procfs: add num_to_str() to speed up /proc/stat

[karo-tx-linux.git] / fs / seq_file.c

diff --git a/fs/seq_file.c b/fs/seq_file.c
index aa242dc99373bec0fe981d22508921454759bd14..7d19816c4cc9799265e6b1b876eb0851bf214b44 100644 (file)
--- a/fs/seq_file.c
+++ b/fs/seq_file.c
@@ -644,6 +644,39 @@ int seq_puts(struct seq_file *m, const char *s)
 }
 EXPORT_SYMBOL(seq_puts);
 
+/*
+ * A helper routine for putting decimal numbers without rich format of printf().
+ * only 'unsigned long long' is supported.
+ * This routine will put one byte delimiter + number into seq_file.
+ * This routine is very quick when you show lots of numbers.
+ * In usual cases, it will be better to use seq_printf(). It's easier to read.
+ */
+int seq_put_decimal_ull(struct seq_file *m, char delimiter,
+                       unsigned long long num)
+{
+       int len;
+
+       if (m->count + 2 >= m->size) /* we'll write 2 bytes at least */
+               goto overflow;
+
+       m->buf[m->count++] = delimiter;
+
+       if (num < 10) {
+               m->buf[m->count++] = num + '0';
+               return 0;
+       }
+
+       len = num_to_str(m->buf + m->count, m->size - m->count, num);
+       if (!len)
+               goto overflow;
+       m->count += len;
+       return 0;
+overflow:
+       m->count = m->size;
+       return -1;
+}
+EXPORT_SYMBOL(seq_put_decimal_ull);
+
 /**
  * seq_write - write arbitrary data to buffer
  * @seq: seq_file identifying the buffer to which data should be written