Adding upstream version 3.45.1.upstream/3.45.1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 106 insertions, 0 deletions

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+This directory houses the [Web Assembly (WASM)](https://en.wikipedia.org/wiki/WebAssembly)
+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](https://emscripten.org/docs/getting_started/downloads.html) 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 2023-07-19*
+
+  *  Remote: Install git, emsdk, and althttpd
+     *  Use a [version of althttpd][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 [SharedArrayBuffer][], 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" (_or_ over an SSL
+connection).  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.
+
+
+[emscripten]: https://emscripten.org
+[althttpd]: https://sqlite.org/althttpd
+[SharedArrayBuffer]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer