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/*
 *  (c) Copyright 1986 HEWLETT-PACKARD COMPANY
 *
 *  To anyone who acknowledges that this file is provided "AS IS"
 *  without any express or implied warranty:
 *      permission to use, copy, modify, and distribute this file
 *  for any purpose is hereby granted without fee, provided that
 *  the above copyright notice and this notice appears in all
 *  copies, and that the name of Hewlett-Packard Company not be
 *  used in advertising or publicity pertaining to distribution
 *  of the software without specific, written prior permission.
 *  Hewlett-Packard Company makes no representations about the
 *  suitability of this software for any purpose.
 */

/*HPUX_ID:      @(#) $Revision: 1.1 $   */
/* strncat(s1,s2,n) : concatonate at most n characters from s2 onto s1 */

#include "DEFS.h"

#define d_addr  r26
#define s_addr  r25
#define count   r24
#define tmp1    r19
#define tmp2    r20
#define tmp3    r21
#define tmp4    r22
#define tmp5    arg3
#define tmp6    r31
#define save    r1
#define tmp7    ret1    /* source offset-- reset to orig source addr if not aligned */


ENTRY(strncat)

        comb,=          r0,s_addr,quit  /* quit if s2=NULL */
        copy      d_addr,ret0          /* The return value is the value of d_addr. DELAY SLOT*/

/* First look for end of s1 (d_addr) */

        extru       d_addr,31,2,tmp1   /* Extract the low two bits of the dest address. */
        combt,=         tmp1,r0,dont_mask
        dep             0,31,2,d_addr   /*set word alignment */
        ldwm            4(d_addr),tmp2
        sh3add          tmp1,r0,save    /* build mask based on tmp1 */
        mtctl           save,11
        zvdepi          -2,32,save
        or              save,tmp2,tmp2
        uxor,nbz        tmp2,r0,save
search:
        b,n             found_end       /* nullified under uxor conditions above and below */
dont_mask:
        ldwm            4(d_addr),tmp2
        comib,tr        r0,r0,search
        uxor,nbz        tmp2,r0,save

found_end:                              /* at this point d_addr points to word */
        extru,<>        save,7,8,r0     /* following word with null */
        addib,tr,n      -4,d_addr,begin_copy    /*set d_addr to end of s1 */
        extru,<>        save,15,8,r0
        addib,tr,n      -3,d_addr,begin_copy
        extru,<>        save,23,8,r0
        addi            -1,d_addr,d_addr
        addi            -1,d_addr,d_addr


begin_copy:
        addibt,<,n  -4,count,byteloop     /* If count is <= 4 don't get fancy.*/

        extru       s_addr,31,2,tmp4   /* Extract the low two bits of the source address.*/
        extru       d_addr,31,2,tmp5   /* Extract the low two bits of the destination address.*/
        add         count,tmp5,count   /* pre increment the count by the byte address so that the count is*/
        copy            s_addr,tmp6     /* save original s_addr in case we find null in first word */
        copy         s_addr, tmp7       /* save s_addr in case we find null before first store */
        comb,<>       tmp5,tmp4,not_aligned /* branch if tmp5<>tmp4. */
        dep         0,31,2,s_addr      /* Compute the word address of the source.  DELAY SLOT.*/
/* aligned*/
        combt,=         tmp5,r0,skip_mask
        ldwm        4(0,s_addr),tmp1   /* tmp1 = *s_addr   s_addr += 4 (DELAY SLOT)*/
        sh3add          tmp5,r0,save    /* compute mask in save*/
        mtctl           save,11
        zvdepi          -2,32,save
        or              save,tmp1,tmp1  /* or mask with data*/
        uxor,nbz        tmp1,r0,save    /* check for null*/
        b,n             null1
        addibt,<        -4,count,back_porch
        stbys,b,m   tmp1,4(0,d_addr)   /* store word (delay slot)*/

chunks:
        ldwm            4(0,s_addr),tmp1 /* get a word*/

skip_mask:
        uxor,nbz        tmp1,r0,save    /* check for null*/
        b,n             align_null1
        addibf,<        -4,count,chunks
        stbys,b,m   tmp1,4(0,d_addr)   /* store word (delay slot)*/

back_porch:                                /* last word to store*/
         addibt,=,n  4,count,done       /* if count = 0 we're, of course, done !*/
         ldws        0(s_addr),tmp1     /* load up the back_porch*/
         sh3add         count,r0, save  /* setup right mask based on count*/
         mtctl          save,r11
         zvdepi         -2,32,save      /*save now has left-hand mask*/
         uaddcm         r0,save,save    /*form right hand mask */
         or             tmp1,save,tmp1  /*and insert data*/
         uxor,nbz       tmp1,r0,save    /* check for null*/
         b,n            null2
         add         d_addr,count,d_addr/* final store address  is +1 too high !*/
         b              done
         stbys,e        tmp1,0(d_addr)  /* done */

