Merge pull request #9131 from poettering/memory-startswith

add new memory_startswith() helper and make use of it everywhere

src/basic/log.c

@@ -1037,13 +1037,9 @@ int log_struct_iovec_internal(
                         return -error;
         }
 
-        for (i = 0; i < n_input_iovec; i++) {
-                if (input_iovec[i].iov_len < STRLEN("MESSAGE="))
-                        continue;
-
-                if (memcmp(input_iovec[i].iov_base, "MESSAGE=", STRLEN("MESSAGE=")) == 0)
+        for (i = 0; i < n_input_iovec; i++)
+                if (memory_startswith(input_iovec[i].iov_base, input_iovec[i].iov_len, "MESSAGE="))
                         break;
-        }
 
         if (_unlikely_(i >= n_input_iovec)) /* Couldn't find MESSAGE=? */
                 return -error;

src/basic/string-util.h

@@ -209,3 +209,21 @@ static inline size_t strlen_ptr(const char *s) {
 
         return strlen(s);
 }
+
+/* Like startswith(), but operates on arbitrary memory blocks */
+static inline void *memory_startswith(const void *p, size_t sz, const char *token) {
+        size_t n;
+
+        assert(token);
+
+        n = strlen(token);
+        if (sz < n)
+                return NULL;
+
+        assert(p);
+
+        if (memcmp(p, token, n) != 0)
+                return NULL;
+
+        return (uint8_t*) p + n;
+}