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/*
*
* Copyright (c) 2020-2021 Project CHIP Authors
* Copyright (c) 2016-2017 Nest Labs, Inc.
*
* 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
*
* http://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.
*/
/**
* @file
* This file defines the chip::System::PacketBuffer class,
* which provides the mechanisms for manipulating packets of *
* octet-serialized data.
*/
#pragma once
// Include configuration header
#include <system/SystemPacketBufferInternal.h>
// Include dependent headers
#include <lib/support/BufferWriter.h>
#include <lib/support/CodeUtils.h>
#include <lib/support/DLLUtil.h>
#include <system/SystemAlignSize.h>
#include <system/SystemError.h>
#include <stddef.h>
#include <utility>
#if CHIP_SYSTEM_CONFIG_USE_LWIP
#include <lwip/mem.h>
#include <lwip/memp.h>
#include <lwip/pbuf.h>
#endif // CHIP_SYSTEM_CONFIG_USE_LWIP
namespace chip {
namespace System {
class PacketBufferHandle;
#if !CHIP_SYSTEM_CONFIG_USE_LWIP
struct pbuf
{
struct pbuf * next;
void * payload;
uint16_t tot_len;
uint16_t len;
uint16_t ref;
#if CHIP_SYSTEM_PACKETBUFFER_FROM_CHIP_HEAP
uint16_t alloc_size;
#endif
};
#endif // !CHIP_SYSTEM_CONFIG_USE_LWIP
/** @class PacketBuffer
*
* @brief
* The packet buffer class is the core structure used for manipulating packets of octet-serialized data, usually in the
* context of a data communications network, like Bluetooth or the Internet protocol.
*
* In LwIP-based environments, this class is built on top of the pbuf structure defined in that library. In the absence of
* LwIP, chip provides either a malloc-based implementation, or a pool-based implementation that closely approximates the
* memory challenges of deeply embedded devices.
*
* The PacketBuffer class, like many similar structures used in layered network stacks, provide a mechanism to reserve space
* for protocol headers at each layer of a configurable communication stack. For details, see `PacketBufferHandle::New()`
* as well as LwIP documentation.
*
* PacketBuffer objects are reference-counted, and normally held and used through a PacketBufferHandle that owns one of the
* counted references. When a PacketBufferHandle goes out of scope, its reference is released. To take ownership, a function
* takes a PacketBufferHandle by value. To borrow ownership, a function takes a `const PacketBufferHandle &`.
*
* New objects of PacketBuffer class are initialized at the beginning of an allocation of memory obtained from the underlying
* environment, e.g. from LwIP pbuf target pools, from the standard C library heap, from an internal buffer pool. In the
* simple pool case, the size of the data buffer is PacketBuffer::kBlockSize.
*
* PacketBuffer objects may be chained to accommodate larger payloads. Chaining, however, is not transparent, and users of the
* class must explicitly decide to support chaining. Examples of classes written with chaining support are as follows:
*
* @ref chip::TLVReader
* @ref chip::TLVWriter
*
* ### PacketBuffer format
*
* <pre>
* ┌────────────────────────────────────┐
* │ ┌────────────────────┐ │
* │ │ │◁──────┴───────▷│
* ┏━━━━━━━━┿━━━━━━━┿━┳━━━━━━━━━━━━━━━━━━┳━━━━━━━━━━━━━━━━┳━━━━━━━━━━━━━━━━━━━━━━━━━┓
* ┃ pbuf len payload ┃ reserve ┃ data ┃ unused ┃
* ┗━━━━━━━━━━━━━━━━━━┻━━━━━━━━━━━━━━━━━━┻━━━━━━━━━━━━━━━━┻━━━━━━━━━━━━━━━━━━━━━━━━━┛
* │ │← ReservedSize() →│← DataLength() →│← AvailableDataLength() →│
* │ │ │← MaxDataLength() → · · · · · · · · · · ·→│
* │ │ Start() │
* │← kStructureSize →│← AllocSize() → · · · · · · · · · · · · · · · · · · · · · · →│
* </pre>
*
*/
class DLL_EXPORT PacketBuffer : private pbuf
{
private:
// The effective size of the packet buffer structure.
