bare-operating-system/packages/bare-os-seeder/kernel/bin/dd

/* BARE_OS_BIN_API 1.0.0 — bump when staged /bin script semantics change (see developer guide). */
/** Shared helpers for drive-resident /bin scripts (prepended before each command). */
function bareStdin(ctx) {
  return typeof ctx.shellStdin === 'string' ? ctx.shellStdin : ''
}

/** @param {number} mode @param {'file' | 'directory' | 'symlink'} type */
function bareFormatModeString(mode, type) {
  const typeChar = type === 'directory' ? 'd' : type === 'symlink' ? 'l' : '-'
  const perm = mode & 0o777
  const r = (bit) => (perm & bit ? 'r' : '-')
  const w = (bit) => (perm & bit ? 'w' : '-')
  const x = (bit) => (perm & bit ? 'x' : '-')
  return (
    typeChar +
    r(0o400) +
    w(0o200) +
    x(0o100) +
    r(0o040) +
    w(0o020) +
    x(0o010) +
    r(0o004) +
    w(0o002) +
    x(0o001)
  )
}

/** @param {number} mtimeMs @param {number} [nowMs] */
function bareFormatLsMtime(mtimeMs, nowMs) {
  const now = nowMs != null ? nowMs : Date.now()
  const d = new Date(mtimeMs)
  const months = [
    'Jan',
    'Feb',
    'Mar',
    'Apr',
    'May',
    'Jun',
    'Jul',
    'Aug',
    'Sep',
    'Oct',
    'Nov',
    'Dec'
  ]
  const mon = months[d.getMonth()]
  const day = String(d.getDate()).padStart(2, ' ')
  const sixMo = 180 * 24 * 3600 * 1000
  if (Math.abs(now - mtimeMs) > sixMo) {
    const yr = String(d.getFullYear()).padStart(4, ' ')
    return mon + ' ' + day + '  ' + yr
  }
  const hh = String(d.getHours()).padStart(2, '0')
  const mm = String(d.getMinutes()).padStart(2, '0')
  return mon + ' ' + day + ' ' + hh + ':' + mm
}

/** @param {number} size */
function barePosixBlocks(size) {
  return Math.ceil(Number(size) / 512) || 0
}

/**
 * Raw stdout for NUL/binary when **`process.stdout.write`** is missing.
 * If **`ctx.bareOsBinWrite(Uint8Array|string)`** is set (tests / host), use it.
 * @param {Record<string, unknown>} ctx
 * @param {string | Uint8Array} chunk
 * @returns {boolean}
 */
function bareOsEmitRaw(ctx, chunk) {
  if (typeof ctx.bareOsBinWrite === 'function') {
    const b4 = ctx.b4a
    const u8 =
      typeof chunk === 'string'
        ? b4 && typeof b4.from === 'function'
          ? b4.from(chunk)
          : new TextEncoder().encode(chunk)
        : chunk
    ctx.bareOsBinWrite(u8 instanceof Uint8Array ? u8 : new Uint8Array(u8))
    return true
  }
  const w = globalThis.process?.stdout?.write
  if (typeof w === 'function') {
    w.call(globalThis.process.stdout, chunk)
    return true
  }
  return false
}

function parseSize(v) {
  const s = String(v || '').trim().toLowerCase()
  const m = /^(\d+)([kmg]?)$/.exec(s)
  if (!m) return null
  const n = Number.parseInt(m[1], 10)
  if (!Number.isFinite(n) || n < 0) return null
  const mul = m[2] === 'k' ? 1024 : m[2] === 'm' ? 1024 * 1024 : m[2] === 'g' ? 1024 * 1024 * 1024 : 1
  return n * mul
}

function concatU8(b4a, chunks) {
  let total = 0
  for (const c of chunks) total += c.byteLength
  const out = b4a.alloc(total)
  let off = 0
  for (const c of chunks) {
    out.set(c, off)
    off += c.byteLength
  }
  return out
}

function parseConvList(v) {
  return String(v || '')
    .split(',')
    .map((x) => x.trim().toLowerCase())
    .filter(Boolean)
}

function padToBlock(u8, bs, b4a) {
  if (bs <= 0) return u8
  const rem = u8.byteLength % bs
  if (rem === 0) return u8
  const pad = bs - rem
  const out = b4a.alloc(u8.byteLength + pad)
  out.set(u8, 0)
  return out
}

async function run(ctx, argv) {
  /** @type {{ if?: string, of?: string, bs: number, count?: number, skip: number, seek: number, status: string, conv: string[] }} */
  const opt = { bs: 512, skip: 0, seek: 0, status: 'progress', conv: [] }

