ppmd_rust/
lib.rs

1//! PPMd compression / decompression. It's a port of the PPMd C-code from 7-Zip to Rust.
2//!
3//! The following variants are provided:
4//!
5//! - The PPMd7 (PPMdH) as used by the 7z archive format
6//! - The PPMd8 (PPMdI rev.1) as used by the zip archive format
7//!
8//! ## Notice
9//!
10//! There are two ways to properly bound the uncompressed data:
11//! 1. Save the uncompressed size along the compressed data and use `std::io::Read::read_exact()`
12//!    to read the data (this is what is used in the 7z archive format).
13//! 2. Encode an end marker by calling `finish(true)` on the encoder when finishing the encoder
14//!    process. You can then use `std::io::Read::read_to_end()` to read the data. You are of course
15//!    free to also use the `std::io::Read::read_exact()` if you have stored the uncompressed data
16//!    size (this is what is used in the zip archive format).
17//!
18//! Failing to do so will result in garbage symbols at the end of the actual data.
19//!
20//! ## Acknowledgement
21//!
22//! This port is based on the 7zip version of PPMd by Igor Pavlov, which in turn was based on the
23//! PPMd var.H (2001) / PPMd var.I (2002) code by Dmitry Shkarin. The carryless range coder of
24//! PPMd8 was originally written by Dmitry Subbotin (1999).
25//!
26//! ## License
27//!
28//! The code in this crate is in the public domain as the original code by their authors.
29
30mod internal;
31
32mod decoder_7;
33mod decoder_8;
34mod encoder_7;
35mod encoder_8;
36
37pub use decoder_7::Ppmd7Decoder;
38pub use decoder_8::Ppmd8Decoder;
39pub use encoder_7::Ppmd7Encoder;
40pub use encoder_8::Ppmd8Encoder;
41
42/// The minimal order PPMd7 supports.
43pub const PPMD7_MIN_ORDER: u32 = 2;
44
45/// The maximal order PPMd7 supports.
46pub const PPMD7_MAX_ORDER: u32 = 64;
47
48/// The minimal memory that PPMd7 supports.
49pub const PPMD7_MIN_MEM_SIZE: u32 = 2048;
50
51#[cfg(feature = "unstable-tagged-offsets")]
52/// The maximal memory that PPMd7 supports (512 MiB).
53pub const PPMD7_MAX_MEM_SIZE: u32 = 1 << 29;
54#[cfg(not(feature = "unstable-tagged-offsets"))]
55/// The maximal memory that PPMd7 supports (~4 GiB).
56pub const PPMD7_MAX_MEM_SIZE: u32 = u32::MAX - 36;
57
58/// The minimal order PPMd8 supports.
59pub const PPMD8_MIN_ORDER: u32 = 2;
60
61/// The maximal order PPMd8 supports.
62pub const PPMD8_MAX_ORDER: u32 = 16;
63
64/// The minimal memory that PPMd8 supports.
65pub const PPMD8_MIN_MEM_SIZE: u32 = 2048;
66
67#[cfg(feature = "unstable-tagged-offsets")]
68/// The maximal memory that PPMd8 supports (512 MiB).
69pub const PPMD8_MAX_MEM_SIZE: u32 = 1 << 29;
70#[cfg(not(feature = "unstable-tagged-offsets"))]
71/// The maximal memory that PPMd8 supports (4 GiB).
72pub const PPMD8_MAX_MEM_SIZE: u32 = u32::MAX;
73
74const SYM_END: i32 = -1;
75const SYM_ERROR: i32 = -2;
76
77/// Error type of the crate.
78pub type Result<T> = core::result::Result<T, Error>;
79
80/// The restore method used in PPMd8.
81#[derive(Debug, Copy, Clone, Ord, PartialOrd, Eq, PartialEq, Hash)]
82pub enum RestoreMethod {
83    Restart = 0 as _,
84    CutOff = 1 as _,
85    Unsupported = 2 as _,
86}
87
88macro_rules! impl_from_int_for_restore_method {
89    ($($int_type:ty),+ $(,)?) => {
90        $(
91            impl From<$int_type> for RestoreMethod {
92                fn from(value: $int_type) -> Self {
93                    match value {
94                        0 => RestoreMethod::Restart,
95                        1 => RestoreMethod::CutOff,
96                        _ => RestoreMethod::Unsupported,
97                    }
98                }
99            }
100        )+
101    };
102}
103
104impl_from_int_for_restore_method!(u8, u16, u32, u64, u128, usize);
105impl_from_int_for_restore_method!(i8, i16, i32, i64, i128, isize);
106
107/// Crate error type.
108pub enum Error {
109    /// The range decoder could not be properly initialized.
110    RangeDecoderInitialization,
111    /// Invalid parameters provided.
112    InvalidParameter,
113    /// General IO error.
114    IoError(std::io::Error),
115    /// The needed memory could not be allocated.
116    MemoryAllocation,
117}
118
119impl std::fmt::Debug for Error {
120    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
121        match self {
122            Error::RangeDecoderInitialization => {
123                write!(f, "Could not initialize the range decoder")
124            }
125            Error::InvalidParameter => write!(f, "Wrong PPMd parameter"),
126            Error::IoError(err) => write!(f, "Io error: {err}"),
127            Error::MemoryAllocation => write!(f, "Memory allocation error (out of memory?)"),
128        }
129    }
130}
131
132impl std::fmt::Display for Error {
133    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
134        std::fmt::Debug::fmt(self, f)
135    }
136}
137
138impl std::error::Error for Error {}
ppmd_rust/lib.rs

ppmd_rust/
lib.rs
