Potential fix for code scanning alert no. 17: Multiplication result converted to larger type

[HTHou]

Potential fix for https://github.com/apache/tsfile/security/code-scanning/17

To fix the issue, we need to ensure that the multiplication is performed using a larger integer type (e.g., int64_t) to prevent overflow. This can be achieved by explicitly casting one of the operands to int64_t before the multiplication. This ensures that the multiplication is performed in 64-bit arithmetic, avoiding overflow.

The specific change will be made on line 191, where the multiplication points_per_device * device_num occurs. We will cast points_per_device to int64_t before the multiplication. This change does not alter the logic or functionality of the code but ensures that the multiplication is safe.

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