library/contrib/byteswap/byteswap.h
#ifndef __BYTESWAP_H
#define __BYTESWAP_H
#include <sys/types.h>
#include <stdint.h>
#if defined(__GNUC__)
#define __CONST_FUNC __attribute__((const))
#else
#define __CONST_FUNC /* Nothing */
#endif
/* Single value byteswap functions. */
extern __CONST_FUNC uint16_t bswap16(uint16_t);
extern __CONST_FUNC uint32_t bswap24(uint32_t);
extern __CONST_FUNC uint32_t bswap32(uint32_t);
#ifdef INT64_MIN
extern __CONST_FUNC uint64_t bswap64(uint64_t);
#endif
/* Block byteswap functions. The swab() function usually resides in unistd.h, so perhaps it should be moved there? */
/* NOTE: Contrary to the standard swab(), this version returns the "to" pointer and the pointers are not restrict
* qualified - so swapping buffer-contents in-place is supported.
* Also, swab24(), swab32() and swab64() are non-standard functions.
*/
extern void *swab(void *from,void *to,ssize_t nbytes);
extern void *swab24(void *from,void *to,ssize_t nbytes); /* Same as swab(), but operates on 24-bit words instead. */
extern void *swab32(void *from,void *to,ssize_t nbytes); /* Same as swab(), but operates on 32-bit words instead. */
extern void *swab64(void *from,void *to,ssize_t nbytes); /* Same as swab(), but operates on 64-bit words instead. */
#define swab16(x) swab(x)
/*
* Optimized inline-versions for the single-value functions follow.
* Only GCC+PPC and GCC+m68k support for now.
*/
#if defined(__GNUC__)
/* Select implementation. */
#define bswap16(x) (__builtin_constant_p(x))?__const_swap16(x):__swap16(x)
#define bswap24(x) (__builtin_constant_p(x))?__const_swap24(x):__swap24(x)
#define bswap32(x) (__builtin_constant_p(x))?__const_swap32(x):__swap32(x)
#define bswap64(x) (__builtin_constant_p(x))?__const_swap64(x):__swap64(x)
/* Assembler implementations */
#if defined(__PPC__)
static __inline__ __CONST_FUNC uint16_t __swap16(uint16_t u16) {
uint_fast16_t result;
__asm__("\
rlwinm %[result],%[u16],8,16,24\n\
rlwimi %[result],%[u16],24,24,31\n\
":[result]"=&r"(result):[u16]"r"(u16));
return(result);
}
static __inline__ __CONST_FUNC uint32_t __swap24(uint32_t u32) {
uint_fast32_t result;
__asm__("\
rlwinm %[result],%[u32],16,8,31\n\
rlwimi %[result],%[u32],0,16,24\n\
":[result]"=&r"(result):[u32]"r"(u32));
return(result);
}
static __inline__ __CONST_FUNC uint32_t __swap32(uint32_t u32) {
uint_fast32_t result;
__asm__("\
rlwinm %[result],%[u32],8,8,31\n\
rlwimi %[result],%[u32],24,0,7\n\
rlwimi %[result],%[u32],24,16,23\n\
":[result]"=&r"(result):[u32]"r"(u32));
return(result);
}
/*
* Note: __swap64() might perhaps be optimized a bit more by scheduling the
* instructions to alternate register-use, but this instead means there
* are two less registers free since "u64" and "result" may no longer overlap.
* Decisions, decisions....
*/
static __inline__ __CONST_FUNC uint64_t __swap64(uint64_t u64) {
uint_fast64_t result;
uint_fast32_t tmp;
__asm__("\
rlwinm %[tmp],%[u64],8,8,31\n\
rlwimi %[tmp],%[u64],24,0,7\n\
rlwimi %[tmp],%[u64],24,16,23\n\
rlwinm %[result],%L[u64],8,8,31\n\
rlwimi %[result],%L[u64],24,0,7\n\
rlwimi %[result],%L[u64],24,16,23\n\
or %L[result],%[tmp],%[tmp]\n\
":[result]"=r"(result),[tmp]"=&r"(tmp):[u64]"r"(u64));
return(result);
}
#elif defined(__mc68020__)
static __inline__ __CONST_FUNC uint16_t __swap16(uint16_t u16) {
__asm__("\
rol.w #8,%[u16]\n\
":[u16]"+d"(u16)::"cc");
return(u16);
}
static __inline__ __CONST_FUNC uint32_t __swap24(uint32_t u32) {
__asm__("\
rol.w #8,%[u32]\n\
swap %[u32]\n\
rol.w #8,%[u32]\n\
ror.l #8,%[u32]\n\
":[u32]"+d"(u32)::"cc");
return(u32);
}
static __inline__ __CONST_FUNC uint32_t __swap32(uint32_t u32) {
__asm__("\
rol.w #8,%[u32]\n\
swap %[u32]\n\
rol.w #8,%[u32]\n\
":[u32]"+d"(u32)::"cc");
return(u32);
}
static __inline__ __CONST_FUNC uint64_t __swap64(uint64_t u64) {
__asm__("\
rol.w #8,%[u64]\n\
rol.w #8,%L[u64]\n\
swap %[u64]\n\
swap %L[u64]\n\
rol.w #8,%[u64]\n\
rol.w #8,%L[u64]\n\
exg %[u64],L%[u64]\n\
":[u64]"+d"(u64)::"cc");
return(u64);
}
#else
/* Unknown or undefined architecture. Perhaps compiling with "-strict -ansi", but should not use this header then anyway. */
#undef bswap16
#undef bswap24
#undef bswap32
#undef bswap64
#define bswap16(x) (__builtin_constant_p(x))?__const_swap16(x):bswap16(x)
#define bswap24(x) (__builtin_constant_p(x))?__const_swap24(x):bswap24(x)
#define bswap32(x) (__builtin_constant_p(x))?__const_swap32(x):bswap32(x)
#define bswap64(x) (__builtin_constant_p(x))?__const_swap64(x):bswap64(x)
#endif
/* C implementations for constant values */
static __inline__ uint16_t __const_swap16(uint16_t u16) {
return(u16>>8|u16<<8);
}
static __inline__ uint32_t __const_swap24(uint32_t u32) {
return(((u32&0xff)<<16)|((u32&0xff00))|((u32&0xff0000)>>16));
}
static __inline__ uint32_t __const_swap32(uint32_t u32) {
return(((u32&0xff)<<24)|((u32&0xff00)<<8)|((u32&0xff0000)>>8)|((u32&0xff000000)>>24));
}
static __inline__ uint64_t __const_swap64(uint64_t u64) {
return(((u64&0xffLL)<<56)|((u64&0xff00LL)<<40)|((u64&0xff0000LL)<<24)|((u64&0xff000000LL)<<8)|
((u64&0xff00000000LL)>>8)|((u64&0xff0000000000LL)>>24)|((u64&0xff000000000000LL)>>40)|((u64&0xff00000000000000LL)>>56));
}
#endif /* __GNUC__ */
#endif /* __BYTESWAP_H */
/* vi:set ts=3: */