grib_reader/
lib.rs

1//! Pure-Rust GRIB file reader.
2//!
3//! The current implementation supports the production-critical baseline for both
4//! GRIB1 and GRIB2: regular latitude/longitude grids with simple packing.
5//!
6//! # Example
7//!
8//! ```no_run
9//! use grib_reader::GribFile;
10//!
11//! let file = GribFile::open("gfs.grib2")?;
12//! println!("messages: {}", file.message_count());
13//!
14//! for msg in file.messages() {
15//!     println!(
16//!         "  {} {:?} {:04}-{:02}-{:02}T{:02}:{:02}:{:02}Z",
17//!         msg.parameter_name(),
18//!         msg.grid_shape(),
19//!         msg.reference_time().year,
20//!         msg.reference_time().month,
21//!         msg.reference_time().day,
22//!         msg.reference_time().hour,
23//!         msg.reference_time().minute,
24//!         msg.reference_time().second,
25//!     );
26//! }
27//!
28//! let data = file.message(0)?.read_data_as_f64()?;
29//! println!("shape: {:?}", data.shape());
30//! # Ok::<(), grib_reader::Error>(())
31//! ```
32
33pub mod data;
34pub mod error;
35pub mod grib1;
36pub mod grid;
37pub mod indicator;
38pub mod metadata;
39pub mod parameter;
40pub mod product;
41pub mod sections;
42mod util;
43
44pub use error::{Error, Result};
45pub use metadata::{Parameter, ReferenceTime};
46pub use product::{FixedSurface, Identification, ProductDefinition};
47
48use std::path::Path;
49
50use memmap2::Mmap;
51use ndarray::{ArrayD, IxDyn};
52
53use crate::data::{bitmap_payload as grib2_bitmap_payload, decode_field, DataRepresentation};
54use crate::grib1::{BinaryDataSection, GridDescription};
55use crate::grid::GridDefinition;
56use crate::indicator::Indicator;
57use crate::sections::{index_fields, FieldSections, SectionRef};
58
59#[cfg(feature = "rayon")]
60use rayon::prelude::*;
61
62const GRIB_MAGIC: &[u8; 4] = b"GRIB";
63
64/// Configuration for opening GRIB data.
65#[derive(Debug, Clone, Copy)]
66pub struct OpenOptions {
67    /// When `true`, the first malformed GRIB candidate aborts opening.
68    ///
69    /// When `false`, malformed candidates are skipped and scanning continues.
70    pub strict: bool,
71}
72
73impl Default for OpenOptions {
74    fn default() -> Self {
75        Self { strict: true }
76    }
77}
78
79/// A parsed GRIB field.
80#[derive(Debug, Clone)]
81pub struct MessageMetadata {
82    pub edition: u8,
83    pub center_id: u16,
84    pub subcenter_id: u16,
85    pub discipline: Option<u8>,
86    pub reference_time: ReferenceTime,
87    pub parameter: Parameter,
88    pub grid: GridDefinition,
89    pub data_representation: DataRepresentation,
90    pub forecast_time_unit: Option<u8>,
91    pub forecast_time: Option<u32>,
92    pub message_offset: u64,
93    pub message_length: u64,
94    pub field_index_in_message: usize,
95    grib1_product: Option<grib1::ProductDefinition>,
96    grib2_identification: Option<Identification>,
97    grib2_product: Option<ProductDefinition>,
98}
99
100/// A GRIB file containing one or more logical fields.
101pub struct GribFile {
102    data: GribData,
103    messages: Vec<MessageIndex>,
104}
105
106#[derive(Clone)]
107struct MessageIndex {
108    offset: usize,
109    length: usize,
110    metadata: MessageMetadata,
111    decode_plan: DecodePlan,
112}
113
114#[derive(Clone, Copy)]
115enum DecodePlan {
116    Grib1 {
117        bitmap: Option<SectionRef>,
118        data: SectionRef,
119    },
120    Grib2(FieldSections),
121}
122
123enum GribData {
124    Mmap(Mmap),
125    Bytes(Vec<u8>),
126}
127
128impl GribData {
129    fn as_bytes(&self) -> &[u8] {
130        match self {
131            GribData::Mmap(m) => m,
132            GribData::Bytes(b) => b,
133        }
134    }
135}
136
137impl GribFile {
138    /// Open a GRIB file from disk using memory-mapped I/O.
