/* * arch/alpha/lib/strncat.S * Contributed by Richard Henderson (rth@tamu.edu) * * Append no more than COUNT characters from the null-terminated string SRC * to the null-terminated string DST. Always null-terminate the new DST. * * This differs slightly from the semantics in libc in that we never write * past count, whereas libc may write to count+1. This follows the generic * implementation in lib/string.c and is, IMHO, more sensible. */ .text .align 3 .globl strncat .ent strncat strncat: .frame $30, 0, $26 .prologue 0 mov $16, $0 # set up return value beq $18, $zerocount /* Find the end of the string. */ ldq_u $1, 0($16) # load first quadword ($16 may be misaligned) lda $2, -1($31) insqh $2, $16, $2 andnot $16, 7, $16 or $2, $1, $1 cmpbge $31, $1, $2 # bits set iff byte == 0 bne $2, $found $loop: ldq $1, 8($16) addq $16, 8, $16 cmpbge $31, $1, $2 beq $2, $loop $found: negq $2, $3 # clear all but least set bit and $2, $3, $2 and $2, 0xf0, $3 # binary search for that set bit and $2, 0xcc, $4 and $2, 0xaa, $5 cmovne $3, 4, $3 cmovne $4, 2, $4 cmovne $5, 1, $5 addq $3, $4, $3 addq $16, $5, $16 addq $16, $3, $16 /* Now do the append. */ bsr $23, __stxncpy /* Worry about the null termination. */ zapnot $1, $27, $2 # was last byte a null? bne $2, 0f ret 0: cmplt $27, $24, $2 # did we fill the buffer completely? or $2, $18, $2 bne $2, 2f and $24, 0x80, $2 # no zero next byte bne $2, 1f /* Here there are bytes left in the current word. Clear one. */ addq $24, $24, $24 # end-of-count bit 2: zap $1, $24, $1 stq_u $1, 0($16) ret 1: /* Here we must read the next DST word and clear the first byte. */ ldq_u $1, 8($16) zap $1, 1, $1 stq_u $1, 8($16) $zerocount: ret .end strncat
