disk: Distinguish between IEC, SI and custom prefixes

* IEC: Ki, Mi, Gi, Ti (powers of 1024)
* SI: k, M, G, T (powers of 1000)
* custom: K, M, G, T (powers of 1024)

4 files changed, 51 insertions, 22 deletions

diff --git a/i3status.c b/i3status.c
index e2befbc..b359370 100644
--- a/i3status.c
+++ b/i3status.c
@@ -288,6 +288,7 @@ int main(int argc, char *argv[]) {
 
         cfg_opt_t disk_opts[] = {
                 CFG_STR("format", "%free", CFGF_NONE),
+                CFG_STR("prefix_type", "binary", CFGF_NONE),
                 CFG_END()
         };
 
@@ -497,7 +498,7 @@ int main(int argc, char *argv[]) {
 
                         CASE_SEC_TITLE("disk") {
                                 SEC_OPEN_MAP("disk_info");
-                                print_disk_info(json_gen, buffer, title, cfg_getstr(sec, "format"));
+                                print_disk_info(json_gen, buffer, title, cfg_getstr(sec, "format"), cfg_getstr(sec, "prefix_type"));
                                 SEC_CLOSE_MAP;
                         }
 
diff --git a/include/i3status.h b/include/i3status.h
index e64cde5..5ab310b 100644
--- a/include/i3status.h
+++ b/include/i3status.h
@@ -145,7 +145,7 @@ char *auto_detect_format();
 void set_timezone(const char *tz);
 
 void print_ipv6_info(yajl_gen json_gen, char *buffer, const char *format_up, const char *format_down);
-void print_disk_info(yajl_gen json_gen, char *buffer, const char *path, const char *format);
+void print_disk_info(yajl_gen json_gen, char *buffer, const char *path, const char *format, const char *prefix_type);
 void print_battery_info(yajl_gen json_gen, char *buffer, int number, const char *path, const char *format, const char *format_down, int low_threshold, char *threshold_type, bool last_full_capacity, bool integer_battery_capacity);
 void print_time(yajl_gen json_gen, char *buffer, const char *format, const char *tz, time_t t);
 void print_ddate(yajl_gen json_gen, char *buffer, const char *format, time_t t);
diff --git a/man/i3status.man b/man/i3status.man
index e18dbc7..88cb572 100644
--- a/man/i3status.man
+++ b/man/i3status.man
@@ -184,12 +184,26 @@ Gets used, free, available and total amount of bytes on the given mounted filesy
 These values can also be expressed in percentages with the percentage_used,
 percentage_free, percentage_avail and percentage_used_of_avail formats.
 
+Byte sizes are presented in a human readable format using a set of prefixes
+whose type can be specified via the "prefix_type" option. Three sets of
+prefixes are available:
+
+binary::
+IEC prefixes (Ki, Mi, Gi, Ti) represent multiples of powers of 1024.
+This is the default.
+decimal::
+SI prefixes (k, M, G, T) represent multiples of powers of 1000.
+custom::
+The custom prefixes (K, M, G, T) represent multiples of powers of 1024.
+
 *Example order*: +disk /mnt/usbstick+
 
 *Example format*: +%free (%avail)/ %total+
 
 *Example format*: +%percentage_used used, %percentage_free free, %percentage_avail avail+
 
+*Example prefix_type*: +custom+
+
 === Run-watch
 
 Expands the given path to a pidfile and checks if the process ID found inside
diff --git a/src/print_disk_info.c b/src/print_disk_info.c
index f49fe66..2308305 100644
--- a/src/print_disk_info.c
+++ b/src/print_disk_info.c
@@ -15,26 +15,40 @@
 
 #include "i3status.h"
 
