GDSII Format

GDSII Stream Format is the industry-standard format for IC layout data. LayKit provides complete support for reading and writing GDSII files.

Overview

GDSII is a binary format with these characteristics:

• Binary encoding: Big-endian byte order
• Record-based structure: Each record has type, data type, and data
• Hierarchical organization: Libraries contain structures (cells)
• Custom floating point: 8-byte Real8 format
• File extension: .gds

Main Types

GDSIIFile

The root structure representing a complete GDSII file:

#![allow(unused)]
fn main() {
pub struct GDSIIFile {
    pub version: i16,
    pub library_name: String,
    pub units: (f64, f64),  // (user_unit, database_unit) in meters
    pub structures: Vec<GDSStructure>,
}
}

Key methods:

• new(library_name: String) -> Self - Create empty file
• read_from_file(path: &str) -> Result<Self, Box<dyn Error>> - Read from disk
• write_to_file(&self, path: &str) -> Result<(), Box<dyn Error>> - Write to disk

GDSStructure

Represents a cell/structure in the design:

#![allow(unused)]
fn main() {
pub struct GDSStructure {
    pub name: String,
    pub creation_time: GDSTime,
    pub modification_time: GDSTime,
    pub elements: Vec<GDSElement>,
}
}

GDSElement

An enum of all possible GDSII elements:

#![allow(unused)]
fn main() {
pub enum GDSElement {
    Boundary(Boundary),      // Polygons
    Path(GPath),             // Wires/traces
    Text(GText),             // Text labels
    StructRef(StructRef),    // Cell instances
    ArrayRef(ArrayRef),      // Cell arrays
    Node(Node),              // Net topology
    Box(GDSBox),             // Box elements
}
}

Supported Elements

Binary Format Details

Record Structure

[2 bytes: length] [1 byte: record type] [1 byte: data type] [n bytes: data]

Units

Units are stored as a pair of f64 values in meters:

• units.0 - User unit (typically 1e-6 for micrometers)
• units.1 - Database unit (typically 1e-9 for nanometers)

Coordinates

All coordinates are 32-bit signed integers (i32) in database units.

Next Steps

• Reading GDSII Files
• Writing GDSII Files
• GDSII Elements