Function patch_seq_read_n 

#[unsafe(no_mangle)]
pub unsafe extern "C" fn patch_seq_read_n(stack: Stack) -> Stack

Read exactly N bytes from stdin

Returns the bytes read and a status flag:

• ( string 1 ) on success (read all N bytes)
• ( string 0 ) at EOF, partial read, or error (string may be shorter than N)

Stack effect: ( Int – String Int )

Like io.read-line+, this returns a result pattern (value + status) to allow explicit EOF detection. The function name omits the + suffix for brevity since byte-count reads are inherently status-oriented.

Errors are values, not crashes.

This is used for protocols like LSP where message bodies are byte-counted and don’t have trailing newlines.

UTF-8 Handling

The bytes are interpreted as UTF-8. Invalid UTF-8 sequences are replaced with the Unicode replacement character (U+FFFD). This is appropriate for text-based protocols like LSP but may not be suitable for binary data.

Safety

Stack must have an Int on top. The integer must be non-negative and not exceed READ_N_MAX_BYTES (10MB).