一个linux下共享内存的应用(页 1) - C/C++ (STL/boost) - Linux伊甸园论坛

ljq1000 发表于 2008-3-24 15:33

一个linux下共享内存的应用

大家好：
这是一个我在工作中使用的基于linux共享内存的类。设计它的目的是为了在两个或多个进程间同步或异步的传输结构化数据。
该类的实现涉及到以下知识点：共享内存、信号量、信号和ARM上的内存对齐方式等。k/ie [B
我是想借此机会抛砖引玉，在和大家共同学习之余，也希望各位能够不吝发表高见，讨论一下这个类的优缺点以及实现进程间通信更好更高效的方法。vn%U/oIp l
我的联系方式是 [email=ljq1000@hotmail.com]ljq1000@hotmail.com[/email]，欢迎大家与我联系。 P1PX;uO?;A$WA3E
[code]/*********************************************************************

  Auther: Li Jieqian3fE;y;nHN&Ej"I+CX0Q

  The MQShm class provides transporting structural data synchronously
between two process.2R,^ kzN%D Y-N
~\FHtHfK fQo!o
  One of the process is called Data-Maker, the other called Data-Customer.
The functionaly of process is relative. gI@1S2G
;^7v:l?s]*zN
  Usage in Data-Maker:C#F:` j1\p5zE
  lock -> set status to busy -> fill data in shm -> set status to ready -> 7}-q*Wv.@x)dr#S
unlock -> wait status OK

  Usage in Data-Customer:
  wait status ready -> lock -> get data -> clear shm -> set status to OK#Lp~ }){hE
PWWgx7[dW0ot
  Note that: MQShm class use a unix share memory and two semphones. Hw phr+zV
Share memory is created with a KEY user defined, semphones is created $Pl~+[!C YA
with key KEY and KEY + 1.GS+`S$p

************************************************************************/lL)C7W`h.J

#ifndef MQSHM_H[6U$lH| Pj$|w
#define MQSHM_H-p3j Hro*K
MP!u"l+L b(z6H_"@b
#include <sys/ipc.h>
#include <sys/shm.h>9H},i^k9M
/p@0r$@y-T#I-Lg$H
typedef unsigned int  uint;
typedef unsigned char uchar;
typedef unsigned short ushort;z+Uf}]%VZ#c
typedef unsigned short link_t;b'fV h@;Uic0p:[&e{c

const link_t ALIGN_MASK = 0x8000;

struct MQShmPriv;
Cv lt.zC~
class MQShm7yE'@Q3}8VsJ0@
{7kX2Sl0N?1c
public:
  // shm status5sNv:}u4nM7I|a
  enum {
StUnknown = 0, L)S!vI6CAwi
StOK = 1, $GZ\U7ON}S+k
StError = 2,
StBusy = 4,
StReady = 8'R,q#\LZ3qp
  };
%^ ~ l7Zk6k*x
  static const link_t null = (link_t) -1 & ~ALIGN_MASK;gKC5icu
@;IN5M3}]4W"n$W
private:)U} v @!R
  int _shmId;
  int _shmSemId;k8s1c/K{7\2W/k
  int _pidSemId;
  size_t _size;Q7n([/Ey!r
  uchar *_shm;,`]HzY[^
  MQShmPriv *_priv;
  int _myPidIdx;vL#Yfs*P.Z
B](V%bWZ]
private:
  void pidLock();
  void pidUnlock();2VXGrj @

public:
  MQShm(key_t key, size_t size, bool init = false);
  virtual ~MQShm();
g.L_zHwJ m5i[p
  void close();
&h-F9f9pn P8my:W8U
  void lock(); N?1_1H7{;g"j p
  void unlock();
  bool locked();
/|m1De h$Z
  uint freeSpace() const;

  uint itemCount() const;i9Xqx i$S

  // user defined counter operation
  void clrCounter();
  uint getCounter() const;Q&Pq6G9]+N
  void setCounter(uint n);c0lk} _

