/*
* Copyright 2013 MongoDB, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include "bson-compat.h"
#include <limits.h>
#include <stdarg.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#if defined(__linux__)
#include <sys/syscall.h>
#endif
#include "bson-atomic.h"
#include "bson-clock.h"
#include "bson-context.h"
#include "bson-context-private.h"
#include "bson-md5.h"
#include "bson-memory.h"
#include "bson-thread-private.h"
#ifndef HOST_NAME_MAX
#define HOST_NAME_MAX 256
#endif
/*
* Globals.
*/
static bson_context_t gContextDefault;
#if defined(__linux__)
static uint16_t
gettid (void)
{
return syscall (SYS_gettid);
}
#endif
/*
*--------------------------------------------------------------------------
*
* _bson_context_get_oid_host --
*
* Retrieves the first three bytes of MD5(hostname) and assigns them
* to the host portion of oid.
*
* Returns:
* None.
*
* Side effects:
* @oid is modified.
*
*--------------------------------------------------------------------------
*/
static void
_bson_context_get_oid_host (bson_context_t *context, /* IN */
bson_oid_t *oid) /* OUT */
{
uint8_t *bytes = (uint8_t *)oid;
uint8_t digest[16];
bson_md5_t md5;
char hostname[HOST_NAME_MAX];
BSON_ASSERT (context);
BSON_ASSERT (oid);
gethostname (hostname, sizeof hostname);
hostname[HOST_NAME_MAX - 1] = '\0';
bson_md5_init (&md5);
bson_md5_append (&md5, (const uint8_t *)hostname, (uint32_t)strlen (hostname));
bson_md5_finish (&md5, &digest[0]);
bytes[4] = digest[0];
bytes[5] = digest[1];
bytes[6] = digest[2];
}
/*
*--------------------------------------------------------------------------
*
* _bson_context_get_oid_host_cached --
*
* Fetch the cached copy of the MD5(hostname).
*
* Returns:
* None.
*
* Side effects:
* @oid is modified.
*
*--------------------------------------------------------------------------
*/
static void
_bson_context_get_oid_host_cached (bson_context_t *context, /* IN */
bson_oid_t *oid) /* OUT */
{
BSON_ASSERT (context);
BSON_ASSERT (oid);
oid->bytes[4] = context->md5[0];
oid->bytes[5] = context->md5[1];
oid->bytes[6] = context->md5[2];
}
static BSON_INLINE uint16_t
_bson_getpid (void)
{
uint16_t pid;
#ifdef BSON_OS_WIN32
DWORD real_pid;
real_pid = GetCurrentProcessId ();
pid = (real_pid & 0xFFFF) ^ ((real_pid >> 16) & 0xFFFF);
#else
pid = getpid ();
#endif
return pid;
}
/*
*--------------------------------------------------------------------------
*
* _bson_context_get_oid_pid --
*
* Initialize the pid field of @oid.
*
* The pid field is 2 bytes, big-endian for memcmp().
*
* Returns:
* None.
*
* Side effects:
* @oid is modified.
*
*--------------------------------------------------------------------------
*/
static void
_bson_context_get_oid_pid (bson_context_t *context, /* IN */
bson_oid_t *oid) /* OUT */
{
uint16_t pid = _bson_getpid ();
uint8_t *bytes = (uint8_t *)&pid;
BSON_ASSERT (context);
BSON_ASSERT (oid);
pid = BSON_UINT16_TO_BE (pid);
oid->bytes[7] = bytes[0];
oid->bytes[8] = bytes[1];
}
/*
*--------------------------------------------------------------------------
*
* _bson_context_get_oid_pid_cached --
*
* Fetch the cached copy of the current pid.
* This helps avoid multiple calls to getpid() which is slower
* on some systems.
*
* Returns:
* None.
*
* Side effects:
* @oid is modified.
