third_party/ulib/musl/src/mman/shm_open.c

#include <errno.h>
#include <fcntl.h>
#include <limits.h>
#include <string.h>
#include <sys/mman.h>
#include <unistd.h>

char* __strchrnul(const char*, int);

char* __shm_mapname(const char* name, char* buf) {
    char* p;
    while (*name == '/')
        name++;
    if (*(p = __strchrnul(name, '/')) || p == name ||
        (p - name <= 2 && name[0] == '.' && p[-1] == '.')) {
        errno = EINVAL;
        return 0;
    }
    if (p - name > NAME_MAX) {
        errno = ENAMETOOLONG;
        return 0;
    }
    memcpy(buf, "/dev/shm/", 9);
    memcpy(buf + 9, name, p - name + 1);
    return buf;
}

int shm_open(const char* name, int flag, mode_t mode) {
    char buf[NAME_MAX + 10];
    if (!(name = __shm_mapname(name, buf)))
        return -1;
    return open(name, flag | O_NOFOLLOW | O_CLOEXEC | O_NONBLOCK, mode);
}

int shm_unlink(const char* name) {
    char buf[NAME_MAX + 10];
    if (!(name = __shm_mapname(name, buf)))
        return -1;
    return unlink(name);
}