  // status operation
  int status() const;
  void setStatus(int st);8bYw6n&lHy2f
  bool waitStatus(int st, uint timeout = 20);!K+Kj5I\&NI n?$S
)_8Cn]3fqh
  void append(const uchar *data, uint len);HM q7L8b
N \e5y8XA\T
  // clear all items in the shm, but do not change
  // the user defined counter and status value
  void clear();
&u$wV%iD+{/Wn!h2U+m
  class const_iterator;,gxO0N X*vi3k
  friend class const_iterator;
  class const_iterator
  {m9Gy(B'n+^}
  private:
const MQShm *_mqShm;
link_t _linkv;!?s3L^E R

// constructor for MQShm
const_iterator(const MQShm *mqShm, link_t linkv)
   : _mqShm(mqShm), _linkv(linkv) {}{9}8~&Kv9x@7~ Q5f

  public:
~const_iterator() {}
np0w&FE'dK2dP
const uchar *data() const;
uint size() const;
?)Yq i&{)XZ
const_iterator &operator++();(k1aih4?

bool operator==(const const_iterator &rhs) const;
bool operator!=(const const_iterator &rhs) const;

friend class MQShm;
  };!~4N:Y]%qzp,K:EX
"WFB qF;B
  MQShm::const_iterator begin() const;
  MQShm::const_iterator end() const;
};
D}\/]Lr
#endif[/code]

[[i] 本帖最后由 flag 于 2008-3-25 22:12 编辑 [/i]]

ljq1000 发表于 2008-3-24 15:37

实现

[code]Xg\}Y-Oa
*x0U;YCQ
#include <stdio.h>
#include <stdlib.h>J B0\%hkeO
#include <string.h>
#include <fcntl.h>2@+m'gGX_*z3a
#include <unistd.h>
#include <signal.h>
#include <sys/sem.h>%sV/h?B1~&D4r
#include "mqshm.h"

#define LINKER_SIZE (sizeof(link_t)) LI `8F!Rk n

#ifndef ASSERT ~\M'Q:M4U5y^
#include <assert.h>
#define ASSERT(exp) assert(exp)
#endifM.~jy4T5KP

const int SHM_MAX_PIDS = 8;-Tb N;Jz8zN)aw Y

union semun
{
  int             val; /* Value for SETVAL */
  struct semid_ds *buf; /* Buffer for IPC_STAT, IPC_SET */0gdjtU s @Q
  unsigned short  *array;  /* Array for GETALL, SETALL */'M6q'?']k&q a)jk4I/P
  struct seminfo  *__buf;  /* Buffer for IPC_INFO (Linux specific) */
};

// signal handlerxAU:gv"n)\~g5h6L~
(V![-df{MM^(T
static bool isTimeout = false;%L$]'z,O)b!qX7@%B {*y'q
0i!k5Fa&l
static void catchSignal(int sig)Yx1n nGn tmM
{D;se(mF%ASWC
  if (sig == SIGALRM)6CnqV_T~Lh
isTimeout = true;
}9pOy[{!O\@0h

// start timer
static void startTimer(int timeout)/G jHW:S
{8N:q&B(F b
  struct sigaction newAction;
  newAction.sa_handler = catchSignal;(^"MH/e@ Pc
  newAction.sa_flags = 0;
  sigaction(SIGALRM, &newAction, NULL);;B@c:r-{Z$y:j&o
  alarm(timeout);
  isTimeout = false;
}6[xFV]o'gpJJj*`

