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-rw-r--r--src/basic/replace-var.c94
1 files changed, 94 insertions, 0 deletions
diff --git a/src/basic/replace-var.c b/src/basic/replace-var.c
new file mode 100644
index 0000000..fd2b5c1
--- /dev/null
+++ b/src/basic/replace-var.c
@@ -0,0 +1,94 @@
+/* SPDX-License-Identifier: LGPL-2.1+ */
+
+#include <errno.h>
+#include <stddef.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "alloc-util.h"
+#include "macro.h"
+#include "replace-var.h"
+#include "string-util.h"
+
+/*
+ * Generic infrastructure for replacing @FOO@ style variables in
+ * strings. Will call a callback for each replacement.
+ */
+
+static int get_variable(const char *b, char **r) {
+ size_t k;
+ char *t;
+
+ assert(b);
+ assert(r);
+
+ if (*b != '@')
+ return 0;
+
+ k = strspn(b + 1, UPPERCASE_LETTERS "_");
+ if (k <= 0 || b[k+1] != '@')
+ return 0;
+
+ t = strndup(b + 1, k);
+ if (!t)
+ return -ENOMEM;
+
+ *r = t;
+ return 1;
+}
+
+char *replace_var(const char *text, char *(*lookup)(const char *variable, void *userdata), void *userdata) {
+ char *r, *t;
+ const char *f;
+ size_t l;
+
+ assert(text);
+ assert(lookup);
+
+ l = strlen(text);
+ r = new(char, l+1);
+ if (!r)
+ return NULL;
+
+ f = text;
+ t = r;
+ while (*f) {
+ _cleanup_free_ char *v = NULL, *n = NULL;
+ char *a;
+ int k;
+ size_t skip, d, nl;
+
+ k = get_variable(f, &v);
+ if (k < 0)
+ goto oom;
+ if (k == 0) {
+ *(t++) = *(f++);
+ continue;
+ }
+
+ n = lookup(v, userdata);
+ if (!n)
+ goto oom;
+
+ skip = strlen(v) + 2;
+
+ d = t - r;
+ nl = l - skip + strlen(n);
+ a = realloc(r, nl + 1);
+ if (!a)
+ goto oom;
+
+ l = nl;
+ r = a;
+ t = r + d;
+
+ t = stpcpy(t, n);
+ f += skip;
+ }
+
+ *t = 0;
+ return r;
+
+oom:
+ return mfree(r);
+}