1 files changed, 58 insertions, 0 deletions
diff --git a/src/strutil.c b/src/strutil.c
new file mode 100644
index 0000000..9192989
--- /dev/null
+++ b/src/strutil.c
@@ -0,0 +1,58 @@
+#include "strutil.h"
+
+#include "arena.h"        // struct arena, new
+#include <assert.h>       // assert
+#include <stdarg.h>       // va_*
+#include <stdbool.h>      // bool, false
+#include <stdio.h>        // vsnprintf
+#include <string.h>       // strlen, strncmp
+
+int aprintf(struct arena *a, char **out, const char *fmt, ...) {
+	va_list ap;
+	va_start(ap, fmt);
+	int ret = vaprintf(a, out, fmt, ap);
+	va_end(ap);
+	return ret;
+}
+
+int vaprintf(struct arena *a, char **out, const char *fmt, va_list args) {
+	// Calculate size.
+	va_list tmp;
+	va_copy(tmp, args);
+	int size = vsnprintf(NULL, 0, fmt, args);
+	va_end(tmp);
+
+	// If e.g. the format string was broken, we cannot continue.
+	if (size < 0) {
+		return -1;
+	}
+
+	// Arena allocation cannot fail.
+	*out = new(a, char, size + 1);
+
+	int t = vsnprintf(*out, size + 1, fmt, args);
+	assert(t == size);
+
+	return size;
+}
+
+char *joinpath(struct arena *a, const char *path_a, const char *path_b) {
+	char *out;
+	int ret = aprintf(a, &out, "%s/%s", path_a, path_b);
+	assert(ret > 0 && "should be infallible");
+	return out;
+}
+
+bool endswith(const char *haystack, const char *needle) {
+	assert(haystack != NULL);
+	assert(needle != NULL);
+
+	size_t haystack_len = strlen(haystack);
+	size_t needle_len = strlen(needle);
+
+	if (needle_len > haystack_len) {
+		return false;
+	}
+
+	return strncmp(haystack + (haystack_len - needle_len), needle, needle_len) == 0;
+}