// reset timer
static void stopTimer()]1N.h*ct"A
{
  alarm(0);
  sigaction(SIGALRM, NULL, NULL);E6Sv5l0ZH[5\L
  isTimeout = false;.n#D^)z,Zr8Y*G
}

static void startWaitStatus()0Z)Di5Gi|5e
{6P Y_LhG$^ \nD
  struct sigaction newAction;r^;PX)nuR0QO
  newAction.sa_handler = catchSignal;u'BL ja~V&N,r
  newAction.sa_flags = 0;
  sigaction(SIGUSR1, &newAction, NULL);i9AS\ cc$PC
}

static void stopWaitStatus()K+C!ZfY)A1i,t m
{
  sigaction(SIGUSR1, NULL, NULL); W+Q;e0Bq8i i8|)y
}
,O'T_L'BrN;ax
// ~
jv}[ln4b
static inline link_t GET_LK_V(link_t *linkp)
{
  return *linkp & ~ALIGN_MASK;)a;hIIfw%?
}
/x9Hm,I/h2G7r^9q
static inline void SET_LK_V(link_t *linkp, link_t linkv)N#U6L!cmhA4d#p3|
{
  *linkp &= ALIGN_MASK;
  *linkp += linkv;
}
A[T6H\$uLp
// MQShmPriv
// MQShm header structure
// use only byte and word elements for ARM word alignmentbQDTC T

struct MQShmPriv
{dqrrcW&P4yY
  int _pids[SHM_MAX_PIDS]; // process who is waiting for status:uL:V3T#W~T?
  ushort _placeholder[1]; // placeholder for DWORD alignment;\a9I-f J
  ushort _status; // status of this shm5p)?$E:Dw4{*B g/Y
  ushort _cx; // user defined counter
  ushort _nItems; // how many items in the shmZsaz6C RU
  link_t _offset; // free block offsetPz!m,]QP8K
  link_t _header; // item list header?h)z3rI[*Q
};!Jn$G(yw6_-D7a
h8g(RnE*Q
#define SHM_GET_PID(i) \
  (_priv->_pids[i])_,h Q3]#?i)_

#define SHM_SET_PID(i, pid) \
  (_priv->_pids[i] = pid)
U7K.}O p F
// MQShm members)F.OXSs{?m
/E.E tw+o
void MQShm::pidLock().L;PGNt m:@]6jk
{
  struct sembuf sembuf;HT0Gc1j-wd7F
  sembuf.sem_num = 0;+R!}_5uR7a"^o[
  sembuf.sem_op = -1;5Z$r$r&xC"q_R4H
  sembuf.sem_flg = SEM_UNDO;
  if (semop(_pidSemId, &sembuf, 1) == -1) {9Om2xy0hUd
perror("semop (pid semphone)");Z/GR/T@&u*k+G j3[
exit(1); ` R} I4G(Dj&a f
  }
}iud+T6K8^6t&[f7T

void MQShm::pidUnlock()E+o(C*`2[
{+B8T-@,?Vi;ju
  struct sembuf sembuf;
  sembuf.sem_num = 0;
  sembuf.sem_op = +1;
  sembuf.sem_flg = SEM_UNDO;b"vq'nj/IPX
  if (semop(_pidSemId, &sembuf, 1) == -1) {
perror("semop (pid semphone)");Jhd.sH;N
exit(1);B4pJ2\s)e'`K9x
  }
}1P0P4|qY
"\Wt3I6P^z
MQShm::MQShm(key_t key, size_t size, bool init)(r\7i:jd'CU(t
{
  bool isCreater = true;
  _size = size;
  _myPidIdx = -1;-~B`r_W7G Rx9T
Iy0vqqE
  // create shm*j7YZLs,KE3A
  if ((_shmId = shmget(key, _size, O_RDWR | IPC_CREAT | IPC_EXCL)) == -1) {
char msg[32];3Pgab"N0H'a$WMK6D
sprintf(msg, "shmget (0x%x)", key);!L5R:@arEhB
perror(msg);
isCreater = false;

