jwoertink · February 7, 2022 01:56
diff --git a/README.md b/README.md
diff --git a/encoding.cr b/encoding.cr
 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
diff --git a/glue.js b/glue.js
 window.onload = ()=> {
  window.crystal = {}
  fetch("crystal.wasm")
    .then(res => res.arrayBuffer())
    .then(bytes => WebAssembly.instantiate(bytes))
    .then(obj => crystal = obj.instance.exports)
 }
diff --git a/index.php b/index.php
 <html>
  <body>
    <script src="glue.js"></script>
  </body>
 </html>
diff --git a/wasm.cr b/wasm.cr
 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
	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)
	}
	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