139    pub fn open<P: AsRef<Path>>(path: P) -> Result<Self> {
140        Self::open_with_options(path, OpenOptions::default())
141    }
142
143    /// Open a GRIB file from disk using explicit decoder options.
144    pub fn open_with_options<P: AsRef<Path>>(path: P, options: OpenOptions) -> Result<Self> {
145        let file = std::fs::File::open(path.as_ref())
146            .map_err(|e| Error::Io(e, path.as_ref().display().to_string()))?;
147        let mmap = unsafe { Mmap::map(&file) }
148            .map_err(|e| Error::Io(e, path.as_ref().display().to_string()))?;
149        Self::from_data(GribData::Mmap(mmap), options)
150    }
151
152    /// Open a GRIB file from an owned byte buffer.
153    pub fn from_bytes(data: Vec<u8>) -> Result<Self> {
154        Self::from_bytes_with_options(data, OpenOptions::default())
155    }
156
157    /// Open a GRIB file from an owned byte buffer using explicit decoder options.
158    pub fn from_bytes_with_options(data: Vec<u8>, options: OpenOptions) -> Result<Self> {
159        Self::from_data(GribData::Bytes(data), options)
160    }
161
162    fn from_data(data: GribData, options: OpenOptions) -> Result<Self> {
163        let messages = scan_messages(data.as_bytes(), options)?;
164        if messages.is_empty() {
165            return Err(Error::NoMessages);
166        }
167        Ok(Self { data, messages })
168    }
169
170    /// Returns the GRIB edition of the first field.
171    pub fn edition(&self) -> u8 {
172        self.messages
173            .first()
174            .map(|message| message.metadata.edition)
175            .unwrap_or(0)
176    }
177
178    /// Returns the number of logical fields in the file.
179    pub fn message_count(&self) -> usize {
180        self.messages.len()
181    }
182
183    /// Access a field by index.
184    pub fn message(&self, index: usize) -> Result<Message<'_>> {
185        let record = self
186            .messages
187            .get(index)
188            .ok_or(Error::MessageNotFound(index))?;
189        let bytes = &self.data.as_bytes()[record.offset..record.offset + record.length];
190        Ok(Message {
191            index,
192            bytes,
193            metadata: &record.metadata,
194            decode_plan: record.decode_plan,
195        })
196    }
197
198    /// Iterate over all fields.
199    pub fn messages(&self) -> MessageIter<'_> {
200        MessageIter {
201            file: self,
202            index: 0,
203        }
204    }
205
206    /// Decode every field in the file.
207    pub fn read_all_data_as_f64(&self) -> Result<Vec<ArrayD<f64>>> {
208        #[cfg(feature = "rayon")]
209        {
210            (0..self.message_count())
211                .into_par_iter()
212                .map(|index| self.message(index)?.read_data_as_f64())
213                .collect()
214        }
215        #[cfg(not(feature = "rayon"))]
216        {
217            (0..self.message_count())
218                .map(|index| self.message(index)?.read_data_as_f64())
219                .collect()
220        }
221    }
222}
223
224/// A single logical GRIB field.
225pub struct Message<'a> {
226    bytes: &'a [u8],
227    metadata: &'a MessageMetadata,
228    decode_plan: DecodePlan,
229    index: usize,
230}
231
232impl<'a> Message<'a> {
233    pub fn edition(&self) -> u8 {
234        self.metadata.edition
235    }
236
237    pub fn index(&self) -> usize {
238        self.index
239    }
240
241    pub fn metadata(&self) -> &MessageMetadata {
242        self.metadata
243    }
244
245    pub fn reference_time(&self) -> &ReferenceTime {
246        &self.metadata.reference_time
247    }
248
249    pub fn parameter(&self) -> &Parameter {
250        &self.metadata.parameter
251    }
252
253    pub fn center_id(&self) -> u16 {
254        self.metadata.center_id
255    }
256
257    pub fn subcenter_id(&self) -> u16 {
258        self.metadata.subcenter_id
259    }
260
261    pub fn identification(&self) -> Option<&Identification> {
262        self.metadata.grib2_identification.as_ref()
263    }
264
265    pub fn product_definition(&self) -> Option<&ProductDefinition> {
266        self.metadata.grib2_product.as_ref()
267    }
268
269    pub fn grib1_product_definition(&self) -> Option<&grib1::ProductDefinition> {
270        self.metadata.grib1_product.as_ref()
271    }
272