#if CHIP_SYSTEM_CONFIG_USE_LWIP
static constexpr uint16_t kStructureSize = LWIP_MEM_ALIGN_SIZE(sizeof(struct ::pbuf));
#else // CHIP_SYSTEM_CONFIG_USE_LWIP
static constexpr uint16_t kStructureSize = CHIP_SYSTEM_ALIGN_SIZE(sizeof(::chip::System::pbuf), 4u);
#endif // CHIP_SYSTEM_CONFIG_USE_LWIP
public:
/**
* The maximum size buffer an application can allocate with no protocol header reserve.
*/
#if CHIP_SYSTEM_CONFIG_USE_LWIP
static constexpr uint16_t kMaxSizeWithoutReserve = LWIP_MEM_ALIGN_SIZE(PBUF_POOL_BUFSIZE);
#else
static constexpr uint16_t kMaxSizeWithoutReserve = CHIP_SYSTEM_CONFIG_PACKETBUFFER_CAPACITY_MAX;
#endif
/**
* The number of bytes to reserve in a network packet buffer to contain all the possible protocol encapsulation headers
* before the application data.
*/
static constexpr uint16_t kDefaultHeaderReserve = CHIP_SYSTEM_CONFIG_HEADER_RESERVE_SIZE;
/**
* The maximum size buffer an application can allocate with the default protocol header reserve.
*/
static constexpr uint16_t kMaxSize = kMaxSizeWithoutReserve - kDefaultHeaderReserve;
/**
* Return the size of the allocation including the reserved and payload data spaces but not including space
* allocated for the PacketBuffer structure.
*
* @note The allocation size is equal to or greater than the \c aAllocSize parameter to the \c Create method).
*
* @return size of the allocation
*/
uint16_t AllocSize() const
{
#if CHIP_SYSTEM_PACKETBUFFER_FROM_LWIP_STANDARD_POOL || CHIP_SYSTEM_PACKETBUFFER_FROM_CHIP_POOL
return kMaxSizeWithoutReserve;
#elif CHIP_SYSTEM_PACKETBUFFER_FROM_CHIP_HEAP
return this->alloc_size;
#elif CHIP_SYSTEM_PACKETBUFFER_FROM_LWIP_CUSTOM_POOL
// Temporary workaround for custom pbufs by assuming size to be PBUF_POOL_BUFSIZE
if (this->flags & PBUF_FLAG_IS_CUSTOM)
return LWIP_MEM_ALIGN_SIZE(PBUF_POOL_BUFSIZE) - kStructureSize;
else
return LWIP_MEM_ALIGN_SIZE(memp_sizes[this->pool]) - kStructureSize;
#else
#error "Unimplemented PacketBuffer storage case"
#endif
}
/**
* Get a pointer to the start of data in a buffer.
*
* @return pointer to the start of data.
*/
uint8_t * Start() const { return static_cast<uint8_t *>(this->payload); }
/**
* Set the the start of data in a buffer, adjusting length and total length accordingly.
*
* @note The data within the buffer is not moved, only accounting information is changed. The function is commonly used to
* either strip or prepend protocol headers in a zero-copy way.
*
* @note This call should not be used on any buffer that is not the head of a buffer chain, as it only alters the current
* buffer.
*
* @param[in] aNewStart - A pointer to where the new payload should start. newStart will be adjusted internally to fall within
* the boundaries of the first buffer in the PacketBuffer chain.
*/
void SetStart(uint8_t * aNewStart);
/**
* Get the length, in bytes, of data in a packet buffer.
*
* @return length, in bytes (current payload length).
