◆ memlsh_BE()

void Chusov::Memory::memlsh_BE	(	void *	pResult,
		std::size_t	cbResult,
		const void *	pValue,
		std::size_t	cbValue,
		std::size_t	nShift
	)

noexcept

Performs a linear bit shift of data representing an unsigned arbitrary precision integer in the Big-Endian format to the left.

Parameters

[out]	pResult	is a pointer to an output buffer of size `cbResult` bytes. The buffer receives the shifted result modulo `2^cbResult`. The buffers `pResult` and `pValue` may overlap.
	cbResult	Capacity of the output buffer pointed to by `pResult`, in bytes. The result of the operation is computed modulo `2^cbResult`.
[in]	pValue	is a pointer to the input data to shift.
	cbValue	is a byte size of the input data pointed to by `pValue`.
	nShift	specifies a number of bits by which to shift the input data.

The function performs a left bit-shift of an unsigned integer specified as a byte vector in the Big-Endian order. That is, given that \(b_i\) and \(b_j\) are bytes in the vector pValue, such that \(i, j\in\mathbb{N}_0\land i < j\), byte \(b_i\) is more significant that \(b_j\). Therefore, the operation shifts the value towards the beginning of the buffer pValue.

For instance, given that \(B\) is a size of a byte in bits, a vector \(\left\{b_0, b_1, b_2, b_3, b_4\right\}\) representing a number \(b_0 B^4 + b_1 B^3 + b_2 B^2 + b_3 B^1 + b_4 B^0 = \overline{b_0 b_1 b_2 b_3 b_4}\), when shifted to the left by \(2B\), results in the value \(\overline{b_2 b_3 b_4 0 0} = b_2\cdot B^4 + b_3\cdot B^3 + b_4 B^2 + 0 \cdot B^1 + 0 \cdot B^0\) which is represented by the vector \(\left\{b_2, b_3, b_4, 0, 0\right\}\). The bit order within a byte is not taken into account, that is platform-defined bit shift to the left is used.

Unlike memlsh_BE_copy and memlsh_BE_inplace, the function allows shifting of data in overlapping buffers pointed to by pResult and pValue of possibly differing sizes. The result of the shift is calculated modulo 2^cbResult, that is the actual result, depending on the value of cbResult, is either zero-extended or truncated (preserving low-order bytes) to fit the capacity.

See also: memlsh_BE_copy;
memlsh_BE_inplace;
memrsh_BE;
memlsh_LE.

Examples: chsvmem\memory_shifts.c.