Module ipc_codec 

Low-level helpers for encoding/decoding IpcMessage payloads.

Overview

IPC messages carry a fixed 240-byte payload. This module provides safe, bounds-checked helpers to pack and unpack structured data into that payload without external allocators or serde.

Layers

1. Scalar helpers : put_u16/get_u16, put_u32/get_u32, put_u64/get_u64.
2. Variable-length helpers : put_bytes/get_bytes, put_str/get_str.
3. Fixed-size helpers : encode_fixed/decode_fixed for repr(C) zerocopy structs.
4. InlineBlobHeader : minimal framing for inline variable-length data.

All helpers are bounds-checked: they return Option instead of panicking.

Payload layout conventions

• Fixed messages: the entire payload[0..48] (or a prefix) is a repr(C) struct. Use encode_fixed/decode_fixed.
• Variable messages: the fixed-size part goes first (e.g. flags + u64s), followed by an InlineBlobHeader (4 bytes) and the inline data. Use the put/get helpers for the fixed part, then InlineBlobHeader::write for the variable tail.

Safety

All functions are pure safe-Rust: no unsafe required at this layer. The zerocopy traits used by payload structs are derived safely.

Examples

Fixed-size message

use strat9_abi::data::IpcMessage;
use strat9_abi::ipc_codec::{encode_fixed, decode_fixed};

// Encode a struct into a message
#[derive(FromBytes, IntoBytes)]
#[repr(C)]
struct OpenReq { flags: u32, mode: u32 }

let msg = encode_fixed(0x01, &OpenReq { flags: 0x02, mode: 0o644 });

// Decode it back
let req: &OpenReq = decode_fixed(&msg).unwrap();
assert_eq!(req.flags, 0x02);

Variable-length message

use strat9_abi::ipc_codec::{put_u32, InlineBlobHeader};

let mut msg = IpcMessage::new(0x03);
put_u32(&mut msg.payload, 0, 0o755).unwrap(); // mode
InlineBlobHeader::write(&mut msg.payload, 4, 0, b"/dev/null").unwrap();

Structs

InlineBlobHeader

Minimal framing header for variable-length data embedded in an IPC payload.

Constants

PAYLOAD_CAPACITY

Capacity of the IpcMessage.payload field (240 bytes).

Functions

decode_fixed

Try to decode a fixed-size repr(C) struct from an IpcMessage payload.

encode_fixed

Encode a fixed-size repr(C) struct as an IpcMessage.

encode_fixed_reply

Encode a fixed-size reply targeting sender.

get_bytes

Return a reference to payload[off..off + len].

get_i32

Read an i32 at offset off (little-endian), or None if out of bounds.

get_str

Decode a UTF-8 string of len bytes from payload[off..].

get_u16

Read a u16 at offset off (little-endian), or None if out of bounds.

get_u32

Read a u32 at offset off (little-endian), or None if out of bounds.

get_u64

Read a u64 at offset off (little-endian), or None if out of bounds.

put_bytes

Copy src into payload[off..off + src.len()].

put_i32

Write an i32 at offset off (little-endian).

put_str

Encode a UTF-8 string into payload[off..].

put_u16

Write a u16 at offset off (little-endian).

put_u32

Write a u32 at offset off (little-endian).

put_u64

Write a u64 at offset off (little-endian).