Set dims in C code

[Bisaloo]

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[github-actions]

This is how benchmark results would change (along with a 95% confidence interval in relative change) if dd5b1d7 is merged into main:

• ❗🐌pkg_load: 5.15ms -> 5.33ms [+0.92%, +6.05%]
• ✔️read_bigendian: 11.2ms -> 11.2ms [-1.04%, +0.46%]
• ✔️read_bool: 11.6ms -> 11.6ms [-0.94%, +1.28%]
• ✔️read_empty: 11.3ms -> 11.4ms [-0.73%, +1.33%]
• ✔️read_float32: 12ms -> 12.1ms [-0.98%, +1.45%]
• ✔️read_float64: 12ms -> 12ms [-1.27%, +1.63%]
• ✔️read_int16: 12ms -> 12ms [-1.59%, +1.28%]
• ✔️read_int32: 11.3ms -> 11.3ms [-1.11%, +0.68%]
• ✔️read_int64: 11.7ms -> 11.8ms [-0.37%, +0.91%]
• ✔️read_int8: 12.1ms -> 12.1ms [-1.48%, +1.36%]
• ✔️read_npz: 13ms -> 12.9ms [-1.38%, +0.04%]
• ✔️read_string: 11.5ms -> 11.4ms [-1.93%, +0.12%]
• ✔️read_structured: 12.4ms -> 12.3ms [-1.25%, +1.05%]
• ✔️read_uint16: 11.4ms -> 11.4ms [-1.28%, +1.01%]
• ✔️read_uint32: 11.4ms -> 11.4ms [-0.49%, +0.9%]
• ✔️read_uint64: 11.6ms -> 11.6ms [-0.78%, +0.11%]
• ✔️read_uint8: 11.3ms -> 11.3ms [-0.94%, +0.96%]
• ✔️read_unicode: 11.7ms -> 11.8ms [-0.21%, +2.12%]
  Further explanation regarding interpretation and methodology can be found in the documentation.