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+/*
+ * Simple & stupid dynamic array single-header implementation.  You can use the
+ * macros defined in this file with any structure that has the following fields:
+ *
+ *  struct dyn_array {
+ *      T *buf  // Array of items
+ *      N  len  // Length of array
+ *      N  cap  // Capacity of array
+ *  }
+ *
+ * The type ‘T’ is whatever type you want to store.  The type ‘N’ is any numeric
+ * type, most likely ‘size_t’.
+ *
+ * You should include ‘err.h’ and ‘stdlib.h’ along with this file.  If you want
+ * to use da_remove(), include ‘string.h’.  The da_remove() macro also doesn’t
+ * bother with shrinking your array when the length is far lower than the
+ * capacity.  If you care about that, do it yourself.
+ *
+ *
+ * Macro Overview
+ * ――――――――――――――
+ * The argument ‘a’ to all of the below macros is a pointer to the dynamic array
+ * structure.
+ *
+ * da_init(a, n)             Initialize the array with a capacity of ‘n’ items.
+ * da_append(a, x)           Append the item ‘x’ to the array
+ * da_remove(a, x)           Remove the item ‘x’ from the array
+ * da_remove_range(a, x, y)  Remove the items between the range [x, y)
+ */
+
+#ifndef MANGO_DA_H
+#define MANGO_DA_H
+
+#define __da_s(a) (sizeof(*(a)->buf))
+
+#define da_init(a, n) \
+	do { \
+		(a)->cap = n; \
+		(a)->len = 0; \
+		(a)->buf = malloc((a)->cap * __da_s(a)); \
+		if ((a)->buf == NULL) \
+			err(EXIT_FAILURE, "malloc"); \
+	} while (0)
+
+#define da_append(a, x) \
+	do { \
+		if ((a)->len >= (a)->cap) { \
+			(a)->cap = (a)->cap * 2 + 1; \
+			(a)->buf = realloc((a)->buf, (a)->cap * __da_s(a)); \
+			if ((a)->buf == NULL) \
+				err(EXIT_FAILURE, "realloc"); \
+		} \
+		(a)->buf[(a)->len++] = (x); \
+	} while (0)
+
+#define da_remove(a, i) da_remove_range((a), (i), (i) + 1)
+
+#define da_remove_range(a, i, j) \
+	do { \
+		memmove((a)->buf + (i), (a)->buf + (j), ((a)->len - (j)) * __da_s(a)); \
+		(a)->len -= j - i; \
+	} while (0)
+
+#endif /* !MANGO_DA_H */