if ((_shmId = shmget(key, _size, O_RDWR | IPC_CREAT)) == -1) {
   perror(msg);
   exit(1);/vM$s#W P {S
}
  }
  if ((_shm = (uchar *)shmat(_shmId, NULL, 0)) == (void *)-1) {
perror("shmat");5yvh8b~L^H
exit(1);nJl7g&T2B2dH\?Z
  }
I n*S/iC8zN
  // create shm semphone-h+Y%P^ QK%Of
  if ((_shmSemId = semget(key, 1, O_RDWR | IPC_CREAT)) == -1) { I)pHh'F G ~ N
perror("semget (shm semphone)");:s9kp2N(Zg/_
exit(1);
  }
P0@q,z6A6}1X%i~
  // create pid semphoneU$o'g%^1T
  if ((_pidSemId = semget(key + 1, 1, O_RDWR | IPC_CREAT)) == -1) {
perror("semget (pid semphone)");"U-j"H~tN+?A2y
exit(1);
  }

  _priv = (MQShmPriv *)_shm;
HrS9Pp/C
  if (isCreater || init) {
printf("to initialize the MQShm (0x%x)\n", _shmId);
// initialize the shm by creater fn _;AUa c
memset(_priv->_pids, 0, sizeof(_priv->_pids));9ONV d,H
memset(_priv->_placeholder, 0XCC, sizeof(_priv->_placeholder));`\U.|A H XL#I*N
_priv->_status = MQShm::StUnknown;
_priv->_cx = 0;
_priv->_nItems = 0;
_priv->_offset = sizeof(MQShmPriv);G | h M(g3cB
_priv->_header = MQShm::null;t+{DS"nJF
// initialize shm and pid semphone/A0fs/[ i[|7Wx3qZ'E
union semun data;/F%OCT``C5[
data.val = 1;
if (semctl(_shmSemId, 0, SETVAL, data) == -1) {
   perror("semctl (shm semphone)");
   exit(1);:bf FGL
}
if (semctl(_pidSemId, 0, SETVAL, data) == -1) {M|s%Sp2G#c^S
   perror("semctl (pid semphone)");
   exit(1);
}
  }8^4gq k/V6I R#V
} g%E\-c"O.rU8~
IiqM t5R6v vq&~M
MQShm::~MQShm()2WFQ0uU5O\bK)Z
{ Gv*D k a
  if (shmdt(_shm) == -1)
perror("shmdt");
}Wb8PI*q3IT)E
kN2b9E:N\0C
void MQShm::close()
{
  printf("close MQShm (0x%x)\n", _shmId);!No~k8WHp

  if (shmdt(_shm) == -1)L`:Evq8hPr!e
perror("shmdt");
  if (shmctl(_shmId, IPC_RMID, NULL) == -1) YyW#KY8?6a&f
perror("shmctl");7Q'C a"S6kT
  if (semctl(_shmSemId, 0, IPC_RMID) == -1)'g/tl+Bq-L,|"JW
perror("semctl (shm semphone)");
  if (semctl(_pidSemId, 0, IPC_RMID) == -1)
perror("semctl (pid semphone)");
y1@z)p.?D a*o
  _shmId = -1;6y[$v)@y"GN!A
  _shmSemId = -1;
  _pidSemId = -1;
  _shm = NULL;
  _priv = NULL; Fwx#t$})^
}
{LTV%p#W
void MQShm::lock()
{
  struct sembuf sembuf;
  sembuf.sem_num = 0;
  sembuf.sem_op = -1;
  sembuf.sem_flg = SEM_UNDO;b"b i0^%q|g
  if (semop(_shmSemId, &sembuf, 1) == -1) {wknjO?NQi
perror("semop");$NHu-b@
exit(1);/E fi&o\6zS3`
  }\Kl+a-M%sk
}

void MQShm::unlock()
{d3|9w'L]q?1Vv0JK
#ifndef NDEBUG
  ASSERT(locked());h/](V.cqkE j
#endif
  struct sembuf sembuf;
  sembuf.sem_num = 0;(^EJpM^1Pa
  sembuf.sem_op = +1;KI1K)W)j?G
  sembuf.sem_flg = SEM_UNDO; f,{f5[W1W
  if (semop(_shmSemId, &sembuf, 1) == -1) {'d\&FNy8eJJG
perror("semop");o0C#LW$h
exit(1);GHL6uu(S~y;e M
  }
};UK%\9s\

