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/*
* C Implementation: string
*
* Description: General string functions, not directly related to file system operations
*
* original implementation by Radek Podgorny
*
* License: BSD-style license
* Copyright: Radek Podgorny <radek@podgorny.cz>,
* Bernd Schubert <bernd-schubert@gmx.de>
*
*/
#include <stdio.h>
#include <stdarg.h>
#include <string.h>
#include <strings.h>
#include <unistd.h>
#include <stdbool.h>
#include <errno.h>
#include "unionfs.h"
#include "opts.h"
#include "debug.h"
#include "general.h"
/**
* Check if the given fname suffixes the hide tag
*/
char *whiteout_tag(const char *fname) {
DBG("%s\n", fname);
char *tag = strstr(fname, HIDETAG);
// check if fname has tag, fname is not only the tag, file name ends with the tag
// TODO: static strlen(HIDETAG)
if (tag && tag != fname && strlen(tag) == strlen(HIDETAG)) {
return tag;
}
return NULL;
}
/**
* copy one or more char arrays into dest and check for maximum size
*
* arguments: maximal string length and one or more char* string arrays
*
* check if the sum of the strings is larger than PATHLEN_MAX
*
* This function requires a NULL as last argument!
*
* path already MUST have been allocated!
*/
int build_path(char *path, int max_len, const char *callfunc, int line, ...) {
va_list ap; // argument pointer
int len = 0;
char *str_ptr = path;
(void)str_ptr; // please the compile to avoid warning in non-debug mode
(void)line;
(void)callfunc;
path[0] = '\0'; // that way can easily strcat even the first element
va_start(ap, line);
while (1) {
char *str = va_arg (ap, char *); // the next path element
if (!str) break;
/* Prevent '//' in pathes, if len > 0 we are not in the first
* loop-run. This is rather ugly, but I don't see another way to
* make sure there really is a '/'. By simply cutting off
* the initial '/' of the added string, we could run into a bug
* and would not have a '/' between path elements at all
* if somewhere else a directory slash has been forgotten... */
if (len > 0) {
// walk to the end of path
while (*path != '\0') path++;
// we are on '\0', now go back to the last char
path--;
if (*path == '/') {
int count = len;
// count makes sure nobody tricked us and gave
// slashes as first path only...
while (*path == '/' && count > 1) {
// possibly there are several slashes...
// But we want only one slash
path--;
count--;
}
// now we are *before* '/', walk to slash again
path++;
// eventually we walk over the slashes of the
// next string
while (*str == '/') str++;
} else if (*str != '/') {
// neither path ends with a slash, nor str
// starts with a slash, prevent a wrong path
strcat(path, "/");
len++;
}
}
va_end(ap);
len += strlen(str);
// +1 for final \0 not counted by strlen
if (len + 1 > max_len) {
usyslog (LOG_WARNING, "%s():%d Path too long \n", callfunc, line);
errno = ENAMETOOLONG;
return -errno;
}
strcat (path, str);
}
if (len == 0) {
usyslog(LOG_ERR, "from: %s():%d : No argument given?\n", callfunc, line);
errno = EIO;
return -errno;
}
DBG("from: %s():%d path: %s\n", callfunc, line, str_ptr);
return 0;
}
/**
* dirname() in libc might not be thread-save, at least the man page states
* "may return pointers to statically allocated memory", so we need our own
* implementation
*/
char *u_dirname(const char *path) {
DBG("%s\n", path);
char *ret = strdup(path);
if (ret == NULL) {
usyslog(LOG_WARNING, "strdup failed, probably out of memory!\n");
return ret;
}
char *ri = rindex(ret, '/');
if (ri != NULL) {
*ri = '\0'; // '/' found, so a full path
} else {
strcpy(ret, "."); // '/' not found, so path is only a file
}
return ret;
}
/**
* general elf hash (32-bit) function
*
* Algorithm taken from URL: http://www.partow.net/programming/hashfunctions/index.html,
* but rewritten from scratch due to incompatible license.
*
* str needs to NULL terminated
*/
static unsigned int elfhash(const char *str) {
DBG("%s\n", str);
unsigned int hash = 0;
while (*str) {
hash = (hash << 4) + (*str); // hash * 16 + c
// 0xF is 1111 in dual system, so highbyte is the highest byte of hash (which is 32bit == 4 Byte)
unsigned int highbyte = hash & 0xF0000000UL;
if (highbyte != 0) hash ^= (highbyte >> 24);
// example (if the condition is met):
// hash = 10110000000000000000000010100000
// highbyte = 10110000000000000000000000000000
// (highbyte >> 24) = 00000000000000000000000010110000
// after XOR: hash = 10110000000000000000000000010000
hash &= ~highbyte;
// ~highbyte = 01001111111111111111111111111111
// after AND: hash = 00000000000000000000000000010000
str++;
}
return hash;
}
/**
* Just a hash wrapper function, this way we can easily exchange the default
* hash algorith.
*/
unsigned int string_hash(void *s) {
return elfhash(s);
}
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