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 SYNOPSIS
38 	#include <string.h>
39 	size_t strlen(const char *<[str]>);
40 
41 DESCRIPTION
42 	The <<strlen>> function works out the length of the string
43 	starting at <<*<[str]>>> by counting chararacters until it
44 	reaches a <<NULL>> character.
45 
46 RETURNS
47 	<<strlen>> returns the character count.
48 
49 PORTABILITY
50 <<strlen>> is ANSI C.
51 
52 <<strlen>> requires no supporting OS subroutines.
53 
54 QUICKREF
55 	strlen ansi pure
56 */
57 
58 #include <picolibc.h>
59 
60 #include <string.h>
61 #include <limits.h>
62 
63 #define LBLOCKSIZE   (sizeof (long))
64 #define UNALIGNED(X) ((long)X & (LBLOCKSIZE - 1))
65 
66 #if LONG_MAX == 2147483647L
67 #define DETECTNULL(X) (((X) - 0x01010101) & ~(X) & 0x80808080)
68 #else
69 #if LONG_MAX == 9223372036854775807L
70 /* Nonzero if X (a long int) contains a NULL byte. */
71 #define DETECTNULL(X) (((X) - 0x0101010101010101) & ~(X) & 0x8080808080808080)
72 #else
73 #error long int is not a 32bit or 64bit type.
74 #endif
75 #endif
76 
77 #ifndef DETECTNULL
78 #error long int is not a 32bit or 64bit byte
79 #endif
80 
81 size_t
strlen(const char * str)82 strlen (const char *str)
83 {
84 
85 #ifndef HAVE_HW_PCMP
86 
87 #if defined(PREFER_SIZE_OVER_SPEED) || defined(__OPTIMIZE_SIZE__)
88   const char *start = str;
89 
90   while (*str)
91     str++;
92 
93   return str - start;
94 #else
95   const char *start = str;
96   unsigned long *aligned_addr;
97 
98   if (!UNALIGNED (str))
99     {
100       /* If the string is word-aligned, we can check for the presence of
101          a null in each word-sized block.  */
102       aligned_addr = (unsigned long*)str;
103       while (!DETECTNULL (*aligned_addr))
104         aligned_addr++;
105 
106       /* Once a null is detected, we check each byte in that block for a
107          precise position of the null.  */
108       str = (char*)aligned_addr;
109     }
110 
111   while (*str)
112     str++;
113   return str - start;
114 #endif /* not PREFER_SIZE_OVER_SPEED */
115 
116 #else
117 
118 #include "mb_endian.h"
119 
120   __asm__ volatile ("                                               \n\
121         or      r9, r0, r0              /* Index register */    \n\
122 check_alignment:                                                \n\
123         andi    r3, r5, 3                                       \n\
124         bnei    r3, align_arg                                   \n\
125 len_loop:                                                       \n"
126         LOAD4BYTES("r3", "r5", "r9")
127 "                                                               \n\
128         pcmpbf  r4, r3, r0                                      \n\
129         bnei    r4, end_len                                     \n\
130         brid    len_loop                                        \n\
131         addik   r9, r9, 4                                       \n\
132 end_len:                                                        \n\
133         lbu     r3, r5, r9                                      \n\
134         beqi    r3, done_len                                    \n\
135         brid    end_len                                         \n\
136         addik   r9, r9, 1                                       \n\
137 done_len:                                                       \n\
138         rtsd    r15, 8                                          \n\
139         or      r3, r0, r9              /* Return len */        \n\
140 align_arg:                                                      \n\
141         rsubik  r10, r3, 4                                      \n\
142 align_loop:                                                     \n\
143         lbu     r3, r5, r9                                      \n\
144         beqid   r3, done_len                                    \n\
145         addik   r10, r10, -1                                    \n\
146         bneid   r10, align_loop                                 \n\
147         addik   r9, r9, 1                                       \n\
148         bri     len_loop");
149 
150 #endif  /* ! HAVE_HW_PCMP */
151 }
152