libsqsh

squashfs is an open and free compressed read-only filesystem. It is used in embedded devices, live-CDs, or in packaging. The original implementation resides in the linux kernel, but there are also userspace implementations.

libsqsh is a purely 2-Clause BSD Licensed implementation of the squashfs filesystem in C11. It covers the complete squashfs feature set, while still being as minimal as possible.

libsqsh consists of a C library and a command line tools to interact with squashfs archives.

Note that libsqsh only supports reading squashfs archives. If you want to create squashfs archives, you can either use squashfs-tools, which provides a command line interface, or squashfs-tools-ng, which provides both a command-line interface and a C library interface.

Features

Complete feature set: libsqsh supports all features of the squashfs file system.
Modern C11 implementation: Written in modern C11, libsqsh is designed for efficiency and compatibility with C++, C, and other languages.
High-Level API: The high-level API provides easy-to-use functions to access the contents of a to the contents of a squashfs archive. It is designed to be easy to use and fast to develop with.
Low-Level API: The low-level API provides zero-copy interfaces to the squashfs archive. It is designed to be both memory and CPU efficient.
Pure 2-Clause-BSD License: libsqsh is licensed under the 2-Clause BSD license. This allows you to use libsqsh in any project, even commercial ones.

Example

This is a simple example that a) prints the content of a file and b) lists the content of a directory.

struct SqshArchive *archive =
		sqsh_archive_open("/path/to/archive.squashfs", NULL, NULL);

uint8_t *contents = sqsh_easy_file_content(archive, "/path/to/file", NULL);
assert(contents != NULL);
const size_t size = sqsh_easy_file_size(archive, "/path/to/file", NULL);
fwrite(contents, 1, size, stdout);
free(contents);

char **files = sqsh_easy_directory_list(archive, "/path/to/dir", NULL);
assert(files != NULL);
for (int i = 0; files[i] != NULL; i++) {
	puts(files[i]);
}
free(files);

sqsh_archive_close(archive);

Find further examples in the examples directory.

Building

Dependencies

libc: both musl and glibc are supported.
zlib optional: For gzip compression support.
liblz4 optional: For lz4 compression support.
liblzma optional: For lzma compression support.
libzstd optional: For zstd compression support.
fuse3 optional: For mounting squashfs archives.
fuse2 optional: For mounting squashfs archives on systems that don't support fuse3. e.g. OpenBSD.
libcurl optional: For transparently reading squashfs archives from the internet without downloading them first.

Note that to do anything useful with libsqsh, you need to have at least one of the compression libraries enabled.

Compile & Install

meson setup build
cd build
meson compile
meson install

LZO2

LZO2 is a fast compression algorithm. Unfortunately the current implementation is GPL licensed and therefore not included in this library. If you want to use LZO2 there's and independent glue library called libsqsh-lzo.

Resource

https://dr-emann.github.io/squashfs/squashfs.html - A detailed description of the squashfs file format.
https://github.com/plougher/squashfs-tools/ - The original squashfs-tools implementation.
https://github.com/AgentD/squashfs-tools-ng/ - A rewrite of the squashfs-tools implementation with library support. In contrast to libsqsh, this library is able to write squashfs archives.

Dr-Emann / libsqsh