*/
uint16_t DataLength() const { return this->len; }
/**
* Set the length, in bytes, of data in a packet buffer, adjusting total length accordingly.
*
* The function sets the length, in bytes, of the data in the buffer, adjusting the total length appropriately. When the buffer
* is not the head of the buffer chain (common case: the caller adds data to the last buffer in the PacketBuffer chain prior to
* calling higher layers), the aChainHead __must__ be passed in to properly adjust the total lengths of each buffer ahead of
* the current buffer.
*
* @param[in] aNewLen - new length, in bytes, of this buffer.
*
* @param[in,out] aChainHead - the head of the buffer chain the current buffer belongs to. May be \c nullptr if the current
* buffer is the head of the buffer chain.
*/
void SetDataLength(uint16_t aNewLen, const PacketBufferHandle & aChainHead);
void SetDataLength(uint16_t aNewLen) { SetDataLength(aNewLen, nullptr); }
/**
* Get the total length of packet data in the buffer chain.
*
* @return total length, in octets.
*/
uint16_t TotalLength() const { return this->tot_len; }
/**
* Get the maximum amount, in bytes, of data that will fit in the buffer given the current start position and buffer size.
*
* @return number of bytes that fits in the buffer given the current start position.
*/
uint16_t MaxDataLength() const;
/**
* Get the number of bytes of data that can be added to the current buffer given the current start position and data length.
*
* @return the length, in bytes, of data that will fit in the current buffer given the current start position and data length.
*/
uint16_t AvailableDataLength() const;
/**
* Get the number of bytes within the current buffer between the start of the buffer and the current data start position.
*
* @return the amount, in bytes, of space between the start of the buffer and the current data start position.
*/
uint16_t ReservedSize() const;
/**
* Determine whether there are any additional buffers chained to the current buffer.
*
* @return \c true if there is a chained buffer.
*/
bool HasChainedBuffer() const { return ChainedBuffer() != nullptr; }
/**
* Add the given packet buffer to the end of the buffer chain, adjusting the total length of each buffer in the chain
* accordingly.
*
* @note The current packet buffer must be the head of the buffer chain for the lengths to be adjusted properly.
*
* @note Ownership is transferred from the argument to the `next` link at the end of the current chain.
*
* @param[in] aPacket - the packet buffer to be added to the end of the current chain.
*/
void AddToEnd(PacketBufferHandle && aPacket);
/**
* Move data from subsequent buffers in the chain into the current buffer until it is full.
*
* Only the current buffer is compacted: the data within the current buffer is moved to the front of the buffer, eliminating
* any reserved space. The remaining available space is filled with data moved from subsequent buffers in the chain, until the
* current buffer is full. If a subsequent buffer in the chain is moved into the current buffer in its entirety, it is removed
* from the chain and freed. The method takes no parameters, returns no results and cannot fail.
*/
void CompactHead();
/**
* Adjust the current buffer to indicate the amount of data consumed.
*
* Advance the data start position in the current buffer by the specified amount, in bytes, up to the length of data in the
* buffer. Decrease the length and total length by the amount consumed.
*
* @param[in] aConsumeLength - number of bytes to consume from the current buffer.
*/
void ConsumeHead(uint16_t aConsumeLength);
/**
* Ensure the buffer has at least the specified amount of reserved space.
*
* Ensure the buffer has at least the specified amount of reserved space, moving the data in the buffer forward to make room if
* necessary.
*
* @param[in] aReservedSize - number of bytes desired for the headers.
*
* @return \c true if the requested reserved size is available, \c false if there's not enough room in the buffer.
*/
CHECK_RETURN_VALUE bool EnsureReservedSize(uint16_t aReservedSize);
/**
* Align the buffer payload on the specified bytes boundary.
*
* Moving the payload in the buffer forward if necessary.
*
* @param[in] aAlignBytes - specifies number of bytes alignment for the payload start pointer.
*
* @return \c true if alignment is successful, \c false if there's not enough room in the buffer.