*
*--------------------------------------------------------------------------
*/
static void
_bson_context_get_oid_pid_cached (bson_context_t *context, /* IN */
bson_oid_t *oid) /* OUT */
{
oid->bytes[7] = context->pidbe[0];
oid->bytes[8] = context->pidbe[1];
}
/*
*--------------------------------------------------------------------------
*
* _bson_context_get_oid_seq32 --
*
* 32-bit sequence generator, non-thread-safe version.
*
* Returns:
* None.
*
* Side effects:
* @oid is modified.
*
*--------------------------------------------------------------------------
*/
static void
_bson_context_get_oid_seq32 (bson_context_t *context, /* IN */
bson_oid_t *oid) /* OUT */
{
uint32_t seq = context->seq32++;
seq = BSON_UINT32_TO_BE (seq);
memcpy (&oid->bytes[9], ((uint8_t *)&seq) + 1, 3);
}
/*
*--------------------------------------------------------------------------
*
* _bson_context_get_oid_seq32_threadsafe --
*
* Thread-safe version of 32-bit sequence generator.
*
* Returns:
* None.
*
* Side effects:
* @oid is modified.
*
*--------------------------------------------------------------------------
*/
static void
_bson_context_get_oid_seq32_threadsafe (bson_context_t *context, /* IN */
bson_oid_t *oid) /* OUT */
{
int32_t seq = bson_atomic_int_add (&context->seq32, 1);
seq = BSON_UINT32_TO_BE (seq);
memcpy (&oid->bytes[9], ((uint8_t *)&seq) + 1, 3);
}
/*
*--------------------------------------------------------------------------
*
* _bson_context_get_oid_seq64 --
*
* 64-bit oid sequence generator, non-thread-safe version.
*
* Returns:
* None.
*
* Side effects:
* @oid is modified.
*
*--------------------------------------------------------------------------
*/
static void
_bson_context_get_oid_seq64 (bson_context_t *context, /* IN */
bson_oid_t *oid) /* OUT */
{
uint64_t seq;
BSON_ASSERT (context);
BSON_ASSERT (oid);
seq = BSON_UINT64_TO_BE (context->seq64++);
memcpy (&oid->bytes[4], &seq, sizeof (seq));
}
/*
*--------------------------------------------------------------------------
*
* _bson_context_get_oid_seq64_threadsafe --
*
* Thread-safe 64-bit sequence generator.
*
* Returns:
* None.
*
* Side effects:
* @oid is modified.
*
*--------------------------------------------------------------------------
*/
static void
_bson_context_get_oid_seq64_threadsafe (bson_context_t *context, /* IN */
bson_oid_t *oid) /* OUT */
{
int64_t seq = bson_atomic_int64_add (&context->seq64, 1);
seq = BSON_UINT64_TO_BE (seq);
memcpy (&oid->bytes[4], &seq, sizeof (seq));
}
static void
_bson_context_init (bson_context_t *context, /* IN */
bson_context_flags_t flags) /* IN */
{
struct timeval tv;
uint16_t pid;
unsigned int seed[3];
unsigned int real_seed;
bson_oid_t oid;
context->flags = flags;
context->oid_get_host = _bson_context_get_oid_host_cached;
context->oid_get_pid = _bson_context_get_oid_pid_cached;
context->oid_get_seq32 = _bson_context_get_oid_seq32;
context->oid_get_seq64 = _bson_context_get_oid_seq64;
/*
* Generate a seed for our the random starting position of our increment
* bytes. We mask off the last nibble so that the last digit of the OID will
* start at zero. Just to be nice.
*
* The seed itself is made up of the current time in seconds, milliseconds,
* and pid xored together. I welcome better solutions if at all necessary.
