replace const sized array with dynamic array for handling modes

1 files changed, 39 insertions, 0 deletions

diff --git a/src/sbuffer.h b/src/sbuffer.h
new file mode 100644
index 0000000..92ac811
--- /dev/null
+++ b/src/sbuffer.h
@@ -0,0 +1,39 @@
+#ifndef SBUFFER_H
+#define SBUFFER_H
+
+#include <stdlib.h>
+#include <stdint.h>
+
+struct buf_hdr
+{
+    size_t len;
+    size_t cap;
+    char buf[0];
+};
+
+#define MAX(a, b) ((a) > (b) ? (a) : (b))
+#define OFFSETOF(t, f) (size_t)((char *)&(((t *)0)->f) - (char *)0)
+
+#define buf__hdr(b) ((struct buf_hdr *)((char *)(b) - OFFSETOF(struct buf_hdr, buf)))
+#define buf__should_grow(b, n) (buf_len(b) + (n) >= buf_cap(b))
+#define buf__fit(b, n) (buf__should_grow(b, n) ? ((b) = buf__grow_f(b, buf_len(b) + (n), sizeof(*(b)))) : 0)
+
+#define buf_len(b) ((b) ? buf__hdr(b)->len : 0)
+#define buf_cap(b) ((b) ? buf__hdr(b)->cap : 0)
+#define buf_push(b, x) (buf__fit(b, 1), (b)[buf_len(b)] = (x), buf__hdr(b)->len++)
+#define buf_last(b) ((b)[buf_len(b)-1])
+#define buf_free(b) ((b) ? free(buf__hdr(b)) : 0)
+
+static void *buf__grow_f(const void *buf, size_t new_len, size_t elem_size)
+{
+    size_t new_cap = MAX(1 + 2*buf_cap(buf), new_len);
+    size_t new_size = OFFSETOF(struct buf_hdr, buf) + new_cap*elem_size;
+    struct buf_hdr *new_hdr = realloc(buf ? buf__hdr(buf) : 0, new_size);
+    new_hdr->cap = new_cap;
+    if (!buf) {
+        new_hdr->len = 0;
+    }
+    return new_hdr->buf;
+}
+
+#endif