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