Patched code sample

def safe_extract_layout_text(pdf_page):
    """
    A conceptual representation of a fix for an infinite loop vulnerability.

    The actual vulnerability (likely CVE-2023-36464, as the one in the prompt
    is invalid) was fixed within the pypdf library's internal logic. This code
    demonstrates the principle of tracking visited elements to prevent cycles
    during text extraction, which is the core of such a fix.

    Args:
        pdf_page: A pseudo-object representing a PDF page with a content stream.
    """
    # In a real scenario, this would be a stream of operators and operands.
    # We simulate this with a list of instructions.
    content_stream = getattr(pdf_page, 'content_stream', [])
    if not content_stream:
        return

    # The core of the fix: Track the indices/positions we have already processed.
    visited_indices = set()
    current_index = 0

    # As a secondary failsafe, limit the total number of operations.
    max_ops = len(content_stream) * 2

    while 0 <= current_index < len(content_stream) and len(visited_indices) < max_ops:
        # If we encounter an index that has already been processed, we have
        # detected a cycle. A malicious PDF could use this to cause an
        # infinite loop. By breaking here, we prevent it.
        if current_index in visited_indices:
            # Cycle detected, abort processing this stream.
            break

        visited_indices.add(current_index)

        instruction = content_stream[current_index]

        # --- Simulate processing and pointer movement ---
        # A vulnerable parser might unconditionally follow a jump instruction.
        # A malicious PDF could have an instruction like ('JUMP', -5) to
        # move the instruction pointer backward, creating a loop.
        if isinstance(instruction, tuple) and instruction[0] == 'JUMP':
            # Follow the jump, but the check at the start of the loop
            # will protect against infinite cycles.
            current_index += instruction[1]
        else:
            # Process text or other operators and move to the next instruction.
            current_index += 1
        # --- End of simulation ---