tsiry-sandratraina.com
A modern Music Player Daemon based on Rockbox open source high quality audio player
libadwaita
audio
rust
zig
deno
mpris
rockbox
mpd
1/*
2FUNCTION
3 <<memchr>>---search for character in memory
4
5INDEX
6 memchr
7
8ANSI_SYNOPSIS
9 #include <string.h>
10 void * memchr(const void *<[s1]>, int <[c]>, size_t <[n]>);
11
12TRAD_SYNOPSIS
13 #include <string.h>
14 void * memchr(<[s1]>, <[c]>, <[n]>);
15 void *<[string]>;
16 int *<[c]>;
17 size_t *<[n]>;
18
19DESCRIPTION
20 This function scans the first <[n]> bytes of the memory pointed
21 to by <[s1]> for the character <[c]> (converted to a char).
22
23RETURNS
24 Returns a pointer to the matching byte, or a null pointer if
25 <[c]> does not occur in <[s1]>.
26
27PORTABILITY
28<<memchr>> is ANSI C.
29
30<<memchr>> requires no supporting OS subroutines.
31
32QUICKREF
33 memchr ansi pure
34*/
35
36#include <string.h>
37#include <limits.h>
38#include "_ansi.h" /* for _DEFUN */
39
40/* Nonzero if X is not aligned on a "long" boundary. */
41#define ROCKBOX_UNALIGNED(X) ((long)X & (sizeof (long) - 1))
42
43/* How many bytes are loaded each iteration of the word copy loop. */
44#define LBLOCKSIZE (sizeof (long))
45
46#if LONG_MAX == 2147483647L
47#define DETECTNULL(X) (((X) - 0x01010101) & ~(X) & 0x80808080)
48#else
49#if LONG_MAX == 9223372036854775807L
50/* Nonzero if X (a long int) contains a NULL byte. */
51#define DETECTNULL(X) (((X) - 0x0101010101010101) & ~(X) & 0x8080808080808080)
52#else
53#error long int is not a 32bit or 64bit type.
54#endif
55#endif
56
57/* DETECTCHAR returns nonzero if (long)X contains the byte used
58 to fill (long)MASK. */
59#define DETECTCHAR(X,MASK) (DETECTNULL(X ^ MASK))
60
61void *
62_DEFUN (memchr, (s1, i, n),
63 _CONST void *s1 _AND
64 int i _AND size_t n)
65{
66 _CONST unsigned char *s = (_CONST unsigned char *)s1;
67#if defined(PREFER_SIZE_OVER_SPEED) || defined(__OPTIMIZE_SIZE__)
68 unsigned char c = (unsigned char)i;
69
70 while (n-- > 0)
71 {
72 if (*s == c)
73 {
74 return (void *)s;
75 }
76 s++;
77 }
78
79 return NULL;
80#else
81 unsigned char c = (unsigned char)i;
82 unsigned long mask,j;
83 unsigned long *aligned_addr;
84
85 if (!ROCKBOX_UNALIGNED (s))
86 {
87 mask = 0;
88 for (j = 0; j < LBLOCKSIZE; j++)
89 mask = (mask << 8) | c;
90
91 aligned_addr = (unsigned long*)s;
92 while ((!DETECTCHAR (*aligned_addr, mask)) && (n>LBLOCKSIZE))
93 {
94 aligned_addr++;
95 n -= LBLOCKSIZE;
96 }
97
98 /* The block of bytes currently pointed to by aligned_addr
99 may contain the target character or there may be less than
100 LBLOCKSIZE bytes left to search. We check the last few
101 bytes using the bytewise search. */
102
103 s = (unsigned char*)aligned_addr;
104 }
105
106 while (n-- > 0)
107 {
108 if (*s == c)
109 {
110 return (void *)s;
111 }
112 s++;
113 }
114
115 return NULL;
116#endif /* not PREFER_SIZE_OVER_SPEED */
117}