Move printSize() into libutil

Also always include the unit (i.e. "MiB" instead of "M").

src/libutil/util.cc

@@ -112,6 +112,21 @@ std::string rewriteStrings(std::string s, const StringMap & rewrites)
 }
 
 
+std::string renderSize(uint64_t value)
+{
+    static const std::array<char, 9> prefixes{{
+        'K', 'K', 'M', 'G', 'T', 'P', 'E', 'Z', 'Y'
+    }};
+    size_t power = 0;
+    double res = value;
+    while (res > 1024 && power < prefixes.size()) {
+        ++power;
+        res /= 1024;
+    }
+    return fmt("%6.1f %ciB", power == 0 ? res / 1024 : res, prefixes.at(power));
+}
+
+
 bool hasPrefix(std::string_view s, std::string_view prefix)
 {
     return s.compare(0, prefix.size(), prefix) == 0;

src/libutil/util.hh

@@ -137,6 +137,12 @@ N string2IntWithUnitPrefix(std::string_view s)
     throw UsageError("'%s' is not an integer", s);
 }
 
+/**
+ * Pretty-print a byte value, e.g. 12433615056 is rendered as `11.6
+ * GiB`.
+ */
+std::string renderSize(uint64_t value);
+
 /**
  * Parse a string into a float.
  */

src/nix/path-info.cc

@@ -139,21 +139,10 @@ struct CmdPathInfo : StorePathsCommand, MixJSON
 
     void printSize(uint64_t value)
     {
-        if (!humanReadable) {
+        if (humanReadable)
+            std::cout << fmt("\t%s", renderSize(value));
+        else
             std::cout << fmt("\t%11d", value);
-            return;
-        }
-
-        static const std::array<char, 9> idents{{
-            ' ', 'K', 'M', 'G', 'T', 'P', 'E', 'Z', 'Y'
-        }};
-        size_t power = 0;
-        double res = value;
-        while (res > 1024 && power < idents.size()) {
-            ++power;
-            res /= 1024;
-        }
-        std::cout << fmt("\t%6.1f%c", res, idents.at(power));
     }
 
     void run(ref<Store> store, StorePaths && storePaths) override

src/nix/path-info.md

@@ -26,8 +26,8 @@ R""(
 
   ```console
   # nix path-info --recursive --size --closure-size --human-readable nixpkgs#rustc
-  /nix/store/01rrgsg5zk3cds0xgdsq40zpk6g51dz9-ncurses-6.2-dev      386.7K   69.1M
+  /nix/store/01rrgsg5zk3cds0xgdsq40zpk6g51dz9-ncurses-6.2-dev      386.7 KiB   69.1 MiB
-  /nix/store/0q783wnvixpqz6dxjp16nw296avgczam-libpfm-4.11.0          5.9M   37.4M
+  /nix/store/0q783wnvixpqz6dxjp16nw296avgczam-libpfm-4.11.0          5.9 MiB   37.4 MiB
   …
   ```