rumpy 0.1.1

A reimplementation of NumPy for use with rustpython in embedded interpreters
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246

//! Reader/writer for the numpy `.npz` format.
//!
//! `.npz` is a plain (or DEFLATEd) ZIP archive whose members are individual
//! `.npy` files. `np.savez` uses STORED (no compression); we do the same.
//! `np.load` on a `.npz` returns a lazy `NpzFile`; for embedded use we
//! return a `dict[str, ndarray]`.
//!
//! We implement just enough of the ZIP spec to round-trip with CPython:
//!
//! ```text
//!   per file:
//!     local file header     (30 bytes + filename)
//!     file data             (raw .npy bytes)
//!   end:
//!     central directory     (one entry per file, 46 bytes + filename each)
//!     end-of-central-directory record (22 bytes)
//! ```
//!
//! No compression, no encryption, no zip64, no extra fields.

use crate::dtype::ArraysD;
use crate::npy;
use std::fs::File;
use std::io::{BufWriter, Read, Write};
use std::path::Path;

const LFH_SIG: u32 = 0x04034b50;
const CDH_SIG: u32 = 0x02014b50;
const EOCD_SIG: u32 = 0x06054b50;

// =====================================================================
// Write
// =====================================================================

pub fn save(path: &Path, named: &[(String, ArraysD)]) -> std::io::Result<()> {
    let mut f = BufWriter::new(File::create(path)?);
    write_to(&mut f, named)?;
    f.flush()?;
    Ok(())
}

/// Write an .npz to any `Write + Seek`-like target by buffering into a Vec
/// internally (so we don't need Seek).
pub fn write_to<W: Write>(w: &mut W, named: &[(String, ArraysD)]) -> std::io::Result<()> {
    let mut offset: u32 = 0;
    let mut cd_entries: Vec<Vec<u8>> = Vec::with_capacity(named.len());

    for (name, arr) in named {
        let payload = npy::save_to_bytes(arr);
        let fname = format!("{name}.npy");
        let crc = crc32_ieee(&payload);
        let local_offset = offset;

        // Local file header
        let fname_bytes = fname.as_bytes();
        w.write_all(&LFH_SIG.to_le_bytes())?;
        w.write_all(&20u16.to_le_bytes())?; // version needed
        w.write_all(&0u16.to_le_bytes())?; // gp flag
        w.write_all(&0u16.to_le_bytes())?; // method = STORED
        w.write_all(&0u16.to_le_bytes())?; // mtime
        w.write_all(&0u16.to_le_bytes())?; // mdate
        w.write_all(&crc.to_le_bytes())?;
        w.write_all(&(payload.len() as u32).to_le_bytes())?; // compressed
        w.write_all(&(payload.len() as u32).to_le_bytes())?; // uncompressed
        w.write_all(&(fname_bytes.len() as u16).to_le_bytes())?;
        w.write_all(&0u16.to_le_bytes())?; // extra len
        w.write_all(fname_bytes)?;
        w.write_all(&payload)?;
        offset += 30 + fname_bytes.len() as u32 + payload.len() as u32;

        // Stash the corresponding central directory entry for the trailer.
        let mut cd = Vec::with_capacity(46 + fname_bytes.len());
        cd.extend_from_slice(&CDH_SIG.to_le_bytes());
        cd.extend_from_slice(&20u16.to_le_bytes()); // version made by
        cd.extend_from_slice(&20u16.to_le_bytes()); // version needed
        cd.extend_from_slice(&0u16.to_le_bytes()); // gp flag
        cd.extend_from_slice(&0u16.to_le_bytes()); // method
        cd.extend_from_slice(&0u16.to_le_bytes()); // mtime
        cd.extend_from_slice(&0u16.to_le_bytes()); // mdate
        cd.extend_from_slice(&crc.to_le_bytes());
        cd.extend_from_slice(&(payload.len() as u32).to_le_bytes());
        cd.extend_from_slice(&(payload.len() as u32).to_le_bytes());
        cd.extend_from_slice(&(fname_bytes.len() as u16).to_le_bytes());
        cd.extend_from_slice(&0u16.to_le_bytes()); // extra len
        cd.extend_from_slice(&0u16.to_le_bytes()); // comment len
        cd.extend_from_slice(&0u16.to_le_bytes()); // disk #
        cd.extend_from_slice(&0u16.to_le_bytes()); // internal attrs
        cd.extend_from_slice(&0u32.to_le_bytes()); // external attrs
        cd.extend_from_slice(&local_offset.to_le_bytes());
        cd.extend_from_slice(fname_bytes);
        cd_entries.push(cd);
    }

    let cd_offset = offset;
    let mut cd_size: u32 = 0;
    for entry in &cd_entries {
        w.write_all(entry)?;
        cd_size += entry.len() as u32;
    }

    // End of central directory record.
    w.write_all(&EOCD_SIG.to_le_bytes())?;
    w.write_all(&0u16.to_le_bytes())?; // disk #
    w.write_all(&0u16.to_le_bytes())?; // disk start
    w.write_all(&(cd_entries.len() as u16).to_le_bytes())?;
    w.write_all(&(cd_entries.len() as u16).to_le_bytes())?;
    w.write_all(&cd_size.to_le_bytes())?;
    w.write_all(&cd_offset.to_le_bytes())?;
    w.write_all(&0u16.to_le_bytes())?; // comment length

