From 69bb53aca1cdb5861fd19b3b1345d20e4139e938 Mon Sep 17 00:00:00 2001 From: Jacopo Mondi Date: Tue, 22 Oct 2019 01:52:08 +0200 Subject: libcamera: Add ByteStreamBuffer The ByteStreamBuffer class wraps a memory area, expected to be allocated by the user of the class and provides operations to perform sequential access in read and write modes. Signed-off-by: Jacopo Mondi Signed-off-by: Laurent Pinchart --- src/libcamera/byte_stream_buffer.cpp | 286 +++++++++++++++++++++++++++++++++++ 1 file changed, 286 insertions(+) create mode 100644 src/libcamera/byte_stream_buffer.cpp (limited to 'src/libcamera/byte_stream_buffer.cpp') diff --git a/src/libcamera/byte_stream_buffer.cpp b/src/libcamera/byte_stream_buffer.cpp new file mode 100644 index 00000000..23d624dd --- /dev/null +++ b/src/libcamera/byte_stream_buffer.cpp @@ -0,0 +1,286 @@ +/* SPDX-License-Identifier: LGPL-2.1-or-later */ +/* + * Copyright (C) 2019, Google Inc. + * + * byte_stream_buffer.cpp - Byte stream buffer + */ + +#include "byte_stream_buffer.h" + +#include +#include + +#include "log.h" + +namespace libcamera { + +LOG_DEFINE_CATEGORY(Serialization); + +/** + * \file byte_stream_buffer.h + * \brief Managed memory container for serialized data + */ + +/** + * \class ByteStreamBuffer + * \brief Wrap a memory buffer and provide sequential data read and write + * + * The ByteStreamBuffer class wraps a memory buffer and exposes sequential read + * and write operation with integrated boundary checks. Access beyond the end + * of the buffer are blocked and logged, allowing error checks to take place at + * the of of access operations instead of at each access. This simplifies + * serialization and deserialization of data. + * + * A byte stream buffer is created with a base memory pointer and a size. If the + * memory pointer is const, the buffer operates in read-only mode, and write + * operations are denied. Otherwise the buffer operates in write-only mode, and + * read operations are denied. + * + * Once a buffer is created, data is read or written with read() and write() + * respectively. Access is strictly sequential, the buffer keeps track of the + * current access location and advances it automatically. Reading or writing + * the same location multiple times is thus not possible. Bytes may also be + * skipped with the skip() method. + * + * The ByteStreamBuffer also supports carving out pieces of memory into other + * ByteStreamBuffer instances. Like a read or write operation, a carveOut() + * advances the internal access location, but allows the carved out memory to + * be accessed at a later time. + * + * All accesses beyond the end of the buffer (read, write, skip or carve out) + * are blocked. The first of such accesses causes a message to be logged, and + * the buffer being marked as having overflown. If the buffer has been carved + * out from a parent buffer, the parent buffer is also marked as having + * overflown. Any later access on an overflown buffer is blocked. The buffer + * overflow status can be checked with the overflow() method. + */ + +/** + * \brief Construct a read ByteStreamBuffer from the memory area \a base + * of \a size + * \param[in] base The address of the memory area to wrap + * \param[in] size The size of the memory area to wrap + */ +ByteStreamBuffer::ByteStreamBuffer(const uint8_t *base, size_t size) + : parent_(nullptr), base_(base), size_(size), overflow_(false), + read_(base), write_(nullptr) +{ +} + +/** + * \brief Construct a write ByteStreamBuffer from the memory area \a base + * of \a size + * \param[in] base The address of the memory area to wrap + * \param[in] size The size of the memory area to wrap + */ +ByteStreamBuffer::ByteStreamBuffer(uint8_t *base, size_t size) + : parent_(nullptr), base_(base), size_(size), overflow_(false), + read_(nullptr), write_(base) +{ +} + +/** + * \brief Construct a ByteStreamBuffer from the contents of \a other using move + * semantics + * \param[in] other The other buffer + * + * After the move construction the \a other buffer is invalidated. Any attempt + * to access its contents will be considered as an overflow. + */ +ByteStreamBuffer::ByteStreamBuffer(ByteStreamBuffer &&other) +{ + *this = std::move(other); +} + +/** + * \brief Replace the contents of the buffer with those of \a other using move + * semantics + * \param[in] other The other buffer + * + * After the assignment the \a other buffer is invalidated. Any attempt to + * access its contents will be considered as an overflow. + */ +ByteStreamBuffer &ByteStreamBuffer::operator=(ByteStreamBuffer &&other) +{ + parent_ = other.parent_; + base_ = other.base_; + size_ = other.size_; + overflow_ = other.overflow_; + read_ = other.read_; + write_ = other.write_; + + other.parent_ = nullptr; + other.base_ = nullptr; + other.size_ = 0; + other.overflow_ = false; + other.read_ = nullptr; + other.write_ = nullptr; + + return *this; +} + +/** + * \fn ByteStreamBuffer::base() + * \brief Retrieve a pointer to the start location of the managed memory buffer + * \return A pointer to the managed memory buffer + */ + +/** + * \fn ByteStreamBuffer::offset() + * \brief Retrieve the offset of the current access location from the base + * \return The offset in bytes + */ + +/** + * \fn ByteStreamBuffer::size() + * \brief Retrieve the size of the managed memory buffer + * \return The size of managed memory buffer + */ + +/** + * \fn ByteStreamBuffer::overflow() + * \brief Check if the buffer has overflown + * \return True if the buffer has overflow, false otherwise + */ + +void ByteStreamBuffer::setOverflow() +{ + if (parent_) + parent_->setOverflow(); + + overflow_ = true; +} + +/** + * \brief Carve out an area of \a size bytes into a new ByteStreamBuffer + * \param[in] size The size of the newly created memory buffer + * + * This method carves out an area of \a size bytes from the buffer into a new + * ByteStreamBuffer, and returns the new buffer. It operates identically to a + * read or write access from the point of view of the current buffer, but allows + * the new buffer to be read or written at a later time after other read or + * write accesses on the current buffer. + * + * \return A newly created ByteStreamBuffer of \a size + */ +ByteStreamBuffer ByteStreamBuffer::carveOut(size_t size) +{ + if (!size_ || overflow_) + return ByteStreamBuffer(static_cast(nullptr), 0); + + const uint8_t *curr = read_ ? read_ : write_; + if (curr + size > base_ + size_) { + LOG(Serialization, Error) + << "Unable to reserve " << size << " bytes"; + setOverflow(); + + return ByteStreamBuffer(static_cast(nullptr), 0); + } + + if (read_) { + ByteStreamBuffer b(read_, size); + b.parent_ = this; + read_ += size; + return b; + } else { + ByteStreamBuffer b(write_, size); + b.parent_ = this; + write_ += size; + return b; + } +} + +/** + * \brief Skip \a size bytes from the buffer + * \param[in] size The number of bytes to skip + * + * This method skips the next \a size bytes from the buffer. + * + * \return 0 on success, a negative error code otherwise + * \retval -ENOSPC no more space is available in the managed memory buffer + */ +int ByteStreamBuffer::skip(size_t size) +{ + if (overflow_) + return -ENOSPC; + + const uint8_t *curr = read_ ? read_ : write_; + if (curr + size > base_ + size_) { + LOG(Serialization, Error) + << "Unable to skip " << size << " bytes"; + setOverflow(); + + return -ENOSPC; + } + + if (read_) { + read_ += size; + } else { + memset(write_, 0, size); + write_ += size; + } + + return 0; +} + +/** + * \fn template int ByteStreamBuffer::read(T *t) + * \brief Read \a size \a data from the managed memory buffer + * \param[out] t Pointer to the memory containing the read data + * \return 0 on success, a negative error code otherwise + * \retval -EACCES attempting to read from a write buffer + * \retval -ENOSPC no more space is available in the managed memory buffer + */ + +/** + * \fn template int ByteStreamBuffer::write(const T *t) + * \brief Write \a data of \a size to the managed memory buffer + * \param[in] t The data to write to memory + * \return 0 on success, a negative error code otherwise + * \retval -EACCES attempting to write to a read buffer + * \retval -ENOSPC no more space is available in the managed memory buffer + */ + +int ByteStreamBuffer::read(uint8_t *data, size_t size) +{ + if (!read_) + return -EACCES; + + if (overflow_) + return -ENOSPC; + + if (read_ + size > base_ + size_) { + LOG(Serialization, Error) + << "Unable to read " << size << " bytes: out of bounds"; + setOverflow(); + return -ENOSPC; + } + + memcpy(data, read_, size); + read_ += size; + + return 0; +} + +int ByteStreamBuffer::write(const uint8_t *data, size_t size) +{ + if (!write_) + return -EACCES; + + if (overflow_) + return -ENOSPC; + + if (write_ + size > base_ + size_) { + LOG(Serialization, Error) + << "Unable to write " << size << " bytes: no space left"; + setOverflow(); + return -ENOSPC; + } + + memcpy(write_, data, size); + write_ += size; + + return 0; +} + +} /* namespace libcamera */ -- cgit v1.2.1