1 files changed, 221 insertions, 0 deletions
diff --git a/lib/generic/pack.h b/lib/generic/pack.h
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--- /dev/null
+++ b/lib/generic/pack.h
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+/*  Copyright (C) CZ.NIC, z.s.p.o. <knot-resolver@labs.nic.cz>
+ *  SPDX-License-Identifier: GPL-3.0-or-later
+ */
+
+/**
+ * @file pack.h
+ * @brief A length-prefixed list of objects, also an array list.
+ *
+ * Each object is prefixed by item length, unlike array this structure
+ * permits variable-length data. It is also equivalent to forward-only list
+ * backed by an array.
+ *
+ * @note Maximum object size is 2^16 bytes, see  ::pack_objlen_t
+ * @todo If some mistake happens somewhere, the access may end up in an infinite loop.
+ *       (equality comparison on pointers)
+ *
+ * # Example usage:
+ *
+ * @code{.c}
+ *      pack_t pack;
+ *      pack_init(pack);
+ *
+ *      // Reserve 2 objects, 6 bytes total
+ *      pack_reserve(pack, 2, 4 + 2);
+ *
+ *      // Push 2 objects
+ *      pack_obj_push(pack, U8("jedi"), 4)
+ *      pack_obj_push(pack, U8("\xbe\xef"), 2);
+ *
+ *      // Iterate length-value pairs
+ *      uint8_t *it = pack_head(pack);
+ *      while (it != pack_tail(pack)) {
+ *          uint8_t *val = pack_obj_val(it);
+ *          it = pack_obj_next(it);
+ *      }
+ *
+ *      // Remove object
+ *      pack_obj_del(pack, U8("jedi"), 4);
+ *
+ *      pack_clear(pack);
+ * @endcode
+ *
+ * \addtogroup generics
+ * @{
+ */
+
+#pragma once
+
+#include <stdint.h>
+#include <string.h>
+#include "array.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/** Packed object length type. */
+typedef uint16_t pack_objlen_t;
+
+/** Pack is defined as an array of bytes */
+typedef array_t(uint8_t) pack_t;
+
+/** Zero-initialize the pack. */
+#define pack_init(pack) \
+	array_init(pack)
+
+/** Make the pack empty and free pointed-to memory (plain malloc/free). */
+#define pack_clear(pack) \
+	array_clear(pack)
+
+/** Make the pack empty and free pointed-to memory.
+ * Mempool usage: pass mm_free and a knot_mm_t* . */
+#define pack_clear_mm(pack, free, baton) \
+	array_clear_mm((pack), (free), (baton))
+
+/** Reserve space for *additional* objects in the pack (plain malloc/free).
+ * @return 0 if success, <0 on failure */
+#define pack_reserve(pack, objs_count, objs_len) \
+	pack_reserve_mm((pack), (objs_count), (objs_len), array_std_reserve, NULL)
+
+/** Reserve space for *additional* objects in the pack.
+ * Mempool usage: pass kr_memreserve and a knot_mm_t* .
+ * @return 0 if success, <0 on failure */
+#define pack_reserve_mm(pack, objs_count, objs_len, reserve, baton) \
+	array_reserve_mm((pack), (pack).len + (sizeof(pack_objlen_t)*(objs_count) + (objs_len)), (reserve), (baton))
+
+/** Return pointer to first packed object.
