@thi.ng/wasm-api
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Generic, modular, extensible API bridge, glue code and bindings code generator for hybrid JS & WebAssembly projects
This project is part of the @thi.ng/umbrella monorepo.
Generic, modular, extensible API bridge, glue code and bindings code generator for hybrid JS & WebAssembly projects.
This package provides a the following:
WasmBridge
class as interop basis and much reduced boilerplate for hybrid JS/WebAssembly
applications.The
WasmBridge is
extensible via custom defined API modules. Such API extensions will consist of a
collection of JS/TS functions & variables, their related counterparts (import
definitions) for the WASM target and (optionally) some shared data types
(bindings for which can be generated by this package
too).
On the JS side, custom API modules can be easily integrated via the IWasmAPI
interface. The
following example provides a brief overview:
import { IWasmAPI, WasmBridge } from "@thi.ng/wasm-api";
export class CustomAPI implements IWasmAPI {
parent!: WasmBridge;
async init(parent: WasmBridge) {
this.parent = parent;
this.parent.logger.debug("initializing custom API");
// any other tasks you might need to do...
return true;
}
/**
* Returns object of functions to import as externals into
* the WASM module. These imports are merged into a larger
* imports object alongside the bridge's core API...
*/
getImports(): WebAssembly.Imports {
return {
/**
* Writes 2 random float32 numbers to given address
*/
randomVec2: (addr: number) => {
this.parent.f32.set(
[Math.random(), Math.random()],
addr >> 2
);
}
};
}
}
Now we can supply this custom API when creating the main WASM bridge:
export const bridge = new WasmBridge({ custom: new CustomAPI() });
In Zig (or any other language of your choice) we can then utilize this custom API like so (Please also see /test/index.ts` & the example further below in this readme):
// Import JS core API
const js = @import("wasmapi");
/// JS external to fill vec2 w/ random values
/// Note: Each API module uses a separate import object to avoid naming clashes
/// Here we declare an external binding belonging to the "custom" import group
extern "custom" fn randomVec2(addr: usize) void;
export fn test_randomVec2() void {
var foo = [2]f32{ 0, 0 };
// print original
js.printF32Array(foo[0..]);
// populate foo with random numbers
randomVec2(@ptrToInt(&foo));
// print result
js.printF32Array(foo[0..]);
}
The package provides an extensible codegeneration framework to simplify the bilateral design & exchange of data structures shared between the WASM & JS host env. Currently, code generators for TypeScript & Zig are supplied (more are planned). A CLI wrapper is worked on too.
The package includes a small CLI wrapper to invoke the codegenerator(s) from JSON type definitions and to write the generated source code(s) to different files:
$ npx @thi.ng/wasm-api
█ █ █ │
██ █ │
█ █ █ █ █ █ █ █ │ @thi.ng/wasm-api 0.6.0
█ █ █ █ █ █ █ █ █ │ Multi-language data bindings code generator
█ │
█ █ │
usage: wasm-api [OPTS] JSON-INPUT-FILE(S) ...
wasm-api --help
Flags:
-d, --debug enable debug output
--dry-run enable dry run (don't overwrite files)
Main:
-c FILE, --config FILE JSON config file with codegen options
-l ID[,..], --lang ID[,..] [multiple] target language: "ts", "zig" (default: ["ts","zig"])
-o FILE, --out FILE [multiple] output file path
By default, the CLI generates sources for both TypeScript and Zig (in this order!). Order is important, since the output file paths must be given in the same order as the target languages. It's recommended to be more explicit. An example invocation looks like:
wasm-api --config codegen-opts.json \
--lang ts -o src/generated.ts \
--lang zig -o src.zig/generated.zig \
typedefs.json
The structure of the config file is as follows (all optional):
{
global: { ... },
ts: { ... },
zig: { ... },
}
More details about possible
global,
ts and
zig config
options & values.
