crystal wasm.crphp -S localhost:3000crystal.add(1, 2)This writes the WASM bytes with the built-in add_function named add to a file called crystal.wasm.
Then a fetch call loads the result in to WebAssembly, and puts that function in to a JS object called crystal.
You're calling an add function from WASM that was generated using crystal... It's kinda neat, but pretty useless.
| struct Int32 | |
| # this is a patch because Crystal (or ruby for that matter) | |
| # don't have this `>>>` zero-fill right shift bitwise operator | |
| # https://github.com/rjanse/demo-s3-swf-upload/blob/7acf16be7d2f75c42935aa1aa9af10b73d4376f7/vendor/plugins/s3-swf-upload-plugin/lib/patch/integer.rb#L8 | |
| def zfrs(n : Int32) | |
| self >> n & (2**(32-n)-1) | |
| end | |
| end | |
| module Encoding | |
| # https://www.geeksforgeeks.org/ieee-standard-754-floating-point-numbers/ | |
| def ieee754(n : UInt8) | |
| String.build do |io| | |
| io.write_byte n | |
| end | |
| end | |
| def encode_string(str : String) : Array(Int32) | |
| [str.size] + str.codepoints | |
| end | |
| # https://docs.rs/leb128/0.2.4/leb128/ | |
| def signed_LEB128(n : Int) : Array(Int32) | |
| buffer = [] of Int32 | |
| more = true | |
| while more | |
| byte = n & 0x7f | |
| n = n.zfrs(7) | |
| if (n == 0 && (byte & 0x40) == 0) || (n == -1 && (byte & 0x40) != 0) | |
| more = false | |
| else | |
| byte |= 0x80 | |
| end | |
| buffer << byte | |
| end | |
| buffer | |
| end | |
| def unsigned_LEB128(n : Int) | |
| buffer = [] of Int32 | |
| loop do | |
| byte = n & 0x7f | |
| n = n.zfrs(7) | |
| if n != 0 | |
| byte |= 0x80 | |
| end | |
| buffer << byte | |
| break if n == 0 | |
| end | |
| buffer | |
| end | |
| end |
| window.onload = ()=> { | |
| window.crystal = {} | |
| fetch("crystal.wasm") | |
| .then(res => res.arrayBuffer()) | |
| .then(bytes => WebAssembly.instantiate(bytes)) | |
| .then(obj => crystal = obj.instance.exports) | |
| } |
| <html> | |
| <body> | |
| <script src="glue.js"></script> | |
| </body> | |
| </html> |
| require "./encoding" | |
| include Encoding | |
| # https://webassembly.github.io/spec/core/binary/modules.html#sections | |
| enum Section : UInt8 | |
| Custom | |
| Type | |
| Import | |
| Func | |
| Table | |
| Memory | |
| Global | |
| Export | |
| Start | |
| Element | |
| Code | |
| Data | |
| end | |
| # https://webassembly.github.io/spec/core/binary/types.html | |
| module Valtype | |
| I32 = 0x7f | |
| I64 = 0x7e | |
| F32 = 0x7d | |
| end | |
| # https://webassembly.github.io/spec/core/binary/instructions.html | |
| module Opcodes | |
| End = 0x0b | |
| GetLocal = 0x20 | |
| F32Add = 0x92 | |
| end | |
| # http://webassembly.github.io/spec/core/binary/modules.html#export-section | |
| module ExportType | |
| Func = 0x00 | |
| Table = 0x01 | |
| Mem = 0x02 | |
| Global = 0x03 | |
| end | |
| # http://webassembly.github.io/spec/core/binary/types.html#function-types | |
| FunctionType = 0x60 | |
| EmptyArray = 0x0 | |
| # https://webassembly.github.io/spec/core/binary/conventions.html#binary-vec | |
| def encode_vector(data) : Array(UInt8) | |
| size = [data.size.to_u8] of UInt8 | |
| size + data.flatten.map(&.to_u8) | |
| end | |
| # https://webassembly.github.io/spec/core/binary/modules.html#sections | |
| def create_section(type : Section, data) : Array(UInt8) | |
| type = [type.value] of UInt8 | |
| type + encode_vector(data) | |
| end | |
| magic_module_header = [0x00, 0x61, 0x73, 0x6d] of UInt8 | |
| module_version = [0x01, 0x00, 0x00, 0x00] of UInt8 | |
| header = magic_module_header + module_version | |
| add_function_type = [FunctionType] + encode_vector([Valtype::F32, Valtype::F32]) + encode_vector([Valtype::F32]) | |
| type_section = create_section(Section::Type, encode_vector([add_function_type])) | |
| func_section = create_section(Section::Func, encode_vector([0x00])) | |
| export_section = create_section(Section::Export, encode_vector([encode_string("add") + [ExportType::Func, 0x00]])) | |
| code = [ | |
| Opcodes::GetLocal, | |
| unsigned_LEB128(0), | |
| Opcodes::GetLocal, | |
| unsigned_LEB128(1), | |
| Opcodes::F32Add | |
| ].flatten | |
| function_body = encode_vector([ | |
| EmptyArray, | |
| code, | |
| Opcodes::End | |
| ].flatten) | |
| code_section = create_section(Section::Code, encode_vector([function_body])) | |
| buffer = (header + type_section + func_section + export_section + code_section) | |
| File.open("crystal.wasm", "wb") do |f| | |
| ptr = (buffer.to_unsafe.as(UInt8*)) | |
| f.write(ptr.to_slice(buffer.size * sizeof(UInt8))) | |
| end |