musl/src/multibyte/internal.h

/* 
 * This code was written by Rich Felker in 2010; no copyright is claimed.
 * This code is in the public domain. Attribution is appreciated but
 * unnecessary.
 */

#define bittab __fsmu8

#if 100*__GNUC__+__GNUC_MINOR__ >= 303 || defined(__PCC__) || defined(__TINYC__)
extern const uint32_t bittab[] __attribute__((visibility("hidden")));
#else
extern const uint32_t bittab[];
#endif

/* Upper 6 state bits are a negative integer offset to bound-check next byte */
/*    equivalent to: ( (b-0x80) | (b+offset) ) & ~0x3f      */
#define OOB(c,b) (((((b)>>3)-0x10)|(((b)>>3)+((int32_t)(c)>>26))) & ~7)

/* Interval [a,b). Either a must be 80 or b must be c0, lower 3 bits clear. */
#define R(a,b) ((uint32_t)((a==0x80 ? 0x40-b : -a) << 23))
#define FAILSTATE R(0x80,0x80)

#define SA 0xc2u
#define SB 0xf5u