273    pub fn grid_definition(&self) -> &GridDefinition {
274        &self.metadata.grid
275    }
276
277    pub fn parameter_name(&self) -> &'static str {
278        self.metadata.parameter.short_name
279    }
280
281    pub fn parameter_description(&self) -> &'static str {
282        self.metadata.parameter.description
283    }
284
285    pub fn grid_shape(&self) -> (usize, usize) {
286        self.metadata.grid.shape()
287    }
288
289    pub fn latitudes(&self) -> Option<Vec<f64>> {
290        match &self.metadata.grid {
291            GridDefinition::LatLon(grid) => Some(grid.latitudes()),
292            GridDefinition::Unsupported(_) => None,
293        }
294    }
295
296    pub fn longitudes(&self) -> Option<Vec<f64>> {
297        match &self.metadata.grid {
298            GridDefinition::LatLon(grid) => Some(grid.longitudes()),
299            GridDefinition::Unsupported(_) => None,
300        }
301    }
302
303    pub fn read_data_as_f64(&self) -> Result<ArrayD<f64>> {
304        let grid = match &self.metadata.grid {
305            GridDefinition::LatLon(grid) => grid,
306            GridDefinition::Unsupported(template) => {
307                return Err(Error::UnsupportedGridTemplate(*template));
308            }
309        };
310
311        let decoded = match self.decode_plan {
312            DecodePlan::Grib2(field) => {
313                let data_section = section_bytes(self.bytes, field.data);
314                let bitmap_section = match field.bitmap {
315                    Some(section) => grib2_bitmap_payload(section_bytes(self.bytes, section))?,
316                    None => None,
317                };
318                decode_field(
319                    data_section,
320                    &self.metadata.data_representation,
321                    bitmap_section,
322                    self.metadata.grid.num_points(),
323                )?
324            }
325            DecodePlan::Grib1 { bitmap, data } => {
326                let bitmap_section = match bitmap {
327                    Some(section) => grib1::bitmap_payload(section_bytes(self.bytes, section))?,
328                    None => None,
329                };
330                let data_section = section_bytes(self.bytes, data);
331                if data_section.len() < 11 {
332                    return Err(Error::InvalidSection {
333                        section: 4,
334                        reason: format!("expected at least 11 bytes, got {}", data_section.len()),
335                    });
336                }
337                grib1::decode_simple_field(
338                    &data_section[11..],
339                    &self.metadata.data_representation,
340                    bitmap_section,
341                    self.metadata.grid.num_points(),
342                )?
343            }
344        };
345
346        let ordered = grid.reorder_for_ndarray(decoded)?;
347        ArrayD::from_shape_vec(IxDyn(&self.metadata.grid.ndarray_shape()), ordered)
348            .map_err(|e| Error::Other(format!("failed to build ndarray from decoded field: {e}")))
349    }
350
351    pub fn raw_bytes(&self) -> &[u8] {
352        self.bytes
353    }
354}
355
356/// Iterator over fields in a GRIB file.
357pub struct MessageIter<'a> {
358    file: &'a GribFile,
359    index: usize,
360}
361
362impl<'a> Iterator for MessageIter<'a> {
363    type Item = Message<'a>;
364
365    fn next(&mut self) -> Option<Self::Item> {
366        if self.index >= self.file.message_count() {
367            return None;
368        }
369        let message = self.file.message(self.index).ok()?;
370        self.index += 1;
371        Some(message)
372    }
373}
374
375fn section_bytes(msg_bytes: &[u8], section: SectionRef) -> &[u8] {
376    &msg_bytes[section.offset..section.offset + section.length]
377}
378
379fn scan_messages(data: &[u8], options: OpenOptions) -> Result<Vec<MessageIndex>> {
380    let mut messages = Vec::new();
381    let mut pos = 0usize;
382
383    while pos + 8 <= data.len() {
384        if &data[pos..pos + 4] != GRIB_MAGIC {
385            pos += 1;
386            continue;
387        }
388
389        match try_index_message(data, pos) {
390            Ok((indexed, next_pos)) => {
391                messages.extend(indexed);
392                pos = next_pos;
393            }
394            Err(err) if !options.strict => {