*/
bool AlignPayload(uint16_t aAlignBytes);
/**
* Return the next buffer in a buffer chain.
*
* If there is no next buffer, the handle will have \c IsNull() \c true.
*
* @return a handle to the next buffer in the buffer chain.
*/
CHECK_RETURN_VALUE PacketBufferHandle Next();
/**
* Return the last buffer in a buffer chain.
*
* @return a handle to the last buffer in the buffer chain.
*/
CHECK_RETURN_VALUE PacketBufferHandle Last();
/**
* Copies data from the payloads of a chain of packet buffers until a given amount of data has been copied.
*
* @param[in] buf Destination buffer; must be at least @a length bytes.
* @param[in] length Destination buffer length.
*
* @retval #CHIP_ERROR_BUFFER_TOO_SMALL If the total length of the payloads in the chain is less than the requested @a length.
* @retval #CHIP_ERROR_INTERNAL In case of an inconsistency in the buffer chain.
* @retval #CHIP_NO_ERROR If the requested payload has been copied.
*/
CHIP_ERROR Read(uint8_t * buf, size_t length) const;
template <size_t N>
inline CHIP_ERROR Read(uint8_t (&buf)[N]) const
{
return Read(buf, N);
}
/**
* Perform an implementation-defined check on the validity of a PacketBuffer pointer.
*
* Unless enabled by #CHIP_CONFIG_MEMORY_DEBUG_CHECKS == 1, this function does nothing.
*
* When enabled, it performs an implementation- and configuration-defined check on
* the validity of the packet buffer. It MAY log an error and/or abort the program
* if the packet buffer or the implementation-defined memory management system is in
* a faulty state. (Some configurations may not actually perform any check.)
*
* @note A null pointer is not considered faulty.
*
* @param[in] buffer - the packet buffer to check.
*/
static void Check(const PacketBuffer * buffer)
{
#if CHIP_SYSTEM_PACKETBUFFER_HAS_CHECK
InternalCheck(buffer);
#endif
}
private:
// Memory required for a maximum-size PacketBuffer.
static constexpr uint16_t kBlockSize = PacketBuffer::kStructureSize + PacketBuffer::kMaxSizeWithoutReserve;
// Note: this condition includes DOXYGEN to work around a Doxygen error. DOXYGEN is never defined in any actual build.
#if CHIP_SYSTEM_PACKETBUFFER_FROM_CHIP_POOL || defined(DOXYGEN)
typedef union
{
pbuf Header;
uint8_t Block[PacketBuffer::kBlockSize];
} BufferPoolElement;
static BufferPoolElement sBufferPool[CHIP_SYSTEM_CONFIG_PACKETBUFFER_POOL_SIZE];
static PacketBuffer * sFreeList;
static PacketBuffer * BuildFreeList();
#endif // CHIP_SYSTEM_PACKETBUFFER_FROM_CHIP_POOL || defined(DOXYGEN)
#if CHIP_SYSTEM_PACKETBUFFER_HAS_CHECK
static void InternalCheck(const PacketBuffer * buffer);
#endif
void AddRef();
bool HasSoleOwnership() const { return (this->ref == 1); }
static void Free(PacketBuffer * aPacket);
static PacketBuffer * FreeHead(PacketBuffer * aPacket);
PacketBuffer * ChainedBuffer() const { return static_cast<PacketBuffer *>(this->next); }
PacketBuffer * Consume(uint16_t aConsumeLength);
void Clear();
void SetDataLength(uint16_t aNewLen, PacketBuffer * aChainHead);
/**
* Get a pointer to the start of the reserved space (which comes before the
* payload). The actual reserved space is the ReservedSize() bytes starting
* at this pointer.
*/
uint8_t * ReserveStart();
const uint8_t * ReserveStart() const;
friend class PacketBufferHandle;
friend class TestSystemPacketBuffer;
};
static_assert(sizeof(pbuf) == sizeof(PacketBuffer), "PacketBuffer must not have additional members");
/**
* @class PacketBufferHandle
*
* @brief
* Tracks ownership of a PacketBuffer.
