grib/
decoder.rs

1use std::vec::IntoIter;
2
3use grib_template_helpers::TryFromSlice as _;
4
5use crate::{
6    context::{SectionBody, SubMessage},
7    decoder::{
8        bitmap::{BitmapDecodeIterator, dummy_bitmap_for_nonnullable_data},
9        complex::ComplexPackingDecoded,
10        simple::SimplePackingDecoder,
11        stream::NBitwiseIterator,
12    },
13    def::grib2::{DataRepresentationTemplate, Section5},
14    error::*,
15    reader::Grib2Read,
16};
17
18/// Decoder for grid point values of GRIB2 submessages.
19///
20/// # Examples
21/// ```
22/// use grib::Grib2SubmessageDecoder;
23///
24/// fn main() -> Result<(), Box<dyn std::error::Error>> {
25///     let f = std::fs::File::open(
26///         "testdata/Z__C_RJTD_20160822020000_NOWC_GPV_Ggis10km_Pphw10_FH0000-0100_grib2.bin",
27///     )?;
28///     let f = std::io::BufReader::new(f);
29///     let grib2 = grib::from_reader(f)?;
30///     let (_index, first_submessage) = grib2.iter().next().unwrap();
31///
32///     let decoder = Grib2SubmessageDecoder::from(first_submessage)?;
33///     let mut decoded = decoder.dispatch()?;
34///     assert_eq!(decoded.size_hint(), (86016, Some(86016)));
35///
36///     let first_value = decoded.next();
37///     assert_eq!(first_value.map(|f| f.is_nan()), Some(true));
38///
39///     let non_nan_value = decoded.find(|f| !f.is_nan());
40///     assert_eq!(non_nan_value.map(|f| f.round()), Some(1.0_f32));
41///
42///     let last_value = decoded.last();
43///     assert_eq!(last_value.map(|f| f.is_nan()), Some(true));
44///     Ok(())
45/// }
46/// ```
47///
48/// If the byte sequences for Sections 5, 6, and 7 of the GRIB2 data are known,
49/// and the number of grid points (described in Section 3) is also known, it is
50/// also possible to create a decoder instance by passing them to
51/// [`Grib2SubmessageDecoder::new`]. The example above is equivalent to the
52/// following:
53///
54/// ```
55/// use std::io::Read;
56///
57/// use grib::Grib2SubmessageDecoder;
58///
59/// fn main() -> Result<(), Box<dyn std::error::Error>> {
60///     let f = std::fs::File::open(
61///         "testdata/Z__C_RJTD_20160822020000_NOWC_GPV_Ggis10km_Pphw10_FH0000-0100_grib2.bin",
62///     )?;
63///     let mut f = std::io::BufReader::new(f);
64///     let mut buf = Vec::new();
65///     f.read_to_end(&mut buf)?;
66///
67///     let decoder = Grib2SubmessageDecoder::new(
68///         86016,
69///         buf[0x0000008f..0x000000a6].to_vec(),
70///         buf[0x000000a6..0x000000ac].to_vec(),
71///         buf[0x000000ac..0x0000061b].to_vec(),
72///     )?;
73///     let mut decoded = decoder.dispatch()?;
74///     assert_eq!(decoded.size_hint(), (86016, Some(86016)));
75///
76///     let first_value = decoded.next();
77///     assert_eq!(first_value.map(|f| f.is_nan()), Some(true));
78///
79///     let non_nan_value = decoded.find(|f| !f.is_nan());
80///     assert_eq!(non_nan_value.map(|f| f.round()), Some(1.0_f32));
81///
82///     let last_value = decoded.last();
83///     assert_eq!(last_value.map(|f| f.is_nan()), Some(true));
84///     Ok(())
85/// }
86/// ```
87pub struct Grib2SubmessageDecoder {
88    num_points_total: usize,
89    sect5_param: Section5,
90    sect6_bytes: Vec<u8>,
91    sect7_bytes: Vec<u8>,
92}
93
94impl Grib2SubmessageDecoder {
95    /// Creates an instance from the number of grid points (described in Section
96    /// 3) and byte sequences for Sections 5, 6, and 7 of the GRIB2 data.
97    ///
98    /// For code examples, refer to the description of this `struct`.
99    pub fn new(
100        num_points_total: usize,
101        sect5_bytes: Vec<u8>,
102        sect6_bytes: Vec<u8>,
103        sect7_bytes: Vec<u8>,
104    ) -> Result<Self, GribError> {
105        let mut pos = 0;
106        let sect5_param = Section5::try_from_slice(&sect5_bytes, &mut pos)
107            .map_err(|e| GribError::DecodeError(DecodeError::from(e)))?;
108        let sect6_bytes = match sect6_bytes[5] {
109            0x00 => sect6_bytes,
110            0xff => {
111                let mut sect6_bytes = sect6_bytes;
112                sect6_bytes.append(&mut dummy_bitmap_for_nonnullable_data(num_points_total));
113                sect6_bytes
114            }
115            n => {
116                return Err(GribError::DecodeError(DecodeError::NotSupported(
117                    "GRIB2 code table 6.0 (bit map indicator)",
118                    n.into(),
119                )));
120            }
121        };
122
123        Ok(Self {
124            num_points_total,
125            sect5_param,
126            sect6_bytes,
127            sect7_bytes,
128        })
129    }
130
131    /// Sets up a decoder for grid point values of `submessage`.
