Updated HDR histogram from upsteam after they merged our fix in #10606. (#10755)

The code is based on upstream https://github.com/HdrHistogram/HdrHistogram_c
master branch latest commit (e4448cf6d1cd08fff519812d3b1e58bd5a94ac42).
The reason to pull this in now is that their final version of our optimization is even faster.
See: https://github.com/HdrHistogram/HdrHistogram_c/pull/107.

deps/README.md

@@ -100,8 +100,8 @@ Hdr_Histogram
 ---
 
 Updated source can be found here: https://github.com/HdrHistogram/HdrHistogram_c
-We use a customized version 0.11.5
-1. Compare all changes under /hdr_histogram directory to version 0.11.5
+We use a customized version based on master branch commit e4448cf6d1cd08fff519812d3b1e58bd5a94ac42.
+1. Compare all changes under /hdr_histogram directory to upstream master commit e4448cf6d1cd08fff519812d3b1e58bd5a94ac42
 2. Copy updated files from newer version onto files in /hdr_histogram.
 3. Apply the changes from 1 above to the updated files.
 

deps/hdr_histogram/README.md

@@ -1,10 +1,78 @@
-HdrHistogram_c v0.11.5
+HdrHistogram_c: 'C' port of High Dynamic Range (HDR) Histogram
 
+HdrHistogram
 ----------------------------------------------
 
-This port contains a subset of the 'C' version of High Dynamic Range (HDR) Histogram available at [github.com/HdrHistogram/HdrHistogram_c](https://github.com/HdrHistogram/HdrHistogram_c).
+[![Gitter chat](https://badges.gitter.im/HdrHistogram/HdrHistogram.png)](https://gitter.im/HdrHistogram/HdrHistogram)
 
+This port contains a subset of the functionality supported by the Java
+implementation.  The current supported features are:
 
-The code present on `hdr_histogram.c`, `hdr_histogram.h`, and `hdr_atomic.c` was Written by Gil Tene, Michael Barker,
-and Matt Warren, and released to the public domain, as explained at
-http://creativecommons.org/publicdomain/zero/1.0/.
+* Standard histogram with 64 bit counts (32/16 bit counts not supported)
+* All iterator types (all values, recorded, percentiles, linear, logarithmic)
+* Histogram serialisation (encoding version 1.2, decoding 1.0-1.2)
+* Reader/writer phaser and interval recorder
+
+Features not supported, but planned
+
+* Auto-resizing of histograms
+
+Features unlikely to be implemented
+
+* Double histograms
+* Atomic/Concurrent histograms
+* 16/32 bit histograms
+
+# Simple Tutorial
+
+## Recording values
+
+```C
+#include <hdr_histogram.h>
+
+struct hdr_histogram* histogram;
+
+// Initialise the histogram
+hdr_init(
+    1,  // Minimum value
+    INT64_C(3600000000),  // Maximum value
+    3,  // Number of significant figures
+    &histogram)  // Pointer to initialise
+
+// Record value
+hdr_record_value(
+    histogram,  // Histogram to record to
+    value)  // Value to record
+
+// Record value n times
+hdr_record_values(
+    histogram,  // Histogram to record to
+    value,  // Value to record
+    10)  // Record value 10 times
+
+// Record value with correction for co-ordinated omission.
+hdr_record_corrected_value(
+    histogram,  // Histogram to record to
+    value,  // Value to record
+    1000)  // Record with expected interval of 1000.
+
+// Print out the values of the histogram
+hdr_percentiles_print(
+    histogram,
+    stdout,  // File to write to
+    5,  // Granularity of printed values
+    1.0,  // Multiplier for results
+    CLASSIC);  // Format CLASSIC/CSV supported.
+```
+
+## More examples
+
+For more detailed examples of recording and logging results look at the
+[hdr_decoder](examples/hdr_decoder.c)
+and [hiccup](examples/hiccup.c)
+examples.  You can run hiccup and decoder
+and pipe the results of one into the other.
+
+```
+$ ./examples/hiccup | ./examples/hdr_decoder
+```

deps/hdr_histogram/hdr_histogram.c

@@ -165,16 +165,6 @@ static int32_t count_leading_zeros_64(int64_t value)
 #endif
 }
 
-static int64_t get_count_at_index_given_bucket_base_idx(const struct hdr_histogram* h, int32_t bucket_base_idx, int32_t sub_bucket_idx)
-{
-    return h->counts[(bucket_base_idx + sub_bucket_idx) - h->sub_bucket_half_count];
-}
-
-static int32_t get_bucket_base_index(const struct hdr_histogram* h, int32_t bucket_index)
-{
-    return (bucket_index + 1) << h->sub_bucket_half_count_magnitude;
-}
-
 static int32_t get_bucket_index(const struct hdr_histogram* h, int64_t value)
 {
     int32_t pow2ceiling = 64 - count_leading_zeros_64(value | h->sub_bucket_mask); /* smallest power of 2 containing value */
@@ -679,33 +669,21 @@ int64_t hdr_min(const struct hdr_histogram* h)
 static int64_t get_value_from_idx_up_to_count(const struct hdr_histogram* h, int64_t count_at_percentile)
 {
     int64_t count_to_idx = 0;
-    int64_t value_from_idx = 0;
-    int32_t sub_bucket_idx = -1;
-    int32_t bucket_idx = 0;
-    int32_t bucket_base_idx = get_bucket_base_index(h, bucket_idx);
 
-    // Overflow check
-    if (count_at_percentile > h->total_count)
+    count_at_percentile = 0 < count_at_percentile ? count_at_percentile : 1;
+    for (int32_t idx = 0; idx < h->counts_len; idx++)
     {
-        count_at_percentile = h->total_count;
+        count_to_idx += h->counts[idx];
+        if (count_to_idx >= count_at_percentile)
+        {
+            return hdr_value_at_index(h, idx);
+        }
     }
 
-    while (count_to_idx < count_at_percentile)
-    {
-        // increment bucket
-        sub_bucket_idx++;
-        if (sub_bucket_idx >= h->sub_bucket_count)
-        {
-            sub_bucket_idx = h->sub_bucket_half_count;
-            bucket_idx++;
-            bucket_base_idx = get_bucket_base_index(h, bucket_idx);
-        }
-        count_to_idx += get_count_at_index_given_bucket_base_idx(h, bucket_base_idx, sub_bucket_idx);
-        value_from_idx = ((int64_t)(sub_bucket_idx)) << (((int64_t)(bucket_idx)) + h->unit_magnitude);
-    }
-    return value_from_idx;
+    return 0;
 }
 
+
 int64_t hdr_value_at_percentile(const struct hdr_histogram* h, double percentile)
 {
     double requested_percentile = percentile < 100.0 ? percentile : 100.0;