*
* PacketBuffer objects are reference-counted, and normally held and used through a PacketBufferHandle that owns one of the
* counted references. When a PacketBufferHandle goes out of scope, its reference is released. To take ownership, a function
* takes a PacketBufferHandle by value. To borrow ownership, a function takes a `const PacketBufferHandle &`.
*/
class DLL_EXPORT PacketBufferHandle
{
public:
/**
* Construct an empty PacketBufferHandle.
*/
PacketBufferHandle() : mBuffer(nullptr) {}
PacketBufferHandle(decltype(nullptr)) : mBuffer(nullptr) {}
/**
* Construct a PacketBufferHandle that takes ownership of a PacketBuffer from another.
*/
PacketBufferHandle(PacketBufferHandle && aOther)
{
mBuffer = aOther.mBuffer;
aOther.mBuffer = nullptr;
}
~PacketBufferHandle() { *this = nullptr; }
/**
* Take ownership of a PacketBuffer from another PacketBufferHandle, freeing any existing owned buffer.
*/
PacketBufferHandle & operator=(PacketBufferHandle && aOther)
{
if (mBuffer != nullptr)
{
PacketBuffer::Free(mBuffer);
}
mBuffer = aOther.mBuffer;
aOther.mBuffer = nullptr;
return *this;
}
/**
* Free any buffer owned by this handle.
*/
PacketBufferHandle & operator=(decltype(nullptr))
{
if (mBuffer != nullptr)
{
PacketBuffer::Free(mBuffer);
}
mBuffer = nullptr;
return *this;
}
/**
* Get a new handle to an existing buffer.
*
* @return a PacketBufferHandle that shares ownership with this.
*/
PacketBufferHandle Retain() const
{
mBuffer->AddRef();
return PacketBufferHandle(mBuffer);
}
/**
* Access a PackerBuffer's public methods.
*/
PacketBuffer * operator->() const { return mBuffer; }
/**
* Test whether this PacketBufferHandle is empty, or conversely owns a PacketBuffer.
*
* @return \c true if this PacketBufferHandle is empty; return \c false if it owns a PacketBuffer.
*/
bool IsNull() const { return mBuffer == nullptr; }
/**
* Test whether the PacketBuffer owned by this PacketBufferHandle has unique ownership.
*
* @return \c true if the PacketBuffer owned by this PacketBufferHandle is solely owned; return \c false if
* it has more than one ownership.
*/
bool HasSoleOwnership() const { return mBuffer->HasSoleOwnership(); }
/**
* Detach and return the head of a buffer chain while updating this handle to point to the remaining buffers.
* The current buffer must be the head of the chain.
*
* This PacketBufferHandle now holds the ownership formerly held by the head of the chain.
* The returned PacketBufferHandle holds the ownership formerly held by this.
*
* @return the detached buffer formerly at the head of the buffer chain.
*/
CHECK_RETURN_VALUE PacketBufferHandle PopHead();
/**
* Free the first buffer in a chain.
*
* @note When the buffer chain is referenced by multiple handles, `FreeHead()` will detach the head, but will not forcibly
* deallocate the head buffer.
*/
void FreeHead()
{
// `PacketBuffer::FreeHead()` frees the current head; this takes ownership from the `next` link.
mBuffer = PacketBuffer::FreeHead(mBuffer);
}
/**
* Add the given packet buffer to the end of the buffer chain, adjusting the total length of each buffer in the chain
* accordingly.
*
* @note The current packet buffer handle must either be the head of the buffer chain for the lengths to be adjusted properly,
* or be null (in which case it becomes the head).
*
* @note Ownership is transferred from the argument to the `next` link at the end of the current chain,
* or to the handle if it's currently null.
