What is hdrhistogram_c?

HdrHistogram_c is a C library for measuring and analyzing performance metrics with extreme precision. It solves a real problem: when you're timing things in software, like how fast a web request is processed or how long a database query takes, you often need to know not just the average time, but also the slowest outliers. This library lets you record thousands or millions of individual measurements and then ask questions like "what's the 99th percentile response time?" or "what's the worst-case scenario I should plan for?" The way it works is straightforward: you create a histogram, feed it measurements as your program runs, and then ask it statistical questions about those measurements. The "High Dynamic Range" part of the name means it can handle measurements that span a huge range, from 1 nanosecond to hours, all at the same time without losing precision on the small numbers or wasting memory on the large ones. The library automatically organizes your data into buckets and can calculate percentiles, find min/max values, and print detailed reports. You'd use this if you're building performance-critical systems where knowing your worst cases matters. For example, a trading platform needs to know not just the average latency of trades, but the 99.99th percentile, because even one very slow trade can be costly. A game developer cares about frame time outliers because one dropped frame ruins the player experience. DevOps engineers use it to monitor server response times and spot performance degradation. The library is written in C, which means it's fast and can be embedded directly into applications that need minimal overhead. This particular port brings the functionality from the original Java HdrHistogram library to C programs. It supports the core features, recording values, multiple ways to iterate through the data, and saving/loading histograms from disk, but doesn't include some of the more specialized variants like atomic histograms (used in multithreaded Java) or floating-point histograms, keeping the C version lean and focused.