OpenEuphoria

Pastey "dumping" a map demo

• Posted by ghaberek (admin) Feb 17, 2023

--
-- "dumping" a map demo 
-- https://openeuphoria.org/forum/137580.wc 
-- 
-- Here is an example of how to save and load objects on disk. The file format 
-- is incredibly simple: we just pretty_print() the key/value for each map on 
-- each line, and then read them back with get(). This creates a human-readable 
-- (and editable!) data storage format. Note that this method only supports 
-- nesting maps at a single level, such as users properties nested by user id. 
-- 
 
include std/get.e 
include std/map.e 
include std/pretty.e 
include std/filesys.e 
include std/error.e 
 
--** 
-- Extend the default pretty_print() format to print huamn 
-- readable strings and skip any newline/indent formatting. 
-- 
sequence PRETTY_INLINE = PRETTY_DEFAULT 
PRETTY_INLINE[DISPLAY_ASCII] = 2 -- print strings 
PRETTY_INLINE[LINE_BREAKS]   = 0 -- no line breaks 
 
--** 
-- Store a sequence of maps by writing each as a sequence 
-- of key/value pairs, separated by newline. 
-- 
-- e.g. {{"key","value"},{"key","value},...} 
-- 
procedure save_maps( sequence file, sequence maps ) 
 
	integer fn = open( file, "w" ) 
 
	if fn = -1 then 
		error:crash( "Could not write file: %s", {file} ) 
	end if 
 
	for i = 1 to length( maps ) do 
 
		-- get the key/value pairs 
		sequence data = map:pairs( maps[i] ) 
 
		-- write object to disk 
		pretty_print( fn, data, PRETTY_INLINE ) 
 
		-- add a newline separator 
		puts( fn, "\n" ) 
 
	end for 
 
	close( fn ) 
 
end procedure 
 
--** 
-- Load a sequence of maps by reading each key/value set 
-- from disk. 
-- 
function load_maps( object file ) 
 
	integer fn = open( file, "r" ) 
 
	if fn = -1 then 
		error:crash( "Could not read file: %s", {file} ) 
	end if 
 
	sequence maps = {} 
 
	while 1 do 
 
		-- load an object from disk 
 
		sequence result = stdget:get( fn ) 
 
		-- result[1] could be: 
		-- GET_SUCCESS - result[2] will be an object (yay!) 
		-- GET_NOTHING - result[2] will be zero (so quit!) 
		-- GET_EOF - result[2] will be zero (also quit!) 
		-- GET_FAIL - crash with error message (boo!) 
 
		if result[1] = GET_FAIL then 
			error:crash( "get() failed!" ) 
		end if 
 
		if result[1] = GET_NOTHING or result[1] = GET_EOF then 
			exit 
		end if 
 
		-- convert the key/value pairs to a map 
		object data = map:new_from_kvpairs( result[2] ) 
 
		-- add the map to the list 
		maps = append( maps, data ) 
 
	end while 
 
	close( fn ) 
 
	return maps 
end function 
 
--** 
-- Create several maps and store them all to a single file. 
-- 
procedure test_save( sequence file ) 
 
	-- create several user objects 
 
	map user1 = map:new() 
	map:put( user1, "id", "abc123" ) 
	map:put( user1, "name", "Alice" ) 
 
	map user2 = map:new() 
	map:put( user2, "id", "def456" ) 
	map:put( user2, "name", "Bob" ) 
 
	map user3 = map:new() 
	map:put( user3, "id", "ghi789" ) 
	map:put( user3, "name", "Carol" ) 
 
	-- store each user in a "master" map using its id 
 
	map users = map:new() 
	map:put( users, map:get(user1,"id"), user1 ) 
	map:put( users, map:get(user2,"id"), user2 ) 
	map:put( users, map:get(user3,"id"), user3 ) 
 
	-- demonstrate use of nested_put() to set values 
 
	map:nested_put( users, {"abc123","email"}, "alice@example.com" ) 
	map:nested_put( users, {"def456","email"}, "bob@example.com" ) 
	map:nested_put( users, {"ghi789","email"}, "carol@example.com" ) 
 
	-- get the maps stored in the master map and write them to disk 
 
	save_maps( file, map:values(users) ) 
 
end procedure 
 
--** 
-- Read all the maps from disk and print their key/value pairs. 
-- 
procedure test_load( sequence file ) 
 
	-- get the maps stored on disk 
 
	sequence maps = load_maps( file ) 
 
	-- store each user in the "master" map using its id 
 
	map users = map:new() 
 
	for i = 1 to length( maps ) do 
		map:put( users, map:get(maps[i],"id"), maps[i] ) 
	end for 
 
	-- demonstrate use of nested_get() to get properties 
 
	sequence alice_id = map:nested_get( users, {"abc123","id"} ) 
	printf( 1, "Alice's id: \"%s\"\n", {alice_id} ) 
 
	sequence bob_email = map:nested_get( users, {"def456","email"} ) 
	printf( 1, "Bob's email: \"%s\"\n", {bob_email} ) 
 
	sequence carol_name = map:nested_get( users, {"ghi789","name"} ) 
	printf( 1, "Carol's name: \"%s\"\n", {carol_name} ) 
 
end procedure 
 
procedure main() 
 
	sequence file = "users.map" 
 
	if not file_exists( file ) then 
		test_save( file ) 
	end if 
 
	test_load( file ) 
 
end procedure 
 
main()