diff --git a/Cargo.toml b/Cargo.toml
index 2d4db4d..56f42e8 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "mettrics"
-version = "0.0.5"
+version = "0.0.6"
 description = "Makes publishing meaningful metrics from applications easier."
 authors = ["Dominik Werder <dominik.werder@gmail.com>"]
 license = "GPL-3.0-only"
@@ -8,4 +8,5 @@ edition = "2024"
 
 [dependencies]
 serde = { version = "1", features = ["derive"] }
-mettrics-macros = { version = "0.0.5", path = "../mettrics-macros" }
+serde_json = "1"
+mettrics-macros = { version = "0.0.6", path = "../mettrics-macros" }
diff --git a/src/lib.rs b/src/lib.rs
index aae71ec..a1db89a 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -3,4 +3,5 @@ pub mod types;
 
 pub mod rexport {
     pub use serde;
+    pub use serde_json;
 }
diff --git a/src/types.rs b/src/types.rs
index 546c2e2..3b3815a 100644
--- a/src/types.rs
+++ b/src/types.rs
@@ -1,3 +1,7 @@
+mod histolog2;
+
+pub use histolog2::HistoLog2;
+
 use crate::rexport::serde;
 
 #[derive(Debug, serde::Serialize)]
diff --git a/src/types/histolog2.rs b/src/types/histolog2.rs
new file mode 100644
index 0000000..b775f53
--- /dev/null
+++ b/src/types/histolog2.rs
@@ -0,0 +1,171 @@
+use std::fmt;
+use std::time::Duration;
+
+use crate::rexport::serde;
+
+#[derive(Debug, serde::Serialize)]
+pub struct HistoLog2 {
+    sum: u64,
+    histo: Vec<u32>,
+}
+
+#[allow(unused)]
+macro_rules! rep20 {
+    ([$x:expr]) => {
+        [
+            $x, $x, $x, $x, $x, $x, $x, $x, $x, $x, $x, $x, $x, $x, $x, $x, $x, $x, $x, $x,
+        ]
+    };
+}
+
+impl HistoLog2 {
+    pub fn new(n: u16) -> Self {
+        let histo = vec![0; n as usize];
+        Self { sum: 0, histo }
+    }
+
+    #[inline]
+    pub fn push_val(&mut self, v: u32) {
+        self.sum = self.sum.wrapping_add(v as u64);
+        let w = 32 - v.leading_zeros();
+        let i = w.min(self.histo.len() as u32 - 1);
+        let h = &mut self.histo[i as usize];
+        *h = h.wrapping_add(1);
+    }
+
+    #[inline]
+    pub fn push_dur_10us(&mut self, dt: Duration) {
+        let v = 1000000 * dt.as_secs() as u32 + dt.subsec_micros();
+        let v = v / 10;
+        self.push_val(v);
+    }
+
+    #[inline]
+    pub fn push_dur_100us(&mut self, dt: Duration) {
+        let v = 1000000 * dt.as_secs() as u32 + dt.subsec_micros();
+        let v = v / 100;
+        self.push_val(v);
+    }
+
+    #[inline]
+    pub fn push_dur_1ms(&mut self, dt: Duration) {
+        let v = 1000000 * dt.as_secs() as u32 + dt.subsec_micros();
+        let v = v / 1000;
+        self.push_val(v);
+    }
+
+    #[inline]
+    pub fn push_dur_10ms(&mut self, dt: Duration) {
+        let v = 1000000 * dt.as_secs() as u32 + dt.subsec_micros();
+        let v = v / 10000;
+        self.push_val(v);
+    }
+
+    pub fn ingest_upstream(&mut self, inp: Self) {
+        self.sum += inp.sum;
+        for (x, y) in inp.histo.into_iter().zip(self.histo.iter_mut()) {
+            *y += x;
+        }
+    }
+
+    pub fn to_flatten_prometheus(&self, name: &str) -> Vec<String> {
+        // https://prometheus.io/docs/instrumenting/exposition_formats/
+        let mut ret = String::with_capacity(2048);
+        ret.push_str("# HELP ");
+        ret.push_str(name);
+        ret.push_str(" help-text-missing\n");
+        ret.push_str("# TYPE ");
+        ret.push_str(name);
+        ret.push_str(" histogram\n");
+        let mut cnt = 0;
+        let lastix = (self.histo.len() - 1) as u32;
+        for (i, &v) in self.histo.iter().enumerate() {
+            let i = i as u32;
+            let le = if i == 0 {
+                0
+            } else {
+                u32::MAX >> (u32::BITS - i)
+            };
+            cnt += v;
+            ret.push_str(name);
+            ret.push_str("_bucket{le=\"");
+            if i == lastix {
+                ret.push_str("+Inf");
+            } else {
+                ret.push_str(&le.to_string());
+            }
+            ret.push_str("\"} ");
+            ret.push_str(&cnt.to_string());
+            ret.push_str("\n");
+        }
+        ret.push_str(name);
+        ret.push_str("_count ");
+        ret.push_str(&cnt.to_string());
+        ret.push_str("\n");
+
+        let sum = self.sum;
+        ret.push_str(name);
+        ret.push_str("_sum ");
+        ret.push_str(&sum.to_string());
+        let ret = vec![ret];
+        ret
+    }
+
+    pub fn to_display(&self) -> HistoLog2Display {
+        HistoLog2Display { inner: self }
+    }
+}
+
+pub struct HistoLog2Display<'a> {
+    inner: &'a HistoLog2,
+}
+
+impl<'a> fmt::Display for HistoLog2Display<'a> {
+    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
+        let histo: Vec<_> = self.inner.histo.iter().map(|&x| x).collect();
+        write!(
+            fmt,
+            "HistoLog2 {{ histo: {:?}, sum: {:?} }}",
+            histo, self.inner.sum
+        )
+    }
+}
+
+#[test]
+fn histo_00() {
+    let mut histo = HistoLog2::new(20);
+    // histo.ingest(0);
+    // histo.ingest(1);
+    // histo.ingest(2);
+    histo.push_val(3);
+    histo.push_val(4);
+    histo.push_val(262143);
+    histo.push_val(262144);
+    let s = histo.to_flatten_prometheus("the_metric");
+    // eprintln!("{s}");
+    let exp = r##"# HELP the_metric help-text-missing
+# TYPE the_metric histogram
+the_metric_bucket{le="0"} 0
+the_metric_bucket{le="1"} 0
+the_metric_bucket{le="3"} 1
+the_metric_bucket{le="7"} 2
+the_metric_bucket{le="15"} 2
+the_metric_bucket{le="31"} 2
+the_metric_bucket{le="63"} 2
+the_metric_bucket{le="127"} 2
+the_metric_bucket{le="255"} 2
+the_metric_bucket{le="511"} 2
+the_metric_bucket{le="1023"} 2
+the_metric_bucket{le="2047"} 2
+the_metric_bucket{le="4095"} 2
+the_metric_bucket{le="8191"} 2
+the_metric_bucket{le="16383"} 2
+the_metric_bucket{le="32767"} 2
+the_metric_bucket{le="65535"} 2
+the_metric_bucket{le="131071"} 2
+the_metric_bucket{le="262143"} 3
+the_metric_bucket{le="+Inf"} 4
+the_metric_count 4
+the_metric_sum 524294"##;
+    assert_eq!(s.join("\n"), exp);
+}