/* Begin non_aligned code. */
not_aligned:
        sub,>=       tmp5,tmp4,tmp6     /* compute the shift amt.and skip load if tmp5 > tmp4.*/
        ldwm         4(0,s_addr),tmp1   /* load up the first word from the source. tmp1 = *s_addr++*/
        zdep         tmp6,28,29,tmp4    /* compute the number of bits to shift */
        mtctl        tmp4,11            /* load the shift count into cr11 = shift count register.*/
        addibt,<,n   -4,count,chkchnk2 /* first step in pre adjustment of count for looping.*/

        ldwm        4(0,s_addr),tmp2    /* get either first or second word from source. */
        combt,=         tmp5,r0,skip_mask4 /* don't mask if whole word is valid*/
        vshd        tmp1,tmp2,tmp3      /* position data !  (delay slot)*/
        sh3add          tmp5,r0,save    /* setup r1*/
        mtctl           save,r11        /* setup mask in save*/
        zvdepi          -2,32,save
        or              save, tmp3, tmp3
        mtctl           tmp4,11            /* re-load the shift count into cr11 */

skip_mask4:
        uxor,nbz        tmp3, r0, save
        b,n             null4           /* special case for first word */
        copy            r0, tmp5        /* zero out tmp5 so we don't try to mask again*/
        copy            r0, tmp7        /* zero out tmp7 so we don't try to use original s_addr anymore */
        b               continue
        stbys,b,m   tmp3,4(0,d_addr)    /* store ! */

chunk2:
        ldwm        4(0,s_addr),tmp2
        vshd        tmp1,tmp2,tmp3 

skip_mask2:
        uxor,nbz        tmp3, r0, save
        b,n             null3
        stbys,b,m   tmp3,4(0,d_addr)    /* store ! */

continue:
        ldwm        4(0,s_addr),tmp1    /* get 2nd word ! */
        vshd        tmp2,tmp1,tmp3      /* position data ! */
        uxor,nbz        tmp3, r0, save
        b,n             null3

        addibf,<    -8,count,chunk2    /* If count is still >= 8 do another loop.*/
        stbys,b,m   tmp3,4(0,d_addr)    /* store !*/

chkchnk2:
        addibt,<,n  4,count,bp_0       /* if we don't have 4 bytes left then do the back porch (bp_0)*/

subchnk2: /* we have less than 8 chars to copy*/

        ldwm        4(0,s_addr),tmp2    /* get next word !*/
        combt,=         tmp5,r0,skip_mask3
        vshd        tmp1,tmp2,tmp3      /* position data !*/
        sh3add          tmp5,r0,save    /* setup r1*/
        mtctl           save,r11        /* setup mask in save*/
        zvdepi          -2,32,save
        or              save, tmp3, tmp3
        mtctl           tmp4,11         /* restore shift value again */
skip_mask3:
        uxor,nbz        tmp3,r0,save
        b,n             null3
        copy            r0,tmp5   /* zero out tmp5 so null3 does correct alignment */
        copy            r0,tmp7   /* zero out tmp7 so we don't use orignal s_addr since no longer valid */
        b               bp_1 /* we now have less than 4 bytes to move*/
        stbys,b,m   tmp3,4(0,d_addr)    /* store !*/

bp_0:    
        copy            tmp1,tmp2       /* switch registers for shift process */
        addibt,<=,n  4,count,done        /* if count = -4 this implies that count = 0 -> done */

bp_1:
        ldwm        4(0,s_addr),tmp1    /* get final word !        */
        vshd        tmp2,tmp1,tmp3      /* position data !*/
        uxor,nbz        tmp3,r0,save    /* if no-byte-zero */
        b,n             bp_null         /* don't goto no_null-find which null instead */
no_null:
        add         d_addr,count,d_addr /* set up d_addr for stbys,e */
        b               done            /* were done*/
        stbys,e     tmp3,0(0,d_addr)    /* store the data !*/

/* here we do ye old byte-at-a-time moves.*/
align_null1:
        b       byteloop
        addi    -4,s_addr,s_addr
null1:
        copy            tmp6,s_addr             /* restore orig s_addr (aligned only) */
byteloop:
        addibt,=     4,count,done
null2:
        ldbs,ma     1(s_addr),tmp1
encore:
        combt,=,n       tmp1,r0, done
        stbs,ma     tmp1,1(d_addr) 
        addibf,=,n  -1,count,encore
        ldbs,ma     1(s_addr),tmp1
        b,n             done

bp_null:
        addi    -4,count,count          /* fudge count 'cause byteloop will re-increment */

null3:  /* not_aligned case reset s_addr and finish byte-wise */
        combt,=,n  r0,tmp7,null3a       /* if tmp7 is not valid address then branch below */
        b       byteloop                        /* otherwise reset s_addr to tmp7 and finish */
        copy    tmp7, s_addr

null3a: /* right shift target */
        addibt,<,n  0,tmp6,null3b       /* if left shifting */
        sub     r0,tmp6,tmp6            /* do null3b code */
        addi    -4,tmp6,tmp6
        b       byteloop
        add     tmp6,s_addr,s_addr      /* reset s_addr by 4 + shift_amt */

null3b:
        subi    -8,tmp6,tmp6
        add     tmp5,tmp6,tmp6  /* adjust by the dest offset if this is our first store */
        b       byteloop
        add     tmp6,s_addr,s_addr      /* adjust s_addr by (8-shift_amt-dest_off) */

null4:
        add,>   tmp6,r0,tmp6            /* if left shift */
        b,n     null3                   /* then do null3 */
        b       byteloop
        addi    -4,s_addr,s_addr        /* adj source only by 4 */
        
done:    
        bv              0(r2)
        stbs            r0,0(d_addr)
quit:
EXIT(strncat)