Implement basic slurp module

Also fixes problem with missing diff when running `copy`.

Makefile

@@ -1,6 +1,6 @@
 .PHONY: all
 
-all: ./library/copy.lua ./library/file.lua ./library/lineinfile.lua ./library/opkg.lua ./library/stat.lua ./library/ubus.lua ./library/uci.lua
+all: ./library/copy.lua ./library/file.lua ./library/lineinfile.lua ./library/opkg.lua ./library/slurp.lua ./library/stat.lua ./library/ubus.lua ./library/uci.lua
 
 WHITELIST=io,os,posix.,ubus
 FATPACKARGS=--whitelist $(WHITELIST) --truncate

src/base64.lua

@@ -0,0 +1,40 @@
+-- Lua 5.1+ base64 v3.0 (c) 2009 by Alex Kloss <alexthkloss@web.de>,
+-- 2018 Piotr Śliwka <contact@psliwka.info>
+-- licensed under the terms of the LGPL2
+
+local base64 = {}
+
+-- character table string
+local b='ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/'
+
+-- encoding
+function base64.encode(data)
+    return ((data:gsub('.', function(x)
+        local r,b='',x:byte()
+        for i=8,1,-1 do r=r..(b%2^i-b%2^(i-1)>0 and '1' or '0') end
+        return r;
+    end)..'0000'):gsub('%d%d%d?%d?%d?%d?', function(x)
+        if (#x < 6) then return '' end
+        local c=0
+        for i=1,6 do c=c+(x:sub(i,i)=='1' and 2^(6-i) or 0) end
+        return b:sub(c+1,c+1)
+    end)..({ '', '==', '=' })[#data%3+1])
+end
+
+-- decoding
+function base64.decode(data)
+    data = string.gsub(data, '[^'..b..'=]', '')
+    return (data:gsub('.', function(x)
+        if (x == '=') then return '' end
+        local r,f='',(b:find(x)-1)
+        for i=6,1,-1 do r=r..(f%2^i-f%2^(i-1)>0 and '1' or '0') end
+        return r;
+    end):gsub('%d%d%d?%d?%d?%d?%d?%d?', function(x)
+        if (#x ~= 8) then return '' end
+        local c=0
+        for i=1,8 do c=c+(x:sub(i,i)=='1' and 2^(8-i) or 0) end
+        return string.char(c)
+    end))
+end
+
+return base64

src/slurp.lua

@@ -0,0 +1,26 @@
+#!/usr/bin/lua
+-- WANT_JSON
+
+local Ansible = require("ansible")
+local base64  = require("base64")
+
+function main(arg)
+	local module = Ansible.new({
+		src = { required=true, aliases={"path"} },
+	})
+
+	module:parse(arg[1])
+
+	local source = module:get_params()["src"]
+
+	-- FIXME: add IO error handling
+	local file = io.open(source, "rb")
+	local content = file:read "*a"
+	file:close()
+
+	local encoded = base64.encode(content)
+
+	module:exit_json({content=encoded, source=source, encoding='base64'})
+end
+
+main(arg)