*
* @param[in] aPacket - the packet buffer to be added to the end of the current chain.
*/
void AddToEnd(PacketBufferHandle && aPacket)
{
if (IsNull())
{
mBuffer = aPacket.mBuffer;
aPacket.mBuffer = nullptr;
}
else
{
mBuffer->AddToEnd(std::move(aPacket));
}
}
/**
* Consume data in a chain of buffers.
*
* Consume data in a chain of buffers starting with the current buffer and proceeding through the remaining buffers in the
* chain. Each buffer that is completely consumed is freed and the handle holds the first buffer (if any) containing the
* remaining data. The current buffer must be the head of the buffer chain.
*
* @param[in] aConsumeLength - number of bytes to consume from the current chain.
*/
void Consume(uint16_t aConsumeLength) { mBuffer = mBuffer->Consume(aConsumeLength); }
/**
* Copy the given buffer to a right-sized buffer if applicable.
*
* Only operates on single buffers (for chains, use \c CompactHead() and RightSize the tail).
* Requires that this handle be the only reference to the underlying buffer.
*/
void RightSize()
{
#if CHIP_SYSTEM_PACKETBUFFER_HAS_RIGHTSIZE
InternalRightSize();
#endif
}
/**
* Get a new handle to a raw PacketBuffer pointer.
*
* @brief The caller's ownership is transferred to this.
*
* @note This should only be used in low-level code, e.g. to import buffers from LwIP or a similar stack.
*/
static PacketBufferHandle Adopt(PacketBuffer * buffer) { return PacketBufferHandle(buffer); }
#if CHIP_SYSTEM_CONFIG_USE_LWIP
static PacketBufferHandle Adopt(pbuf * buffer) { return Adopt(reinterpret_cast<PacketBuffer *>(buffer)); }
#endif // CHIP_SYSTEM_CONFIG_USE_LWIP
/**
* Advance this PacketBufferHandle to the next buffer in a chain.
*
* @note This differs from `FreeHead()` in that it does not touch any content in the currently referenced packet buffer;
* it only changes which buffer this handle owns. (Note that this could result in the previous buffer being freed,
* if there is no other owner.) `Advance()` is designed to be used with an additional handle to traverse a buffer chain,
* whereas `FreeHead()` modifies a chain.
*/
void Advance() { *this = Hold(mBuffer->ChainedBuffer()); }
/**
* Export a raw PacketBuffer pointer.
*
* @brief The PacketBufferHandle's ownership is transferred to the caller.
*
* @note This should only be used in low-level code. The caller owns one counted reference to the \c PacketBuffer
* and is responsible for managing it safely.
*
* @note The ref-qualifier `&&` requires the caller to use `std::move` to emphasize that ownership is
* moved out of this handle.
*/
CHECK_RETURN_VALUE PacketBuffer * UnsafeRelease() &&
{
PacketBuffer::Check(mBuffer);
PacketBuffer * buffer = mBuffer;
mBuffer = nullptr;
return buffer;
}
/**
* Allocates a packet buffer.
*
* A packet buffer is conceptually divided into two parts:
* @li Space reserved for network protocol headers. The size of this space normally defaults to a value determined
* by the network layer configuration, but can be given explicity by \c aReservedSize for special cases.
* @li Space for application data. The minimum size of this space is given by \c aAvailableSize, and then \c Start()
* provides a pointer to the start of this space.
*
* Fails and returns \c nullptr if no memory is available, or if the size requested is too large.
* When the sum of \a aAvailableSize and \a aReservedSize is no greater than \c PacketBuffer::kMaxSizeWithoutReserve,
* that is guaranteed not to be too large.
*
* On success, it is guaranteed that \c AvailableDataSize() is no less than \a aAvailableSize.
*
* @param[in] aAvailableSize Minimum number of octets to for application data (at `Start()`).
* @param[in] aReservedSize Number of octets to reserve for protocol headers (before `Start()`).
