Fix WKB writing on big-endian systems

`shapely.to_wkb` (called in `pyogrio.geopandas.write_dataframe` via
`geopandas.array.to_wkb`) defaults to machine byte order, so simply
reading the first byte (of a 4-byte integer geometry type) is broken on
big-endian machines. And since some geometry type could be 2 bytes, this
also seems broken on little-endian machines, though I did not check if
any 2-byte types could be produced.

The commented-out code here indicates the correct course of action
(reading the first byte to determine byte order). Instead of using
`int.from_bytes`, I wrote it out as bitshifting operations, which
compile directly to 1 or 2 (if byte swapping) assembly instructions.

Also, change `wkb_buffer` to be `const`, as it doesn't need to be
writeable (and perhaps this will save a copy.)

CHANGES.md

@@ -2,6 +2,10 @@
 
 ## 0.11.0 (TBD)
 
+### Bug fixes
+
+-   Fix WKB writing on big-endian systems (#497).
+
 ### Packaging
 
 -   the GDAL library included in the wheels is upgraded from 3.9.2 to 3.10.0 (#499).

pyogrio/_io.pyx

@@ -2253,7 +2253,8 @@ def ogr_write(
     cdef OGRGeometryH ogr_geometry_multi = NULL
     cdef OGRFeatureDefnH ogr_featuredef = NULL
     cdef OGRFieldDefnH ogr_fielddef = NULL
-    cdef unsigned char *wkb_buffer = NULL
+    cdef const unsigned char *wkb_buffer = NULL
+    cdef unsigned int wkbtype = 0
     cdef int supports_transactions = 0
     cdef int err = 0
     cdef int i = 0
@@ -2373,15 +2374,18 @@ def ogr_write(
             # TODO: geometry must not be null or errors
             wkb = None if geometry is None else geometry[i]
             if wkb is not None:
-                wkbtype = <int>bytearray(wkb)[1]
-                # may need to consider all 4 bytes: int.from_bytes(wkb[0][1:4], byteorder="little")
-                # use "little" if the first byte == 1
+                wkb_buffer = wkb
+                if wkb_buffer[0] == 1:
+                    # Little endian WKB type.
+                    wkbtype = wkb_buffer[1] + (wkb_buffer[2] << 8) + (wkb_buffer[3] << 16) + (<unsigned int>wkb_buffer[4] << 24)
+                else:
+                    # Big endian WKB type.
+                    wkbtype = (<unsigned int>(wkb_buffer[1]) << 24) + (wkb_buffer[2] << 16) + (wkb_buffer[3] << 8) + wkb_buffer[4]
                 ogr_geometry = OGR_G_CreateGeometry(<OGRwkbGeometryType>wkbtype)
                 if ogr_geometry == NULL:
                     raise GeometryError(f"Could not create geometry at index {i} for WKB type {wkbtype}") from None
 
                 # import the WKB
-                wkb_buffer = wkb
                 err = OGR_G_ImportFromWkb(ogr_geometry, wkb_buffer, len(wkb))
                 if err:
                     raise GeometryError(f"Could not create geometry from WKB at index {i}") from None