395                pos += 4;
396                let _ = err;
397            }
398            Err(err) => return Err(err),
399        }
400    }
401
402    Ok(messages)
403}
404
405fn try_index_message(data: &[u8], pos: usize) -> Result<(Vec<MessageIndex>, usize)> {
406    let indicator = Indicator::parse(&data[pos..]).ok_or_else(|| {
407        Error::InvalidMessage(format!("failed to parse indicator at byte offset {pos}"))
408    })?;
409    let length = indicator.total_length as usize;
410    if length < 12 {
411        return Err(Error::InvalidMessage(format!(
412            "message at byte offset {pos} reports impossible length {length}"
413        )));
414    }
415    let end = pos
416        .checked_add(length)
417        .ok_or_else(|| Error::InvalidMessage("message length overflow".into()))?;
418    if end > data.len() {
419        return Err(Error::Truncated { offset: end as u64 });
420    }
421    if &data[end - 4..end] != b"7777" {
422        return Err(Error::InvalidMessage(format!(
423            "message at byte offset {pos} does not end with 7777"
424        )));
425    }
426
427    let message_bytes = &data[pos..end];
428    let indexed = match indicator.edition {
429        1 => index_grib1_message(message_bytes, pos)?,
430        2 => index_grib2_message(message_bytes, pos, &indicator)?,
431        other => return Err(Error::UnsupportedEdition(other)),
432    };
433
434    Ok((indexed, end))
435}
436
437fn index_grib1_message(message_bytes: &[u8], offset: usize) -> Result<Vec<MessageIndex>> {
438    let sections = grib1::parse_message_sections(message_bytes)?;
439    let grid_ref = sections.grid.ok_or_else(|| {
440        Error::InvalidSectionOrder(
441            "GRIB1 decoding requires an explicit grid definition section".into(),
442        )
443    })?;
444    let grid_description = GridDescription::parse(section_bytes(message_bytes, grid_ref))?;
445    let grid = grid_description.grid;
446
447    let bitmap_present_count = match sections.bitmap {
448        Some(bitmap) => count_bitmap_present_points(
449            grib1::bitmap_payload(section_bytes(message_bytes, bitmap))?,
450            grid.num_points(),
451        )?,
452        None => grid.num_points(),
453    };
454
455    let (_bds, data_representation) = BinaryDataSection::parse(
456        section_bytes(message_bytes, sections.data),
457        sections.product.decimal_scale,
458        bitmap_present_count,
459    )?;
460    let parameter = sections.product.parameter();
461
462    Ok(vec![MessageIndex {
463        offset,
464        length: message_bytes.len(),
465        decode_plan: DecodePlan::Grib1 {
466            bitmap: sections.bitmap,
467            data: sections.data,
468        },
469        metadata: MessageMetadata {
470            edition: 1,
471            center_id: sections.product.center_id as u16,
472            subcenter_id: sections.product.subcenter_id as u16,
473            discipline: None,
474            reference_time: sections.product.reference_time,
475            parameter,
476            grid,
477            data_representation,
478            forecast_time_unit: Some(sections.product.forecast_time_unit),
479            forecast_time: sections.product.forecast_time(),
480            message_offset: offset as u64,
481            message_length: message_bytes.len() as u64,
482            field_index_in_message: 0,
483            grib1_product: Some(sections.product),
484            grib2_identification: None,
485            grib2_product: None,
486        },
487    }])
488}
489
490fn index_grib2_message(
491    message_bytes: &[u8],
492    offset: usize,
493    indicator: &Indicator,
494) -> Result<Vec<MessageIndex>> {
495    let fields = index_fields(message_bytes)?;
496    let mut messages = Vec::with_capacity(fields.len());
497
498    for (field_index_in_message, field_sections) in fields.into_iter().enumerate() {
499        let identification =
500            Identification::parse(section_bytes(message_bytes, field_sections.identification))?;
501        let grid = GridDefinition::parse(section_bytes(message_bytes, field_sections.grid))?;
502        let product =
503            ProductDefinition::parse(section_bytes(message_bytes, field_sections.product))?;
504        let data_representation = DataRepresentation::parse(section_bytes(
