copybook-overflow

Overflow-safe integer narrowing and bounds arithmetic for copybook-rs.

Overview

This microcrate isolates checked arithmetic and checked narrowing conversions that are performance-sensitive and correctness-critical. All functions return structured copybook_error::Result<T> with domain-specific error codes on overflow, ensuring COBOL array bounds and record sizes are computed safely.

Usage

use copybook_overflow::{safe_array_bound, safe_u64_to_u32};

// Safely compute array end offset: base + (count * item_size)
let end = safe_array_bound(10, 3, 4, "my-array").unwrap();
assert_eq!(end, 22);

// Safely narrow u64 to u32
let narrow = safe_u64_to_u32(42, "record-length").unwrap();
assert_eq!(narrow, 42u32);

Public API

• safe_array_bound — Overflow-checked base + count * item_size
• safe_u64_to_u32 — Checked narrowing from u64 to u32
• safe_u64_to_u16 — Checked narrowing from u64 to u16
• safe_usize_to_u32 — Checked narrowing from usize to u32

License

AGPL-3.0-or-later