Currently, the code generator supports structs and enums. See API docs for further details:
Below is an example file with JSON type definitions and the resulting source codes:
⬇︎ CLICK TO EXPAND EACH CODE BLOCK ⬇︎
[
{
"name": "Foo",
"type": "struct",
"doc": "Example struct",
"auto": true,
"fields": [
{ "name": "id", "type": "u8", "doc": "Unique ID" },
{ "name": "bars", "type": "Bar", "tag": "array", "len": 3 },
{ "name": "color", "type": "f32", "tag": "vec", "len": 4 }
]
},
{
"name": "Bar",
"type": "struct",
"fields": [
{ "name": "kind", "type": "Kind" },
{ "name": "flags", "type": "u32" }
]
},
{
"name": "Kind",
"type": "enum",
"tag": "u16",
"values": [
"unknown",
{ "name": "good", "value": 100 },
{ "name": "best", "value": 1000 }
]
}
]
/** Generated by @thi.ng/wasm-api at 2022-08-15T22:32:21.189Z - DO NOT EDIT! */
import type { WasmTypeBase, WasmTypeConstructor } from "@thi.ng/wasm-api";
/** Example struct */
export interface Foo extends WasmTypeBase {
color: Float32Array;
bars: Bar[];
/** Unique ID */
id: number;
}
export const $Foo: WasmTypeConstructor<Foo> = (mem) => ({
get align() { return 16; },
get size() { return 48; },
instance: (base) => ({
get __base() { return base; },
get __bytes() { return mem.u8.subarray(base, base + 48); },
get color(): Float32Array {
const addr = base >>> 2;
return mem.f32.subarray(addr, addr + 4);
},
get bars(): Bar[] {
const addr = (base + 16);
const inst = $Bar(mem);
const slice: Bar[] = [];
for(let i = 0; i < 3; i++) slice.push(inst.instance(addr + i * 24));
return slice;
},
get id(): number {
return mem.u8[(base + 40)];
},
set id(x: number) {
mem.u8[(base + 40)] = x;
},
})
});
export interface Bar extends WasmTypeBase {
kind: Kind;
flags: number;
}
export const $Bar: WasmTypeConstructor<Bar> = (mem) => ({
get align() { return 4; },
get size() { return 8; },
instance: (base) => ({
get __base() { return base; },
get __bytes() { return mem.u8.subarray(base, base + 8); },
get kind(): Kind {
return mem.u16[base >>> 1];
},
set kind(x: Kind) {
mem.u16[base >>> 1] = x;
},
get flags(): number {
return mem.u32[(base + 4) >>> 2];
},
set flags(x: number) {
mem.u32[(base + 4) >>> 2] = x;
},
})
});
export enum Kind {
UNKNOWN,
GOOD = 100,
BEST = 1000,
}
//! Generated by @thi.ng/wasm-api at 2022-08-15T22:32:21.191Z - DO NOT EDIT!
/// Example struct
pub const Foo = struct {
color: @Vector(4, f32),
bars: [3]Bar,
/// Unique ID
id: u8,
};
pub const Bar = struct {
kind: Kind,
flags: u32,
};
pub const Kind = enum(u16) {
unknown,
good = 100,
best = 1000,
};
On the TypeScript/JS side, the memory-mapped wrappers (e.g. $Foo and $Bar)
can be used in combination with the WasmBridge to obtain fully typed views
(according to the generated types) of the underlying WASM memory. Basic usage is
like:
import { WasmBridge } from "@thi.ng/wasm-api";
import { $Foo, Kind } from "./generated.ts";
const bridge = new WasmBridge();
// bridge initialization omitted here (see other examples below)
// ...
// Create an instance using the bridge's memory views
// and mapping a `Foo` struct from given address
// (e.g. obtained from an exported WASM function/value)
const foo = $Foo(bridge).instance(0x10000);
// then use like normal JS object
foo.color
// Float32Array(4) [0.1, 0.2, 0.3, 0.4]
// this even applies to arrays using other types
foo.bars[2].kind = Kind.BEST;
// IMPORTANT: any modifications like this are directly
// applied to the underlying WASM memory...
IMPORTANT: Struct field setters are currently only supported for single values, incl. enums, strings, structs. The latter 2 will always be copied by value (mem copy). Arrays or slices of strings do not currently provide write access...
Most low-level languages deal with strings very differently and alas there's no
general standard. Some have UTF-8/16 support, others don't. In some languages
(incl. C & Zig), strings are stored as zero terminated, in others they aren't...