*
* @return On success, a PacketBufferHandle to the allocated buffer. On fail, \c nullptr.
*/
static PacketBufferHandle New(size_t aAvailableSize, uint16_t aReservedSize = PacketBuffer::kDefaultHeaderReserve);
/**
* Allocates a packet buffer with initial contents.
*
* @param[in] aData Initial buffer contents.
* @param[in] aDataSize Size of initial buffer contents.
* @param[in] aAdditionalSize Size of additional application data space after the initial contents.
* @param[in] aReservedSize Number of octets to reserve for protocol headers.
*
* @return On success, a PacketBufferHandle to the allocated buffer. On fail, \c nullptr.
*/
static PacketBufferHandle NewWithData(const void * aData, size_t aDataSize, uint16_t aAdditionalSize = 0,
uint16_t aReservedSize = PacketBuffer::kDefaultHeaderReserve);
/**
* Creates a copy of a packet buffer (or chain).
*
* @returns empty handle on allocation failure. Otherwise, the returned buffer has the same sizes and contents as the original.
*/
PacketBufferHandle CloneData() const;
/**
* Perform an implementation-defined check on the validity of a PacketBufferHandle.
*
* Unless enabled by #CHIP_CONFIG_MEMORY_DEBUG_CHECKS == 1, this function does nothing.
*
* When enabled, it performs an implementation- and configuration-defined check on
* the validity of the packet buffer. It MAY log an error and/or abort the program
* if the packet buffer or the implementation-defined memory management system is in
* a faulty state. (Some configurations may not actually perform any check.)
*
* @note A null handle is not considered faulty.
*/
void Check() const
{
#if CHIP_SYSTEM_PACKETBUFFER_HAS_CHECK
PacketBuffer::Check(mBuffer);
#endif
}
protected:
#if CHIP_SYSTEM_CONFIG_USE_LWIP
// For use via LwIPPacketBufferView only.
static struct pbuf * GetLwIPpbuf(const PacketBufferHandle & handle)
{
PacketBuffer::Check(handle.mBuffer);
return static_cast<struct pbuf *>(handle.mBuffer);
}
#endif // CHIP_SYSTEM_CONFIG_USE_LWIP
private:
PacketBufferHandle(const PacketBufferHandle &) = delete;
PacketBufferHandle & operator=(const PacketBufferHandle &) = delete;
// The caller's ownership is transferred to this.
explicit PacketBufferHandle(PacketBuffer * buffer) : mBuffer(buffer) {}
static PacketBufferHandle Hold(PacketBuffer * buffer)
{
if (buffer != nullptr)
{
buffer->AddRef();
}
return PacketBufferHandle(buffer);
}
PacketBuffer * Get() const { return mBuffer; }
bool operator==(const PacketBufferHandle & aOther) const { return mBuffer == aOther.mBuffer; }
#if CHIP_SYSTEM_PACKETBUFFER_HAS_RIGHTSIZE
void InternalRightSize();
#endif
PacketBuffer * mBuffer;
friend class PacketBuffer;
friend class TestSystemPacketBuffer;
};
inline void PacketBuffer::SetDataLength(uint16_t aNewLen, const PacketBufferHandle & aChainHead)
{
SetDataLength(aNewLen, aChainHead.mBuffer);
}
inline PacketBufferHandle PacketBuffer::Next()
{
return PacketBufferHandle::Hold(ChainedBuffer());
}
inline PacketBufferHandle PacketBuffer::Last()
{
PacketBuffer * p = this;
while (p->HasChainedBuffer())
p = p->ChainedBuffer();
return PacketBufferHandle::Hold(p);
}
} // namespace System
namespace Encoding {
class PacketBufferWriterUtil
{
private:
template <typename>
friend class PacketBufferWriterBase;
static System::PacketBufferHandle Finalize(BufferWriter & aBufferWriter, System::PacketBufferHandle & aPacket);
};
/**
* BufferWriter backed by packet buffer.
