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upper_32_bits(9) [centos man page]

UPPER_32_BITS(9)						   Driver Basics						  UPPER_32_BITS(9)

NAME
upper_32_bits - return bits 32-63 of a number SYNOPSIS
upper_32_bits(n); ARGUMENTS
n the number we're accessing DESCRIPTION
A basic shift-right of a 64- or 32-bit quantity. Use this to suppress the "right shift count >= width of type" warning when that quantity is 32-bits. COPYRIGHT
Kernel Hackers Manual 3.10 June 2014 UPPER_32_BITS(9)

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swap_lw_bytes(9r)														 swap_lw_bytes(9r)

NAME
swap_lw_bytes, swap_word_bytes, swap_words - General: Perform byte-swapping operations SYNOPSIS
unsigned int swap_lw_bytes( unsigned int buffer ); unsigned int swap_word_bytes( unsigned int buffer ); unsigned int swap_words( unsigned int buffer ); ARGUMENTS
Specifies a 32-bit (4 bytes) quantity. DESCRIPTION
The swap_lw_bytes interface performs a longword byte swap. The swap_word_bytes interface performs a short word byte swap. The swap_words interface performs a word byte swap. Many computer vendors support devices that use a big endian model of byte ordering. Because Digital devices support the little endian model of byte ordering, there is a need for these byte-swapping interfaces. In addition, some buses (for example, the VMEbus) can have specific or implied byte ordering that may require the use of these interfaces. Given that a longword is equal to 4 bytes; a short word is equal to 2 bytes; and 1 byte is equal to 8 bits, these interfaces swap bytes as follows: The swap_lw_bytes interface takes the 32-bit quantity specified by the buffer argument and swaps all 4 bytes. The swap_word_bytes interface takes the 32-bit quantity specified by the buffer argument and swaps the individual bytes that make up each word of the 32-bit quantity. The swap_words interface takes the 32-bit quantity specified by the buffer argument and swaps the two 16-bit words. The following illustration compares the byte swapping performed by these interfaces. 31 0 +---+---+---+---+ Starting value: | a | b | c | d | +---+---+---+---+ Long word byte swap (swap_lw_bytes) 31 0 +---+---+---+---+ Ending value: | d | c | b | a | +-------+---+---+ Short word byte swap (swap_word_bytes) 31 0 +---+---+---+---+ Ending value: | b | a | d | c | +---+---+---+---+ 31 0 +---+---+---+---+ Starting value: | ab | cd | +---+---+---+---+ Word byte swap (swap_words) 31 0 +---+---+---+---+ Ending value: | cd | ab | +---+---+---+---+ RETURN VALUES
Upon successful completion, these interfaces return the swapped bytes. swap_lw_bytes(9r)
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