1 files changed, 59 insertions, 0 deletions
diff --git a/src/scratch.c b/src/scratch.c
new file mode 100644
index 0000000..ae48ff6
--- /dev/null
+++ b/src/scratch.c
@@ -0,0 +1,59 @@
+#include <sys/mman.h>
+
+#include <errno.h>
+#include <stdint.h>
+
+#include "alloc.h"
+#include "common.h"
+#include "errors.h"
+
+/* TODO: Support malloc() backend for systems without MAP_ANON */
+#ifndef MAP_ANON
+#	error "System not supported (missing MAP_ANON)"
+#endif
+
+#if DEBUG
+#	define TMP_DFLT_BUFSZ (8)
+#else /* Probably super overkill, but that’s fine */
+#	define TMP_DFLT_BUFSZ (1 * 1024)
+#endif
+
+#define MAX(x, y) ((x) > (y) ? (x) : (y))
+
+void *
+tmpalloc(scratch_t *s, size_t nmemb, size_t size)
+{
+	if (unlikely(size > SIZE_MAX / nmemb)) {
+		errno = ENOMEM;
+		err("%s:", __func__);
+	}
+	size *= nmemb;
+
+	if (s->p == NULL) {
+#if !__linux__
+do_mmap:
+#endif
+		s->sz = MAX(size, TMP_DFLT_BUFSZ);
+		s->p = mmap(s->p, s->sz, PROT_READ | PROT_WRITE,
+		            MAP_PRIVATE | MAP_ANON, -1, 0);
+		if (s->p == MAP_FAILED)
+			err("mmap:");
+	} else if (size > s->sz) {
+#if __linux__
+		if ((s->p = mremap(s->p, s->sz, size, MREMAP_MAYMOVE)) == MAP_FAILED)
+			err("mremap:");
+		s->sz = size;
+#else
+		munmap(s->p, s->sz);
+		goto do_mmap;
+#endif
+	}
+
+	return s->p;
+}
+
+void
+tmpfree(scratch_t *s)
+{
+	munmap(s->p, s->sz);
+}