From 05f19de969c9782ffa53e8f021c3a4e29388e1ed Mon Sep 17 00:00:00 2001
From: "Arthur G.P. Schuster" <arthur@apuhapu.at>
Date: Thu, 7 Aug 2025 21:10:17 +0200
Subject: [PATCH] initial commit

---
 .gitignore          |   1 +
 Cargo.lock          | 495 ++++++++++++++++++++++++++++++++++++++++++++
 Cargo.toml          |  12 ++
 cel_js_example.wasm |   1 +
 index.html          |  76 +++++++
 src/lib.rs          |  42 ++++
 6 files changed, 627 insertions(+)
 create mode 100644 .gitignore
 create mode 100644 Cargo.lock
 create mode 100644 Cargo.toml
 create mode 120000 cel_js_example.wasm
 create mode 100644 index.html
 create mode 100644 src/lib.rs

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..b83d222
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+/target/
diff --git a/Cargo.lock b/Cargo.lock
new file mode 100644
index 0000000..2e38df4
--- /dev/null
+++ b/Cargo.lock
@@ -0,0 +1,495 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 4
+
+[[package]]
+name = "aho-corasick"
+version = "1.1.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8e60d3430d3a69478ad0993f19238d2df97c507009a52b3c10addcd7f6bcb916"
+dependencies = [
+ "memchr",
+]
+
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+name = "antlr4rust"
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+dependencies = [
+ "better_any",
+ "bit-set",
+ "byteorder",
+ "lazy_static",
+ "murmur3",
+ "once_cell",
+ "parking_lot",
+ "typed-arena",
+ "uuid",
+]
+
+[[package]]
+name = "autocfg"
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+
+[[package]]
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+checksum = "1795ebc740ea791ffbe6685e0688ab1effec16c2864e0476db40bfdf0c02cb3d"
+
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+[[package]]
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+[[package]]
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+checksum = "6cb40e65631e7ca197aab1540bf50f9484289f2a7e3d93c1db4319766157a8f2"
+dependencies = [
+ "antlr4rust",
+ "chrono",
+ "lazy_static",
+ "nom",
+ "paste",
+ "regex",
+ "serde",
+ "thiserror",
+]
+
+[[package]]
+name = "cel_js_example"
+version = "0.0.0"
+dependencies = [
+ "cel",
+]
+
+[[package]]
+name = "cfg-if"
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+source = "registry+https://github.com/rust-lang/crates.io-index"
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+ "serde",
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+
+[[package]]
+name = "js-sys"
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+checksum = "1cfaf33c695fc6e08064efbc1f72ec937429614f25eef83af942d0e227c3a28f"
+dependencies = [
+ "once_cell",
+ "wasm-bindgen",
+]
+
+[[package]]
+name = "lazy_static"
+version = "1.5.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "bbd2bcb4c963f2ddae06a2efc7e9f3591312473c50c6685e1f298068316e66fe"
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+[[package]]
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+checksum = "96936507f153605bddfcda068dd804796c84324ed2510809e5b2a624c81da765"
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+
+[[package]]
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+ "byteorder",
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+[[package]]
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+dependencies = [
+ "memchr",
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+
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+ "autocfg",
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+
+[[package]]
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+]
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+[[package]]
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+ "cfg-if",
+ "libc",
+ "redox_syscall",
+ "smallvec",
+ "windows-targets",
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+dependencies = [
+ "js-sys",
+ "wasm-bindgen",
+]
+
+[[package]]
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+dependencies = [
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+ "once_cell",
+ "rustversion",
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+]
+
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+ "syn",
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+]
+
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+ "wasm-bindgen-backend",
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+]
+
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+dependencies = [
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+]
+
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+checksum = "9b724f72796e036ab90c1021d4780d4d3d648aca59e491e6b98e725b84e99973"
+dependencies = [
+ "windows_aarch64_gnullvm",
+ "windows_aarch64_msvc",
+ "windows_i686_gnu",
+ "windows_i686_gnullvm",
+ "windows_i686_msvc",
+ "windows_x86_64_gnu",
+ "windows_x86_64_gnullvm",
+ "windows_x86_64_msvc",
+]
+
+[[package]]
+name = "windows_aarch64_gnullvm"
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+
+[[package]]
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+
+[[package]]
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+[[package]]
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+[[package]]
