bionic: reimplement property area as hybrid trie/binary tree
See the comments for an explanation of how properties are stored. The trie structure is designed to scale better than the previous array-based implementation. Searching an array with n properties required average O(n) string compares of the entire key; searching the trie requires average O(log n) string compares of each token (substrings between '.' characters). Change-Id: I491305bc7aca59609abcd871a5f33d97f89ce714 Signed-off-by: Greg Hackmann <ghackmann@google.com>
This commit is contained in:
Greg Hackmann
parent
a823883548
commit
6ac8e6a46d
@ -34,6 +34,7 @@
|
||||
#include <poll.h>
|
||||
#include <fcntl.h>
|
||||
#include <stdbool.h>
|
||||
#include <string.h>
|
||||
|
||||
#include <sys/mman.h>
|
||||
|
||||
@ -51,12 +52,15 @@
|
||||
#include <sys/atomics.h>
|
||||
#include <bionic_atomic_inline.h>
|
||||
|
||||
#define ALIGN(x, a) (((x) + (a - 1)) & ~(a - 1))
|
||||
|
||||
struct prop_area {
|
||||
unsigned volatile count;
|
||||
unsigned bytes_used;
|
||||
unsigned volatile serial;
|
||||
unsigned magic;
|
||||
unsigned version;
|
||||
unsigned toc[1];
|
||||
unsigned reserved[28];
|
||||
char data[0];
|
||||
};
|
||||
|
||||
typedef struct prop_area prop_area;
|
||||
@ -69,11 +73,46 @@ struct prop_info {
|
||||
|
||||
typedef struct prop_info prop_info;
|
||||
|
||||
/*
|
||||
* Properties are stored in a hybrid trie/binary tree structure.
|
||||
* Each property's name is delimited at '.' characters, and the tokens are put
|
||||
* into a trie structure. Siblings at each level of the trie are stored in a
|
||||
* binary tree. For instance, "ro.secure"="1" could be stored as follows:
|
||||
*
|
||||
* +-----+ children +----+ children +--------+
|
||||
* | |-------------->| ro |-------------->| secure |
|
||||
* +-----+ +----+ +--------+
|
||||
* / \ / |
|
||||
* left / \ right left / | prop +===========+
|
||||
* v v v +-------->| ro.secure |
|
||||
* +-----+ +-----+ +-----+ +-----------+
|
||||
* | net | | sys | | com | | 1 |
|
||||
* +-----+ +-----+ +-----+ +===========+
|
||||
*/
|
||||
|
||||
typedef volatile uint32_t prop_off_t;
|
||||
struct prop_bt {
|
||||
char name[PROP_NAME_MAX];
|
||||
uint8_t namelen;
|
||||
uint8_t reserved[3];
|
||||
|
||||
prop_off_t prop;
|
||||
|
||||
prop_off_t left;
|
||||
prop_off_t right;
|
||||
|
||||
prop_off_t children;
|
||||
};
|
||||
|
||||
typedef struct prop_bt prop_bt;
|
||||
|
||||
static const char property_service_socket[] = "/dev/socket/" PROP_SERVICE_NAME;
|
||||
static char property_filename[PATH_MAX] = PROP_FILENAME;
|
||||
|
||||
prop_area *__system_property_regions__[PA_REGION_COUNT] = { NULL, };
|
||||
|
||||
const size_t PA_DATA_SIZE = PA_SIZE - sizeof(prop_area);
|
||||
|
||||
static int get_fd_from_env(void)
|
||||
{
|
||||
char *env = getenv("ANDROID_PROPERTY_WORKSPACE");
|
||||
@ -120,6 +159,11 @@ static int map_prop_region_rw(size_t region)
