Linux Kernel Function fls (), Linux kernel function fls

Linux Kernel Function fls (), Linux kernel function fls

Functions of Linux kernel functions fls ()

/*** Fls-find last (most-significant) bit set * @ x: the word to search ** This is defined the same way as ffs. * Note fls (0) = 0, fls (1) = 1, fls (0x80000000) = 32. */static _ always_inline int fls (int x) {int r = 32; if (! X) return 0; if (! (X & 0xffff0000u) {x <= 16; r-= 16;} if (! (X & 0xff000000u) {x <= 8; r-= 8;} if (! (X & 0xf0000000u) {x <= 4; r-= 4;} if (! (X & 0xc0000000u) {x <= 2; r-= 2;} if (! (X & 0x80000000u) {x <= 1; r-= 1;} return r ;}

Purpose: return the sequence number of the highest valid bit (from low to left) of the input parameter. This sequence number is different from the Starting sequence number of normal 0, it starts with 1 (0 is returned if there is no valid bit ).