fly-socket/www/js/struct/struct.js
2019-07-31 01:08:19 +02:00

60 lines
3.0 KiB
JavaScript

// https://github.com/lyngklip/structjs
"use strict"
const rechk = /^([<>])?(([1-9]\d*)?([xcbB?hHiIfdsp]))*$/
const refmt = /([1-9]\d*)?([xcbB?hHiIfdsp])/g
const str = (v,o,c) => String.fromCharCode(
...new Uint8Array(v.buffer, v.byteOffset + o, c))
const rts = (v,o,c,s) => new Uint8Array(v.buffer, v.byteOffset + o, c)
.set(s.split('').map(str => str.charCodeAt(0)))
const pst = (v,o,c) => str(v, o + 1, Math.min(v.getUint8(o), c - 1))
const tsp = (v,o,c,s) => { v.setUint8(o, s.length); rts(v, o + 1, c - 1, s) }
const lut = le => ({
x: c=>[1,c,0],
c: c=>[c,1,o=>({u:v=>str(v, o, 1) , p:(v,c)=>rts(v, o, 1, c) })],
'?': c=>[c,1,o=>({u:v=>Boolean(v.getUint8(o)),p:(v,B)=>v.setUint8(o,B)})],
b: c=>[c,1,o=>({u:v=>v.getInt8( o ), p:(v,b)=>v.setInt8( o,b )})],
B: c=>[c,1,o=>({u:v=>v.getUint8( o ), p:(v,B)=>v.setUint8( o,B )})],
h: c=>[c,2,o=>({u:v=>v.getInt16( o,le), p:(v,h)=>v.setInt16( o,h,le)})],
H: c=>[c,2,o=>({u:v=>v.getUint16( o,le), p:(v,H)=>v.setUint16( o,H,le)})],
i: c=>[c,4,o=>({u:v=>v.getInt32( o,le), p:(v,i)=>v.setInt32( o,i,le)})],
I: c=>[c,4,o=>({u:v=>v.getUint32( o,le), p:(v,I)=>v.setUint32( o,I,le)})],
f: c=>[c,4,o=>({u:v=>v.getFloat32(o,le), p:(v,f)=>v.setFloat32(o,f,le)})],
d: c=>[c,8,o=>({u:v=>v.getFloat64(o,le), p:(v,d)=>v.setFloat64(o,d,le)})],
s: c=>[1,c,o=>({u:v=>str(v,o,c), p:(v,s)=>rts(v,o,c,s.slice(0,c ) )})],
p: c=>[1,c,o=>({u:v=>pst(v,o,c), p:(v,s)=>tsp(v,o,c,s.slice(0,c - 1) )})]
})
const errbuf = new RangeError("Structure larger than remaining buffer")
const errval = new RangeError("Not enough values for structure")
const struct = format => {
let fns = [], size = 0, m = rechk.exec(format)
if (!m) { throw new RangeError("Invalid format string") }
const t = lut('<' === m[1]), lu = (n, c) => t[c](n ? parseInt(n, 10) : 1)
while ((m = refmt.exec(format))) { ((r, s, f) => {
for (let i = 0; i < r; ++i, size += s) { if (f) {fns.push(f(size))} }
})(...lu(...m.slice(1)))}
const unpack_from = (arrb, offs) => {
if (arrb.byteLength < (offs|0) + size) { throw errbuf }
let v = new DataView(arrb, offs|0)
return fns.map(f => f.u(v))
}
const pack_into = (arrb, offs, ...values) => {
if (values.length < fns.length) { throw errval }
if (arrb.byteLength < offs + size) { throw errbuf }
const v = new DataView(arrb, offs)
new Uint8Array(arrb, offs, size).fill(0)
fns.forEach((f, i) => f.p(v, values[i]))
}
const pack = (...values) => {
let b = new ArrayBuffer(size)
pack_into(b, 0, ...values)
return b
}
const unpack = arrb => unpack_from(arrb, 0)
function* iter_unpack(arrb) {
for (let offs = 0; offs + size <= arrb.byteLength; offs += size) {
yield unpack_from(arrb, offs);
}
}
return Object.freeze({
unpack, pack, unpack_from, pack_into, iter_unpack, format, size})
}