Our C program is c_src/main.c. We need a few system headers before we can define the embed_quantiles interface:
#include <stdint.h> #include <stdio.h> #include <stdlib.h> #include <time.h>
The only slightly unusual one is time.h. We pull that in because we're going to be pushing random floats into the CKMS structure. Not cryptographically secure randomness, mind. Here's the C view of the Rust API we just created:
struct ckms; struct ckms* alloc_ckms(double error); void free_ckms(struct ckms* ckms); void ckms_insert(struct ckms* ckms, float value); int8_t query(struct ckms* ckms, double q, float* quant);
Notice the CKMS struct . That's the opaque struct. C is now aware there is a structure but it doesn't know how big it is. That's ...
