xapian-applications/omega/cdb_init.cc

   1 /* $Id: cdb_init.c,v 1.9 2003/11/03 21:42:20 mjt Exp $
   2  * cdb_init, cdb_free and cdb_read routines
   3  *
   4  * This file is a part of tinycdb package by Michael Tokarev, mjt@corpit.ru.
   5  * Public domain.
   6  */
   7
   8 #include <config.h>
   9
  10 #include <sys/types.h>
  11 #ifdef HAVE_MMAP
  12 # include <sys/mman.h>
  13 #else
  14 # include "safeunistd.h"
  15 # include <cstdlib>
  16 #endif
  17 #ifdef __WIN32__
  18 # include "safewindows.h"
  19 #endif
  20 #include "safesysstat.h"
  21 #include "cdb_int.h"
  22 #include <cstring>
  23
  24 using namespace std;
  25
  26 int
  27 cdb_init(struct cdb *cdbp, int fd)
  28 {
  29   struct stat st;
  30   unsigned char *mem;
  31   unsigned fsize, dend;
  32 #ifndef HAVE_MMAP
  33 #ifdef _WIN32
  34   HANDLE hFile, hMapping;
  35 #else
  36   size_t size;
  37   unsigned char *p;
  38 #endif
  39 #endif
  40
  41   /* get file size */
  42   if (fstat(fd, &st) < 0)
  43     return -1;
  44   /* trivial sanity check: at least toc should be here */
  45   if (st.st_size < 2048)
  46     return errno = EPROTO, -1;
  47   fsize = (unsigned)(st.st_size & 0xffffffffu);
  48   /* memory-map file */
  49 #ifndef HAVE_MMAP
  50 #ifdef _WIN32
  51   hFile = (HANDLE) _get_osfhandle(fd);
  52   if(hFile == (HANDLE) -1) return -1;
  53   hMapping = CreateFileMapping(hFile, NULL, PAGE_READONLY, 0, 0, NULL);
  54   if (!hMapping) return -1;
  55   mem = (unsigned char *)MapViewOfFile(hMapping, FILE_MAP_READ, 0, 0, 0);
  56   if (!mem) return -1;
  57 #else
  58   // No mmap, so take the very crude approach of malloc and read the whole file in!
  59   if ((mem = (unsigned char *)malloc(fsize)) == NULL)
  60     return -1;
  61   size = fsize;
  62   p = mem;
  63   while (size > 0) {
  64     ssize_t n = read(fd, (void*)p, size);
  65     if (n == -1)
  66       return -1;
  67     p += n;
  68     size -= n;
  69   }
  70 #endif
  71 #else
  72   mem = (unsigned char *)mmap(NULL, fsize, PROT_READ, MAP_SHARED, fd, 0);
  73   if (mem == (unsigned char *)-1)
  74     return -1;
  75 #endif /* _WIN32 */
  76
  77   cdbp->cdb_fd = fd;
  78   cdbp->cdb_fsize = fsize;
  79   cdbp->cdb_mem = mem;
  80
  81 #if 0
  82   /* XXX don't know well about madvise syscall -- is it legal
  83      to set different options for parts of one mmap() region?
  84      There is also posix_madvise() exist, with POSIX_MADV_RANDOM etc...
  85   */
  86 #ifdef MADV_RANDOM
  87   /* set madvise() parameters. Ignore errors for now if system
  88      doesn't support it */
  89   madvise(mem, 2048, MADV_WILLNEED);
  90   madvise(mem + 2048, cdbp->cdb_fsize - 2048, MADV_RANDOM);
  91 #endif
  92 #endif
  93
  94   cdbp->cdb_vpos = cdbp->cdb_vlen = 0;
  95   cdbp->cdb_kpos = cdbp->cdb_klen = 0;
  96   dend = cdb_unpack(mem);
  97   if (dend < 2048) dend = 2048;
  98   else if (dend >= fsize) dend = fsize;
  99   cdbp->cdb_dend = dend;
 100
 101   return 0;
 102 }
 103
 104 #ifdef __cplusplus
 105 class VoidStarOrCharStar {
 106     void *p;
 107   public:
 108     VoidStarOrCharStar(const void *p_) : p(const_cast<void*>(p_)) { }
 109     VoidStarOrCharStar(const char *p_) : p(const_cast<char*>(p_)) { }
 110     operator void*() { return p; }
 111     operator char*() { return static_cast<char*>(p); }
 112 };
 113 #endif
 114
 115 void
 116 cdb_free(struct cdb *cdbp)
 117 {
 118   if (cdbp->cdb_mem) {
 119 #ifdef _WIN32
 120     HANDLE hFile, hMapping;
 121 #endif
 122
 123 #ifndef HAVE_MMAP
 124 #ifdef __cplusplus
 125     void * p = const_cast<void*>((const void*)cdbp->cdb_mem);
 126 #else
 127     void * p = (void*)cdbp->cdb_mem;
 128 #endif
 129 #ifdef _WIN32
 130     hFile = (HANDLE) _get_osfhandle(cdbp->cdb_fd);
 131     hMapping = CreateFileMapping(hFile, NULL, PAGE_READONLY, 0, 0, NULL);
 132     UnmapViewOfFile(p);
 133     CloseHandle(hMapping);
 134 #else
 135     free(p);
 136 #endif
 137 #else
 138 #ifdef __cplusplus
 139     /* Solaris sys/mman.h defines munmap as taking char* unless __STDC__ is
 140      * defined (which it isn't in C++).
 141      */
 142     VoidStarOrCharStar p(cdbp->cdb_mem);
 143 #else
 144     void * p = (void*)cdbp->cdb_mem;
 145 #endif
 146     munmap(p, cdbp->cdb_fsize);
 147 #endif /* _WIN32 */
 148     cdbp->cdb_mem = NULL;
 149   }
 150   cdbp->cdb_fsize = 0;
 151 }
 152
 153 const void *
 154 cdb_get(const struct cdb *cdbp, unsigned len, unsigned pos)
 155 {
 156   if (pos > cdbp->cdb_fsize || cdbp->cdb_fsize - pos < len) {
 157     errno = EPROTO;
 158     return NULL;
 159   }
 160   return cdbp->cdb_mem + pos;
 161 }
 162
 163 int
 164 cdb_read(const struct cdb *cdbp, void *buf, unsigned len, unsigned pos)
 165 {
 166   const void *data = cdb_get(cdbp, len, pos);
 167   if (!data) return -1;
 168   memcpy(buf, data, len);
 169   return 0;
 170 }