|
||||
pa->magic = PROP_AREA_MAGIC;
|
||||
pa->version = PROP_AREA_VERSION;
|
||||
|
||||
if (!region) {
|
||||
/* reserve root node */
|
||||
pa->bytes_used += sizeof(prop_bt);
|
||||
}
|
||||
|
||||
/* plug into the lib property services */
|
||||
__system_property_regions__[region] = pa;
|
||||
|
||||
@ -225,83 +269,183 @@ int __system_properties_init()
|
||||
return map_prop_region(0);
|
||||
}
|
||||
|
||||
int __system_property_foreach(
|
||||
void (*propfn)(const prop_info *pi, void *cookie),
|
||||
void *cookie)
|
||||
static void *new_prop_obj(size_t size, prop_off_t *off)
|
||||
{
|
||||
size_t region;
|
||||
prop_area *pa;
|
||||
size_t i, idx;
|
||||
size = ALIGN(size, sizeof(uint32_t));
|
||||
|
||||
for (region = 0; region < PA_REGION_COUNT; region++) {
|
||||
prop_area *pa;
|
||||
unsigned i;
|
||||
|
||||
int err = map_prop_region(region);
|
||||
if (err < 0)
|
||||
break;
|
||||
pa = __system_property_regions__[region];
|
||||
|
||||
for (i = 0; i < pa->count; i++) {
|
||||
unsigned entry = pa->toc[i];
|
||||
prop_info *pi = TOC_TO_INFO(pa, entry);
|
||||
propfn(pi, cookie);
|
||||
for (i = 0; i < PA_REGION_COUNT; i++) {
|
||||
int err = map_prop_region_rw(i);
|
||||
if (err < 0) {
|
||||
return NULL;
|
||||
}
|
||||
|
||||
pa = __system_property_regions__[i];
|
||||
if (pa->bytes_used + size <= PA_DATA_SIZE)
|
||||
break;
|
||||
}
|
||||
|
||||
return 0;
|
||||
if (i == PA_REGION_COUNT)
|
||||
return NULL;
|
||||
|
||||
idx = pa->bytes_used;
|
||||
*off = idx + i * PA_DATA_SIZE;
|
||||
pa->bytes_used += size;
|
||||
return pa->data + idx;
|
||||
}
|
||||
|
||||
const prop_info *__system_property_find_nth(unsigned n)
|
||||
static prop_bt *new_prop_bt(const char *name, uint8_t namelen, prop_off_t *off)
|
||||
{
|
||||
size_t region = n / PA_COUNT_MAX;
|
||||
prop_area *pa;
|
||||
prop_off_t off_tmp;
|
||||
prop_bt *bt = new_prop_obj(sizeof(prop_bt), &off_tmp);
|
||||
if (bt) {
|
||||
memcpy(bt->name, name, namelen);
|
||||
bt->name[namelen] = '\0';
|
||||
bt->namelen = namelen;
|
||||
ANDROID_MEMBAR_FULL();
|
||||
*off = off_tmp;
|
||||
}
|
||||
|
||||
int err = map_prop_region(region);
|
||||
if (err < 0)
|
||||
return bt;
|
||||
}
|
||||
|
||||
static prop_info *new_prop_info(const char *name, uint8_t namelen,
|
||||
const char *value, uint8_t valuelen, prop_off_t *off)
|
||||
{
|
||||
prop_off_t off_tmp;
|
||||
prop_info *info = new_prop_obj(sizeof(prop_info), &off_tmp);
|
||||
if (info) {
|
||||
memcpy(info->name, name, namelen);
|
||||
info->name[namelen] = '\0';
|
||||
info->serial = (valuelen << 24);
|
||||
memcpy(info->value, value, valuelen);
|
||||
info->value[valuelen] = '\0';
|
||||
ANDROID_MEMBAR_FULL();
|
||||
*off = off_tmp;
|
||||
}
|
||||
|
||||
return info;
|
||||
}
|
||||
|
||||
static void *to_prop_obj(prop_off_t off)
|
||||
{
|
||||
size_t region = off / PA_DATA_SIZE;
|
||||