505            message_bytes,
506            field_sections.data_representation,
507        ))?;
508        let parameter = Parameter::new_grib2(
509            indicator.discipline,
510            product.parameter_category,
511            product.parameter_number,
512            product.parameter_name(indicator.discipline),
513            product.parameter_description(indicator.discipline),
514        );
515
516        messages.push(MessageIndex {
517            offset,
518            length: message_bytes.len(),
519            decode_plan: DecodePlan::Grib2(field_sections),
520            metadata: MessageMetadata {
521                edition: indicator.edition,
522                center_id: identification.center_id,
523                subcenter_id: identification.subcenter_id,
524                discipline: Some(indicator.discipline),
525                reference_time: ReferenceTime {
526                    year: identification.reference_year,
527                    month: identification.reference_month,
528                    day: identification.reference_day,
529                    hour: identification.reference_hour,
530                    minute: identification.reference_minute,
531                    second: identification.reference_second,
532                },
533                parameter,
534                grid,
535                data_representation,
536                forecast_time_unit: product.forecast_time_unit,
537                forecast_time: product.forecast_time,
538                message_offset: offset as u64,
539                message_length: message_bytes.len() as u64,
540                field_index_in_message,
541                grib1_product: None,
542                grib2_identification: Some(identification),
543                grib2_product: Some(product),
544            },
545        });
546    }
547
548    Ok(messages)
549}
550
551fn count_bitmap_present_points(bitmap: Option<&[u8]>, num_grid_points: usize) -> Result<usize> {
552    let Some(payload) = bitmap else {
553        return Ok(0);
554    };
555
556    let mut present = 0usize;
557    for bit_index in 0..num_grid_points {
558        let byte = payload
559            .get(bit_index / 8)
560            .copied()
561            .ok_or(Error::MissingBitmap)?;
562        if ((byte >> (7 - (bit_index % 8))) & 1) != 0 {
563            present += 1;
564        }
565    }
566
567    Ok(present)
568}
569
570#[cfg(test)]
571mod tests {
572    use super::*;
573
574    fn grib_i32_bytes(value: i32) -> [u8; 4] {
575        if value >= 0 {
576            (value as u32).to_be_bytes()
577        } else {
578            ((-value) as u32 | 0x8000_0000).to_be_bytes()
579        }
580    }
581
582    fn build_indicator(total_len: usize, discipline: u8) -> Vec<u8> {
583        let mut indicator = Vec::with_capacity(16);
584        indicator.extend_from_slice(b"GRIB");
585        indicator.extend_from_slice(&[0, 0]);
586        indicator.push(discipline);
587        indicator.push(2);
588        indicator.extend_from_slice(&(total_len as u64).to_be_bytes());
589        indicator
590    }
591
592    fn build_identification() -> Vec<u8> {
593        let mut section = vec![0u8; 21];
594        section[..4].copy_from_slice(&(21u32).to_be_bytes());
595        section[4] = 1;
596        section[5..7].copy_from_slice(&7u16.to_be_bytes());
597        section[7..9].copy_from_slice(&0u16.to_be_bytes());
598        section[9] = 35;
599        section[10] = 1;
600        section[11] = 1;
601        section[12..14].copy_from_slice(&2026u16.to_be_bytes());
602        section[14] = 3;
603        section[15] = 20;
604        section[16] = 12;
605        section[17] = 0;
606        section[18] = 0;
607        section[19] = 0;
608        section[20] = 1;
609        section
610    }
611
612    fn build_grid(ni: u32, nj: u32, scanning_mode: u8) -> Vec<u8> {
613        let mut section = vec![0u8; 72];
614        section[..4].copy_from_slice(&(72u32).to_be_bytes());
615        section[4] = 3;
616        section[6..10].copy_from_slice(&(ni * nj).to_be_bytes());
617        section[12..14].copy_from_slice(&0u16.to_be_bytes());
618        section[30..34].copy_from_slice(&ni.to_be_bytes());
619        section[34..38].copy_from_slice(&nj.to_be_bytes());
620        section[46..50].copy_from_slice(&grib_i32_bytes(50_000_000));
