[lib] add full_write() utility function

Signed-off-by: Denys Vlasenko <[email protected]>

Author: dvlasenk

include/rpminspect.h

@@ -322,6 +322,9 @@ void dump_cfg(const struct rpminspect *);
 void *read_file_bytes(const char *path, off_t *len);
 string_list_t *read_file(const char *);
 
+/* io.c */
+ssize_t full_write(int fd, const void *buf, size_t len);
+
 /* release.c */
 char *read_release(const rpmfile_t *);
 const char *get_before_rel(struct rpminspect *);

lib/io.c

@@ -0,0 +1,39 @@
+/*
+ * Copyright The rpminspect Project Authors
+ * SPDX-License-Identifier: LGPL-3.0-or-later
+ */
+
+#include <unistd.h>
+
+/*
+ * Write *all* of the supplied buffer out to a fd.
+ * Do multiple writes if necessary.
+ * Returns the amount written, or -1 if error was seen
+ * on the very first write.
+ * The write will be incomplete only if an error occurs
+ * on one of subsequent writes.
+ */
+ssize_t full_write(int fd, const void *buf, size_t len)
+{
+    ssize_t total = 0;
+
+    while (len != 0) {
+        ssize_t cc = write(fd, buf, len);
+
+        if (cc < 0) {
+            if (total) {
+                /* we already wrote some! */
+                /* user can do another write to know the error code */
+                return total;
+            }
+
+            return cc;  /* write() returns -1 on failure. */
+        }
+
+        total += cc;
+        buf = ((const char *)buf) + cc;
+        len -= cc;
+    }
+
+    return total;
+}

lib/meson.build

@@ -77,6 +77,7 @@ librpminspect_sources = [
     'inspect_upstream.c',
     'inspect_virus.c',
     'inspect_xml.c',
+    'io.c',
     'joinpath.c',
     'koji.c',
     'listfuncs.c',