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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
/** @} */
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