621        section[50..54].copy_from_slice(&grib_i32_bytes(-120_000_000));
622        section[55..59].copy_from_slice(&grib_i32_bytes(49_000_000));
623        section[59..63].copy_from_slice(&grib_i32_bytes(-119_000_000));
624        section[63..67].copy_from_slice(&1_000_000u32.to_be_bytes());
625        section[67..71].copy_from_slice(&1_000_000u32.to_be_bytes());
626        section[71] = scanning_mode;
627        section
628    }
629
630    fn build_product(parameter_category: u8, parameter_number: u8) -> Vec<u8> {
631        let mut section = vec![0u8; 34];
632        section[..4].copy_from_slice(&(34u32).to_be_bytes());
633        section[4] = 4;
634        section[7..9].copy_from_slice(&0u16.to_be_bytes());
635        section[9] = parameter_category;
636        section[10] = parameter_number;
637        section[11] = 2;
638        section[17] = 1;
639        section[18..22].copy_from_slice(&0u32.to_be_bytes());
640        section[22] = 103;
641        section[23] = 0;
642        section[24..28].copy_from_slice(&850u32.to_be_bytes());
643        section[28] = 255;
644        section
645    }
646
647    fn build_simple_representation(encoded_values: usize, bits_per_value: u8) -> Vec<u8> {
648        let mut section = vec![0u8; 21];
649        section[..4].copy_from_slice(&(21u32).to_be_bytes());
650        section[4] = 5;
651        section[5..9].copy_from_slice(&(encoded_values as u32).to_be_bytes());
652        section[9..11].copy_from_slice(&0u16.to_be_bytes());
653        section[11..15].copy_from_slice(&0f32.to_be_bytes());
654        section[19] = bits_per_value;
655        section[20] = 0;
656        section
657    }
658
659    fn pack_u8_values(values: &[u8]) -> Vec<u8> {
660        values.to_vec()
661    }
662
663    fn build_bitmap(bits: &[bool]) -> Vec<u8> {
664        let payload_len = bits.len().div_ceil(8) + 1;
665        let mut section = vec![0u8; payload_len + 5];
666        section[..4].copy_from_slice(&((payload_len + 5) as u32).to_be_bytes());
667        section[4] = 6;
668        section[5] = 0;
669        for (index, bit) in bits.iter().copied().enumerate() {
670            if bit {
671                section[6 + index / 8] |= 1 << (7 - (index % 8));
672            }
673        }
674        section
675    }
676
677    fn build_data(payload: &[u8]) -> Vec<u8> {
678        let mut section = vec![0u8; payload.len() + 5];
679        section[..4].copy_from_slice(&((payload.len() + 5) as u32).to_be_bytes());
680        section[4] = 7;
681        section[5..].copy_from_slice(payload);
682        section
683    }
684
685    fn assemble_grib2_message(sections: &[Vec<u8>]) -> Vec<u8> {
686        let total_len = 16 + sections.iter().map(|section| section.len()).sum::<usize>() + 4;
687        let mut message = build_indicator(total_len, 0);
688        for section in sections {
689            message.extend_from_slice(section);
690        }
691        message.extend_from_slice(b"7777");
692        message
693    }
694
695    fn build_grib1_message(values: &[u8]) -> Vec<u8> {
696        let mut pds = vec![0u8; 28];
697        pds[..3].copy_from_slice(&[0, 0, 28]);
698        pds[3] = 2;
699        pds[4] = 7;
700        pds[5] = 255;
701        pds[6] = 0;
702        pds[7] = 0b1000_0000;
703        pds[8] = 11;
704        pds[9] = 100;
705        pds[10..12].copy_from_slice(&850u16.to_be_bytes());
706        pds[12] = 26;
707        pds[13] = 3;
708        pds[14] = 20;
709        pds[15] = 12;
710        pds[16] = 0;
711        pds[17] = 1;
712        pds[18] = 0;
713        pds[19] = 0;
714        pds[20] = 0;
715        pds[24] = 21;
716        pds[25] = 0;
717
718        let mut gds = vec![0u8; 32];
719        gds[..3].copy_from_slice(&[0, 0, 32]);
720        gds[5] = 0;
721        gds[6..8].copy_from_slice(&2u16.to_be_bytes());
722        gds[8..10].copy_from_slice(&2u16.to_be_bytes());
723        gds[10..13].copy_from_slice(&[0x01, 0x4d, 0x50]);
724        gds[13..16].copy_from_slice(&[0x81, 0xd4, 0xc0]);
725        gds[16] = 0x80;
726        gds[17..20].copy_from_slice(&[0x01, 0x49, 0x68]);
727        gds[20..23].copy_from_slice(&[0x81, 0xd0, 0xd8]);
728        gds[23..25].copy_from_slice(&1000u16.to_be_bytes());
729        gds[25..27].copy_from_slice(&1000u16.to_be_bytes());
730
731        let mut bds = vec![0u8; 11 + values.len()];
