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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 $   */
/*
 * strncpy(s1, s2, n)
 *
 * Copy s2 to s1, truncating or null-padding to always copy n bytes
 * return 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 save    r1


ENTRY(strncpy)

        combt,=   s_addr,r0,pad_null_bytes1     /* if s2==NULL then pad nulls and exit */
        copy      d_addr,ret0          /* The return value is defined to be the value of d_addr. DELAY SLOT*/
        addibt,<,n  -4,count,byteloop     /* If count is <= 4 don't get fancy.*/

        extru       s_addr,31,2,tmp1   /* 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*/
        comb,<>       tmp5,tmp1,not_aligned /* branch if tmp5<>tmp1. */
        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
        b               skip_mask       /* don't reload tmp1*/
        or              save,tmp1,tmp1  /* or mask with data*/

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

skip_mask:
        uxor,nbz        tmp1,r0,save    /* check for null*/
        b,n             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*/
         add         d_addr,count,d_addr/* final store address  is +1 too high !*/
         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
         bv             0(r2)
         stbys,e        tmp1,0(d_addr)  /* done */

/* Begin non_aligned code. */
not_aligned:
        sub,>=       tmp5,tmp1,tmp3     /* compute the shift amt.and skip load if tmp5 > tmp1.*/
        ldwm         4(0,s_addr),tmp1   /* load up the first word from the source. tmp1 = *s_addr++*/
        zdep         tmp3,28,29,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_mask2 /* 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 */
        b               skip_mask2
        copy            r0, tmp5        /* zero out tmp5 so we don't try to mask again*/

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 ! */

        ldwm        4(0,s_addr),tmp1    /* get 2nd word ! */
        vshd        tmp2,tmp1,tmp3      /* position data ! */
        uxor,nbz        tmp3, r0, save
        b,n             null4

        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 */
        copy            r0, tmp5        /* zero out tmp5 so we don't try to mask again*/
skip_mask3:
        uxor,nbz        tmp3,r0,save
        b,n             null4
        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 used in the 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,sbz        tmp3,r0,save    /* if some-byte-zero */
        b               no_null         /* don't goto no_null-find which null instead */
        add             d_addr,count,d_addr     /* get d_addr ready for stbys,e */
        extru,<>        save,7,8,r0
        b               found_null5
        copy            r0, tmp5
        extru,<>        save,15,8,r0
        b               found_null5
        ldil            0x1FE000,tmp5           /* setup mask (FF000000)*/
        extru,<>        save,23,8,r0
        b               found_null5
        ldil            0x1FFFE0,tmp5           /* setup mask (FFFF0000)*/
        ldo             -1(r0),tmp5             /* setup mask (FFFFFFFF)*/
found_null5:
        and             tmp3,tmp5,tmp3  /* zero out tmp5 based on mask in tmp5*/
no_null:
        bv              0(r2)           /* were done*/
        stbys,e     tmp3,0(0,d_addr)    /* store the data !*/

/* here we do ye old byte-at-a-time moves.*/
byteloop: 
        addibt,=,n     4,count,done
        comb,=    0,s_addr,done
        stbs      r0,0(d_addr)          /* store null in case s_addr == NULL */
        ldbs,ma     1(s_addr),tmp1
encore:
        combt,=,n       tmp1,r0, pad_null_bytes1
        stbs,ma     tmp1,1(d_addr) 
        addibf,=,n  -1,count,encore
        ldbs,ma     1(s_addr),tmp1
        b,n             done

pnb_1:
        addibt,=,n      4,count,done /* if count was already 0 then we're done*/

pad_null_bytes1:
        combt,=,n       count,r0,done   /* if count==0 then exit */
pad_null_bytes2:
        addibf,=        -1,count,pad_null_bytes2
        stbs,ma         r0,1(d_addr)
        b,n             done

pad_nulls:
        addibf,<=,n     -4,count,pad_nulls
        stwm            r0,4(d_addr)
        b,n             pnb_1


null1:
        extru,<>        save,7,8,r0
        b               found_null1
        copy            r0, tmp5
        extru,<>        save,15,8,r0
        b               found_null1
        ldil            0x1FE000,tmp5           /* setup mask (FF000000)*/
        extru,<>        save,23,8,r0
        b               found_null1
        ldil            0x1FFFE0,tmp5           /* setup mask (FFFF0000)*/
        ldo             -1(r0),tmp5             /* setup mask (FFFFFFFF)*/
found_null1:
        and             tmp1,tmp5,tmp1          /*zero out tmp1 according to mask*/
        b               pad_nulls               /* nullify remaining count bytes*/
        stbys,b,m       tmp1,4(0,d_addr)        /* first word (account for alignment)*/


null2:  /* back porch case. We have less than 4 bytes to go.*/
        extru,<>        save,7,8,r0     /* is null in 1st byte? */
        b               found_null2
        copy            r0, tmp5
        extru,<>        save,15,8,r0    /* is null in 2nd byte? */
        b               found_null2
        ldil            0x1FE000,tmp5           /* setup mask (FF000000)*/
        b               found_null2     /* null must be in 3rd byte */
        ldil            0x1FFFE0,tmp5           /* setup mask (FFFF0000)*/
found_null2:    
        and             tmp1,tmp5,tmp1          /*zero out tmp1 according to mask*/
        bv              0(r2)                   /* we're done*/
        stbys,e         tmp1,0(0,d_addr)        /* last word (back porch)*/

null3:  /* not_aligned case where null is found in first of two words--adjust count*/
        extru,<>        save,7,8,r0
        b               found_null3
        copy            r0, tmp5
        extru,<>        save,15,8,r0
        b               found_null3
        ldil            0x1FE000,tmp5           /* setup mask (FF000000)*/
        extru,<>        save,23,8,r0
        b               found_null3
        ldil            0x1FFFE0,tmp5           /* setup mask (FFFF0000)*/
        ldo             -1(r0),tmp5             /* setup mask (FFFFFFFF)*/
found_null3:
        addi            4,count,count           /* fix count since null is in first of two words*/
        and             tmp3,tmp5,tmp3          /*zero out tmp3 according to mask*/
        b               pad_nulls               /* nullify remaining count bytes*/
        stbys,b,m       tmp3,4(d_addr)

null4:  /* not_aligned case where null is found in second of two words*/
        extru,<>        save,7,8,r0
        b               found_null4
        copy            r0, tmp5
        extru,<>        save,15,8,r0
        b               found_null4
        ldil            0x1FE000,tmp5           /* setup mask (FF000000)*/
        extru,<>        save,23,8,r0
        b               found_null4
        ldil            0x1FFFE0,tmp5           /* setup mask (FFFF0000)*/
        ldo             -1(r0),tmp5             /* setup mask (FFFFFFFF)*/
found_null4:
        and             tmp3,tmp5,tmp3          /*zero out tmp4 according to mask*/
        b               pad_nulls               /* nullify remaining count bytes*/
        stbys,b,m       tmp3,4(d_addr)

done:    
EXIT(strncpy)