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cdefs(3) [netbsd man page]

CDEFS(3)						   BSD Library Functions Manual 						  CDEFS(3)

cdefs -- common definitions and macros SYNOPSIS
#include <sys/cdefs.h> DESCRIPTION
The <sys/cdefs.h> header includes some common definitions and macros typical to the C language conventions of NetBSD. Among these are: o Certain C language properties and definitions that are versioned according to the support in compilers. Examples include the __func__ keyword and the restrict type qualifier from C99. o Macros and definitions specific to compilers, preprocessors, and linkers; see __CONCAT(3), __UNCONST(3), __insn_barrier(3), and attribute(3). o Utility macros provided for convenience; see __arraycount(3) and bits(3). The header also contains the __RCSID() and __KERNEL_RCSID() macros used for version control system (VCS) identifiers. Thus, all NetBSD source code files typically include <sys/cdefs.h>, included as the first thing right after any possible copyright texts; /*- * Copyright (c) 1984 John Doe * All rights reserved. * * Redistribution and use in source and binary forms, * with or without modification, are permitted. */ #include <sys/cdefs.h> __RCSID("$NetBSD: cdefs.3,v 1.3 2011/04/08 07:55:04 jruoho Exp $"); It is possible to identify the RCS keyword strings by using ident(1). SEE ALSO
ident(1), param(3), stddef(3), types(3), c(7) HISTORY
The <sys/cdefs.h> header was originally imported from 386BSD. BSD
April 8, 2011 BSD

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BITS(3) 						   BSD Library Functions Manual 						   BITS(3)

__BIT, __BITS, __SHIFTIN, __SHIFTOUT, __SHIFTOUT_MASK -- macros for preparing bitmasks and operating on bit fields SYNOPSIS
#include <sys/param.h> #include <sys/cdefs.h> uintmax_t __BIT(n); uintmax_t __BITS(m, n); __SHIFTIN(v, mask); __SHIFTOUT(v, mask); __SHIFTOUT_MASK(mask); DESCRIPTION
These macros prepare bitmasks, extract bitfields from words, and insert bitfields into words. A ``bitfield'' is a span of consecutive bits defined by a bitmask, where 1s select the bits in the bitfield. Use __BIT() and __BITS() to define bitmasks: __BIT(n) Return a bitmask with bit n set, where the least significant bit is bit 0. __BITS(m, n) Return a bitmask with bits m through n, inclusive, set. It does not matter whether m > n or m <= n. The least significant bit is bit 0. __SHIFTIN(), __SHIFTOUT(), and __SHIFTOUT_MASK() help read and write bitfields from words: __SHIFTIN(v, mask) Left-shift bits v into the bitfield defined by mask, and return them. No side-effects. __SHIFTOUT(v, mask) Extract and return the bitfield selected by mask from v, right-shifting the bits so that the rightmost selected bit is at bit 0. No side-effects. __SHIFTOUT_MASK(mask) Right-shift the bits in mask so that the rightmost non-zero bit is at bit 0. This is useful for finding the greatest unsigned value that a bitfield can hold. No side-effects. Note that __SHIFTOUT_MASK(m) = __SHIFTOUT(m, m). EXAMPLES
The following example demonstrates basic usage of the bits macros: uint32_t bits, mask, val; bits = __BITS(2, 3); /* 00001100 */ mask = __BIT(2) | __BIT(3); /* 00001100 */ val = __SHIFTIN(0x03, mask); /* 00001100 */ val = __SHIFTOUT(0xf, mask); /* 00000011 */ SEE ALSO
bitops(3), cdefs(3) HISTORY
The bits macros first appeared in atw(4), with different names and implementation. In their current form these macros appeared in NetBSD 4.0. AUTHORS
The bits macros were written by David Young <>. Matt Thomas <> suggested important improvements to the implementation, and contributed the macro names SHIFTIN() and SHIFTOUT(). BUGS
__BIT() and __BITS() can only express 32-bit bitmasks. BSD
October 17, 2012 BSD
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