annotate open.cpp @ 392:78fed0d4c108 api-inversion

Include some necessary information in struct adb.

Now the struct adb contains a database fd, the flags used to open that
fd (so that we can later tell if it was for write or not) and a database
header pointer.

audiodb_open() is now responsible for filling in all of that
information.  To do that, it needs to take an open(2) flag; that's good,
because it means that the call to open(2) is no longer invoking
undefined behaviour.  (Also, the previous version of audiodb_open()
leaked an fd).  Unfortunately, that means we have broken ABI and API
compatibility.  (Fortunately, we have fewer than 12 users).

Use audiodb_open() in audioDB::initDBHeader().

We've temporarily(?) put acquire_lock(int, bool) in the API header; that
means we need to include <stdbool.h> and compile C files with -std=c99.
Do so.

Make audiodb_close() free resources allocated by audiodb_open().

Include a struct adb * field in the audioDB C++ object...
... which lets us actually implement memory-correctness, by
audiodb_close()ing the database in audioDB::cleanup().

[ The lock is, I think, correctly disposed of; man fcntl(2) on Linux
  says that the locks are released once any file descriptor relating to
  the file is closed, and we close the fd in audiodb_close(). ]

#include "audioDB.h"
extern "C" {
#include "audioDB_API.h"
}

bool audiodb_check_header(adb_header_t *header) {
  /* FIXME: use syslog() or write to stderr or something to give the
     poor user some diagnostics. */
  if(header->magic == O2_OLD_MAGIC) {
    return false;
  }
  if(header->magic != O2_MAGIC) {
    return false;
  }
  if(header->version != O2_FORMAT_VERSION) {
    return false;
  }
  if(header->headerSize != O2_HEADERSIZE) {
    return false;
  }
  return true;
}

adb_t *audiodb_open(const char *path, int flags) {
  adb_t *adb = 0;
  int fd = -1;

  flags &= (O_RDONLY|O_RDWR);
  fd = open(path, flags);
  if(fd == -1) {
    goto error;
  }
  if(acquire_lock(fd, flags == O_RDWR)) {
    goto error;
  }

  adb = (adb_t *) malloc(sizeof(adb_t));
  if(!adb) {
    goto error;
  }
  adb->fd = fd;
  adb->flags = flags;
  adb->path = (char *) malloc(1+strlen(path));
  if(!(adb->path)) {
    goto error;
  }
  strcpy(adb->path, path);

  adb->header = (adb_header_t *) malloc(sizeof(adb_header_t));
  if(!(adb->header)) {
    goto error;
  }
  if(read(fd, (char *) adb->header, O2_HEADERSIZE) != O2_HEADERSIZE) {
    goto error;
  }
  if(!audiodb_check_header(adb->header)) {
    goto error;
  }

  return adb;

 error:
  if(adb) {
    if(adb->header) {
      free(adb->header);
    }
    if(adb->path) {
      free(adb->path);
    }
    free(adb);
  }
  if(fd != -1) {
    close(fd);
  }
  return NULL;
}