1 /* Copyright (c) 2009 Xilinx, Inc.  All rights reserved.
2 
3    Redistribution and use in source and binary forms, with or without
4    modification, are permitted provided that the following conditions are
5    met:
6 
7    1.  Redistributions source code must retain the above copyright notice,
8    this list of conditions and the following disclaimer.
9 
10    2.  Redistributions in binary form must reproduce the above copyright
11    notice, this list of conditions and the following disclaimer in the
12    documentation and/or other materials provided with the distribution.
13 
14    3.  Neither the name of Xilinx nor the names of its contributors may be
15    used to endorse or promote products derived from this software without
16    specific prior written permission.
17 
18    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER AND CONTRIBUTORS "AS
19    IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
20    TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
21    PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
22    HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
23    SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
24    TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
25    PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
26    LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
27    NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
28    SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
29 
30 
31 FUNCTION
32 	<<strlen>>---character string length
33 
34 INDEX
35 	strlen
36 
37 ANSI_SYNOPSIS
38 	#include <string.h>
39 	size_t strlen(const char *<[str]>);
40 
41 TRAD_SYNOPSIS
42 	#include <string.h>
43 	size_t strlen(<[str]>)
44 	char *<[src]>;
45 
46 DESCRIPTION
47 	The <<strlen>> function works out the length of the string
48 	starting at <<*<[str]>>> by counting chararacters until it
49 	reaches a <<NULL>> character.
50 
51 RETURNS
52 	<<strlen>> returns the character count.
53 
54 PORTABILITY
55 <<strlen>> is ANSI C.
56 
57 <<strlen>> requires no supporting OS subroutines.
58 
59 QUICKREF
60 	strlen ansi pure
61 */
62 
63 #include <_ansi.h>
64 #include <string.h>
65 #include <limits.h>
66 
67 #define LBLOCKSIZE   (sizeof (long))
68 #define UNALIGNED(X) ((long)X & (LBLOCKSIZE - 1))
69 
70 #if LONG_MAX == 2147483647L
71 #define DETECTNULL(X) (((X) - 0x01010101) & ~(X) & 0x80808080)
72 #else
73 #if LONG_MAX == 9223372036854775807L
74 /* Nonzero if X (a long int) contains a NULL byte. */
75 #define DETECTNULL(X) (((X) - 0x0101010101010101) & ~(X) & 0x8080808080808080)
76 #else
77 #error long int is not a 32bit or 64bit type.
78 #endif
79 #endif
80 
81 #ifndef DETECTNULL
82 #error long int is not a 32bit or 64bit byte
83 #endif
84 
85 size_t
86 _DEFUN (strlen, (str),
87 	_CONST char *str)
88 {
89 
90 #ifndef HAVE_HW_PCMP
91 
92 #if defined(PREFER_SIZE_OVER_SPEED) || defined(__OPTIMIZE_SIZE__)
93   _CONST char *start = str;
94 
95   while (*str)
96     str++;
97 
98   return str - start;
99 #else
100   _CONST char *start = str;
101   unsigned long *aligned_addr;
102 
103   if (!UNALIGNED (str))
104     {
105       /* If the string is word-aligned, we can check for the presence of
106          a null in each word-sized block.  */
107       aligned_addr = (unsigned long*)str;
108       while (!DETECTNULL (*aligned_addr))
109         aligned_addr++;
110 
111       /* Once a null is detected, we check each byte in that block for a
112          precise position of the null.  */
113       str = (char*)aligned_addr;
114     }
115 
116   while (*str)
117     str++;
118   return str - start;
119 #endif /* not PREFER_SIZE_OVER_SPEED */
120 
121 #else
122 
123 #include "mb_endian.h"
124 
125   asm volatile ("                                               \n\
126         or      r9, r0, r0              /* Index register */    \n\
127 check_alignment:                                                \n\
128         andi    r3, r5, 3                                       \n\
129         bnei    r3, align_arg                                   \n\
130 len_loop:                                                       \n"
131         LOAD4BYTES("r3", "r5", "r9")
132 "                                                               \n\
133         pcmpbf  r4, r3, r0                                      \n\
134         bnei    r4, end_len                                     \n\
135         brid    len_loop                                        \n\
136         addik   r9, r9, 4                                       \n\
137 end_len:                                                        \n\
138         lbu     r3, r5, r9                                      \n\
139         beqi    r3, done_len                                    \n\
140         brid    end_len                                         \n\
141         addik   r9, r9, 1                                       \n\
142 done_len:                                                       \n\
143         rtsd    r15, 8                                          \n\
144         or      r3, r0, r9              /* Return len */        \n\
145 align_arg:                                                      \n\
146         rsubik  r10, r3, 4                                      \n\
147 align_loop:                                                     \n\
148         lbu     r3, r5, r9                                      \n\
149         beqid   r3, done_len                                    \n\
150         addik   r10, r10, -1                                    \n\
151         bneid   r10, align_loop                                 \n\
152         addik   r9, r9, 1                                       \n\
153         bri     len_loop");
154 
155 #endif  /* ! HAVE_HW_PCMP */
156 }
157