This directory houses the Web Assembly (WASM) parts of the sqlite3 build.
It requires emscripten and that the build environment be set up for emscripten. A mini-HOWTO for setting that up follows...
First, install the Emscripten SDK, as documented here and summarized below for Linux environments:
# Clone the emscripten repository:
$ sudo apt install git
$ git clone https://github.com/emscripten-core/emsdk.git
$ cd emsdk
# Download and install the latest SDK tools:
$ ./emsdk install latest
# Make the "latest" SDK "active" for the current user:
$ ./emsdk activate latest
Those parts only need to be run once, but the SDK can be updated using:
$ git pull
$ ./emsdk install latest
$ ./emsdk activate latest
The following needs to be run for each shell instance which needs the
emcc compiler:
# Activate PATH and other environment variables in the current terminal:
$ source ./emsdk_env.sh
$ which emcc
/path/to/emsdk/upstream/emscripten/emcc
Optionally, add that to your login shell's resource file (~/.bashrc
or equivalent).
That env script needs to be sourced for building this application
from the top of the sqlite3 build tree:
$ make fiddle
Or:
$ cd ext/wasm
$ make
That will generate the a number of files required for a handful of
test and demo applications which can be accessed via
index.html. WASM content cannot, due to XMLHttpRequest security
limitations, be loaded if the containing HTML file is opened directly
in the browser (i.e. if it is opened using a file:// URL), so it
needs to be served via an HTTP server. For example, using
althttpd:
$ cd ext/wasm
$ althttpd --enable-sab --max-age 1 --page index.html
That will open the system's browser and run the index page, from which all of the test and demo applications can be accessed.
Note that when serving this app via althttpd, it must be a version
from 2022-09-26 or newer so that it recognizes the --enable-sab
flag, which causes althttpd to emit two HTTP response headers which
are required to enable JavaScript's SharedArrayBuffer and Atomics
APIs. Those APIs are required in order to enable the OPFS-related
features in the apps which use them.
Testing on a remote machine that is accessed via SSH
NB: The following are developer notes, last validated on 2022-08-18
- Remote: Install git, emsdk, and althttpd
- Use a version of althttpd from September 26, 2022 or newer.
- Remote: Install the SQLite source tree. CD to ext/wasm
- Remote: "
make" to build WASM - Remote:
althttpd --enable-sab --port 8080 --popup - Local:
ssh -L 8180:localhost:8080 remote - Local: Point your web-browser at http://localhost:8180/index.html
In order to enable SharedArrayBuffers, the web-browser requires that the two extra Cross-Origin lines be present in HTTP reply headers and that the request must come from "localhost". Since the web-server is on a different machine from the web-broser, the localhost requirement means that the connection must be tunneled using SSH.