size_t idx = off % PA_DATA_SIZE;
|
||||
|
||||
if (region > PA_REGION_COUNT)
|
||||
return NULL;
|
||||
pa = __system_property_regions__[region];
|
||||
|
||||
if((n % PA_COUNT_MAX) >= pa->count) {
|
||||
return 0;
|
||||
if (map_prop_region(region) < 0)
|
||||
return NULL;
|
||||
|
||||
return __system_property_regions__[region]->data + idx;
|
||||
}
|
||||
|
||||
static prop_bt *root_node()
|
||||
{
|
||||
return to_prop_obj(0);
|
||||
}
|
||||
|
||||
static int cmp_prop_name(const char *one, uint8_t one_len, const char *two,
|
||||
uint8_t two_len)
|
||||
{
|
||||
if (one_len < two_len)
|
||||
return -1;
|
||||
else if (one_len > two_len)
|
||||
return 1;
|
||||
else
|
||||
return strncmp(one, two, one_len);
|
||||
}
|
||||
|
||||
static prop_bt *find_prop_bt(prop_bt *bt, const char *name, uint8_t namelen,
|
||||
bool alloc_if_needed)
|
||||
{
|
||||
while (true) {
|
||||
int ret;
|
||||
if (!bt)
|
||||
return bt;
|
||||
ret = cmp_prop_name(name, namelen, bt->name, bt->namelen);
|
||||
|
||||
if (ret == 0) {
|
||||
return bt;
|
||||
} else if (ret < 0) {
|
||||
if (bt->left) {
|
||||
bt = to_prop_obj(bt->left);
|
||||
} else {
|
||||
if (!alloc_if_needed)
|
||||
return NULL;
|
||||
|
||||
bt = new_prop_bt(name, namelen, &bt->left);
|
||||
}
|
||||
} else {
|
||||
if (bt->right) {
|
||||
bt = to_prop_obj(bt->right);
|
||||
} else {
|
||||
if (!alloc_if_needed)
|
||||
return NULL;
|
||||
|
||||
bt = new_prop_bt(name, namelen, &bt->right);
|
||||
}
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
static const prop_info *find_property(prop_bt *trie, const char *name,
|
||||
uint8_t namelen, const char *value, uint8_t valuelen,
|
||||
bool alloc_if_needed)
|
||||
{
|
||||
const char *remaining_name = name;
|
||||
|
||||
while (true) {
|
||||
char *sep = strchr(remaining_name, '.');
|
||||
bool want_subtree = (sep != NULL);
|
||||
uint8_t substr_size;
|
||||
|
||||
prop_bt *root;
|
||||
|
||||
if (want_subtree) {
|
||||
substr_size = sep - remaining_name;
|
||||
} else {
|
||||
substr_size = strlen(remaining_name);
|
||||
}
|
||||
|
||||
if (!substr_size)
|
||||
return NULL;
|
||||
|
||||
if (trie->children) {
|
||||
root = to_prop_obj(trie->children);
|
||||
} else if (alloc_if_needed) {
|
||||
root = new_prop_bt(remaining_name, substr_size, &trie->children);
|
||||
} else {
|
||||
root = NULL;
|
||||
}
|
||||
|
||||
if (!root)
|
||||
return NULL;
|
||||
|
||||
trie = find_prop_bt(root, remaining_name, substr_size, alloc_if_needed);
|
||||
if (!trie)
|
||||
return NULL;
|
||||
|
||||
if (!want_subtree)
|
||||
break;
|
||||
|
||||
remaining_name = sep + 1;
|
||||
}
|
||||
|
||||
if (trie->prop) {
|
||||
return to_prop_obj(trie->prop);
|
||||
} else if (alloc_if_needed) {
|
||||
return new_prop_info(name, namelen, value, valuelen, &trie->prop);
|
||||
} else {
|
||||
return TOC_TO_INFO(pa, pa->toc[n]);
|
||||
return NULL;
|
||||
}
|
||||
}
|
||||
|
||||
