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Read negative compression levels correctly where char is unsigned - #13
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The array schema stored each compression level in a char. char is unsigned on Linux aarch64 and other non-x86 Linux targets, so there a level of -1, GZIP's default, read back as 255 and GZIP compression failed with Z_STREAM_ERROR. The levels are now stored and read as int8_t: the bytes on disk are unchanged, and they read the same on every platform. Adds a test that GZIP's default level reads back as written.
This was referenced Oct 6, 2026
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The array schema stores each compression level in a
char, andcharis unsigned on Linux aarch64 and other non-x86 Linux targets, so there a level of −1, GZIP's default, reads back as 255 and GZIP compression fails withZ_STREAM_ERROR, as intiledb_array_write_dense_1. The levels are now stored and read asint8_t. The bytes on disk are unchanged, and x86-64 and macOS read them exactly as before; on aarch64 only negative levels read differently, and a level affects only how tiles are compressed, not how they're read. #11 also fixes this, as a side effect of makingcharsigned; this fixes it on its own, whatever happens with #11.A new test checks that GZIP's default level reads back as written. CI has no aarch64 runner, so I checked it in an AlmaLinux 8 container on aarch64 with GCC 15, which needs #12 to build: every test and example passes, and without this change both the new test and the existing "Test array schema backward compatibility 2" fail.