libbb: factor out common code from mpstat/iostat

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 47 insertions, 0 deletions

diff --git a/libbb/get_cpu_count.c b/libbb/get_cpu_count.c
new file mode 100644
index 0000000..a0dcb45
--- /dev/null
+++ b/libbb/get_cpu_count.c
@@ -0,0 +1,47 @@
+/* vi: set sw=4 ts=4: */
+/*
+ * Factored out of mpstat/iostat.
+ *
+ * Copyright (C) 2010 Marek Polacek <mmpolacek@gmail.com>
+ *
+ * Licensed under GPLv2, see file License in this tarball for details.
+ */
+#include "libbb.h"
+
+/* Does str start with "cpu"? */
+int FAST_FUNC starts_with_cpu(const char *str)
+{
+	return ((str[0] - 'c') | (str[1] - 'p') | (str[2] - 'u')) == 0;
+}
+
+/*
+ * Get number of processors. Uses /proc/stat.
+ * Return value 0 means one CPU and non SMP kernel.
+ * Otherwise N means N processor(s) and SMP kernel.
+ */
+unsigned FAST_FUNC get_cpu_count(void)
+{
+	FILE *fp;
+	char line[256];
+	int proc_nr = -1;
+
+	fp = xfopen_for_read("/proc/stat");
+	while (fgets(line, sizeof(line), fp)) {
+		if (!starts_with_cpu(line)) {
+			if (proc_nr >= 0)
+				break; /* we are past "cpuN..." lines */
+			continue;
+		}
+		if (line[3] != ' ') { /* "cpuN" */
+			int num_proc;
+			if (sscanf(line + 3, "%u", &num_proc) == 1
+			 && num_proc > proc_nr
+			) {
+				proc_nr = num_proc;
+			}
+		}
+	}
+
+	fclose(fp);
+	return proc_nr + 1;
+}