132    pub fn from<R: Grib2Read>(submessage: SubMessage<R>) -> Result<Self, GribError> {
133        let mut reader = submessage.9;
134        let sect5 = submessage.5.body;
135        let sect6 = submessage.6.body;
136        let sect7 = submessage.7.body;
137        let sect3_body = match submessage.3.body.body.as_ref() {
138            Some(SectionBody::Section3(b3)) => b3,
139            _ => return Err(GribError::InternalDataError),
140        };
141        let sect3_num_points = sect3_body.num_points() as usize;
142
143        Self::new(
144            sect3_num_points,
145            reader.read_sect_as_slice(sect5)?,
146            reader.read_sect_as_slice(sect6)?,
147            reader.read_sect_as_slice(sect7)?,
148        )
149    }
150
151    /// Dispatches a decoding process and gets an iterator of decoded values.
152    pub fn dispatch(
153        &self,
154    ) -> Result<Grib2DecodedValues<'_, impl Iterator<Item = f32> + '_>, GribError> {
155        let decoder = match &self.sect5_param.payload.template {
156            DataRepresentationTemplate::_5_0(template) => {
157                Grib2ValueIterator::SigSTNS(simple::Simple(self, template).iter()?)
158            }
159            DataRepresentationTemplate::_5_2(template) => {
160                Grib2ValueIterator::SigSC(complex::Complex(self, template).iter()?)
161            }
162            DataRepresentationTemplate::_5_3(template) => {
163                Grib2ValueIterator::SigSSCI(complex::ComplexSpatial(self, template).iter()?)
164            }
165            #[cfg(feature = "jpeg2000-unpack-with-openjpeg")]
166            DataRepresentationTemplate::_5_40(template) => {
167                Grib2ValueIterator::SigSIm(jpeg2000::Jpeg2000(self, template).iter()?)
168            }
169            #[cfg(feature = "png-unpack-with-png-crate")]
170            DataRepresentationTemplate::_5_41(template) => {
171                Grib2ValueIterator::SigSNV(png::Png(self, template).iter()?)
172            }
173            #[cfg(feature = "ccsds-unpack-with-libaec")]
174            DataRepresentationTemplate::_5_42(template) => {
175                Grib2ValueIterator::SigSNV(ccsds::Ccsds(self, template).iter()?)
176            }
177            DataRepresentationTemplate::_5_200(template) => {
178                Grib2ValueIterator::SigI(run_length::RunLength(self, template).iter()?)
179            }
180            #[allow(unreachable_patterns)]
181            _ => {
182                return Err(GribError::DecodeError(DecodeError::NotSupported(
183                    "GRIB2 code table 5.0 (data representation template number)",
184                    self.sect5_param.payload.template_num,
185                )));
186            }
187        };
188
189        let bitmap_slice = &self.sect6_bytes[6..];
190        bitmap::check_consistency(
191            self.num_points_total,
192            self.num_encoded_points(),
193            bitmap_slice,
194        )?;
195        let decoder =
196            BitmapDecodeIterator::new(bitmap_slice.iter(), decoder, self.num_points_total);
197        Ok(Grib2DecodedValues(decoder))
198    }
199
200    pub(crate) fn num_encoded_points(&self) -> usize {
201        self.sect5_param.payload.num_encoded_points as usize
202    }
203
204    pub(crate) fn sect7_payload(&self) -> &[u8] {
205        &self.sect7_bytes[5..]
206    }
207
208    /// Provides access to the parameters in Section 5.
