cutils: add functions for IEC and SI prefixes

Extract the knowledge of IEC and SI prefixes out of size_to_str and
freq_to_str, so that it can be reused when printing statistics.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 25 insertions, 9 deletions

diff --git a/util/cutils.c b/util/cutils.c
index a58bcfd..6d04e52 100644
--- a/util/cutils.c
+++ b/util/cutils.c
@@ -872,6 +872,25 @@ int parse_debug_env(const char *name, int max, int initial)
     return debug;
 }
 
+const char *si_prefix(unsigned int exp10)
+{
+    static const char *prefixes[] = {
+        "a", "f", "p", "n", "u", "m", "", "K", "M", "G", "T", "P", "E"
+    };
+
+    exp10 += 18;
+    assert(exp10 % 3 == 0 && exp10 / 3 < ARRAY_SIZE(prefixes));
+    return prefixes[exp10 / 3];
+}
+
+const char *iec_binary_prefix(unsigned int exp2)
+{
+    static const char *prefixes[] = { "", "Ki", "Mi", "Gi", "Ti", "Pi", "Ei" };
+
+    assert(exp2 % 10 == 0 && exp2 / 10 < ARRAY_SIZE(prefixes));
+    return prefixes[exp2 / 10];
+}
+
 /*
  * Return human readable string for size @val.
  * @val can be anything that uint64_t allows (no more than "16 EiB").
@@ -880,7 +899,6 @@ int parse_debug_env(const char *name, int max, int initial)
  */
 char *size_to_str(uint64_t val)
 {
-    static const char *suffixes[] = { "", "Ki", "Mi", "Gi", "Ti", "Pi", "Ei" };
     uint64_t div;
     int i;
 
@@ -891,25 +909,23 @@ char *size_to_str(uint64_t val)
      * (see e41b509d68afb1f for more info)
      */
     frexp(val / (1000.0 / 1024.0), &i);
-    i = (i - 1) / 10;
-    div = 1ULL << (i * 10);
+    i = (i - 1) / 10 * 10;
+    div = 1ULL << i;
 
-    return g_strdup_printf("%0.3g %sB", (double)val / div, suffixes[i]);
+    return g_strdup_printf("%0.3g %sB", (double)val / div, iec_binary_prefix(i));
 }
 
 char *freq_to_str(uint64_t freq_hz)
 {
-    static const char *const suffixes[] = { "", "K", "M", "G", "T", "P", "E" };
     double freq = freq_hz;
-    size_t idx = 0;
+    size_t exp10 = 0;
 
     while (freq >= 1000.0) {
         freq /= 1000.0;
-        idx++;
+        exp10 += 3;
     }
-    assert(idx < ARRAY_SIZE(suffixes));
 
-    return g_strdup_printf("%0.3g %sHz", freq, suffixes[idx]);
+    return g_strdup_printf("%0.3g %sHz", freq, si_prefix(exp10));
 }
 
 int qemu_pstrcmp0(const char **str1, const char **str2)