src/ipc/mem/Segment.cc

   1 /*
   2  * $Id$
   3  *
   4  * DEBUG: section 54    Interprocess Communication
   5  *
   6  */
   7
   8 #include "config.h"
   9
  10 #include "ipc/mem/Segment.h"
  11 #include "protos.h"
  12
  13 #include <fcntl.h>
  14 #include <sys/mman.h>
  15 #include <sys/stat.h>
  16 #include <sys/types.h>
  17 #include <unistd.h>
  18
  19 Ipc::Mem::Segment::Segment(const char *const id):
  20     theName(GenerateName(id)), theFD(-1), theSize(-1), theMem(NULL)
  21 {
  22 }
  23
  24 Ipc::Mem::Segment::~Segment() {
  25     if (theFD >= 0) {
  26         detach();
  27         if (close(theFD) != 0)
  28             debugs(54, 5, HERE << "close: " << xstrerror());
  29     }
  30 }
  31
  32 void
  33 Ipc::Mem::Segment::create(const int aSize)
  34 {
  35     assert(aSize > 0);
  36     assert(theFD < 0);
  37
  38     theFD = shm_open(theName.termedBuf(), O_CREAT | O_RDWR | O_TRUNC,
  39                      S_IRUSR | S_IWUSR);
  40     if (theFD < 0) {
  41         debugs(54, 5, HERE << "shm_open: " << xstrerror());
  42         fatal("Ipc::Mem::Segment::create failed to shm_open");
  43     }
  44
  45     if (ftruncate(theFD, aSize)) {
  46         debugs(54, 5, HERE << "ftruncate: " << xstrerror());
  47         fatal("Ipc::Mem::Segment::create failed to ftruncate");
  48     }
  49
  50     theSize = aSize;
  51
  52     attach();
  53 }
  54
  55 void
  56 Ipc::Mem::Segment::open()
  57 {
  58     assert(theFD < 0);
  59
  60     theFD = shm_open(theName.termedBuf(), O_RDWR, 0);
  61     if (theFD < 0) {
  62         debugs(54, 5, HERE << "shm_open: " << xstrerror());
  63         String s = "Ipc::Mem::Segment::open failed to shm_open";
  64         s.append(theName);
  65         fatal(s.termedBuf());
  66     }
  67
  68     {
  69         struct stat s;
  70         memset(&s, 0, sizeof(s));
  71         if (fstat(theFD, &s)) {
  72             debugs(54, 5, HERE << "fstat: " << xstrerror());
  73         String s = "Ipc::Mem::Segment::open failed to fstat";
  74         s.append(theName);
  75         fatal(s.termedBuf());
  76         }
  77
  78         theSize = s.st_size;
  79     }
  80
  81     attach();
  82 }
  83
  84 /// Map the shared memory segment to the process memory space.
  85 void
  86 Ipc::Mem::Segment::attach()
  87 {
  88     assert(theFD >= 0);
  89     assert(theSize >= 0);
  90     assert(!theMem);
  91
  92     void *const p =
  93         mmap(NULL, theSize, PROT_READ | PROT_WRITE, MAP_SHARED, theFD, 0);
  94     if (p == MAP_FAILED) {
  95         debugs(54, 5, HERE << "mmap: " << xstrerror());
  96         fatal("Ipc::Mem::Segment::attach failed to mmap");
  97     }
  98     theMem = p;
  99 }
 100
 101 /// Unmap the shared memory segment from the process memory space.
 102 void
 103 Ipc::Mem::Segment::detach()
 104 {
 105     if (!theMem)
 106         return;
 107
 108     if (munmap(theMem, theSize)) {
 109         debugs(54, 5, HERE << "munmap: " << xstrerror());
 110         fatal("Ipc::Mem::Segment::detach failed to munmap");
 111     }
 112     theMem = 0;
 113 }
 114
 115 /// Generate name for shared memory segment. Replaces all slashes with dots.
 116 String
 117 Ipc::Mem::Segment::GenerateName(const char *id)
 118 {
 119     String name("/squid-");
 120     for (const char *slash = strchr(id, '/'); slash; slash = strchr(id, '/')) {
 121         if (id != slash) {
 122             name.append(id, slash - id);
 123             name.append('.');
 124         }
 125         id = slash + 1;
 126     }
 127     name.append(id);
 128     return name;
 129 }