    Ok(())
}

// =====================================================================
// Read
// =====================================================================

#[derive(Debug)]
pub enum NpzError {
    Io(std::io::Error),
    Format(String),
    Compression,
}

impl From<std::io::Error> for NpzError {
    fn from(e: std::io::Error) -> Self {
        NpzError::Io(e)
    }
}

impl std::fmt::Display for NpzError {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        match self {
            NpzError::Io(e) => write!(f, "io: {e}"),
            NpzError::Format(s) => write!(f, "format: {s}"),
            NpzError::Compression => write!(f, "compressed .npz not supported"),
        }
    }
}

pub fn load(path: &Path) -> Result<Vec<(String, ArraysD)>, NpzError> {
    let mut data = Vec::new();
    File::open(path)?.read_to_end(&mut data)?;
    read_from(&data)
}

pub fn read_from(data: &[u8]) -> Result<Vec<(String, ArraysD)>, NpzError> {
    let eocd = find_eocd(data)
        .ok_or_else(|| NpzError::Format("no end-of-central-directory".to_string()))?;
    let entries = u16::from_le_bytes([data[eocd + 10], data[eocd + 11]]) as usize;
    let cd_offset = u32::from_le_bytes([
        data[eocd + 16],
        data[eocd + 17],
        data[eocd + 18],
        data[eocd + 19],
    ]) as usize;
    let mut out = Vec::with_capacity(entries);

    let mut p = cd_offset;
    for _ in 0..entries {
        if data[p..p + 4] != CDH_SIG.to_le_bytes() {
            return Err(NpzError::Format("bad central directory header".to_string()));
        }
        let method = u16::from_le_bytes([data[p + 10], data[p + 11]]);
        if method != 0 {
            return Err(NpzError::Compression);
        }
        let comp_size =
            u32::from_le_bytes([data[p + 20], data[p + 21], data[p + 22], data[p + 23]]) as usize;
        let name_len = u16::from_le_bytes([data[p + 28], data[p + 29]]) as usize;
        let extra_len = u16::from_le_bytes([data[p + 30], data[p + 31]]) as usize;
        let comment_len = u16::from_le_bytes([data[p + 32], data[p + 33]]) as usize;
        let local_offset = u32::from_le_bytes([
            data[p + 42],
            data[p + 43],
            data[p + 44],
            data[p + 45],
        ]) as usize;
        let name = std::str::from_utf8(&data[p + 46..p + 46 + name_len])
            .map_err(|_| NpzError::Format("non-utf8 name".to_string()))?
            .to_owned();
        p += 46 + name_len + extra_len + comment_len;

        // Local file header: 30 bytes + filename + extra (skip), then data.
        if data[local_offset..local_offset + 4] != LFH_SIG.to_le_bytes() {
            return Err(NpzError::Format("bad local file header".to_string()));
        }
        let l_name_len = u16::from_le_bytes([data[local_offset + 26], data[local_offset + 27]]) as usize;
        let l_extra_len =
            u16::from_le_bytes([data[local_offset + 28], data[local_offset + 29]]) as usize;
        let data_start = local_offset + 30 + l_name_len + l_extra_len;
        let blob = &data[data_start..data_start + comp_size];

        let arr = crate::npy::load_from_bytes(blob)
            .map_err(|e| NpzError::Format(format!("inner .npy: {e}")))?;

        let stripped = name.trim_end_matches(".npy").to_owned();
        out.push((stripped, arr));
    }

    Ok(out)
}

fn find_eocd(data: &[u8]) -> Option<usize> {
    // EOCD is at least 22 bytes; comment can extend it. Scan backwards.
    if data.len() < 22 {
        return None;
    }
    let max = data.len();
    let start = max.saturating_sub(22 + 0xFFFF);
    for i in (start..=max - 22).rev() {
        if data[i..i + 4] == EOCD_SIG.to_le_bytes() {
            return Some(i);
        }
    }
    None
}

// =====================================================================
// CRC-32 (IEEE polynomial 0xedb88320)
// =====================================================================

fn crc32_ieee(buf: &[u8]) -> u32 {
    static TABLE: std::sync::OnceLock<[u32; 256]> = std::sync::OnceLock::new();
    let table = TABLE.get_or_init(|| {
        let mut t = [0u32; 256];
        for n in 0..256u32 {
            let mut c = n;
            for _ in 0..8 {
                c = if c & 1 == 1 {
                    0xedb88320 ^ (c >> 1)
                } else {
                    c >> 1
                };
            }
            t[n as usize] = c;
        }
        t
    });
    let mut crc = 0xFFFFFFFFu32;
    for &b in buf {
        let idx = ((crc ^ b as u32) & 0xFF) as usize;
        crc = table[idx] ^ (crc >> 8);
    }
    crc ^ 0xFFFFFFFF
}