5 --  major versions of a library to exist alongside each other, while
   6 --  providing a mechanism for library upgrades through minor version
   7 --  differences.
   8 --
   9 --  The implementation of DongleStub, including the source code,
  10 --  documentation and related data, is placed into the public domain.
  11 --
  12 --  The original author is James N. Whitehead II
  13 --
  14 --  THIS SOFTWARE IS PROVIDED AS-IS WITHOUT WARRANTY OF ANY KIND, NOT
  15 --  EVEN THE IMPLIED WARRANTY OF MERCHANTABILITY. THE AUTHOR OF THIS
  16 --  SOFTWARE, ASSUMES _NO_ RESPONSIBILITY FOR ANY CONSEQUENCE RESULTING
  17 --  FROM THE USE, MODIFICATION, OR REDISTRIBUTION OF THIS SOFTWARE.
  18 ------------------------------------------------------------------]]--
  19
  20 local major = "DongleStub"
  21 local minor = tonumber(string.match("$Revision: 466 $", "(%d+)") or 1)
  22
  23 local g = getfenv(0)
  24
  25 if not g.DongleStub or g.DongleStub:IsNewerVersion(major, minor) then
  26         local lib = setmetatable({}, {
  27                 __call = function(t,k)
  28                         if type(t.versions) == "table" and t.versions[k] then
  29                                 return t.versions[k].instance
  30                         else
  31                                 error("Cannot find a library with name '"..tostring(k).."'", 2)
  32                         end
  33                 end
  34         })
  35
  36         function lib:HasVersion(major)
  37                 if type(major) ~= "string" then
  38                         error("bad argument #2 to 'HasVersion' (string expected, got " .. type(major) .. ")", 2)
  39                 end
  40
  41                 local instance = self.versions and self.versions[major]
  42                 return instance ~= nil
  43         end
  44
  45         function lib:IsNewerVersion(major, minor)
  46                 local versionData = self.versions and self.versions[major]
  47                 if not versionData then return true end
  48                 local oldmajor,oldminor = versionData.instance:GetVersion()
  49                 return minor > oldminor
  50         end
  51
  52         local function NilCopyTable(src, dest)
  53                 for k,v in pairs(dest) do dest[k] = nil end
  54                 for k,v in pairs(src) do dest[k] = v end
  55         end
  56
  57         function lib:Register(newInstance, activate, deactivate)
  58                 if type(newInstance) ~= "table" then
  59                         error("bad argument #2 to 'Register' (table expected, got " .. type(newInstance) .. ")", 2)
  60                 end
  61
  62                 if type(newInstance.GetVersion) ~= "function" then
  63                         error("Attempt to register a library with DongleStub that does not have a 'GetVersion' method.", 2)
  64                 end
  65
  66                 local major,minor = newInstance:GetVersion()
  67                 if type(major) ~= "string" then
  68                         error("Attempt to register a library with DongleStub that does not have a proper major version.", 2)
  69                 end
  70
  71                 if type(minor) ~= "number" then
  72                         error("Attempt to register a library with DongleStub that does not have a proper minor version.", 2)
  73                 end
  74
  75                 -- Generate a log of all library registrations
  76                 if not self.log then self.log = {} end
  77                 table.insert(self.log, string.format("Register: %s, %s", major, minor))
  78
  79                 if not self:IsNewerVersion(major, minor) then return false end
  80                 if not self.versions then self.versions = {} end
  81
  82                 local versionData = self.versions[major]
  83                 if not versionData then
  84                         -- New major version
  85                         versionData = {
  86                                 ["instance"] = newInstance,
  87                                 ["deactivate"] = deactivate,
  88                         }
  89
  90                         self.versions[major] = versionData
  91                         if type(activate) == "function" then
  92                                 table.insert(self.log, string.format("Activate: %s, %s", major, minor))
  93                                 activate(newInstance)
  94                         end
  95                         return newInstance
  96                 end
  97
  98                 local oldDeactivate = versionData.deactivate
  99                 local oldInstance = versionData.instance
 100
 101                 versionData.deactivate = deactivate
 102
 103                 local skipCopy
 104                 if type(activate) == "function" then
 105                         table.insert(self.log, string.format("Activate: %s, %s", major, minor))
 106                         skipCopy = activate(newInstance, oldInstance)
 107                 end
 108
 109                 -- Deactivate the old libary if necessary
 110                 if type(oldDeactivate) == "function" then
 111                         local major, minor = oldInstance:GetVersion()
 112                         table.insert(self.log, string.format("Deactivate: %s, %s", major, minor))
 113                         oldDeactivate(oldInstance, newInstance)
 114                 end
 115
 116                 -- Re-use the old table, and discard the new one
 117                 if not skipCopy then
 118                         NilCopyTable(newInstance, oldInstance)
 119                 end
 120                 return oldInstance
 121         end
 122
 123         function lib:GetVersion() return major,minor end
 124
 125         local function Activate(new, old)
 126                 -- This code ensures that we'll move the versions table even
 127                 -- if the major version names are different, in the case of
 128                 -- DongleStub
 129                 if not old then old = g.DongleStub end
 130
 131                 if old then
 132                         new.versions = old.versions
 133                         new.log = old.log
 134                 end
 135                 g.DongleStub = new
 136         end
 137
 138         -- Actually trigger libary activation here
 139         local stub = g.DongleStub or lib
 140         lib = stub:Register(lib, Activate)
 141 end