const prop_info *__system_property_find(const char *name)
|
||||
{
|
||||
unsigned len = strlen(name);
|
||||
size_t region;
|
||||
|
||||
if (len >= PROP_NAME_MAX)
|
||||
return 0;
|
||||
if (len < 1)
|
||||
return 0;
|
||||
|
||||
for (region = 0; region < PA_REGION_COUNT; region++) {
|
||||
prop_area *pa;
|
||||
unsigned count;
|
||||
unsigned *toc;
|
||||
prop_info *pi;
|
||||
|
||||
int err = map_prop_region(region);
|
||||
if (err < 0)
|
||||
return 0;
|
||||
pa = __system_property_regions__[region];
|
||||
count = pa->count;
|
||||
toc = pa->toc;
|
||||
|
||||
while(count--) {
|
||||
unsigned entry = *toc++;
|
||||
if(TOC_NAME_LEN(entry) != len) continue;
|
||||
|
||||
pi = TOC_TO_INFO(pa, entry);
|
||||
if(memcmp(name, pi->name, len)) continue;
|
||||
|
||||
return pi;
|
||||
}
|
||||
}
|
||||
|
||||
return 0;
|
||||
return find_property(root_node(), name, strlen(name), NULL, 0, false);
|
||||
}
|
||||
|
||||
int __system_property_read(const prop_info *pi, char *name, char *value)
|
||||
@ -463,10 +607,8 @@ int __system_property_update(prop_info *pi, const char *value, unsigned int len)
|
||||
int __system_property_add(const char *name, unsigned int namelen,
|
||||
const char *value, unsigned int valuelen)
|
||||
{
|
||||
prop_area *pa;
|
||||
prop_info *pa_info_array;
|
||||
prop_info *pi;
|
||||
size_t region;
|
||||
prop_area *pa = __system_property_regions__[0];
|
||||
const prop_info *pi;
|
||||
|
||||
if (namelen >= PROP_NAME_MAX)
|
||||
return -1;
|
||||
@ -475,34 +617,12 @@ int __system_property_add(const char *name, unsigned int namelen,
|
||||
if (namelen < 1)
|
||||
return -1;
|
||||
|
||||
for (region = 0; region < PA_REGION_COUNT; region++)
|
||||
{
|
||||
int err = map_prop_region_rw(region);
|
||||
if (err < 0)
|
||||
return -1;
|
||||
|
||||
pa = __system_property_regions__[region];
|
||||
|
||||
if (pa->count < PA_COUNT_MAX)
|
||||
break;
|
||||
}
|
||||
|
||||
if (region == PA_REGION_COUNT)
|
||||
pi = find_property(root_node(), name, namelen, value, valuelen, true);
|
||||
if (!pi)
|
||||
return -1;
|
||||
|
||||
pa_info_array = (void*) (((char*) pa) + PA_INFO_START);
|
||||
pi = pa_info_array + pa->count;
|
||||
pi->serial = (valuelen << 24);
|
||||
memcpy(pi->name, name, namelen + 1);
|
||||
memcpy(pi->value, value, valuelen + 1);
|
||||
|
||||
pa->toc[pa->count] = (namelen << 24) | (((unsigned) pi) - ((unsigned) pa));
|
||||
ANDROID_MEMBAR_FULL();
|
||||
|
||||
pa->count++;
|
||||
pa->serial++;
|
||||
__futex_wake(&pa->serial, INT32_MAX);
|
||||
|
||||
return 0;
|
||||
}
|
||||
|
||||
@ -521,3 +641,72 @@ unsigned int __system_property_wait_any(unsigned int serial)
|
||||
|
||||
return pa->serial;
|
||||
}
|
||||
|
||||
struct find_nth_cookie {
|
||||
unsigned count;
|
||||
unsigned n;
|
||||
const prop_info *pi;
|
||||
};
|
||||
|
||||
static void find_nth_fn(const prop_info *pi, void *ptr)
|
||||
{
|
||||