+ *
+ * Recommended way to iterate:
+ *   for (uint8_t *it = pack_head(pack); it != pack_tail(pack); it = pack_obj_next(it))
+ */
+#define pack_head(pack) \
+	((pack).len > 0 ? &((pack).at[0]) : NULL)
+
+/** Return pack end pointer. */
+#define pack_tail(pack) \
+	((pack).len > 0 ? &((pack).at[(pack).len]) : NULL)
+
+/** Return packed object length. */
+static inline pack_objlen_t pack_obj_len(uint8_t *it)
+{
+	pack_objlen_t len = 0;
+	if (it != NULL)
+		memcpy(&len, it, sizeof(len));
+	return len;
+}
+
+/** Return packed object value. */
+static inline uint8_t *pack_obj_val(uint8_t *it)
+{
+	if (kr_fails_assert(it))
+		return NULL;
+	return it + sizeof(pack_objlen_t);
+}
+
+/** Return pointer to next packed object. */
+static inline uint8_t *pack_obj_next(uint8_t *it)
+{
+	if (kr_fails_assert(it))
+		return NULL;
+	return pack_obj_val(it) + pack_obj_len(it);
+}
+
+/** Return pointer to the last packed object. */
+static inline uint8_t *pack_last(pack_t pack)
+{
+	if (pack.len == 0)
+		return NULL;
+	uint8_t *it = pack_head(pack);
+	uint8_t *tail = pack_tail(pack);
+	while (true) {
+		uint8_t *next = pack_obj_next(it);
+		if (next == tail)
+			return it;
+		it = next;
+	}
+}
+
+/** Push object to the end of the pack
+  * @return 0 on success, negative number on failure
+  */
+static inline int pack_obj_push(pack_t *pack, const uint8_t *obj, pack_objlen_t len)
+{
+	if (kr_fails_assert(pack && obj))
+		return kr_error(EINVAL);
+	size_t packed_len = len + sizeof(len);
+	if (pack->len + packed_len > pack->cap)
+		return kr_error(ENOSPC);
+
+	uint8_t *endp = pack->at + pack->len;
+	memcpy(endp, (char *)&len, sizeof(len));
+	memcpy(endp + sizeof(len), obj, len);
+	pack->len += packed_len;
+	return 0;
+}
+
+/** Returns a pointer to packed object.
+  * @return pointer to packed object or NULL
+  */
+static inline uint8_t *pack_obj_find(pack_t *pack, const uint8_t *obj, pack_objlen_t len)
+{
+	if (!pack || kr_fails_assert(obj))
+		return NULL;
+	uint8_t *endp = pack_tail(*pack);
+	uint8_t *it = pack_head(*pack);
+	while (it != endp) {
+		uint8_t *val = pack_obj_val(it);
+		if (pack_obj_len(it) == len && memcmp(obj, val, len) == 0)
+			return it;
+		it = pack_obj_next(it);
+	}
+	return NULL;
+}
+
+/** Delete object from the pack
+  * @return 0 on success, negative number on failure
+  */
+static inline int pack_obj_del(pack_t *pack, const uint8_t *obj, pack_objlen_t len)
+{
+	if (!pack || kr_fails_assert(obj))
+		return kr_error(EINVAL);
+	uint8_t *endp = pack_tail(*pack);
+	uint8_t *it = pack_obj_find(pack, obj, len);
+	if (it) {
+		size_t packed_len = len + sizeof(len);
+		memmove(it, it + packed_len, endp - it - packed_len);
+		pack->len -= packed_len;
+		return 0;
+	}
+	return -1;
+}
+
+/** Clone a pack, replacing destination pack; (*dst == NULL) is valid input.
+ * @return kr_error(ENOMEM) on allocation failure. */
+static inline int pack_clone(pack_t **dst, const pack_t *src, knot_mm_t *pool)
+{
+	if (kr_fails_assert(dst && src))
+		return kr_error(EINVAL);
+	/* Get a valid pack_t. */
+	if (!*dst) {
+		*dst = mm_alloc(pool, sizeof(pack_t));
+		if (!*dst) return kr_error(ENOMEM);
+		pack_init(**dst);
+		/* Clone data only if needed */
+		if (src->len == 0) return kr_ok();
+	}
+	/* Replace the contents of the pack_t. */
+	int ret = array_reserve_mm(**dst, src->len, kr_memreserve, pool);
+	if (ret < 0) {
+		return kr_error(ENOMEM);
+	}
+	memcpy((*dst)->at, src->at, src->len);
+	(*dst)->len = src->len;
+	return kr_ok();
+}
+
+#ifdef __cplusplus
+}
+#endif
+
+/** @} */