Files
crosspoint-reader-mod/lib/Xtc
Xuan-Son Nguyen 7f40c3f477 feat: add HalStorage (#656)
## Summary

Continue my changes to introduce the HAL infrastructure from
https://github.com/crosspoint-reader/crosspoint-reader/pull/522

This PR touches quite a lot of files, but most of them are just name
changing. It should not have any impacts to the end behavior.

## Additional Context

My plan is to firstly add this small shim layer, which sounds useless at
first, but then I'll implement an emulated driver which can be helpful
for testing and for development.

Currently, on my fork, I'm using a FS driver that allow "mounting" a
local directory from my computer to the device, much like the `-v` mount
option on docker. This allows me to quickly reset `.crosspoint`
directory if anything goes wrong. I plan to upstream this feature when
this PR get merged.

---

### AI Usage

While CrossPoint doesn't have restrictions on AI tools in contributing,
please be transparent about their usage as it
helps set the right context for reviewers.

Did you use AI tools to help write this code? NO
2026-02-09 07:29:14 +11:00
..
2026-02-09 07:29:14 +11:00
2026-02-09 07:29:14 +11:00
2026-02-05 21:50:11 +11:00

# XTC/XTCH Library

XTC ebook format support for CrossPoint Reader.

## Supported Formats

| Format | Extension | Description                                  |
|--------|-----------|----------------------------------------------|
| XTC    | `.xtc`    | Container with XTG pages (1-bit monochrome)  |
| XTCH   | `.xtch`   | Container with XTH pages (2-bit grayscale)   |

## Format Overview

XTC/XTCH are container formats designed for ESP32 e-paper displays. They store pre-rendered bitmap pages optimized for the XTeink X4 e-reader (480x800 resolution).

### Container Structure (XTC/XTCH)

- 56-byte header with metadata offsets
- Optional metadata (title, author, etc.)
- Page index table (16 bytes per page)
- Page data (XTG or XTH format)

### Page Formats

#### XTG (1-bit monochrome)

- Row-major storage, 8 pixels per byte
- MSB first (bit 7 = leftmost pixel)
- 0 = Black, 1 = White

#### XTH (2-bit grayscale)

- Two bit planes stored sequentially
- Column-major order (right to left)
- 8 vertical pixels per byte
- Grayscale: 0=White, 1=Dark Grey, 2=Light Grey, 3=Black

## Reference

Original format info: <https://gist.github.com/CrazyCoder/b125f26d6987c0620058249f59f1327d>