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427 lines
10 KiB
Markdown
427 lines
10 KiB
Markdown
---
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title: "mem_cast"
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---
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{{< callout type="info">}}
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Header: `mem_cast.h`
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From: `20.11.0`
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{{< /callout >}}
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Helper classes that simplify the interpretation of memory blocks.
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The member functions contain both compile and run time error checks for correct sized buffers.
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```cpp
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etl::mem_cast
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etl::mem_cast_ptr
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etl::mem_cast_types
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```
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## Error types
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```cpp
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class mem_cast_exception : public etl::exception
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```
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The base exception type for mem_cast types.
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```cpp
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class mem_cast_size_exception : public etl::mem_cast_exception
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```
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The exception type when the type size is too large.
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```cpp
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class mem_cast_nullptr_exception : public etl::mem_cast_exception
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```
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The exception type when the buffer pointer is null.
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## mem_cast
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```cpp
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template <size_t Size, size_t Alignment>
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class mem_cast
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```
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The class is parameterised by the required memory block size and alignment.
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## Member constants
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```cpp
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static ETL_CONSTANT size_t Size;
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static ETL_CONSTANT size_t Alignment;
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```
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## Member functions
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```cpp
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mem_cast()
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```
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Default constructor.
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The internal memory block contents are undefined.
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---
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```cpp
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template <size_t Other_Size, size_t Other_Alignment>
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mem_cast(const mem_cast<Other_Size, Other_Alignment>& other)
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```
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Copy constructor.
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Copies the contents of the source buffer.
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Static asserts if the other buffer is not large enough.
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---
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```cpp
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template <size_t Other_Size, size_t Other_Alignment>
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mem_cast& operator =(const mem_cast<Other_Size, Other_Alignment>& rhs)
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```
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Assignment operator.
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Static asserts if the rhs buffer is not large enough.
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---
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```cpp
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template <typename T>
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void assign(const T& value)
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```
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Assign from value.
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Static asserts if the buffer is not large enough.
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---
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```cpp
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template <typename T>
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void assign_at_offset(size_t offset, const T& value)
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```
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Assign from value at an offset from the start of the memory block.
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Raises an `etl::mem_cast_size_exception` `ETL_ASSERT` if the buffer is not large enough.
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---
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```cpp
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template <typename T, size_t Offset>
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void assign_at_offset(const T& value)
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```
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Assign from value at an offset from the start of the memory block.
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Static asserts if the buffer is not large enough.
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---
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```cpp
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template <typename T, typename... TArgs>
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void emplace(TArgs... args)
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```
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Emplace from parameters.
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Static asserts if the buffer is not large enough.
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C++11 or above.
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---
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```cpp
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template <typename T, typename... TArgs>
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void emplace_at_offset(size_t offset, TArgs... args)
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```
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Emplace from parameters at an offset from the start of the memory block.
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Raises an `etl::mem_cast_size_exception` `ETL_ASSERT` if the buffer is not large enough.
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C++11 or above.
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---
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```cpp
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template <typename T, size_t Offset, typename... TArgs>
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void emplace_at_offset(TArgs... args)
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```
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Emplace from parameters at an offset from the start of the memory block.
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Static asserts if the buffer is not large enough.
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C++11 or above.
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---
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```cpp
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template <typename T>
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ETL_NODISCARD T& ref()
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```
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Get a reference to `T`.
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Static asserts if the buffer is not large enough.
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---
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```cpp
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template <typename T>
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ETL_NODISCARD const T& ref() const
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```
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Get a const reference to `T`.
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Static asserts if the buffer is not large enough.
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---
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```cpp
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template <typename T>
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ETL_NODISCARD T& ref_at_offset(size_t offset)
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```
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Get a reference to T at an offset from the start of the memory block (dynamic).
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Raises an `etl::mem_cast_size_exception` `ETL_ASSERT` if the buffer is not large enough.
