muse/book-reading-clip-lamp

split-pcb-preview.mjs

import { readFileSync, writeFileSync } from "node:fs"
import { dirname, join } from "node:path"

// Registry requests cannot carry the monolithic PCB GLB. Keep every buffer view
// byte-identical, but place them in small external glTF buffers for uploading.
export function splitPcbPreview(path) {
  const glb = readFileSync(path)
  if (glb.readUInt32LE(0) !== 0x46546c67 || glb.readUInt32LE(4) !== 2) {
    throw new Error("Expected a glTF 2 GLB")
  }
  const jsonLength = glb.readUInt32LE(12)
  const model = JSON.parse(glb.subarray(20, 20 + jsonLength).toString())
  const binHeader = 20 + jsonLength
  if (model.buffers.length !== 1 || glb.readUInt32LE(binHeader + 4) !== 0x004e4942) {
    throw new Error("Expected one embedded GLB buffer")
  }
  const source = glb.subarray(binHeader + 8)
  const chunks = [Buffer.alloc(0)]
  const limit = 2 * 1024 * 1024
  for (const view of model.bufferViews) {
    if (view.buffer !== 0 || view.byteLength > limit) throw new Error("Buffer view exceeds upload chunk limit")
    const bytes = source.subarray(view.byteOffset ?? 0, (view.byteOffset ?? 0) + view.byteLength)
    let index = chunks.length - 1
    if (chunks[index].length + 3 + bytes.length > limit) { chunks.push(Buffer.alloc(0)); index++ }
    const offset = Math.ceil(chunks[index].length / 4) * 4
    chunks[index] = Buffer.concat([chunks[index], Buffer.alloc(offset - chunks[index].length), bytes])
    if (!chunks[index].subarray(offset, offset + bytes.length).equals(bytes)) throw new Error("Buffer copy mismatch")
    view.buffer = index
    view.byteOffset = offset
  }
  model.buffers = chunks.map((data, index) => {
    const uri = `pcb-buffer-${index}.bin`
    writeFileSync(join(dirname(path), uri), data)
    return { uri, byteLength: data.length }
  })
  writeFileSync(join(dirname(path), "pcb.gltf"), JSON.stringify(model))
  console.log(`Exported byte-identical PCB preview in ${chunks.length} upload-sized buffers`)
}