CI/svg-flatten: add wasm builds

1 files changed, 82 insertions, 0 deletions

diff --git a/svg-flatten/svg_flatten_wasi/__init__.py b/svg-flatten/svg_flatten_wasi/__init__.py
new file mode 100644
index 0000000..fe21b5b
--- /dev/null
+++ b/svg-flatten/svg_flatten_wasi/__init__.py
@@ -0,0 +1,82 @@
+import os
+import sys
+import tempfile
+import wasmtime
+import platform
+import click
+import pathlib
+import hashlib
+import appdirs
+import lzma
+from importlib import resources as importlib_resources
+try:
+    importlib_resources.files # py3.9+ stdlib
+except AttributeError:
+    import importlib_resources # py3.8- shim
+
+
+# ==============================
+# Note on wasmtime path handling
+# ==============================
+#
+# Hack: Right now, wasmtime's preopen_dir / --map functionality is completely borked. AFAICT only the first mapping is
+# even considered, and preopening both / and . simply does not work: Either all paths open'ed by the executable must be
+# absolute, or all paths must be relative. I spent some hours trying to track down where exactly this borkage originates
+# from, but I found the code confusing and did not succeed.
+# 
+# FOR NOW we work around this issue the dumb way: We simply have click parse enough of the command line to transform any
+# paths given on the command line to absolute paths. The actual path resolution is done by click because of
+# resolve_path=True.
+# 
+
+
+def _run_wasm_app(wasm_filename, argv, cachedir="svg-flatten-wasi"):
+
+    module_binary = importlib_resources.read_binary(__package__, wasm_filename)
+
+    module_path_digest = hashlib.sha256(__file__.encode()).hexdigest()
+    module_digest = hashlib.sha256(module_binary).hexdigest()
+    cache_path = pathlib.Path(os.getenv("SVG_FLATTEN_WASI_CACHE_DIR", appdirs.user_cache_dir(cachedir)))
+    cache_path.mkdir(parents=True, exist_ok=True)
+    cache_filename = (cache_path / f'{wasm_filename}-{module_path_digest[:8]}-{module_digest[:16]}')
+    
+    wasi_cfg = wasmtime.WasiConfig()
+    wasi_cfg.argv = argv
+    wasi_cfg.preopen_dir('/', '/')
+    wasi_cfg.inherit_stdin()
+    wasi_cfg.inherit_stdout()
+    wasi_cfg.inherit_stderr()
+    engine = wasmtime.Engine()
+
+    import time
+    try:
+        with cache_filename.open("rb") as cache_file:
+            module = wasmtime.Module.deserialize(engine, lzma.decompress(cache_file.read()))
+    except:
+        print("Preparing to run {}. This might take a while...".format(argv[0]), file=sys.stderr)
+        module = wasmtime.Module(engine, module_binary)
+        with cache_filename.open("wb") as cache_file:
+            cache_file.write(lzma.compress(module.serialize(), preset=0))
+
+    linker = wasmtime.Linker(engine)
+    linker.define_wasi()
+    store = wasmtime.Store(engine)
+    store.set_wasi(wasi_cfg)
+    app = linker.instantiate(store, module)
+    linker.define_instance(store, "app", app)
+
+    try:
+        app.exports(store)["_start"](store)
+        return 0
+    except wasmtime.ExitTrap as trap:
+        return trap.code
+
+
+@click.command(context_settings={'ignore_unknown_options': True})
+@click.argument('other_args', nargs=-1, type=click.UNPROCESSED)
+@click.argument('input_file',  type=click.Path(resolve_path=True, dir_okay=False))
+@click.argument('output_file', type=click.Path(resolve_path=True, dir_okay=False, writable=True))
+def run_usvg(input_file, output_file, other_args):
+
+    cmdline = ['svg-flatten', *other_args, input_file, output_file]
+    sys.exit(_run_wasm_app("svg-flatten.wasm", cmdline))