rumpk/core/fs/tar.nim

# MARKUS MAIWALD (ARCHITECT) | VOXIS FORGE (AI)
# Rumpk L1: Sovereign VFS (Indexing TarFS)

{.push stackTrace: off, lineTrace: off.}

import std/tables

# Kernel Imports
proc kprint(s: cstring) {.importc, cdecl.}
proc kprintln(s: cstring) {.importc, cdecl.}
proc kprint_hex(n: uint64) {.importc, cdecl.}

type
  TarHeader* = array[512, byte]

  FileEntry = object
    offset*: uint64
    size*: uint64
    is_sfs*: bool

  FileHandle = object
    path*: string
    offset*: uint64
    is_sfs*: bool

  VFSInitRD* = object
    start_addr*: uint64
    end_addr*: uint64
    index*: Table[string, FileEntry]
    fds*: Table[int, FileHandle]
    next_fd*: int

var vfs*: VFSInitRD

proc toHexChar(b: byte): char =
  if b < 10: return char(byte('0') + b)
  else: return char(byte('A') + (b - 10))

proc vfs_init*(s: pointer, e: pointer) =
  vfs.start_addr = cast[uint64](s)
  vfs.end_addr = cast[uint64](e)
  vfs.index = initTable[string, FileEntry]()
  vfs.fds = initTable[int, FileHandle]()
  vfs.next_fd = 3

  var p = vfs.start_addr
  while p < vfs.end_addr:
    let h = cast[ptr TarHeader](p)
    if h[][0] == byte(0): break

    var name = ""
    for i in 0..99:
      if h[][i] == byte(0): break
      name.add(char(h[][i]))

    var size: uint64 = 0
    for i in 124..134:
      let b = h[][i]
      if b >= byte('0') and b <= byte('7'):
        size = (size shl 3) or uint64(b - byte('0'))

    # Manual Normalization
    var clean = name
    if clean.len > 2 and clean[0] == '.' and clean[1] == '/':
      # Strip ./
      var new_clean = ""
      for i in 2 ..< clean.len: new_clean.add(clean[i])
      clean = new_clean
    elif clean.len > 1 and clean[0] == '/':
      # Strip /
      var new_clean = ""
      for i in 1 ..< clean.len: new_clean.add(clean[i])
      clean = new_clean

    if clean.len > 0:
      vfs.index[clean] = FileEntry(offset: p + 512'u64, size: size, is_sfs: false)
      kprint("[VFS] Indexed: '")
      kprint(cstring(clean))
      kprint("' Size: ")
      var ss = ""; ss.add($size); kprintln(cstring(ss))
    else:
      kprint("[VFS] Empty Name? Raw: ")
      var r = ""
      for i in 0..min(10, name.len-1):
        r.add(toHexChar(byte(name[i]) shr 4))
        r.add(toHexChar(byte(name[i]) and 0xF))
        r.add(' ')
      kprintln(cstring(r))

    p += 512'u64 + ((size + 511'u64) and not 511'u64)

proc vfs_open*(path: string): int =
  var clean = path
  if clean.len > 0 and clean[0] == '/':
    var nc = ""; for i in 1..<clean.len: nc.add(clean[i]); clean = nc

  if vfs.index.hasKey(clean):
    let entry = vfs.index[clean]
    let fd = vfs.next_fd
    vfs.fds[fd] = FileHandle(path: clean, offset: 0, is_sfs: entry.is_sfs)
    vfs.next_fd += 1
    return fd
  return -1

proc vfs_read_file*(path: string): string =
  var clean = path
  if clean.len > 0 and clean[0] == '/':
    var nc = ""; for i in 1..<clean.len: nc.add(clean[i]); clean = nc

  kprint("[VFS] Reading: '"); kprint(cstring(clean)); kprint("' -> ")

  if vfs.index.hasKey(clean):
    let entry = vfs.index[clean]
    kprintln("FOUND.")
    if entry.is_sfs: return ""
    var s = newString(int(entry.size))
    if entry.size > 0:
      copyMem(addr s[0], cast[pointer](entry.offset), int(entry.size))
    return s

  kprintln("NOT FOUND.")
  # Debug Keys
  kprint("Available: ")
  for k in vfs.index.keys:
    kprint("'"); kprint(cstring(k)); kprint("' ")
  kprintln("")
  return ""

proc ion_vfs_open*(path: cstring): int32 {.exportc, cdecl.} =
  return int32(vfs_open($path))

proc sfs_read_file(name: cstring, dest: pointer, max_len: int): int {.importc, cdecl.}

proc ion_vfs_read*(fd: int32, buf: pointer, count: uint64): int64 {.exportc, cdecl.} =
  let fd_int = int(fd)
  if not vfs.fds.hasKey(fd_int): return -1
  var fh = vfs.fds[fd_int]
  if fh.is_sfs:
    let n = sfs_read_file(cstring(fh.path), buf, int(count))
    if n > 0: fh.offset += uint64(n); vfs.fds[fd_int] = fh; return int64(n)
    return 0
  if vfs.index.hasKey(fh.path):
    let entry = vfs.index[fh.path]
    if fh.offset >= entry.size: return 0
    let to_read = min(uint64(entry.size - fh.offset), count)
    if to_read > 0:
      copyMem(buf, cast[pointer](entry.offset + fh.offset), int(to_read))
      fh.offset += to_read
      vfs.fds[fd_int] = fh
      return int64(to_read)
  return 0

proc ion_vfs_list*(buf: pointer, max_len: uint64): int64 {.exportc, cdecl.} =
  var s = ""
  for name, _ in vfs.index: s.add(name & "\n")
  let n = min(s.len, int(max_len))
  if n > 0: copyMem(buf, addr s[0], n)
  return int64(n)

proc vfs_register_sfs*(name: string, size: uint64) {.exportc, cdecl.} =
  vfs.index[name] = FileEntry(offset: 0, size: size, is_sfs: true)

{.pop.}