  for (let i = 1; i < argv.length; i++) {
    const a = argv[i]
    if (a === '--') continue
    const eq = a.indexOf('=')
    if (eq <= 0) {
      ctx.console.error('dd: expected OPERAND=VALUE: ' + a)
      ctx.exitCode = 1
      return
    }
    const k = a.slice(0, eq)
    const v = a.slice(eq + 1)
    if (k === 'if') opt.if = v
    else if (k === 'of') opt.of = v
    else if (k === 'bs') {
      const n = parseSize(v)
      if (n == null || n <= 0) {
        ctx.console.error('dd: invalid bs=' + v)
        ctx.exitCode = 1
        return
      }
      opt.bs = n
    } else if (k === 'count') {
      const n = Number.parseInt(v, 10)
      if (!Number.isFinite(n) || n < 0) {
        ctx.console.error('dd: invalid count=' + v)
        ctx.exitCode = 1
        return
      }
      opt.count = n
    } else if (k === 'skip') {
      const n = Number.parseInt(v, 10)
      if (!Number.isFinite(n) || n < 0) {
        ctx.console.error('dd: invalid skip=' + v)
        ctx.exitCode = 1
        return
      }
      opt.skip = n
    } else if (k === 'seek') {
      const n = Number.parseInt(v, 10)
      if (!Number.isFinite(n) || n < 0) {
        ctx.console.error('dd: invalid seek=' + v)
        ctx.exitCode = 1
        return
      }
      opt.seek = n
    } else if (k === 'status') {
      if (v !== 'none' && v !== 'progress') {
        ctx.console.error('dd: unsupported status=' + v)
        ctx.exitCode = 1
        return
      }
      opt.status = v
    } else if (k === 'conv') {
      const list = parseConvList(v)
      const allow = new Set(['notrunc', 'sync', 'noerror', 'nocreat'])
      for (const c of list) {
        if (!allow.has(c)) {
          ctx.console.error('dd: unsupported conv=' + c)
          ctx.exitCode = 1
          return
        }
      }
      opt.conv = list
    } else {
      ctx.console.error('dd: unsupported operand ' + k)
      ctx.exitCode = 1
      return
    }
  }

  const finiteCount = opt.count == null ? null : opt.count
  const wantedBytes =
    finiteCount == null ? null : Math.max(0, finiteCount * opt.bs)
  const skipBytes = Math.max(0, opt.skip * opt.bs)
  let chunk
  if (opt.if === '/dev/zero' && wantedBytes != null) {
    chunk = ctx.b4a.alloc(wantedBytes)
  } else if (opt.if === '/dev/urandom' && wantedBytes != null) {
    const raw = await ctx.vfs.readFile('/dev/urandom')
    if (!raw) {
      ctx.console.error('dd: /dev/urandom: unavailable')
      ctx.exitCode = 1
      return
    }
    const seed = raw instanceof Uint8Array ? raw : ctx.b4a.from(raw)
    chunk = ctx.b4a.alloc(wantedBytes)
    for (let i = 0; i < wantedBytes; i++) chunk[i] = seed[i % seed.length]
  } else {
    let src
    if (opt.if) {
      src = await ctx.vfs.readFile(opt.if)
      if (!src) {
        ctx.console.error('dd: ' + opt.if + ': No such file or directory')
        ctx.exitCode = 1
        return
      }
    } else {
      src = ctx.b4a.from(bareStdin(ctx), 'utf8')
    }
    const input = src instanceof Uint8Array ? src : ctx.b4a.from(src)
    const start = Math.min(skipBytes, input.byteLength)
    const end =
      wantedBytes == null
        ? input.byteLength
        : Math.min(input.byteLength, start + wantedBytes)
    chunk = input.subarray(start, end)
  }
  if (opt.conv.includes('sync')) {
    chunk = padToBlock(chunk, opt.bs, ctx.b4a)
  }

  if (!opt.of) {
    if (!bareOsEmitRaw(ctx, chunk)) ctx.console.log(ctx.b4a.toString(chunk))
    if (opt.status !== 'none') {
      ctx.console.error(`${chunk.byteLength} bytes copied`)
    }
    return
  }

  const outOff = opt.seek * opt.bs
  let prev = null
  try {
    prev = await ctx.vfs.readFile(opt.of)
  } catch {
    prev = null
  }
  const prevU8 = prev ? (prev instanceof Uint8Array ? prev : ctx.b4a.from(prev)) : ctx.b4a.alloc(0)
  let out
  if (opt.conv.includes('notrunc')) {
    const want = Math.max(prevU8.byteLength, outOff + chunk.byteLength)
    out = ctx.b4a.alloc(want)
    if (prevU8.byteLength) out.set(prevU8, 0)
    out.set(chunk, outOff)
  } else {
    out = concatU8(ctx.b4a, [ctx.b4a.alloc(outOff), chunk])
  }
  await ctx.vfs.writeFile(opt.of, out)
  if (opt.status !== 'none') {
    ctx.console.error(`${chunk.byteLength} bytes copied`)
  }
}