From f729f51e475ff98d0caf529f0723ef810b1c88ef Mon Sep 17 00:00:00 2001 From: Simon Tatham Date: Sun, 23 May 2021 08:45:55 +0100 Subject: WASM: move save file encoding from JS into C. The previous fix worked OK, but it was conceptually wrong. Puzzles save files are better regarded as binary, not text: the length fields are measured in bytes, so translating the file into a different multibyte character encoding would invalidate them. So it was wrong to fetch a C byte string containing the exactly right binary data, then translate it into a Javascript string as if decoding from UTF-8, then retranslate to a representation of a bytewise encoding via encodeURIComponent, and then label the result as application/octet-stream. This probably wouldn't have caused any problems in practice, because I don't remember any situation in which my save files use characters outside printable ASCII (plus newline). But it's not actually forbidden, so a save file might choose to do that some day, so that UTF-8 decode/reencode hidden in the JS was a latent bug. Now the URI-encoding is done on the C side, while we still know exactly what the binary data ought to look like and can be sure we're translating it byte for byte into the output encoding for the data: URI. By the time the JS receives a string pointer from get_save_file, it's already URI-encoded, which _guarantees_ that it's in ASCII and won't be messed about with by Emscripten's UTF8ToString. --- emccpre.js | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) (limited to 'emccpre.js') diff --git a/emccpre.js b/emccpre.js index 0a498de..caa3250 100644 --- a/emccpre.js +++ b/emccpre.js @@ -379,8 +379,7 @@ function initPuzzle() { "Click to download the ")); var a = document.createElement("a"); a.download = "puzzle.sav"; - a.href = "data:application/octet-stream," + - encodeURIComponent(savefile_text); + a.href = "data:application/octet-stream," + savefile_text; a.appendChild(document.createTextNode("saved-game file")); dlg_form.appendChild(a); dlg_form.appendChild(document.createTextNode(".")); -- cgit v1.1