*/
bson_gettimeofday (&tv);
seed[0] = (unsigned int)tv.tv_sec;
seed[1] = (unsigned int)tv.tv_usec;
seed[2] = _bson_getpid ();
real_seed = seed[0] ^ seed[1] ^ seed[2];
#ifdef BSON_OS_WIN32
/* ms's runtime is multithreaded by default, so no rand_r */
srand(real_seed);
context->seq32 = rand() & 0x007FFFF0;
#else
context->seq32 = rand_r (&real_seed) & 0x007FFFF0;
#endif
if ((flags & BSON_CONTEXT_DISABLE_HOST_CACHE)) {
context->oid_get_host = _bson_context_get_oid_host;
} else {
_bson_context_get_oid_host (context, &oid);
context->md5[0] = oid.bytes[4];
context->md5[1] = oid.bytes[5];
context->md5[2] = oid.bytes[6];
}
if ((flags & BSON_CONTEXT_THREAD_SAFE)) {
context->oid_get_seq32 = _bson_context_get_oid_seq32_threadsafe;
context->oid_get_seq64 = _bson_context_get_oid_seq64_threadsafe;
}
if ((flags & BSON_CONTEXT_DISABLE_PID_CACHE)) {
context->oid_get_pid = _bson_context_get_oid_pid;
} else {
pid = BSON_UINT16_TO_BE (_bson_getpid());
#if defined(__linux__)
if ((flags & BSON_CONTEXT_USE_TASK_ID)) {
int32_t tid;
if ((tid = gettid ())) {
pid = BSON_UINT16_TO_BE (tid);
}
}
#endif
memcpy (&context->pidbe[0], &pid, 2);
}
}
/*
*--------------------------------------------------------------------------
*
* bson_context_new --
*
* Initializes a new context with the flags specified.
*
* In most cases, you want to call this with @flags set to
* BSON_CONTEXT_NONE.
*
* If you are running on Linux, %BSON_CONTEXT_USE_TASK_ID can result
* in a healthy speedup for multi-threaded scenarios.
*
* If you absolutely must have a single context for your application
* and use more than one thread, then %BSON_CONTEXT_THREAD_SAFE should
* be bitwise-or'd with your flags. This requires synchronization
* between threads.
*
* If you expect your hostname to change often, you may consider
* specifying %BSON_CONTEXT_DISABLE_HOST_CACHE so that gethostname()
* is called for every OID generated. This is much slower.
*
* If you expect your pid to change without notice, such as from an
* unexpected call to fork(), then specify
* %BSON_CONTEXT_DISABLE_PID_CACHE.
*
* Returns:
* A newly allocated bson_context_t that should be freed with
* bson_context_destroy().
*
* Side effects:
* None.
*
*--------------------------------------------------------------------------
*/
bson_context_t *
bson_context_new (bson_context_flags_t flags)
{
bson_context_t *context;
context = bson_malloc0 (sizeof *context);
_bson_context_init (context, flags);
return context;
}
/*
*--------------------------------------------------------------------------
*
* bson_context_destroy --
*
* Cleans up a bson_context_t and releases any associated resources.
* This should be called when you are done using @context.
*
* Returns:
* None.
*
* Side effects:
* None.
*
*--------------------------------------------------------------------------
*/
void
bson_context_destroy (bson_context_t *context) /* IN */
{
if (context != &gContextDefault) {
memset (context, 0, sizeof *context);
bson_free (context);
}
}
static
BSON_ONCE_FUN(_bson_context_init_default)
{
_bson_context_init (&gContextDefault,
(BSON_CONTEXT_THREAD_SAFE |
BSON_CONTEXT_DISABLE_PID_CACHE));
BSON_ONCE_RETURN;
}
/*
*--------------------------------------------------------------------------
*
* bson_context_get_default --
*
* Fetches the default, thread-safe implementation of #bson_context_t.
* If you need faster generation, it is recommended you create your
* own #bson_context_t with bson_context_new().
*
* Returns:
* A shared instance to the default #bson_context_t. This should not
* be modified or freed.
*
* Side effects:
* None.
*
*--------------------------------------------------------------------------
*/
bson_context_t *
bson_context_get_default (void)
{
static bson_once_t once = BSON_ONCE_INIT;
bson_once (&once, _bson_context_init_default);
return &gContextDefault;
}