bool MQShm::locked()K d$yni
{
  int val;Y#n{'[@#B
  if ((val = semctl(_shmSemId, 0, GETVAL)) == -1) {
perror("semctl");eq(s'?IM6rU
exit(1);
  }G$wb;n(\w0h9OJ.X`
  return val <= 0;(P'c&?y:Yc)[3[
}*C D@iAA-boZT

uint MQShm::freeSpace() constf+Y:O&p4kyO.M,P6C1v
{
  // the free space must contain a byte for 2-byte alignment1v9D|8m;Gjd*P*`9Fh
  return _size - _priv->_offset - LINKER_SIZE - 1;au3T,d*U#xp,Gb
}GWK6U@_.zN
Jtcx#a
uint MQShm::itemCount() const oYhH,|%_QYk
{
  return _priv->_nItems;
}7V/q YaU1C{~)j

void MQShm::clrCounter() 4{ fw8]4L
{ %k&jq*f,Kg
  _priv->_cx = 0;
}
x,V-`.g?7s*V
uint MQShm::getCounter() const
{
  return _priv->_cx;
}
~!U#X*E!L+_:w6i9bj
void MQShm::setCounter(uint n)
{ W`?5Yl gr%Lg
  _priv->_cx = n; 9U VZI(Qd%p
}.V1h6l$Z:_-G6{)Q4}

int MQShm::status() const
{g([U o2QFysH
  return _priv->_status;`N]3I&r9HB@A
}&}VO&Uqa

void MQShm::setStatus(int st)mDJ(mX r
{
  _priv->_status = st;
8al,K[0n6t1O%]n|4C;_k
  pidLock();[wizO?A%uY
  for (int i = 0; i < SHM_MAX_PIDS; ++i)
if (SHM_GET_PID(i) != 0)
   kill(SHM_GET_PID(i), SIGUSR1);KIa7gFQ
  pidUnlock();
  usleep(50000); // a period for waking up process
               // who block on the status
}/p h b[ SGkh[
(r\Uz*V@X U?
bool MQShm::waitStatus(int st, uint timeout)qyn^ b
{Z6m'xT\R%D
  if (_priv->_status & st)
return true;
7xo?UU!Vj$by
  bool result = true;
  startWaitStatus();^Aq8S.o;@4n_ m4Y
  startTimer(timeout);

  while (!(_priv->_status & st) && result) {
if (_myPidIdx == -1) {
   pidLock();j!l(d n0k#vXVJ
   int i = 0;
   while (i < SHM_MAX_PIDS && SHM_GET_PID(i) != 0)
      ++i;!Hj uLA@DYYS
   ASSERT(i < SHM_MAX_PIDS);;Y&Z;e+\t Hl2N
   SHM_SET_PID(i, getpid());
   _myPidIdx = i;u,w Rl;i
   pidUnlock();
}
Bh8s1H~
pause();$r"z|S4}-`7Z

if (isTimeout)
   result = false;@xcp0?&Hvot
  }
GE5w/`|de$T
  stopWaitStatus();
  stopTimer();

  if (_myPidIdx != -1) {
pidLock();;eV7H]7k
SHM_SET_PID(_myPidIdx, 0);L8S9@?^'Je:N$R
_myPidIdx = -1;
pidUnlock();
  }r&@.x1mi

  return result;)dnrV8r MRNPX
}+QP(c`A(]^Qc1\]

void MQShm::append(const uchar *data, uint len)6di2G:y.j
{%z5C U&r Rb+f+fs
  ASSERT(freeSpace() >= len);N{ @Ag M2F%a