732        let len = bds.len() as u32;
733        bds[..3].copy_from_slice(&[(len >> 16) as u8, (len >> 8) as u8, len as u8]);
734        bds[3] = 0;
735        bds[10] = 8;
736        bds[11..].copy_from_slice(values);
737
738        let total_len = 8 + pds.len() + gds.len() + bds.len() + 4;
739        let mut message = Vec::new();
740        message.extend_from_slice(b"GRIB");
741        message.extend_from_slice(&[
742            ((total_len >> 16) & 0xff) as u8,
743            ((total_len >> 8) & 0xff) as u8,
744            (total_len & 0xff) as u8,
745            1,
746        ]);
747        message.extend_from_slice(&pds);
748        message.extend_from_slice(&gds);
749        message.extend_from_slice(&bds);
750        message.extend_from_slice(b"7777");
751        message
752    }
753
754    #[test]
755    fn scans_single_grib2_message() {
756        let message = assemble_grib2_message(&[
757            build_identification(),
758            build_grid(2, 2, 0),
759            build_product(0, 0),
760            build_simple_representation(4, 8),
761            build_data(&pack_u8_values(&[1, 2, 3, 4])),
762        ]);
763        let messages = scan_messages(&message, OpenOptions::default()).unwrap();
764        assert_eq!(messages.len(), 1);
765        assert_eq!(messages[0].metadata.parameter.short_name, "TMP");
766    }
767
768    #[test]
769    fn decodes_simple_grib2_message_to_ndarray() {
770        let message = assemble_grib2_message(&[
771            build_identification(),
772            build_grid(2, 2, 0),
773            build_product(0, 0),
774            build_simple_representation(4, 8),
775            build_data(&pack_u8_values(&[1, 2, 3, 4])),
776        ]);
777        let file = GribFile::from_bytes(message).unwrap();
778        let array = file.message(0).unwrap().read_data_as_f64().unwrap();
779        assert_eq!(array.shape(), &[2, 2]);
780        assert_eq!(
781            array.iter().copied().collect::<Vec<_>>(),
782            vec![1.0, 2.0, 3.0, 4.0]
783        );
784    }
785
786    #[test]
787    fn applies_bitmap_to_missing_values() {
788        let message = assemble_grib2_message(&[
789            build_identification(),
790            build_grid(2, 2, 0),
791            build_product(0, 1),
792            build_simple_representation(3, 8),
793            build_bitmap(&[true, false, true, true]),
794            build_data(&pack_u8_values(&[10, 20, 30])),
795        ]);
796        let file = GribFile::from_bytes(message).unwrap();
797        let array = file.message(0).unwrap().read_data_as_f64().unwrap();
798        let values = array.iter().copied().collect::<Vec<_>>();
799        assert_eq!(values[0], 10.0);
800        assert!(values[1].is_nan());
801        assert_eq!(values[2], 20.0);
802        assert_eq!(values[3], 30.0);
803    }
804
805    #[test]
806    fn indexes_multiple_fields_in_one_grib2_message() {
807        let message = assemble_grib2_message(&[
808            build_identification(),
809            build_grid(2, 2, 0),
810            build_product(0, 0),
811            build_simple_representation(4, 8),
812            build_data(&pack_u8_values(&[1, 2, 3, 4])),
813            build_product(0, 2),
814            build_simple_representation(4, 8),
815            build_data(&pack_u8_values(&[5, 6, 7, 8])),
816        ]);
817        let file = GribFile::from_bytes(message).unwrap();
818        assert_eq!(file.message_count(), 2);
819        assert_eq!(file.message(0).unwrap().parameter_name(), "TMP");
820        assert_eq!(file.message(1).unwrap().parameter_name(), "POT");
821    }
822
823    #[test]
824    fn decodes_simple_grib1_message_to_ndarray() {
825        let message = build_grib1_message(&[1, 2, 3, 4]);
826        let file = GribFile::from_bytes(message).unwrap();
827        assert_eq!(file.edition(), 1);
828        let field = file.message(0).unwrap();
829        assert_eq!(field.parameter_name(), "TMP");
830        assert!(field.identification().is_none());
831        assert!(field.grib1_product_definition().is_some());
832        let array = field.read_data_as_f64().unwrap();
833        assert_eq!(array.shape(), &[2, 2]);
834        assert_eq!(
835            array.iter().copied().collect::<Vec<_>>(),
836            vec![1.0, 2.0, 3.0, 4.0]
837        );
838    }
839}
grib_reader/lib.rs

grib_reader/
lib.rs
