Add --si flag for base 10 prefixes

This is a slightly modified patch contributed at

  http://dev.yorhel.nl/ncdu/bug/35

doc/ncdu.pod

@@ -97,6 +97,12 @@ option has no effect when C<-o> is used, because there will not be a browser
 interface in that case. It has no effect when C<-f> is used, either, because
 the deletion feature is disabled in that case anyway.
 
+=item --si
+
+List sizes using base 10 prefixes, that is, powers of 1000 (KB, MB, etc), as
+defined in the International System of Units (SI), instead of the usual base 2
+prefixes, that is, powers of 1024 (KiB, MiB, etc).
+
 =back
 
 =head2 Scan Options

src/main.c

@@ -127,10 +127,12 @@ static void argv_parse(int argc, char **argv) {
     {  1,  1, "--exclude" },
     { 'X', 1, "-X,--exclude-from" },
     { 'C', 0, "--exclude-caches" },
+    { 's', 0, "--si" },
     {0,0,NULL}
   };
 
   dir_ui = -1;
+  si = 0;
 
   yopt_init(&yopt, argc, argv, opts);
   while((v = yopt_next(&yopt, &val)) != -1) {
@@ -146,6 +148,7 @@ static void argv_parse(int argc, char **argv) {
       printf("  -o FILE                    Export scanned directory to FILE\n");
       printf("  -f FILE                    Import scanned directory from FILE\n");
       printf("  -0,-1,-2                   UI to use when scanning (0=none,2=full ncurses)\n");
+      printf("  --si                       Use base 10 (SI) prefixes instead of base 2\n");
       printf("  --exclude PATTERN          Exclude files that match PATTERN\n");
       printf("  -X, --exclude-from FILE    Exclude files that match any pattern in FILE\n");
       printf("  --exclude-caches           Exclude directories containing CACHEDIR.TAG\n");
@@ -156,6 +159,7 @@ static void argv_parse(int argc, char **argv) {
       exit(0);
     case 'x': dir_scan_smfs = 1; break;
     case 'r': read_only = 1; break;
+    case 's': si = 1; break;
     case 'o': export = val; break;
     case 'f': import = val; break;
     case '0': dir_ui = 0; break;

src/util.c

@@ -32,6 +32,7 @@
 
 int winrows, wincols;
 int subwinr, subwinc;
+int si;
 char thou_sep;
 
 
@@ -60,14 +61,26 @@ char *formatsize(int64_t from) {
   static char dat[9]; /* "xxx.xMiB" */
   float r = from;
   char c = ' ';
-  if(r < 1000.0f)      { }
-  else if(r < 1023e3f) { c = 'K'; r/=1024.0f; }
-  else if(r < 1023e6f) { c = 'M'; r/=1048576.0f; }
-  else if(r < 1023e9f) { c = 'G'; r/=1073741824.0f; }
-  else if(r < 1023e12f){ c = 'T'; r/=1099511627776.0f; }
-  else if(r < 1023e15f){ c = 'P'; r/=1125899906842624.0f; }
-  else                 { c = 'E'; r/=1152921504606846976.0f; }
-  sprintf(dat, "%5.1f%c%cB", r, c, c == ' ' ? ' ' : 'i');
+  if (si) {
+    if(r < 1000.0f)   { }
+    else if(r < 1e6f) { c = 'K'; r/=1e3f; }
+    else if(r < 1e9f) { c = 'M'; r/=1e6f; }
+    else if(r < 1e12f){ c = 'G'; r/=1e9f; }
+    else if(r < 1e15f){ c = 'T'; r/=1e12f; }
+    else if(r < 1e18f){ c = 'P'; r/=1e15f; }
+    else              { c = 'E'; r/=1e18f; }
+    sprintf(dat, "%5.1f%cB", r, c);
+  }
+  else {
+    if(r < 1000.0f)      { }
+    else if(r < 1023e3f) { c = 'K'; r/=1024.0f; }
+    else if(r < 1023e6f) { c = 'M'; r/=1048576.0f; }
+    else if(r < 1023e9f) { c = 'G'; r/=1073741824.0f; }
+    else if(r < 1023e12f){ c = 'T'; r/=1099511627776.0f; }
+    else if(r < 1023e15f){ c = 'P'; r/=1125899906842624.0f; }
+    else                 { c = 'E'; r/=1152921504606846976.0f; }
+    sprintf(dat, "%5.1f%c%cB", r, c, c == ' ' ? ' ' : 'i');
+  }
   return dat;
 }
 

src/util.h

@@ -35,6 +35,9 @@ extern int winrows, wincols;
 /* used by the nc* functions and macros */
 extern int subwinr, subwinc;
 
+/* used by formatsize to choose between base 2 or 10 prefixes */
+extern int si;
+
 
 /* Instead of using several ncurses windows, we only draw to stdscr.
  * the functions nccreate, ncprint and the macros ncaddstr and ncaddch