It's outside the scope of this package to provide an allround out-of-the-box
solution. The WasmBridge provides read & write accessors to obtain JS strings
from UTF-8 encoded WASM memory. See
getString()
and
setString()
for details.
The code generators too provide a global stringType option to
interpret the string type of a struct field in different ways:
slice (default): Considers strings as Zig-style slices (i.e. pointer + length)ptr: Considers strings as C-style raw *char pointer (without any length)Note: If setting this global option to ptr, it also has to be repeated for the
TypeScript code generator explicitly.
If explicitly enabled on the WASM side, the WasmBridge includes support for
malloc/free-style allocations (within the linear WASM memory) from the JS side
(Note: This is a breaking change in v0.10.0, now using a more flexible approach
& reverse logic of earlier alpha versions).
The actual allocator is implementation specific and suitable generic mechanisms are defined for both the included Zig & C bindings. Please see for further reference:
/include/wasmapi.zig:
comments about WASM-side allocator handling in Zig/include/wasmapi.h:
comments about WASM-side allocator handling in C/C++WasmBridge.allocate():
allocating memory from JS sideWasmBridge.free():
freeing previously allocated memory from JS sideNote: The provided Zig mechanism supports the idiomatic (Zig) pattern of working with multiple allocators in different parts of the application and supports dynamic assignments/swapping of the exposed allocator. See comments in source file for more details...
try {
// allocate 1KB of memory for passing a string to WASM side
const addr = bridge.allocate(256);
// write string to reserved memory
// max. 256 bytes, zero terminated
const num = bridge.setString("hello WASM world!", addr, 256, true);
// call WASM function doing something w/ the string
bridge.exports.doSomethingWithString(addr, num);
// cleanup
bridge.free(addr, 256);
} catch(e) {
// deal with allocation error
// ...
}
Since only numeric values can be exchanged between the WASM module and the JS
host, any JS native objects the WASM side might want to be working with must be
managed manually in JS. For this purpose the ObjectIndex
class can be
used by API modules to handle ID generation (incl. recycling, using
@thi.ng/idgen)
and the indexing of different types of JS objects/values. Only the numeric IDs
(handles) will then need to be exchanged with the WASM module...
import { ObjectIndex } from "@thi.ng/wasm-api";
const canvases = new ObjectIndex<HTMLCanvasElement>({ name: "canvas" });
// index item and assign new ID
canvases.add(document.createElement("canvas"));
// 0
// look up item by ID
canvases.get(0);
// <canvas ...>
// work w/ retrieved item
canvases.get(0).id = "foo";
// check if item for ID exists (O(1))
canvases.has(1)
// false
// by default invalid IDs throw error
canvases.get(1)
// Uncaught Error: Assertion failed: missing canvas for ID: 2
// error can be disabled via 2nd arg
canvases.get(1, false)
// undefined
// find ID using custom predicate (same failure behavior as .get())
canvases.find((x) => x.id == "bar")
// Uncaught Error: Assertion failed: given predicate matched no canvas
canvases.delete(0);
// true
ALPHA - bleeding edge / work-in-progress
Search or submit any issues for this package
yarn add @thi.ng/wasm-api
ES module import:
<script type="module" src="https://cdn.skypack.dev/@thi.ng/wasm-api"></script>
For Node.js REPL:
# with flag only for < v16
node --experimental-repl-await
> const wasmApi = await import("@thi.ng/wasm-api");
Package sizes (gzipped, pre-treeshake): ESM: 4.48 KB
IMPORTANT: The package includes various code generators and supporting functions which are NOT required during runtime. Hence the actual package size in production will be MUCH smaller!
