Only update resolv.conf if changed (avoid logspam)

[project/netifd.git] / utils.c

diff --git a/utils.c b/utils.c
index 14e966a..6b53c22 100644 (file)
--- a/utils.c
+++ b/utils.c
@@ -140,3 +140,31 @@ format_macaddr(uint8_t *mac)
 
        return str;
 }
+
+uint32_t
+crc32_file(FILE *fp)
+{
+       static uint32_t *crcvals = NULL;
+       if (!crcvals) {
+               crcvals = malloc(sizeof(*crcvals) * 256);
+
+               for (size_t i = 0; i < 256; ++i) {
+                       uint32_t c = i;
+                       for (size_t j = 0; j < 8; ++j)
+                               c = (c & 1) ? (0xEDB88320 ^ (c >> 1)) : (c >> 1);
+                       crcvals[i] = c;
+               }
+       }
+
+       uint8_t buf[1024];
+       size_t len;
+       uint32_t c = 0xFFFFFFFF;
+
+       do {
+               len = fread(buf, 1, sizeof(buf), fp);
+               for (size_t i = 0; i < len; ++i)
+                       c = crcvals[(c ^ buf[i]) & 0xFF] ^ (c >> 8);
+       } while (len == sizeof(buf));
+
+       return c ^ 0xFFFFFFFF;
+}