// StringStd — minimal standard string helpers (commonized API)

static box StringStd {
  length(s) {
    if s == null { return 0 }
    return s.length()
  }
  substring(s, start, end) {
    if s == null { return "" }
    if start == null { start = 0 }
    if end == null { end = s.length() }
    return s.substring(start, end)
  }
  indexOf(s, needle, start) {
    if s == null { return -1 }
    if needle == null { needle = "" }
    if start == null { return s.indexOf(needle) }
    return s.indexOf(needle, start)
  }
  lastIndexOf(s, needle, start) {
    if s == null { return -1 }
    if needle == null { needle = "" }
    if start == null { return s.lastIndexOf(needle) }
    return s.lastIndexOf(needle, start)
  }
  esc_json(s) {
    if s == null { return "" }
    local out = ""
    local i = 0
    local n = s.length()
    loop(i < n) {
      local ch = s.substring(i, i+1)
      if ch == "\\" { out = out + "\\\\" } else { if ch == "\"" { out = out + "\\\"" } else { out = out + ch } }
      i = i + 1
    }
    return out
  }
}