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encode.ts
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encode.ts
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import { BinaryInfo } from './BinaryInfo'
import { FLAG_BYTE, FLAG_EVENT, FLAG_EXTENDED, FLAG_FIELD, FLAG_GLOBAL, WEB_EVENTS, WEB_GLOBALS } from './constants'
const getHeaderBitLength = (key: number) => (key < 256 ? 2 : 3)
type Value = number | null | string
export const encodeWAM = (binaryInfo: BinaryInfo) => {
binaryInfo.buffer = []
encodeWAMHeader(binaryInfo)
encodeEvents(binaryInfo)
console.log(binaryInfo.buffer)
const totalSize = binaryInfo.buffer
.map((a) => a.length)
.reduce((a, b) => a + b)
const buffer = Buffer.alloc(totalSize)
let offset = 0
binaryInfo.buffer.forEach((buffer_) => {
buffer_.copy(buffer, offset)
offset += buffer_.length
})
return buffer
}
function encodeWAMHeader(binaryInfo: BinaryInfo) {
const headerBuffer = Buffer.alloc(8) // starting buffer
headerBuffer.write('WAM', 0, 'utf8')
headerBuffer.writeUInt8(binaryInfo.protocolVersion, 3)
headerBuffer.writeUInt8(1, 4) //random flag
headerBuffer.writeUInt16BE(binaryInfo.sequence, 5)
headerBuffer.writeUInt8(0, 7) // regular channel
binaryInfo.buffer.push(headerBuffer)
}
function encodeGlobalAttributes(binaryInfo: BinaryInfo, globals: {[key: string]: Value}) {
for(const [key, _value] of Object.entries(globals)) {
const id = WEB_GLOBALS.find(a => a?.name === key)!.id
let value = _value
if(typeof value === 'boolean') {
value = value ? 1 : 0
}
binaryInfo.buffer.push(serializeData(id, value, FLAG_GLOBAL))
}
}
function encodeEvents(binaryInfo: BinaryInfo) {
for(const [
name,
{ props, globals },
] of binaryInfo.events.map((a) => Object.entries(a)[0])) {
encodeGlobalAttributes(binaryInfo, globals)
const event = WEB_EVENTS.find((a) => a.name === name)!
const props_ = Object.entries(props)
let extended = false
for(const [, value] of props_) {
extended ||= value !== null
}
const eventFlag = extended ? FLAG_EVENT : FLAG_EVENT | FLAG_EXTENDED
binaryInfo.buffer.push(serializeData(event.id, -event.weight, eventFlag))
for(let i = 0; i < props_.length; i++) {
const [key, _value] = props_[i]
const id = (event.props)[key][0]
extended = i < (props_.length - 1)
let value = _value
if(typeof value === 'boolean') {
value = value ? 1 : 0
}
const fieldFlag = extended ? FLAG_EVENT : FLAG_FIELD | FLAG_EXTENDED
binaryInfo.buffer.push(serializeData(id, value as Value, fieldFlag))
}
}
}
function serializeData(key: number, value: Value, flag: number): Buffer {
const bufferLength = getHeaderBitLength(key)
let buffer: Buffer
let offset = 0
if(value === null) {
if(flag === FLAG_GLOBAL) {
buffer = Buffer.alloc(bufferLength)
offset = serializeHeader(buffer, offset, key, flag)
return buffer
}
} else if(typeof value === 'number' && Number.isInteger(value)) {
// is number
if(value === 0 || value === 1) {
buffer = Buffer.alloc(bufferLength)
offset = serializeHeader(buffer, offset, key, flag | ((value + 1) << 4))
return buffer
} else if(-128 <= value && value < 128) {
buffer = Buffer.alloc(bufferLength + 1)
offset = serializeHeader(buffer, offset, key, flag | (3 << 4))
buffer.writeInt8(value, offset)
return buffer
} else if(-32768 <= value && value < 32768) {
buffer = Buffer.alloc(bufferLength + 2)
offset = serializeHeader(buffer, offset, key, flag | (4 << 4))
buffer.writeInt16LE(value, offset)
return buffer
} else if(-2147483648 <= value && value < 2147483648) {
buffer = Buffer.alloc(bufferLength + 4)
offset = serializeHeader(buffer, offset, key, flag | (5 << 4))
buffer.writeInt32LE(value, offset)
return buffer
} else {
buffer = Buffer.alloc(bufferLength + 8)
offset = serializeHeader(buffer, offset, key, flag | (7 << 4))
buffer.writeDoubleLE(value, offset)
return buffer
}
} else if(typeof value === 'number') {
// is float
buffer = Buffer.alloc(bufferLength + 8)
offset = serializeHeader(buffer, offset, key, flag | (7 << 4))
buffer.writeDoubleLE(value, offset)
return buffer
} else if(typeof value === 'string') {
// is string
const utf8Bytes = Buffer.byteLength(value, 'utf8')
if(utf8Bytes < 256) {
buffer = Buffer.alloc(bufferLength + 1 + utf8Bytes)
offset = serializeHeader(buffer, offset, key, flag | (8 << 4))
buffer.writeUint8(utf8Bytes, offset++)
} else if(utf8Bytes < 65536) {
buffer = Buffer.alloc(bufferLength + 2 + utf8Bytes)
offset = serializeHeader(buffer, offset, key, flag | (9 << 4))
buffer.writeUInt16LE(utf8Bytes, offset)
offset += 2
} else {
buffer = Buffer.alloc(bufferLength + 4 + utf8Bytes)
offset = serializeHeader(buffer, offset, key, flag | (10 << 4))
buffer.writeUInt32LE(utf8Bytes, offset)
offset += 4
}
buffer.write(value, offset, 'utf8')
return buffer
}
throw 'missing'
}
function serializeHeader(
buffer: Buffer,
offset: number,
key: number,
flag: number
) {
if(key < 256) {
buffer.writeUInt8(flag, offset)
offset += 1
buffer.writeUInt8(key, offset)
offset += 1
} else {
buffer.writeUInt8(flag | FLAG_BYTE, offset)
offset += 1
buffer.writeUInt16LE(key, offset)
offset += 2
}
return offset
}