copybook-fixed

Fixed-length (LRECL) record framing primitives for copybook-rs.

Overview

This crate provides streaming reader and writer types for fixed-length record framing. FixedRecordReader consumes LRECL-sized records from a byte stream, while FixedRecordWriter produces them with automatic null-byte padding for short payloads.

Usage

use copybook_fixed::{FixedRecordReader, FixedRecordWriter};
use std::io::Cursor;

// Write fixed-length records (LRECL = 8)
let mut output = Vec::new();
let mut writer = FixedRecordWriter::with_lrecl(&mut output, 8).unwrap();
writer.write_record(b"ABCD").unwrap(); // padded to 8 bytes
writer.flush().unwrap();

// Read fixed-length records
let mut reader = FixedRecordReader::with_lrecl(Cursor::new(&output), 8).unwrap();
let record = reader.read_record().unwrap().unwrap();
assert_eq!(&record[..4], b"ABCD");

Public API

• FixedRecordReader<R> — Streaming reader for fixed-length records
• FixedRecordWriter<W> — Streaming writer with automatic padding

The with_lrecl constructors are the canonical schema-independent framing surface. Copybook schema compatibility is validated by copybook-codec before it constructs these framing primitives.

Standalone consumer proof

The repository includes a clean-room consumer that depends directly on only copybook-fixed and copybook-error:

cargo run --locked --manifest-path examples/copybook-fixed-clean-room/Cargo.toml

It proves multi-record read/write, zero padding, EOF, truncated-input rejection, oversized-payload rejection, and the stable CBKR101_FIXED_RECORD_ERROR identity without importing schema, codec, or CLI packages.

Migration from the 0.5 schema-aware helper

The former FixedRecordReader::validate_record_length method was schema-aware and is not part of the schema-independent framing API. Callers that need that compatibility check should use copybook_codec::file::fixed::validate_record_length with the parsed schema, configured LRECL, record index, and record bytes; callers that only need framing should use with_lrecl.

License

AGPL-3.0-or-later