copybook-codec

High-performance COBOL copybook codec for mainframe-style fixed and RDW records.

copybook-codec converts decoded/encoded records between COBOL binary formats (DISPLAY, COMP-3, COMP/BINARY) and JSON.

What it does

• Parse and validate copybook schema output from copybook-core.
• Decode fixed-length and variable-length (RDW) files into JSON records.
• Encode JSON back to binary COBOL layouts with strict or tolerant mode.
• Configure behavior through DecodeOptions / EncodeOptions.
• Handle common mainframe codepages (CP037, CP273, CP500, CP1047, CP1140, ASCII).

Quick start

use copybook_core::parse_copybook;
use copybook_codec::{decode_record, DecodeOptions, Codepage, JsonNumberMode};

let schema = parse_copybook("01 A.\n   05 AMOUNT PIC S9(7)V99 COMP-3.\n")?;
let options = DecodeOptions::new()
    .with_codepage(Codepage::CP037)
    .with_json_number_mode(JsonNumberMode::Lossless);

let json = decode_record(&schema, &vec![0x00; 4], &options)?;
println!("{json}");

Features

• Record streaming for large fixed-width files
• Deterministic conversions with controlled rounding/precision behavior
• Optional metrics and strict compatibility-policy checks
• Optional audit-related feature path for enterprise usage
• Edited PIC decode and encode support (E2/E3 phases)
• Field projection via project_schema() for selective field decoding
• Raw data capture modes (RawMode::Record, RawMode::Field, RawMode::RecordRDW)
• Scratch buffer optimization for hot-path performance (decode_record_with_scratch)

Scratch buffer example

use copybook_core::parse_copybook;
use copybook_codec::{decode_record_with_scratch, DecodeOptions, Codepage, JsonNumberMode};
use copybook_codec::memory::ScratchBuffers;

let schema = parse_copybook("01 A.\n   05 AMOUNT PIC S9(7)V99 COMP-3.\n")?;
let options = DecodeOptions::new()
    .with_codepage(Codepage::CP037)
    .with_json_number_mode(JsonNumberMode::Lossless);

let mut scratch = ScratchBuffers::new();
let json = decode_record_with_scratch(&schema, &record_data, &options, &mut scratch)?;

API docs

See docs.rs/copybook-codec.

License

Licensed under AGPL-3.0-or-later. See LICENSE.