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---
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```cpp
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template <typename T>
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ETL_NODISCARD const T& ref_at_offset(size_t offset) const
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```
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Get a const reference to `T` at an offset from the start of the memory block (dynamic).
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Raises an `etl::mem_cast_size_exception` `ETL_ASSERT` if the buffer is not large enough.
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---
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```cpp
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template <typename T, size_t Offset>
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ETL_NODISCARD T& ref_at_offset()
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```
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Get a reference to `T` at an offset from the start of the memory block (static).
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Static asserts if the buffer is not large enough.
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---
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```cpp
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template <typename T, size_t Offset>
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ETL_NODISCARD const T& ref_at_offset() const
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```
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Get a const reference to `T` at an offset from the start of the memory block (static).
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Static asserts if the buffer is not large enough.
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---
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```cpp
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ETL_NODISCARD static ETL_CONSTEXPR size_t size()
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```
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Get the size of the buffer.
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---
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```cpp
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ETL_NODISCARD static ETL_CONSTEXPR size_t alignment()
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```
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Get the alignment of the buffer.
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---
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```cpp
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ETL_NODISCARD char* data()
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```
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Get a pointer to the internal buffer.
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---
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```cpp
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ETL_NODISCARD const char* data() const
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```
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Get a const pointer to the internal buffer
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## mem_cast_ptr
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This class contains a pointer to an external memory block.
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```cpp
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class mem_cast_ptr
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```
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## Member constants
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```cpp
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static ETL_CONSTANT size_t Undefined_Size;
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```
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## Member functions
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```cpp
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mem_cast_ptr()
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```
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Default constructor.
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The internal pointer to the memory block is initialised as `nullptr`.
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The size is defined as `Undefined_Size`.
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```cpp
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mem_cast_ptr(const mem_cast_ptr& other)
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```
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Copy constructor.
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Copies the memory block pointer, not the contents of the memory block.
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---
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```cpp
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mem_cast_ptr& operator =(const mem_cast_ptr& rhs)
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```
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Assignment operator.
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Copies the memory block pointer, not the contents of the memory block.
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---
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```cpp
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template <typename T>
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void assign(const T& value)
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```
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Assign from value.
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Raises an `etl::mem_cast_nullptr_exception` `ETL_ASSERT` if the memory block pointer is null.
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Raises an `etl::mem_cast_size_exception` `ETL_ASSERT` if the buffer is not large enough.
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---
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```cpp
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template <typename T>
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void assign_at_offset(size_t offset, const T& value)
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```
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Assign from value at an offset from the start of the memory block.
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Raises an `etl::mem_cast_nullptr_exception` `ETL_ASSERT` if the memory block pointer is null.
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Raises an `etl::mem_cast_size_exception` `ETL_ASSERT` if the buffer is not large enough.
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---
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```cpp
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template <typename T, size_t Offset>
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void assign_at_offset(const T& value)
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```
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Assign from value at an offset from the start of the memory block.
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---
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```cpp
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template <typename T, typename... TArgs>
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void emplace(TArgs... args)
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```
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Emplace from parameters.
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C++11 or above.
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---
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```cpp
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template <typename T, typename... TArgs>
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void emplace_at_offset(size_t offset, TArgs... args)
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```
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Emplace from parameters at offset.
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Raises an `etl::mem_cast_nullptr_exception` `ETL_ASSERT` if the memory block pointer is null.
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Raises an `etl::mem_cast_size_exception` `ETL_ASSERT` if the buffer is not large enough.
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C++11 or above.
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---
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```cpp
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template <typename T, size_t Offset, typename... TArgs>
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void emplace_at_offset(TArgs... args)
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```
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Emplace from parameters at offset.
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Raises an `etl::mem_cast_nullptr_exception` `ETL_ASSERT` if the memory block pointer is null.
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Raises an `etl::mem_cast_size_exception` `ETL_ASSERT` if the buffer is not large enough.
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C++11 or above.
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---
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```cpp
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template <typename T>
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ETL_NODISCARD T& ref()
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```
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Get a reference to `T`.
