diff --git a/docs/README-emscripten.md b/docs/README-emscripten.md index 65452c170..1a13eb1c3 100644 --- a/docs/README-emscripten.md +++ b/docs/README-emscripten.md @@ -303,6 +303,48 @@ or the app will fail to start on iOS browsers, but this might be a bug that goes away in the future. +## Data files + +Your game probably has data files. Here's how to access them. + +Filesystem access works like a Unix filesystem; you have a single directory +tree, possibly interpolated from several mounted locations, no drive letters, +'/' for a path separator. You can access them with standard file APIs like +open() or fopen() or SDL_RWops. You can read or write from the filesystem. + +By default, you probably have a "MEMFS" filesystem (all files are stored in +memory, but access to them is immediate and doesn't need to block). There are +other options, like "IDBFS" (files are stored in a local database, so they +don't need to be in RAM all the time and they can persist between runs of the +program, but access is not synchronous). You can mix and match these file +systems, mounting a MEMFS filesystem at one place and idbfs elsewhere, etc, +but that's beyond the scope of this document. Please refer to Emscripten's +[page on the topic](https://emscripten.org/docs/porting/files/file_systems_overview.html) +for more info. + +The _easiest_ (but not the best) way to get at your data files is to embed +them in the app itself. Emscripten's linker has support for automating this. + +```bash +emcc -o index.html loopwave.c --embed-file=../test/sample.wav@/sounds/sample.wav +``` + +This will pack ../test/sample.wav in your app, and make it available at +"/sounds/sample.wav" at runtime. Emscripten makes sure this data is available +before your main() function runs, and since it's in MEMFS, you can just +read it like you do on other platforms. `--embed-file` can also accept a +directory to pack an entire tree, and you can specify the argument multiple +times to pack unrelated things into the final installation. + +Note that this is absolutely the best approach if you have a few small +files to include and shouldn't worry about the issue further. However, if you +have hundreds of megabytes and/or thousands of files, this is not so great, +since the user will download it all every time they load your page, and it +all has to live in memory at runtime. + +[Emscripten's documentation on the matter](https://emscripten.org/docs/porting/files/packaging_files.html) +gives other options and details, and is worth a read. + ## Debugging