209    ///
210    /// # Examples
211    /// ```
212    /// use grib::Grib2SubmessageDecoder;
213    ///
214    /// fn main() -> Result<(), Box<dyn std::error::Error>> {
215    ///     let f = std::fs::File::open(
216    ///         "testdata/Z__C_RJTD_20160822020000_NOWC_GPV_Ggis10km_Pphw10_FH0000-0100_grib2.bin",
217    ///     )?;
218    ///     let f = std::io::BufReader::new(f);
219    ///     let grib2 = grib::from_reader(f)?;
220    ///     let (_index, first_submessage) = grib2.iter().next().unwrap();
221    ///
222    ///     let decoder = Grib2SubmessageDecoder::from(first_submessage)?;
223    ///     let actual = decoder.section5();
224    ///     let expected = grib::def::grib2::Section5 {
225    ///         header: grib::def::grib2::SectionHeader {
226    ///             len: 23,
227    ///             sect_num: 5,
228    ///         },
229    ///         payload: grib::def::grib2::Section5Payload {
230    ///             num_encoded_points: 86016,
231    ///             template_num: 200,
232    ///             template: grib::def::grib2::DataRepresentationTemplate::_5_200(
233    ///                 grib::def::grib2::template::Template5_200 {
234    ///                     num_bits: 8,
235    ///                     max_val: 3,
236    ///                     max_level: 3,
237    ///                     dec: 0,
238    ///                     level_vals: vec![1, 2, 3],
239    ///                 },
240    ///             ),
241    ///         },
242    ///     };
243    ///     assert_eq!(actual, &expected);
244    ///
245    ///     Ok(())
246    /// }
247    /// ```
248    pub fn section5(&self) -> &Section5 {
249        &self.sect5_param
250    }
251}
252
253pub(crate) fn orig_field_type_is_supported(orig_field_type: u8) -> Result<(), DecodeError> {
254    if orig_field_type != 0 {
255        return Err(DecodeError::NotSupported(
256            "GRIB2 code table 5.1 (type of original field values)",
257            orig_field_type.into(),
258        ));
259    }
260    Ok(())
261}
262
263pub struct Grib2DecodedValues<'b, I>(BitmapDecodeIterator<std::slice::Iter<'b, u8>, I>);
264
265impl<I> Iterator for Grib2DecodedValues<'_, I>
266where
267    I: Iterator<Item = f32>,
268{
269    type Item = f32;
270
271    fn next(&mut self) -> Option<Self::Item> {
272        let Self(inner) = self;
273        inner.next()
274    }
275
276    fn size_hint(&self) -> (usize, Option<usize>) {
277        let Self(inner) = self;
278        inner.size_hint()
279    }
280}
281
282enum Grib2ValueIterator<'d> {
283    SigSTNS(SimplePackingDecoder<std::iter::Take<NBitwiseIterator<&'d [u8]>>>),
284    SigSC(SimplePackingDecoder<ComplexPackingDecoded<'d>>),
285    SigSSCI(
286        SimplePackingDecoder<
287            complex::SpatialDifferencingDecodeIterator<ComplexPackingDecoded<'d>, IntoIter<i32>>,
288        >,
289    ),
290    #[allow(dead_code)]
291    SigSI(SimplePackingDecoder<IntoIter<i32>>),
292    #[cfg(feature = "jpeg2000-unpack-with-openjpeg")]
293    SigSIm(SimplePackingDecoder<self::jpeg2000::ImageIntoIter>),
294    #[allow(dead_code)]
295    SigSNV(SimplePackingDecoder<NBitwiseIterator<Vec<u8>>>),
296    SigI(IntoIter<f32>),
297}
298
299impl<'d> Iterator for Grib2ValueIterator<'d> {
300    type Item = f32;
301
302    fn next(&mut self) -> Option<Self::Item> {
303        match self {
304            Self::SigSTNS(inner) => inner.next(),
305            Self::SigSC(inner) => inner.next(),
306            Self::SigSSCI(inner) => inner.next(),
307            Self::SigSI(inner) => inner.next(),
308            #[cfg(feature = "jpeg2000-unpack-with-openjpeg")]
309            Self::SigSIm(inner) => inner.next(),
310            Self::SigSNV(inner) => inner.next(),
311            Self::SigI(inner) => inner.next(),
312        }
313    }
314
315    fn size_hint(&self) -> (usize, Option<usize>) {
316        match self {
317            Self::SigSTNS(inner) => inner.size_hint(),
318            Self::SigSC(inner) => inner.size_hint(),
319            Self::SigSSCI(inner) => inner.size_hint(),
320            Self::SigSI(inner) => inner.size_hint(),
321            #[cfg(feature = "jpeg2000-unpack-with-openjpeg")]
322            Self::SigSIm(inner) => inner.size_hint(),
323            Self::SigSNV(inner) => inner.size_hint(),
324            Self::SigI(inner) => inner.size_hint(),
325        }
326    }
327}
328
329#[derive(Debug, Clone, PartialEq, Eq, Hash)]
330pub enum DecodeError {
331    NotSupported(&'static str, u16),
332    LengthMismatch,
333    UnclassifiedError(String),
334}
335
336impl From<String> for DecodeError {
337    fn from(value: String) -> Self {
338        Self::UnclassifiedError(value)
339    }
340}
341
342impl From<&str> for DecodeError {
343    fn from(value: &str) -> Self {
344        Self::UnclassifiedError(value.to_owned())
345    }
346}
347
348pub(crate) trait Grib2GpvUnpack {
349    type Iter<'a>: Iterator<Item = f32>
350    where
351        Self: 'a;
352
353    fn iter<'a>(&'a self) -> Result<Self::Iter<'a>, DecodeError>;
354}
355
356mod bitmap;
357#[cfg(feature = "ccsds-unpack-with-libaec")]
358mod ccsds;
359mod complex;
360mod helpers;
361#[cfg(feature = "jpeg2000-unpack-with-openjpeg")]
362mod jpeg2000;
363#[cfg(feature = "png-unpack-with-png-crate")]
364mod png;
365mod run_length;
366mod simple;
367mod stream;
grib/decoder.rs

grib/
decoder.rs
