You can think of a Photoshop file as a byte slice &[u8].

These bytes are organized into 5 major sections, each of which have their own sub-sections.

We represent this in our code using the MajorSections type.

# #![allow(unused_variables)]
#fn main() {
// Imported into the book from `src/sections/mod.rs`

pub mod image_data_section;
pub mod image_resources_section;
pub mod layer_and_mask_information_section;

/// References to the different major sections of a PSD file
#[derive(Debug)]
pub struct MajorSections<'a> {
    pub(crate) file_header: &'a [u8],
    pub(crate) color_mode_data: &'a [u8],
    pub(crate) image_resources: &'a [u8],
    pub(crate) layer_and_mask: &'a [u8],
    pub(crate) image_data: &'a [u8],
}

impl<'a> MajorSections<'a> {
    /// Given the bytes of a PSD file, return the slices that correspond to each
    /// of the five major sections.
    ///
    /// ┌──────────────────┐
    /// │   File Header    │
    /// ├──────────────────┤
    /// │ Color Mode Data  │
    /// ├──────────────────┤
    /// │ Image Resources  │
    /// ├──────────────────┤
#}

Our parsing comes down to reading through the bytes in this byte slice and using them to create these five major sections.