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diff --git a/Cargo.toml b/Cargo.toml
new file mode 100644
index 0000000..84867ce
--- /dev/null
+++ b/Cargo.toml
@@ -0,0 +1,12 @@
+[package]
+description = "Example of running cel-rust interpreter in browser"
+edition = "2024"
+name = "cel_js_example"
+publish = false
+version = "0.0.0"
+
+[dependencies]
+cel = "0.11.0"
+
+[lib]
+crate-type = ["cdylib", "rlib"]
diff --git a/cel_js_example.wasm b/cel_js_example.wasm
new file mode 120000
index 0000000..260f674
--- /dev/null
+++ b/cel_js_example.wasm
@@ -0,0 +1 @@
+target/wasm32-unknown-unknown/release/cel_js_example.wasm
\ No newline at end of file
diff --git a/index.html b/index.html
new file mode 100644
index 0000000..b082291
--- /dev/null
+++ b/index.html
@@ -0,0 +1,76 @@
+<!doctype html>
+<html lang="en-US">
+
+<head>
+    <meta charset="utf-8" />
+    <title>Starlark evaluator</title>
+    <style type="text/css">
+        body {
+            font-family: sans-serif;
+        }
+
+        textarea {
+            width: calc(100% - 20px);
+            height: 20em;
+            box-sizing: border-box;
+            margin: 5px;
+            border-radius: 3px;
+            padding: 5px;
+            border-color: lightgray;
+        }
+    </style>
+</head>
+
+<body>
+    <script>
+        function run() {
+            WebAssembly.instantiateStreaming(fetch("cel_js_example.wasm"), {}).then(({ instance }) => {
+                const readString = (offset) => {
+                    const memory = instance.exports.memory.buffer;
+                    const length = new Uint32Array(memory, offset, 1)[0];
+                    const characters = new Uint8Array(memory, offset + 4, length);
+                    return new TextDecoder().decode(characters);
+                };
+
+                const readU8 = (offset) => {
+                    return new Uint8Array(instance.exports.memory.buffer, offset, 1)[0];
+                };
+
+                const writeString = (s) => {
+                    const encoded = new TextEncoder().encode(s.trim());
+                    const offset = instance.exports.allocation(4 + encoded.byteLength);
+                    // TODO(april): this probably isn't guaranteed to be 4-byte aligned? Might need to fix.
+                    const memory = instance.exports.memory.buffer;
+                    const uint32s = new Uint32Array(memory, offset, 1);
+                    uint32s[0] = encoded.byteLength;
+                    const uint8s = new Uint8Array(memory, offset + 4, encoded.byteLength);
+                    uint8s.set(encoded);
+                    return offset;
+                };
+
+                const content = document.getElementById("input").value;
+                const offset = instance.exports.evaluate(writeString(content));
+                const ok = readU8(offset) != 0;
+                const result = readString(offset + 4);
+                const output = document.getElementById("output");
+                output.value = (ok ? "" : "ERROR\n") + result;
+            });
+        }
+
+        window.addEventListener("load", function () {
+            document.getElementById("input").addEventListener("input", run, false);
+            run()
+        })
+    </script>
+    <h1>Starlark evaluator</h1>
+    <p>
+        Using <a href="https://github.com/cel-rust/cel-rust">cel-rust</a> compiled to web assembly.
+        Change the input to see it update.
+    </p>
+    <textarea id="input">
+"Hello " + "world!"</textarea>
+    <textarea id="output" readonly="readonly" style="background-color: lightgray;">
+    </textarea>
+</body>
+
+</html>
diff --git a/src/lib.rs b/src/lib.rs
new file mode 100644
index 0000000..d4b0d0e
--- /dev/null
+++ b/src/lib.rs
@@ -0,0 +1,42 @@
+use std::mem;
+use std::slice;
+use std::str;
+
+use cel::{Context, ExecutionError, Program, Value};
+
+#[unsafe(no_mangle)]
+pub extern "C" fn allocation(n: usize) -> *mut u8 {
+    mem::ManuallyDrop::new(Vec::with_capacity(n)).as_mut_ptr()
+}
+
+#[unsafe(no_mangle)]
+pub unsafe extern "C" fn evaluate(s: *const u8) -> *mut u8 {
+    unsafe {
+        let length = u32::from_le_bytes(*(s as *const [u8; 4])) as usize;
+        let input = slice::from_raw_parts(s.offset(4), length);
+        let output = evaluate_buffers(input);
+        mem::ManuallyDrop::new(output).as_mut_ptr()
+    }
+}
+
+fn evaluate_buffers(input: &[u8]) -> Vec<u8> {
+    let contents = str::from_utf8(input).unwrap();
+    let result = evaluate_cel(contents);
+    let success = result.is_ok();
+    let message = result.unwrap_or_else(|e| e.to_string());
+    let len = message.len();
+    let mut buffer = Vec::with_capacity(len + 8);
+    buffer.push(if success { 1 } else { 0 });
+    buffer.extend(vec![0; 3]);
+    buffer.extend_from_slice(&(len as u32).to_le_bytes());
+    buffer.extend_from_slice(message.as_bytes());
+    buffer
+}
+
+fn evaluate_cel(content: &str) -> Result<String, ExecutionError> {
+    let program = Program::compile(content).unwrap();
+    let mut context = Context::default();
+    // context.add_function("add", |a: i64, b: i64| a + b);
+    let value = program.execute(&context)?;
+    Ok(format!("{:?}", value))
+}