import { WasmBridge, WasmExports } from "@thi.ng/wasm-api";
import { readFileSync } from "fs";
// WASM exports from our dummy module (below)
interface App extends WasmExports {
start: () => void;
}
(async () => {
// new API bridge with defaults
// (i.e. no child API modules and using console logger)
const bridge = new WasmBridge<App>();
// instantiate WASM module using imports provided by the bridge
// this also initializes any bindings & bridge child APIs (if any)
// (also accepts a fetch() `Response` as input)
await bridge.instantiate(readFileSync("hello.wasm"));
// call an exported WASM function
bridge.exports.start();
})();
Requires Zig to be installed:
//! Example Zig application (hello.zig)
/// import externals
/// see build command for configuration
const js = @import("wasmapi");
const std = @import("std");
// set custom memory allocator (here to disable)
pub const WASM_ALLOCATOR: ?std.mem.Allocator = null;
export fn start() void {
js.printStr("hello world!");
}
The WASM binary can be built using the following command (or for more complex
scenarios add the supplied .zig file(s) to your build.zig and/or source
folder):
# compile WASM binary
zig build-lib \
--pkg-begin wasmapi node_modules/@thi.ng/wasm-api/include/wasmapi.zig --pkg-end \
-target wasm32-freestanding \
-O ReleaseSmall -dynamic --strip \
hello.zig
# disassemble WASM
wasm-dis -o hello.wast hello.wasm
The resulting WASM:
(module
(type $i32_i32_=>_none (func (param i32 i32)))
(type $none_=>_none (func))
(type $i32_=>_i32 (func (param i32) (result i32)))
(import "wasmapi" "_printStr" (func $fimport$0 (param i32 i32)))
(global $global$0 (mut i32) (i32.const 65536))
(memory $0 2)
(data (i32.const 65536) "hello world!\00")
(export "memory" (memory $0))
(export "start" (func $0))
(export "_wasm_allocate" (func $1))
(export "_wasm_free" (func $2))
(func $0
(call $fimport$0
(i32.const 65536)
(i32.const 12)
)
)
(func $1 (param $0 i32) (result i32)
(i32.const 0)
)
(func $2 (param $0 i32) (param $1 i32)
)
)
Requires Emscripten to be installed:
#include <wasmapi.h>
void WASM_KEEP start() {
wasm_printStr0("hello world!");
}
Building the WASM module:
emcc -Os -Inode_modules/@thi.ng/wasm-api/include -DWASMAPI_NO_MALLOC \
-sERROR_ON_UNDEFINED_SYMBOLS=0 --no-entry \
-o hello.wasm hello.c
Resulting WASM:
(module
(type $i32_=>_none (func (param i32)))
(type $none_=>_none (func))
(type $i32_=>_i32 (func (param i32) (result i32)))
(type $none_=>_i32 (func (result i32)))
(import "wasmapi" "_printStr0" (func $fimport$0 (param i32)))
(global $global$0 (mut i32) (i32.const 5243936))
(memory $0 256 256)
(data (i32.const 1024) "hello world!")
(table $0 2 2 funcref)
(elem (i32.const 1) $0)
(export "memory" (memory $0))
(export "_wasm_allocate" (func $1))
(export "_wasm_free" (func $2))
(export "start" (func $3))
(export "__indirect_function_table" (table $0))
(export "_initialize" (func $0))
(export "__errno_location" (func $7))
(export "stackSave" (func $4))
(export "stackRestore" (func $5))
(export "stackAlloc" (func $6))
(func $0
(nop)
)
(func $1 (param $0 i32) (result i32)
(i32.const 0)
)
(func $2 (param $0 i32)
(nop)
)
(func $3
(call $fimport$0
(i32.const 1024)
)
)
(func $4 (result i32)
(global.get $global$0)
)
(func $5 (param $0 i32)
(global.set $global$0
(local.get $0)
)
)
(func $6 (param $0 i32) (result i32)
(global.set $global$0
(local.tee $0
(i32.and
(i32.sub
(global.get $global$0)
(local.get $0)
)
(i32.const -16)
)
)
)
(local.get $0)
)
(func $7 (result i32)
(i32.const 1040)
)
)
Karsten Schmidt
If this project contributes to an academic publication, please cite it as:
@misc{thing-wasm-api,
title = "@thi.ng/wasm-api",
author = "Karsten Schmidt",
note = "https://thi.ng/wasm-api",
year = 2022
}
© 2022 Karsten Schmidt // Apache Software License 2.0
FAQs
Generic, modular, extensible API bridge and infrastructure for hybrid JS & WebAssembly projects
The npm package @thi.ng/wasm-api receives a total of 100 weekly downloads. As such, @thi.ng/wasm-api popularity was classified as not popular.
We found that @thi.ng/wasm-api demonstrated a healthy version release cadence and project activity because the last version was released less than a year ago. It has 0 open source maintainers collaborating on the project.
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