-#define TERABYTE (1024ULL * 1024 * 1024 * 1024)
-#define GIGABYTE (1024ULL * 1024 * 1024)
-#define MEGABYTE (1024ULL * 1024)
-#define KILOBYTE (1024ULL)
+#define BINARY_BASE UINT64_C(1024)
+#define DECIMAL_BASE UINT64_C(1000)
+
+#define MAX_EXPONENT 4
+
+static const char * const iec_symbols[MAX_EXPONENT+1] = {"", "Ki", "Mi", "Gi", "Ti"};
+static const char * const si_symbols[MAX_EXPONENT+1] = {"", "k", "M", "G", "T"};
+static const char * const custom_symbols[MAX_EXPONENT+1] = {"", "K", "M", "G", "T"};
+
+/*
+ * Formats bytes according to the given base and set of symbols.
+ *
+ */
+static int format_bytes(char *outwalk, uint64_t bytes, uint64_t base, const char * const symbols[]) {
+        double size = bytes;
+        int exponent = 0;
+        while (size >= base && exponent < MAX_EXPONENT) {
+                size /= base;
+                exponent += 1;
+        }
+        return sprintf(outwalk, "%.1f %sB", size, symbols[exponent]);
+}
 
 /*
  * Prints the given amount of bytes in a human readable manner.
  *
  */
-static int print_bytes_human(char *outwalk, uint64_t bytes) {
-        if (bytes > TERABYTE)
-                return sprintf(outwalk, "%.02f TB", (double)bytes / TERABYTE);
-        else if (bytes > GIGABYTE)
-                return sprintf(outwalk, "%.01f GB", (double)bytes / GIGABYTE);
-        else if (bytes > MEGABYTE)
-                return sprintf(outwalk, "%.01f MB", (double)bytes / MEGABYTE);
-        else if (bytes > KILOBYTE)
-                return sprintf(outwalk, "%.01f KB", (double)bytes / KILOBYTE);
-        else {
-                return sprintf(outwalk, "%.01f B", (double)bytes);
+static int print_bytes_human(char *outwalk, uint64_t bytes, const char *prefix_type) {
+        if (strncmp(prefix_type, "decimal", strlen(prefix_type)) == 0) {
+                return format_bytes(outwalk, bytes, DECIMAL_BASE, si_symbols);
+        } else if (strncmp(prefix_type, "custom", strlen(prefix_type)) == 0) {
+                return format_bytes(outwalk, bytes, BINARY_BASE, custom_symbols);
+        } else {
+                return format_bytes(outwalk, bytes, BINARY_BASE, iec_symbols);
         }
 }
 
@@ -43,7 +57,7 @@ static int print_bytes_human(char *outwalk, uint64_t bytes) {
  * human readable manner.
  *
  */
-void print_disk_info(yajl_gen json_gen, char *buffer, const char *path, const char *format) {
+void print_disk_info(yajl_gen json_gen, char *buffer, const char *path, const char *format, const char *prefix_type) {
         const char *walk;
         char *outwalk = buffer;
 
@@ -68,22 +82,22 @@ void print_disk_info(yajl_gen json_gen, char *buffer, const char *path, const ch
                 }
 
                 if (BEGINS_WITH(walk+1, "free")) {
-                        outwalk += print_bytes_human(outwalk, (uint64_t)buf.f_bsize * (uint64_t)buf.f_bfree);
+                        outwalk += print_bytes_human(outwalk, (uint64_t)buf.f_bsize * (uint64_t)buf.f_bfree, prefix_type);
                         walk += strlen("free");
                 }
 
                 if (BEGINS_WITH(walk+1, "used")) {
-                        outwalk += print_bytes_human(outwalk, (uint64_t)buf.f_bsize * ((uint64_t)buf.f_blocks - (uint64_t)buf.f_bfree));
+                        outwalk += print_bytes_human(outwalk, (uint64_t)buf.f_bsize * ((uint64_t)buf.f_blocks - (uint64_t)buf.f_bfree), prefix_type);
                         walk += strlen("used");
                 }
 
                 if (BEGINS_WITH(walk+1, "total")) {
-                        outwalk += print_bytes_human(outwalk, (uint64_t)buf.f_bsize * (uint64_t)buf.f_blocks);
+                        outwalk += print_bytes_human(outwalk, (uint64_t)buf.f_bsize * (uint64_t)buf.f_blocks, prefix_type);
                         walk += strlen("total");
                 }
 
                 if (BEGINS_WITH(walk+1, "avail")) {
-                        outwalk += print_bytes_human(outwalk, (uint64_t)buf.f_bsize * (uint64_t)buf.f_bavail);
+                        outwalk += print_bytes_human(outwalk, (uint64_t)buf.f_bsize * (uint64_t)buf.f_bavail, prefix_type);
                         walk += strlen("avail");
                 }