lib/kvstore.c

// SPDX-License-Identifier:     BSD-3-Clause
/*
 * Copyright (c) 2018 The Fuchsia Authors
 *
 */

#include <kvstore.h>

// header, key, zero, value, zero
#define RECLEN(ksz, vsz) (2 + (ksz) + 1 + (vsz) + 1)

void kvs_init(kvstore_t *kvs, void *buffer, size_t buflen)
{
	kvs->data = buffer;
	kvs->datamax = buflen;
	kvs->kvcount = 0;
	if (buflen < sizeof(kvshdr_t))
		kvs->datalen = kvs->datamax;
	else
		kvs->datalen = sizeof(kvshdr_t);
}

int kvs_load(kvstore_t *kvs, void *buffer, size_t buflen)
{
	// initially configure kvstore as invalid to provide
	// some protection against using after ignoring the
	// return value of load
	kvs->data = buffer;
	kvs->datalen = buflen;
	kvs->datamax = buflen;
	kvs->kvcount = 0;

	kvshdr_t hdr;

	if (buflen < sizeof(hdr))
		return KVS_ERR_BAD_PARAM;

	memcpy(&hdr, buffer, sizeof(hdr));
	if (hdr.version != KVSTORE_VERSION || hdr.length < sizeof(hdr))
		return KVS_ERR_PARSE_HDR;
	if (hdr.length > buflen)
		return KVS_ERR_PARSE_HDR;
	if (hdr.flags != 0)
		return KVS_ERR_PARSE_HDR;
	if (hdr.reserved != 0)
		return KVS_ERR_PARSE_HDR;

	uint32_t crc = crc32(0, buffer, sizeof(hdr) - sizeof(uint32_t));

	crc = crc32(crc, buffer + sizeof(hdr), hdr.length - sizeof(hdr));
	if (crc != hdr.crc)
		return KVS_ERR_PARSE_CRC;

	size_t count = 0;
	uint8_t *kv = buffer + sizeof(hdr);
	uint8_t *rec = kv;
	size_t avail = hdr.length - sizeof(hdr);

	while (avail > 0) {
		if (avail < 2)
			return KVS_ERR_PARSE_REC;

		size_t klen = rec[0];
		size_t vlen = rec[1];
		size_t reclen = RECLEN(klen, vlen);

		if (avail < reclen)
			return KVS_ERR_PARSE_REC;
		if (rec[2 + klen] != 0)
			return KVS_ERR_PARSE_REC;
		if (rec[2 + klen + 1 + vlen] != 0)
			return KVS_ERR_PARSE_REC;

		rec += reclen;
		avail -= reclen;
		count++;
	}

	kvs->kvcount = count;
	kvs->datalen = sizeof(hdr) + (rec - kv);
	return KVS_OK;
}

int kvs_save(kvstore_t *kvs)
{
	if (kvs->datamax < sizeof(kvshdr_t))
		return KVS_ERR_OUT_OF_SPACE;

	kvshdr_t hdr;

	hdr.version = KVSTORE_VERSION;
	hdr.flags = 0;
	hdr.length = kvs->datalen;
	hdr.reserved = 0;
	hdr.crc = crc32(0, (const void *)&hdr, sizeof(hdr) - sizeof(uint32_t));
	hdr.crc = crc32(hdr.crc, kvs->data + sizeof(hdr), hdr.length - sizeof(hdr));
	memcpy(kvs->data, &hdr, sizeof(hdr));
	return KVS_OK;
}

int kvs_addn(kvstore_t *kvs, const void *key, size_t klen, const void *val, size_t vlen)
{
	// ensure valid parameters
	if (klen == 0 || klen > 255 || vlen > 255)
		return KVS_ERR_BAD_PARAM;

	// ensure available space
	size_t reclen = RECLEN(klen, vlen);

	if (reclen > (kvs->datamax - kvs->datalen))
		return KVS_ERR_OUT_OF_SPACE;

	uint8_t *rec = kvs->data + kvs->datalen;

	*rec++ = klen;
	*rec++ = vlen;
	memcpy(rec, key, klen);
	rec += klen;
	*rec++ = 0;
	memcpy(rec, val, vlen);
	rec += vlen;
	*rec++ = 0;

	kvs->datalen += reclen;
	kvs->kvcount++;
	return KVS_OK;
}

int kvs_add(kvstore_t *kvs, const char *key, const char *value)
{
	return kvs_addn(kvs, key, strlen(key), value, strlen(value));
}

int kvs_getn(kvstore_t *kvs, const void *key, size_t klen, const void **val, size_t *vlen)
{
	uint8_t *rec = kvs->data + sizeof(kvshdr_t);
	size_t count;

	for (count = 0; count < kvs->kvcount; count++) {
		size_t ksz = rec[0];
		size_t vsz = rec[1];

		if (klen == ksz && !memcmp(key, rec + 2, klen)) {
			*val = rec + 2 + klen + 1;
			if (vlen)
				*vlen = vsz;

			return KVS_OK;
		}
		rec += RECLEN(ksz, vsz);
	}
	return KVS_ERR_NOT_FOUND;
}

const char *kvs_get(kvstore_t *kvs, const char *key, const char *fallback)
{
	const void *val;

	if (kvs_getn(kvs, key, strlen(key), &val, NULL) == KVS_OK)
		return (const char *)val;
	else
		return fallback;
}

int kvs_foreach(kvstore_t *kvs, void *cookie,
		int (*func)(void *cookie, const char *key, const char *val))
{
	uint8_t *rec = kvs->data + sizeof(kvshdr_t);
	size_t count;

	for (count = 0; count < kvs->kvcount; count++) {
		size_t ksz = rec[0];
		size_t vsz = rec[1];
		int r = func(cookie, (const char *)(rec + 2), (const char *)(rec + 2 + ksz + 1));

		if (r != KVS_OK)
			return r;

		rec += RECLEN(ksz, vsz);
	}
	return KVS_OK;
}