view create.cpp @ 400:8c7453fb5bd9 api-inversion

Invert audioDB::power_flag / audiodb_power()

Here the exciting discovery is that the mmap(), memcpy(), munmap()
sequence is in fact not safe.  In principle an msync() call should be
inserted before unmapping for in-core changes to mmap()ed files to be
flushed to disk.

In this case we work around the problem entirely, by not mmap()ing
anything and doing everything with file descriptors.  Amusingly, that's
probably not desperately safe either, this time because we have to move
the file descriptor position (which is also a shared resource).  dup()
doesn't save us, as the duplicate file descriptor shares a file
position.

This applies also to the filling of data_buffer in the query loop, and
in fact basically any call to lseek(), which is why I'm not fixing it
now.  Solution: if you have multiple threads all acting at once on a
single database, do one audiodb_open() per thread, for now at least.

#include "audioDB.h"
extern "C" {
#include "audioDB_API.h"
}
/* Make a new database.

IF size(featuredata) < O2_LARGE_ADB_SIZE 
   The database consists of:

   * a header (see dbTableHeader struct definition);
   * keyTable: list of keys of tracks;
   * trackTable: Maps implicit feature index to a feature vector
     matrix (sizes of tracks)
   * featureTable: Lots of doubles;
   * timesTable: (start,end) time points for each feature vector;
   * powerTable: associated power for each feature vector;
   * l2normTable: squared l2norms for each feature vector.
   
ELSE the database consists of:
   
   * a header (see dbTableHeader struct definition);
   * keyTable: list of keys of tracks
   * trackTable: sizes of tracks
   * featureTable: list of feature file names
   * timesTable: list of times file names
   * powerTable: list of power file names

*/

extern "C" {
  adb_t *audiodb_create(const char *path, unsigned datasize, unsigned ntracks, unsigned datadim) {
    int fd;
    adb_header_t *header = 0;
    off_t databytes, auxbytes;
    if(datasize == 0) {
      datasize = O2_DEFAULT_DATASIZE;
    }
    if(ntracks == 0) {
      ntracks = O2_DEFAULT_NTRACKS;
    }
    if(datadim == 0) {
      datadim = O2_DEFAULT_DATADIM;
    }

    if ((fd = open(path, O_RDWR|O_CREAT|O_EXCL, S_IRUSR|S_IWUSR|S_IRGRP|S_IWGRP|S_IROTH|S_IWOTH)) < 0) {
      goto error;
    }
    if (acquire_lock(fd, true)) {
      goto error;
    }

    header = (adb_header_t *) malloc(sizeof(adb_header_t));
    if(!header) {
      goto error;
    }
    
    // Initialize header
    header->magic = O2_MAGIC;
    header->version = O2_FORMAT_VERSION;
    header->numFiles = 0;
    header->dim = 0;
    header->flags = 0;
    header->headerSize = O2_HEADERSIZE;
    header->length = 0;
    header->fileTableOffset = ALIGN_PAGE_UP(O2_HEADERSIZE);
    header->trackTableOffset = ALIGN_PAGE_UP(header->fileTableOffset + O2_FILETABLE_ENTRY_SIZE*ntracks);
    header->dataOffset = ALIGN_PAGE_UP(header->trackTableOffset + O2_TRACKTABLE_ENTRY_SIZE*ntracks);
    
    databytes = ((off_t) datasize) * 1024 * 1024;
    auxbytes = databytes / datadim;

    /* FIXME: what's going on here?  There are two distinct
       preprocessor constants (O2_LSH_N_POINT_BITS, LSH_N_POINT_BITS);
       a third is presumably some default
       (O2_DEFAULT_LSH_N_POINT_BITS), and then there's this magic 28
       bits.  Should this really be part of the flags structure at
       all?  Putting it elsewhere will of course break backwards
       compatibility, unless 14 is the only value that's been used
       anywhere... */
    
    // For backward-compatibility, Record the point-encoding parameter for LSH indexing in the adb header
    // If this value is 0 then it will be set to 14
    
#if O2_LSH_N_POINT_BITS > 15
#error "AudioDB Compile ERROR: consistency check of O2_LSH_POINT_BITS failed (>15)"
#endif
    
    header->flags |= LSH_N_POINT_BITS << 28;
    
    // If database will fit in a single file the vectors are copied into the AudioDB instance
    // Else all the vectors are left on the FileSystem and we use the dataOffset as storage
    // for the location of the features, powers and times files (assuming that arbitrary keys are used for the fileTable)
    if(ntracks<O2_LARGE_ADB_NTRACKS && datasize<O2_LARGE_ADB_SIZE){
      header->timesTableOffset = ALIGN_PAGE_UP(header->dataOffset + databytes);
      header->powerTableOffset = ALIGN_PAGE_UP(header->timesTableOffset + 2*auxbytes);
      header->l2normTableOffset = ALIGN_PAGE_UP(header->powerTableOffset + auxbytes);
      header->dbSize = ALIGN_PAGE_UP(header->l2normTableOffset + auxbytes);
    } else { // Create LARGE_ADB, features and powers kept on filesystem 
      header->flags |= O2_FLAG_LARGE_ADB;
      header->timesTableOffset = ALIGN_PAGE_UP(header->dataOffset + O2_FILETABLE_ENTRY_SIZE*ntracks);
      header->powerTableOffset = ALIGN_PAGE_UP(header->timesTableOffset + O2_FILETABLE_ENTRY_SIZE*ntracks);
      header->l2normTableOffset = ALIGN_PAGE_UP(header->powerTableOffset + O2_FILETABLE_ENTRY_SIZE*ntracks);
      header->dbSize = header->l2normTableOffset;
    } 
    
    if (write(fd, header, O2_HEADERSIZE) != O2_HEADERSIZE) {
      goto error;
    }
    
    // go to the location corresponding to the last byte
    if (lseek (fd, header->dbSize - 1, SEEK_SET) == -1) {
      goto error;
    }

    // write a dummy byte at the last location
    if (write (fd, "", 1) != 1) {
      goto error;
    }

    free(header);
    return audiodb_open(path, O_RDWR);

  error:
    if(header) {
      free(header);
    }
    return NULL;
  }
}