json_parse_limits.pony

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class val JSONParseLimits
  """
  Resource bounds for `JSONTokenParser` over untrusted input.

  These bound the parser's own working memory: the container-depth
  stack, and the single string or number it is part-way through. They
  do not bound how much a `JSONReassembler` — or your own notifier —
  chooses to retain; that memory is the caller's choice, so a
  raw-notifier consumer that drops the tokens it doesn't need stays
  flat no matter how large the document.

  The default constructor applies conservative limits; raise a
  specific bound when a trusted source legitimately has a large value
  or deep nesting, or use `unlimited()` for fully trusted input.

  ```pony
  let parser = JSONTokenParser(notify) // default limits
  let parser = JSONTokenParser(notify, JSONParseLimits(where max_depth' = 32))
  let parser = JSONTokenParser(notify, JSONParseLimits.unlimited())
  ```
  """
  let max_depth: USize
    """Maximum container nesting depth. Bounds the parser's frame stack."""
  let max_string_len: USize
    """
    Maximum length, in bytes, of a single string's source text (the
    bytes between the quotes, before any escapes are decoded).
    """
  let max_number_len: USize
    """Maximum length, in bytes, of a single number's source text."""

  new val create(
    max_depth': USize = 1024,
    max_string_len': USize = 1_048_576,
    max_number_len': USize = 256)
  =>
    max_depth = max_depth'
    max_string_len = max_string_len'
    max_number_len = max_number_len'

  new val unlimited() =>
    """
    No bounds — every limit is set to its maximum. For fully trusted input, such
    as a whole document already held in memory. This is what `JSONParser.parse`
    uses.
    """
    max_depth = USize.max_value()
    max_string_len = USize.max_value()
    max_number_len = USize.max_value()