struct find_nth_cookie *cookie = ptr;
|
||||
|
||||
if (cookie->n == cookie->count)
|
||||
cookie->pi = pi;
|
||||
|
||||
cookie->count++;
|
||||
}
|
||||
|
||||
const prop_info *__system_property_find_nth(unsigned n)
|
||||
{
|
||||
struct find_nth_cookie cookie;
|
||||
int err;
|
||||
|
||||
memset(&cookie, 0, sizeof(cookie));
|
||||
cookie.n = n;
|
||||
|
||||
err = __system_property_foreach(find_nth_fn, &cookie);
|
||||
if (err < 0)
|
||||
return NULL;
|
||||
|
||||
return cookie.pi;
|
||||
}
|
||||
|
||||
static int foreach_property(prop_off_t off,
|
||||
void (*propfn)(const prop_info *pi, void *cookie), void *cookie)
|
||||
{
|
||||
prop_bt *trie = to_prop_obj(off);
|
||||
if (!trie)
|
||||
return -1;
|
||||
|
||||
if (trie->left) {
|
||||
int err = foreach_property(trie->left, propfn, cookie);
|
||||
if (err < 0)
|
||||
return -1;
|
||||
}
|
||||
if (trie->prop) {
|
||||
prop_info *info = to_prop_obj(trie->prop);
|
||||
if (!info)
|
||||
return -1;
|
||||
propfn(info, cookie);
|
||||
}
|
||||
if (trie->children) {
|
||||
int err = foreach_property(trie->children, propfn, cookie);
|
||||
if (err < 0)
|
||||
return -1;
|
||||
}
|
||||
if (trie->right) {
|
||||
int err = foreach_property(trie->right, propfn, cookie);
|
||||
if (err < 0)
|
||||
return -1;
|
||||
}
|
||||
|
||||
return 0;
|
||||
}
|
||||
|
||||
int __system_property_foreach(void (*propfn)(const prop_info *pi, void *cookie),
|
||||
void *cookie)
|
||||
{
|
||||
return foreach_property(0, propfn, cookie);
|
||||
}
|
||||
|
||||
@ -37,7 +37,7 @@
|
||||
typedef struct prop_msg prop_msg;
|
||||
|
||||
#define PROP_AREA_MAGIC 0x504f5250
|
||||
#define PROP_AREA_VERSION 0x45434f76
|
||||
#define PROP_AREA_VERSION 0xfc6ed0ab
|
||||
|
||||
#define PROP_SERVICE_NAME "property_service"
|
||||
#define PROP_FILENAME "/dev/__properties__"
|
||||
@ -45,14 +45,9 @@ typedef struct prop_msg prop_msg;
|
||||
/* (4 header words + 28 toc words) = 128 bytes */
|
||||
/* 128 bytes header and toc + 28 prop_infos @ 128 bytes = 3712 bytes */
|
||||
|
||||
#define PA_COUNT_MAX 28
|
||||
#define PA_REGION_COUNT 128
|
||||
#define PA_INFO_START 128
|
||||
#define PA_SIZE 4096
|
||||
|
||||
#define TOC_NAME_LEN(toc) ((toc) >> 24)
|
||||
#define TOC_TO_INFO(area, toc) ((prop_info*) (((char*) area) + ((toc) & 0xFFFFFF)))
|
||||
|
||||
#define SERIAL_VALUE_LEN(serial) ((serial) >> 24)
|
||||
#define SERIAL_DIRTY(serial) ((serial) & 1)
|
||||
|
||||
@ -84,11 +79,6 @@ struct prop_msg
|
||||
** 1. pi->serial = pi->serial | 1
|
||||
** 2. memcpy(pi->value, local_value, value_len)
|
||||
** 3. pi->serial = (value_len << 24) | ((pi->serial + 1) & 0xffffff)
|
||||
**
|
||||
** Improvements:
|
||||
** - maintain the toc sorted by pi->name to allow lookup
|
||||
** by binary search
|
||||
**
|
||||
*/
|
||||
|
||||
#define PROP_PATH_RAMDISK_DEFAULT "/default.prop"
|
||||
|
||||
Loading…
x
Reference in New Issue
Block a user