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), theMem(NULL),
  21     theSize(0), theReserved(0)
  22 {
  23 }
  24
  25 Ipc::Mem::Segment::~Segment() {
  26     if (theFD >= 0) {
  27         detach();
  28         if (close(theFD) != 0)
  29             debugs(54, 5, HERE << "close: " << xstrerror());
  30     }
  31 }
  32
  33 void
  34 Ipc::Mem::Segment::create(const int aSize)
  35 {
  36     assert(aSize > 0);
  37     assert(theFD < 0);
  38
  39     theFD = shm_open(theName.termedBuf(), O_CREAT | O_RDWR | O_TRUNC,
  40                      S_IRUSR | S_IWUSR);
  41     if (theFD < 0) {
  42         debugs(54, 5, HERE << "shm_open: " << xstrerror());
  43         fatal("Ipc::Mem::Segment::create failed to shm_open");
  44     }
  45
  46     if (ftruncate(theFD, aSize)) {
  47         debugs(54, 5, HERE << "ftruncate: " << xstrerror());
  48         fatal("Ipc::Mem::Segment::create failed to ftruncate");
  49     }
  50
  51     theSize = aSize;
  52     theReserved = 0;
  53
  54     attach();
  55 }
  56
  57 void
  58 Ipc::Mem::Segment::open()
  59 {
  60     assert(theFD < 0);
  61
  62     theFD = shm_open(theName.termedBuf(), O_RDWR, 0);
  63     if (theFD < 0) {
  64         debugs(54, 5, HERE << "shm_open: " << xstrerror());
  65         String s = "Ipc::Mem::Segment::open failed to shm_open";
  66         s.append(theName);
  67         fatal(s.termedBuf());
  68     }
  69
  70     {
  71         struct stat s;
  72         memset(&s, 0, sizeof(s));
  73         if (fstat(theFD, &s)) {
  74             debugs(54, 5, HERE << "fstat: " << xstrerror());
  75         String s = "Ipc::Mem::Segment::open failed to fstat";
  76         s.append(theName);
  77         fatal(s.termedBuf());
  78         }
  79
  80         theSize = s.st_size;
  81     }
  82
  83     attach();
  84 }
  85
  86 /// Map the shared memory segment to the process memory space.
  87 void
  88 Ipc::Mem::Segment::attach()
  89 {
  90     assert(theFD >= 0);
  91     assert(!theMem);
  92
  93     void *const p =
  94         mmap(NULL, theSize, PROT_READ | PROT_WRITE, MAP_SHARED, theFD, 0);
  95     if (p == MAP_FAILED) {
  96         debugs(54, 5, HERE << "mmap: " << xstrerror());
  97         fatal("Ipc::Mem::Segment::attach failed to mmap");
  98     }
  99     theMem = p;
 100 }
 101
 102 /// Unmap the shared memory segment from the process memory space.
 103 void
 104 Ipc::Mem::Segment::detach()
 105 {
 106     if (!theMem)
 107         return;
 108
 109     if (munmap(theMem, theSize)) {
 110         debugs(54, 5, HERE << "munmap: " << xstrerror());
 111         fatal("Ipc::Mem::Segment::detach failed to munmap");
 112     }
 113     theMem = 0;
 114 }
 115
 116 void *
 117 Ipc::Mem::Segment::reserve(size_t chunkSize)
 118 {
 119     assert(chunkSize <= theSize);
 120     assert(theReserved <= theSize - chunkSize);
 121     theReserved += chunkSize;
 122     return reinterpret_cast<char*>(mem()) + theReserved;
 123 }
 124
 125 /// Generate name for shared memory segment. Replaces all slashes with dots.
 126 String
 127 Ipc::Mem::Segment::GenerateName(const char *id)
 128 {
 129     String name("/squid-");
 130     for (const char *slash = strchr(id, '/'); slash; slash = strchr(id, '/')) {
 131         if (id != slash) {
 132             name.append(id, slash - id);
 133             name.append('.');
 134         }
 135         id = slash + 1;
 136     }
 137     name.append(id);
 138     return name;
 139 }