v1.3.0

v1.3.0

Fixed and tested: an upstream test audit

We compared our tests with the eccodes, libaec and openjpeg test suites. That found 80 behaviours we never tested; 21 of them were live bugs. All are fixed and covered by tests.

Round-trips

• WriteMessage is now byte-exact on every fixture. It used to drop three things:
  • the Section 4 pv array (eccodes rejected the rewritten files)
  • Section 1 octets 22 onward
  • the reduced lat/lon point-count list
• Multi-field messages that repeat from Section 2, 3 or 4 decode and rewrite byte-exact. New fields: Field.SharesSection3 and Field.Section2.

Decoding

• Negative forecastTime is read as sign-magnitude.
• A missing level scale factor means the level is used unscaled (it gave 10^127).
• Constant fields (0 bits per value) decode to the reference value R, without the decimal scale factor, as eccodes does.
• PNG at 25–32 bits per value no longer loses data to alpha premultiplication.
• Legacy template numbers 5.40000 and 5.41000 are decoded.
• Bit-map indicator 254 reuses the previous bitmap.
• Inconsistent counts between sections are errors.

Coordinates and lookups

• One shared grid geometry for GridCoordinates, NearestValue, BilinearValue and Sampler:
  • every scanning mode
  • every shape of the Earth, including oblate Lambert
  • basic angle and subdivisions
  • reduced Gaussian sub-areas and reduced lat/lon grids
  • rotated grids' angle of rotation
  • the 0/360 seam and Gaussian rows
• Longitudes are in [0, 360). Inconsistent grid descriptions return errors.
• For projected grids scanned in a mode other than 0x40, the first grid point is the first point in data order, as WMO defines it. eccodes treats it as the south-west corner; the two agree for 0x40, the common case.

Encoding

• The reference value is never above the minimum. It used to give errors of up to 32.
• Encoders reject NaN, infinities, values outside float32 range, and 0 bits per value on varying data. Complex packing stores NaN as missing.
• Constant input encodes with 0 bits per value.
• All-NaN input to complex packing stays missing, and the complex encoder no longer drops an unstored bias.
• AEC/CCSDS: the encoder output now matches libaec byte for byte; it miscoded a run of exactly 5 zero blocks.
• JPEG2000:
  • the decoder is ported from OpenJPEG (tiles, layers, progression orders, all code-block styles);
  • 9/7 and multi-component streams return explicit errors;
  • the encoder writes valid tile-part lengths, so Jasper reads its output;
  • encoding is limited to 30 bits per value.

Reading streams

• Decoder skips junk and GRIB1 messages between messages; a GRIB1 message gives an error wrapping ErrNotEdition2.
• It checks each message's total length.
• A truncated message gives ErrTruncated; a clean end gives io.EOF.
• No more panics on malformed templates.

New API

• Field.SharesSection3, Field.Section2
• Section1.Reserved, Section1.ValidateReferenceTime
• Section6.PreviousBitmap
• MissingScaleFactor
• Section4.Describe(discipline)
• Code-table names now cover every code in WMO table version 35.

Compatibility notes

• Section1 holds a []byte, so it can no longer be compared with ==.
• Inputs that were silently accepted now return errors. That covers invalid encoder input, inconsistent grids, mismatched counts, and a message length that doesn't match the declared total.

Tests

Every test runs from committed data, so anyone can run the full suite:

• an eccodes-derived reference for 317 fields (exact value fingerprints, sampled coordinates, metadata, pv arrays, nearest-point answers)
• golden encoder output that eccodes decoded
• libaec's CCSDS test vectors
• JPEG2000 streams checked with OpenJPEG and Jasper

With eccodes built locally:

• GRIB2_WRITE_ECCODES_REFERENCE=1 go test -run TestEccodesReference_Write . regenerates the data.
• TestEccodesReference_UpToDate checks the committed data still matches eccodes.