*
* Typical use:
* @code
* PacketBufferWriter buf(maximumLength);
* if (buf.IsNull()) { return CHIP_ERROR_NO_MEMORY; }
* buf.Put(...);
* ...
* PacketBufferHandle handle = buf.Finalize();
* if (buf.IsNull()) { return CHIP_ERROR_BUFFER_TOO_SMALL; }
* // valid data
* @endcode
*/
template <class Writer>
class PacketBufferWriterBase : public Writer
{
public:
/**
* Constructs a BufferWriter that writes into a packet buffer, using all available space.
*
* @param[in] aPacket A handle to PacketBuffer, to be used as backing store for the BufferWriter.
*/
PacketBufferWriterBase(System::PacketBufferHandle && aPacket) :
Writer(aPacket->Start() + aPacket->DataLength(), aPacket->AvailableDataLength())
{
mPacket = std::move(aPacket);
}
/**
* Constructs a BufferWriter that writes into a packet buffer, using no more than the requested space.
*
* @param[in] aPacket A handle to PacketBuffer, to be used as backing store for the BufferWriter.
* @param[in] aSize Maximum number of octects to write into the packet buffer.
*/
PacketBufferWriterBase(System::PacketBufferHandle && aPacket, size_t aSize) :
Writer(aPacket->Start() + aPacket->DataLength(), chip::min(aSize, static_cast<size_t>(aPacket->AvailableDataLength())))
{
mPacket = std::move(aPacket);
}
/**
* Test whether this PacketBufferWriter is null, or conversely owns a PacketBuffer.
*
* @retval true The PacketBufferWriter is null; it does not own a PacketBuffer. This implies either that
* construction failed, or that \c Finalize() has previously been called to release the buffer.
* @retval false The PacketBufferWriter owns a PacketBuffer, which can be written using BufferWriter \c Put() methods,
* and (assuming no overflow) obtained by calling \c Finalize().
*/
bool IsNull() const { return mPacket.IsNull(); }
/**
* Obtain the backing packet buffer, if it is valid.
*
* If construction succeeded, \c Finalize() has not already been called, and \c BufferWriter::Fit() is true,
* the caller takes ownership of a buffer containing the desired data. Otherwise, the returned handle tests null,
* and any underlying storage has been released.
*
* @return A packet buffer handle.
*/
System::PacketBufferHandle Finalize() { return PacketBufferWriterUtil::Finalize(*this, mPacket); }
private:
System::PacketBufferHandle mPacket;
};
using PacketBufferWriter = PacketBufferWriterBase<chip::Encoding::BufferWriter>;
namespace LittleEndian {
using PacketBufferWriter = PacketBufferWriterBase<chip::Encoding::LittleEndian::BufferWriter>;
} // namespace LittleEndian
namespace BigEndian {
using PacketBufferWriter = PacketBufferWriterBase<chip::Encoding::BigEndian::BufferWriter>;
} // namespace BigEndian
} // namespace Encoding
} // namespace chip
#if CHIP_SYSTEM_CONFIG_USE_LWIP
namespace chip {
namespace Inet {
class UDPEndPointImplLwIP;
} // namespace Inet
namespace System {
/**
* Provide low-level access to a raw `pbuf *`, limited to specific classes that interface with LwIP.
*/
class LwIPPacketBufferView : public PacketBufferHandle
{
private:
/**
* Borrow a raw LwIP `pbuf *`.
*
* @brief The caller has access but no ownership.
*
* @note This should be used ONLY by low-level code interfacing with LwIP.
*/
static struct pbuf * UnsafeGetLwIPpbuf(const PacketBufferHandle & handle) { return PacketBufferHandle::GetLwIPpbuf(handle); }
friend class Inet::UDPEndPointImplLwIP;
};
} // namespace System
} // namespace chip
#endif // CHIP_SYSTEM_CONFIG_USE_LWIP