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Raises an `etl::mem_cast_nullptr_exception` `ETL_ASSERT` if the memory block pointer is null.
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Raises an `etl::mem_cast_size_exception` `ETL_ASSERT` if the buffer is not large enough.
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---
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```cpp
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template <typename T>
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ETL_NODISCARD const T& ref() const
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```
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Get a const reference to `T`.
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Raises an `etl::mem_cast_nullptr_exception` `ETL_ASSERT` if the memory block pointer is null.
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Raises an `ETL_ASSERT` if the buffer is not large enough.
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---
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```cpp
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template <typename T>
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ETL_NODISCARD T& ref_at_offset(size_t offset)
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```
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Get a reference to `T` at an offset from the start of the memory block (dynamic).
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Raises an `etl::mem_cast_nullptr_exception` `ETL_ASSERT` if the memory block pointer is null.
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Raises an `etl::mem_cast_size_exception` `ETL_ASSERT` if the buffer is not large enough.
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---
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```cpp
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template <typename T>
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ETL_NODISCARD const T& ref_at_offset(size_t offset) const
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```
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Get a const reference to `T` at offset (dynamic).
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Raises an `etl::mem_cast_nullptr_exception` `ETL_ASSERT` if the memory block pointer is null.
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Raises an `etl::mem_cast_size_exception` `ETL_ASSERT` if the buffer is not large enough.
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---
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```cpp
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template <typename T, size_t Offset>
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ETL_NODISCARD T& ref_at_offset()
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```
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Get a reference to `T` at an offset from the start of the memory block (static).
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Raises an `etl::mem_cast_nullptr_exception` `ETL_ASSERT` if the memory block pointer is null.
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Raises an `etl::mem_cast_size_exception` `ETL_ASSERT` if the buffer is not large enough.
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---
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```cpp
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template <typename T, size_t Offset>
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ETL_NODISCARD const T& ref_at_offset() const
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```
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Get a const reference to T at an offset from the start of the memory block (static).
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Raises an `etl::mem_cast_nullptr_exception` `ETL_ASSERT` if the memory block pointer is null.
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Raises an `etl::mem_cast_size_exception` `ETL_ASSERT` if the buffer is not large enough.
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---
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```cpp
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ETL_NODISCARD size_t size() const
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```
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Get the size of the buffer.
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---
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```cpp
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ETL_NODISCARD size_t alignment() const
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```
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Get the alignment of the buffer.
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---
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```cpp
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void data(char* pbuffer, size_t buffer_size = Undefined_Size)
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```
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Set the pointer to the external buffer.
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The default size is `Undefined_Size`.
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---
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```cpp
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ETL_NODISCARD char* data()
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```
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Get a pointer to the internal buffer.
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---
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```cpp
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ETL_NODISCARD const char* data() const
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```
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Get a const pointer to the internal buffer
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## mem_cast_types
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A variant of `etl::mem_cast` that deduces the size and alignment from the supplied list of types.
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### C++03
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```cpp
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template <typename T1, typename T2 = char, typename T3 = char, typename T4 = char,
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typename T5 = char, typename T6 = char, typename T7 = char, typename T8 = char,
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typename T9 = char, typename T10 = char, typename T11 = char, typename T12 = char,
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typename T13 = char, typename T14 = char, typename T15 = char, typename T16 = char>
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struct mem_cast_types :
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public etl::mem_cast<etl::largest<T1, T2, T3, T4, T5, T6, T7, T8,
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T9, T10, T11, T12, T13, T14, T15, T16>::size,
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etl::largest<T1, T2, T3, T4, T5, T6, T7, T8,
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T9, T10, T11, T12, T13, T14, T15, T16>::alignment>
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{
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};
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```
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### C++11 and above
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```cpp
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template <typename... TTypes>
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using mem_cast_types = etl::mem_cast<etl::largest<TTypes...>::size,
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etl::largest<TTypes...>::alignment>;
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```
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