  // append the new itema2_Y(xvW0Q
  uchar *p = _shm + _priv->_offset;S9bU |F7no G
  memcpy(p, data, len);$_PZ x e"_n
:W%F4ANsU8zU@
  // do alignment for arm/No(H }&@8M\U
  bool doAlign = false;
  if ((int)(p += len) % 2 != 0) {
*p++ = 0xcc; // the byte for alignmentyS(H5Bx1O
doAlign = true;
  }
  *((link_t *) p) = MQShm::null;h,]hfa4Xg
  if (doAlign)hn@1iR6WXj
*((link_t *) p) |= ALIGN_MASK;p`2_at w
  *J6auJ;`"@"Wjo
  // link the new item
  link_t new_linker = p - _shm;
  SET_LK_V((link_t *)(_shm + _priv->_offset - LINKER_SIZE), new_linker);
  // update offset pointer8O i ZB j6E!H
  _priv->_offset = new_linker + LINKER_SIZE;
  // update counteri2]3i%p/_a
  ++(_priv->_nItems);
}4j F1wWY;bNWC

void MQShm::clear()#bDqUT#^}?*c"Q
{3u/R7r6jh-` |j
  _priv->_nItems = 0;3{eiiP
  _priv->_offset = sizeof(MQShmPriv);TOW,Zf:lF
  _priv->_header = MQShm::null;Wv qa rFQ6H
}|#v jzq3tr
2P#W(Jlu9q
MQShm::const_iterator MQShm::begin() const
{
  return MQShm::const_iterator(this, sizeof(MQShmPriv) - LINKER_SIZE); Q'V"a-a%\ ^h$qg
}
/xlI PoU
MQShm::const_iterator MQShm::end() constZ(jJ+O)j
{
  link_t linkv = _priv->_offset - LINKER_SIZE;
  ASSERT(GET_LK_V((link_t *)(_shm + linkv)) == MQShm::null);]h6pA}p
  return MQShm::const_iterator(this, linkv);d;r+H7^9c`D^*U
}

// MQShm::const_iterator members"l.DRxI zBk\

const uchar *MQShm::const_iterator::data() const G6h^4_R)C!Y
{
  return (const uchar *)(_mqShm->_shm + _linkv + LINKER_SIZE);1U#mO(h|
}
%k"mF{%P)B$H
uint MQShm::const_iterator::size() const
{
  link_t nextv = GET_LK_V((link_t *)(_mqShm->_shm + _linkv));
  uint nAlginBytes = *(link_t *)(_mqShm->_shm + nextv) & ALIGN_MASK ? 1 : 0;%f2x`I`m~2S-`
  return nextv - _linkv - LINKER_SIZE - nAlginBytes;8Al(W*h'RN.}4L`
}#u8hDhd#W7O%R;|
N!C$f5g:W
MQShm::const_iterator &MQShm::const_iterator::operator++()g;DDPV
{?3vwl)|1D
  _linkv = GET_LK_V((link_t *)(_mqShm->_shm + _linkv)); uWQ-`0X2Y
  return *this; X {s(L"v8TL
}
h |I~|d$P
bool MQShm::const_iterator::operator==(const const_iterator &rhs) const)Rq-b(y1Gs!i
{
  return _mqShm == rhs._mqShm && _linkv == rhs._linkv;L2s+Bi;\$c:X3W R|
}

bool MQShm::const_iterator::operator!=(const const_iterator &rhs) const
{
  return _mqShm != rhs._mqShm || _linkv != rhs._linkv;1}pk j1s1r
} }2S&?e+?[){
%N3z Zlg!s
[/code]

ljq1000 发表于 2008-3-25 16:33

顶
希望我的努力不要白费

flag 发表于 2008-3-25 22:20

现在没有环境试，粗看了一下，觉得出错处理似乎武断了点。不知道楼主自己设计了测试的代码试过没有？

页: [1]

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一个linux下共享内存的应用

实现