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/***
This file is part of systemd.
Copyright 2012 Kay Sievers <kay@vrfy.org>
systemd is free software; you can redistribute it and/or modify it
under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2.1 of the License, or
(at your option) any later version.
systemd is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with systemd; If not, see <http://www.gnu.org/licenses/>.
***/
#include <errno.h>
#include <stdlib.h>
#include <string.h>
#include "alloc-util.h"
#include "strbuf.h"
/*
* Strbuf stores given strings in a single continuous allocated memory
* area. Identical strings are de-duplicated and return the same offset
* as the first string stored. If the tail of a string already exists
* in the buffer, the tail is returned.
*
* A trie (http://en.wikipedia.org/wiki/Trie) is used to maintain the
* information about the stored strings.
*
* Example of udev rules:
* $ ./udevadm test .
* ...
* read rules file: /usr/lib/udev/rules.d/99-systemd.rules
* rules contain 196608 bytes tokens (16384 * 12 bytes), 39742 bytes strings
* 23939 strings (207859 bytes), 20404 de-duplicated (171653 bytes), 3536 trie nodes used
* ...
*/
struct strbuf *strbuf_new(void) {
struct strbuf *str;
str = new0(struct strbuf, 1);
if (!str)
return NULL;
str->buf = new0(char, 1);
if (!str->buf)
goto err;
str->len = 1;
str->root = new0(struct strbuf_node, 1);
if (!str->root)
goto err;
str->nodes_count = 1;
return str;
err:
free(str->buf);
free(str->root);
free(str);
return NULL;
}
static void strbuf_node_cleanup(struct strbuf_node *node) {
size_t i;
for (i = 0; i < node->children_count; i++)
strbuf_node_cleanup(node->children[i].child);
free(node->children);
free(node);
}
/* clean up trie data, leave only the string buffer */
void strbuf_complete(struct strbuf *str) {
if (!str)
return;
if (str->root)
strbuf_node_cleanup(str->root);
str->root = NULL;
}
/* clean up everything */
void strbuf_cleanup(struct strbuf *str) {
if (!str)
return;
if (str->root)
strbuf_node_cleanup(str->root);
free(str->buf);
free(str);
}
static int strbuf_children_cmp(const struct strbuf_child_entry *n1,
const struct strbuf_child_entry *n2) {
return n1->c - n2->c;
}
static void bubbleinsert(struct strbuf_node *node,
uint8_t c,
struct strbuf_node *node_child) {
struct strbuf_child_entry new = {
.c = c,
.child = node_child,
};
int left = 0, right = node->children_count;
while (right > left) {
int middle = (right + left) / 2 ;
if (strbuf_children_cmp(&node->children[middle], &new) <= 0)
left = middle + 1;
else
right = middle;
}
memmove(node->children + left + 1, node->children + left,
sizeof(struct strbuf_child_entry) * (node->children_count - left));
node->children[left] = new;
node->children_count++;
}
/* add string, return the index/offset into the buffer */
ssize_t strbuf_add_string(struct strbuf *str, const char *s, size_t len) {
uint8_t c;
struct strbuf_node *node;
size_t depth;
char *buf_new;
struct strbuf_child_entry *child;
struct strbuf_node *node_child;
ssize_t off;
if (!str->root)
return -EINVAL;
/* search string; start from last character to find possibly matching tails */
if (len == 0)
return 0;
str->in_count++;
str->in_len += len;
node = str->root;
c = s[len-1];
for (depth = 0; depth <= len; depth++) {
struct strbuf_child_entry search;
/* match against current node */
off = node->value_off + node->value_len - len;
if (depth == len || (node->value_len >= len && memcmp(str->buf + off, s, len) == 0)) {
str->dedup_len += len;
str->dedup_count++;
return off;
}
c = s[len - 1 - depth];
/* bsearch is not allowed on a NULL sequence */
if (node->children_count == 0)
break;
/* lookup child node */
search.c = c;
child = bsearch(&search, node->children, node->children_count,
sizeof(struct strbuf_child_entry),
(__compar_fn_t) strbuf_children_cmp);
if (!child)
break;
node = child->child;
}
/* add new string */
buf_new = realloc(str->buf, str->len + len+1);
if (!buf_new)
return -ENOMEM;
str->buf = buf_new;
off = str->len;
memcpy(str->buf + off, s, len);
str->len += len;
str->buf[str->len++] = '\0';
/* new node */
node_child = new0(struct strbuf_node, 1);
if (!node_child)
return -ENOMEM;
node_child->value_off = off;
node_child->value_len = len;
/* extend array, add new entry, sort for bisection */
child = realloc(node->children, (node->children_count + 1) * sizeof(struct strbuf_child_entry));
if (!child) {
free(node_child);
return -ENOMEM;
}
str->nodes_count++;
node->children = child;
bubbleinsert(node, c, node_child);
return off;
}
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