1.\" 2.\" Copyright (c) 2014, Joyent, Inc. 3.\" Copyright (c) 2009, Sun Microsystems, Inc. All Rights Reserved. 4.\" Copyright 1989 AT&T 5.\" Copyright 2021 Oxide Computer Company 6.\" 7.\" The contents of this file are subject to the terms of the 8.\" Common Development and Distribution License (the "License"). 9.\" You may not use this file except in compliance with the License. 10.\" 11.\" You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE 12.\" or http://www.opensolaris.org/os/licensing. 13.\" See the License for the specific language governing permissions 14.\" and limitations under the License. 15.\" 16.\" When distributing Covered Code, include this CDDL HEADER in each 17.\" file and include the License file at usr/src/OPENSOLARIS.LICENSE. 18.\" If applicable, add the following below this CDDL HEADER, with the 19.\" fields enclosed by brackets "[]" replaced with your own identifying 20.\" information: Portions Copyright [yyyy] [name of copyright owner] 21.\" 22.Dd January 25, 2022 23.Dt MEMORY 3C 24.Os 25.Sh NAME 26.Nm memory , 27.Nm memccpy , 28.Nm memchr , 29.Nm memcmp , 30.Nm memcpy , 31.Nm memmem , 32.Nm memmove , 33.Nm memrchr , 34.Nm memset 35.Nd memory operations 36.Sh SYNOPSIS 37.In string.h 38.Ft "void *" 39.Fo memccpy 40.Fa "void *restrict s1" 41.Fa "const void *restrict s2" 42.Fa "int c" 43.Fa "size_t n" 44.Fc 45.Ft "void *" 46.Fo memchr 47.Fa "void *s" 48.Fa "int c" 49.Fa "size_t n" 50.Fc 51.Ft int 52.Fo memcmp 53.Fa "const void *s1" 54.Fa "const void *s2" 55.Fa "size_t n" 56.Fc 57.Ft "void *" 58.Fo memcpy 59.Fa "void *restrict s1" 60.Fa "const void *restrict s2" 61.Fa "size_t n" 62.Fc 63.Ft "void *" 64.Fo memmem 65.Fa "const void *l" 66.Fa "size_t l_len" 67.Fa "const void *s" 68.Fa "size_t s_len" 69.Fc 70.Ft "void *" 71.Fo memmove 72.Fa "void *s1" 73.Fa "const void *s2" 74.Fa "size_t n" 75.Fc 76.Ft "void *" 77.Fo memrchr 78.Fa "void *s" 79.Fa "int c" 80.Fa "size_t n" 81.Fc 82.Ft "void *" 83.Fo memset 84.Fa "void *s" 85.Fa "int c" 86.Fa "size_t n" 87.Fc 88.Sh DESCRIPTION 89These functions operate as efficiently as possible on memory areas (arrays of 90bytes bounded by a count, not terminated by a null character). 91They do not check for the overflow of any receiving memory area. 92.Pp 93The 94.Fn memccpy 95function copies bytes from memory area 96.Fa s2 97into 98.Fa s1 , 99stopping after the first occurrence of 100.Fa c 101.Po 102converted to an 103.Vt unsigned char 104.Pc 105has been copied, or after 106.Fa n 107bytes have been copied, whichever comes first. 108It returns a pointer to the byte after the copy of 109.Fa c 110in 111.Fa s1 , 112or a 113.Dv NULL 114pointer if 115.Fa c 116was not found in the first 117.Fa n 118bytes of 119.Fa s2 . 120.Pp 121The 122.Fn memchr 123function returns a pointer to the first occurrence of 124.Fa c 125.Po 126converted to an 127.Vt unsigned char 128.Pc 129in the first 130.Fa n 131bytes 132.Po 133each interpreted as an 134.Vt unsigned char 135.Pc 136of memory area 137.Fa s , 138or a 139.Dv NULL 140pointer if 141.Fa c 142does not occur. 143.Pp 144The 145.Fn memrchr 146function behaves similarly to the 147.Fn memchr 148function, except that the memory area is searched in reverse from the 149last byte. 150.Pp 151The 152.Fn memcmp 153function compares its arguments, looking at the first 154.Fa n 155bytes 156.Po 157each interpreted as an 158.Vt unsigned char 159.Pc , 160and returns an integer less than, equal to, or greater than 0, according as 161.Fa s1 162is less than, equal to, or greater than 163.Fa s2 164when taken to be unsigned characters. 165.Pp 166The 167.Fn memcpy 168function copies 169.Fa n 170bytes from memory area 171.Fa s2 172to 173.Fa s1 174It returns 175.Fa s1 . 176If copying takes place between objects that overlap, the behavior is undefined. 177In such cases, use 178.Fn memmove 179instead. 180.Pp 181The 182.Fn memmem 183function searches for the 184.Fa s_len 185long byte pattern 186.Fa s 187in the memory region starting at 188.Fa l 189for 190.Fa l_len 191bytes. 192If a match is found, a pointer to the starting location in 193.Fa l 194is returned. 195If no match is found, 196.Fa l_len 197is zero, 198.Fa s_len 199is zero, or 200.Fa l_len 201is less than 202.Fa s_len 203then a 204.Dv NULL 205pointer is return. 206.Pp 207The 208.Fn memmove 209function copies 210.Fa n 211bytes from memory area 212.Fa s2 213to memory area 214.Fa s1 . 215Copying between objects that overlap will take place correctly. 216It returns 217.Fa s1 . 218.Pp 219The 220.Fn memset 221function sets the first 222.Fa n 223bytes in memory area 224.Fa s 225to the value of 226.Fa c 227.Po 228converted to an 229.Vt unsigned char 230.Pc . 231It returns 232.Fa s . 233.Sh USAGE 234Using 235.Fn memcpy 236might be faster than using 237.Fn memmove 238if the 239application knows that the objects being copied do not overlap. 240.Sh INTERFACE STABILITY 241.Sy Committed 242.Sh MT-LEVEL 243.Sy MT-Safe 244.Sh SEE ALSO 245.Xr string 3C , 246.Xr attributes 7 , 247.Xr standards 7 248.Sh NOTES 249Overlap between objects being copied can arise even when their 250.Pq virtual 251address ranges appear to be disjoint; for example, as a result of 252memory-mapping overlapping portions of the same underlying file, or of 253attaching the same shared memory segment more than once. 254