include/openssl/pool.h

// Copyright 2016 The BoringSSL Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#ifndef OPENSSL_HEADER_POOL_H
#define OPENSSL_HEADER_POOL_H

#include <openssl/base.h>  // IWYU pragma: export

#include <openssl/stack.h>

#if defined(__cplusplus)
extern "C" {
#endif


// Buffers and buffer pools.
//
// |CRYPTO_BUFFER|s are simply reference-counted, immutable byte string. A
// single |CRYPTO_BUFFER| can be referenced from multiple parts of an
// application without storing multiple copies of the underlying data in
// memory.
//
// A |CRYPTO_BUFFER_POOL| can be used to additionally deduplicate
// |CRYPTO_BUFFER|s on construction. It maintains weak references to associated
// |CRYPTO_BUFFER|s and returns an existing |CRYPTO_BUFFER| if matching ones
// already exist.
//
// Without a |CRYPTO_BUFFER_POOL|, if two parts of application construct an
// identical |CRYPTO_BUFFER| (e.g. if two TLS connections received the same
// certificate), there will be two copies of the buffer in memory. A
// |CRYPTO_BUFFER_POOL| allows two parts of an application that construct
// |CRYPTO_BUFFER|s to deduplicate their contents, at the cost of more thread
// contention.


DEFINE_STACK_OF(CRYPTO_BUFFER)

// CRYPTO_BUFFER_POOL_new returns a freshly allocated |CRYPTO_BUFFER_POOL| or
// NULL on error.
OPENSSL_EXPORT CRYPTO_BUFFER_POOL *CRYPTO_BUFFER_POOL_new(void);

// CRYPTO_BUFFER_POOL_free decrements the reference count of |pool| and frees it
// if the reference count drops to zero.
OPENSSL_EXPORT void CRYPTO_BUFFER_POOL_free(CRYPTO_BUFFER_POOL *pool);

// CRYPTO_BUFFER_POOL_up_ref increments the reference count of |pool| and
// returns one. It does not mutate |pool| for thread-safety purposes and may be
// used concurrently.
OPENSSL_EXPORT int CRYPTO_BUFFER_POOL_up_ref(CRYPTO_BUFFER_POOL *pool);

// CRYPTO_BUFFER_new returns a |CRYPTO_BUFFER| containing a copy of |data|, or
// else NULL on error. If |pool| is not NULL then the returned value may be a
// reference to a previously existing |CRYPTO_BUFFER| that contained the same
// data. Otherwise, the returned, fresh |CRYPTO_BUFFER| will be added to the
// pool.
//
// There is no requirement that |pool| outlive the |CRYPTO_BUFFER|, or vice
// versa. If the |CRYPTO_BUFFER| is released first, it will be removed from
// |pool|. If |pool| is released first, the |CRYPTO_BUFFER| remains valid.
OPENSSL_EXPORT CRYPTO_BUFFER *CRYPTO_BUFFER_new(const uint8_t *data, size_t len,
                                                CRYPTO_BUFFER_POOL *pool);

// CRYPTO_BUFFER_alloc creates an unpooled |CRYPTO_BUFFER| of the given size and
// writes the underlying data pointer to |*out_data|. It returns NULL on error.
//
// After calling this function, |len| bytes of contents must be written to
// |out_data| before passing the returned pointer to any other BoringSSL
// functions. Once initialized, the |CRYPTO_BUFFER| should be treated as
// immutable.
OPENSSL_EXPORT CRYPTO_BUFFER *CRYPTO_BUFFER_alloc(uint8_t **out_data,
                                                  size_t len);

// CRYPTO_BUFFER_new_from_CBS acts the same as |CRYPTO_BUFFER_new|.
OPENSSL_EXPORT CRYPTO_BUFFER *CRYPTO_BUFFER_new_from_CBS(
    const CBS *cbs, CRYPTO_BUFFER_POOL *pool);

// CRYPTO_BUFFER_new_from_static_data_unsafe behaves like |CRYPTO_BUFFER_new|
// but does not copy |data|. |data| must be immutable and last for the lifetime
// of the address space.
OPENSSL_EXPORT CRYPTO_BUFFER *CRYPTO_BUFFER_new_from_static_data_unsafe(
    const uint8_t *data, size_t len, CRYPTO_BUFFER_POOL *pool);

// CRYPTO_BUFFER_free decrements the reference count of |buf|. If there are no
// other references, or if the only remaining reference is from a pool, then
// |buf| will be freed.
OPENSSL_EXPORT void CRYPTO_BUFFER_free(CRYPTO_BUFFER *buf);

// CRYPTO_BUFFER_up_ref increments the reference count of |buf| and returns
// one.
OPENSSL_EXPORT int CRYPTO_BUFFER_up_ref(CRYPTO_BUFFER *buf);

// CRYPTO_BUFFER_dup_ref increments the reference count of |buf| and returns
// |buf|. The caller must call |CRYPTO_BUFFER_free| on the result to release the
// reference.
OPENSSL_EXPORT CRYPTO_BUFFER *CRYPTO_BUFFER_dup_ref(const CRYPTO_BUFFER *buf);

// CRYPTO_BUFFER_data returns a pointer to the data contained in |buf|.
OPENSSL_EXPORT const uint8_t *CRYPTO_BUFFER_data(const CRYPTO_BUFFER *buf);

// CRYPTO_BUFFER_len returns the length, in bytes, of the data contained in
// |buf|.
OPENSSL_EXPORT size_t CRYPTO_BUFFER_len(const CRYPTO_BUFFER *buf);

// CRYPTO_BUFFER_init_CBS initialises |out| to point at the data from |buf|.
OPENSSL_EXPORT void CRYPTO_BUFFER_init_CBS(const CRYPTO_BUFFER *buf, CBS *out);


#if defined(__cplusplus)
}  // extern C

extern "C++" {

BSSL_NAMESPACE_BEGIN

BORINGSSL_MAKE_DELETER(CRYPTO_BUFFER_POOL, CRYPTO_BUFFER_POOL_free)
BORINGSSL_MAKE_UP_REF(CRYPTO_BUFFER_POOL, CRYPTO_BUFFER_POOL_up_ref)
BORINGSSL_MAKE_DELETER(CRYPTO_BUFFER, CRYPTO_BUFFER_free)
BORINGSSL_MAKE_UP_REF(CRYPTO_BUFFER, CRYPTO_BUFFER_up_ref)

BSSL_NAMESPACE_END

}  // extern C++

#endif

#endif  // OPENSSL_HEADER_POOL_H