diff options
Diffstat (limited to 'src/H5F.c')
| -rw-r--r-- | src/H5F.c | 47 |
1 files changed, 38 insertions, 9 deletions
@@ -566,6 +566,7 @@ H5F_locate_signature(H5FD_t *file) "unable to obtain EOF/EOA value"); } for (maxpow=0; addr; maxpow++) addr>>=1; + maxpow = MAX(maxpow, 9); /* * Search for the file signature at format address zero followed by @@ -906,6 +907,13 @@ H5F_dest(H5F_t *f) * Added decoding of file driver information block, which uses a * formerly reserved address slot in the boot block in order to * be compatible with previous versions of the file format. + * + * Robb Matzke, 1999-08-20 + * Optimizations for opening a file. If the driver can't + * determine when two file handles refer to the same file then + * we open the file in one step. Otherwise if the first attempt + * to open the file fails then we skip the second attempt if the + * arguments would be the same. *------------------------------------------------------------------------- */ H5F_t * @@ -925,17 +933,41 @@ H5F_open(const char *name, uintn flags, hid_t fcpl_id, hid_t fapl_id) haddr_t stored_eoa; /*relative end-of-addr in file */ uintn tent_flags; /*tentative flags */ char driver_name[9]; /*file driver name/version */ + hbool_t driver_has_cmp; /*`cmp' callback defined? */ FUNC_ENTER(H5F_open, NULL); /* - * Open the file very carefully because we don't want to wipe out a file - * which is currently open (which is possible if this call specifies - * truncation of an existing file). So turn off truncation and file - * creation and try opening it. If that fails then open as normal. + * If the driver has a `cmp' method then the driver is capable of + * determining when two file handles refer to the same file and the + * library can insure that when the application opens a file twice that + * the two handles coordinate their operations appropriately. Otherwise + * it is the application's responsibility to never open the same file + * more than once at a time. + */ + driver_has_cmp = H5FD_has_cmp(fapl_id); + + /* + * Opening a file is a two step process. First we try to open the file in + * a way which doesn't affect its state (like not truncating or creating + * it) so we can compare it with files that are already open. If that + * fails then we try again with the full set of flags (only if they're + * different than the original failed attempt). However, if the file + * driver can't distinquish between files then there's no reason to open + * the file tentatively because it's the application's responsibility to + * prevent this situation (there's no way for us to detect it here + * anyway). */ - tent_flags = flags & ~(H5F_ACC_CREAT|H5F_ACC_TRUNC|H5F_ACC_EXCL); + if (driver_has_cmp) { + tent_flags = flags & ~(H5F_ACC_CREAT|H5F_ACC_TRUNC|H5F_ACC_EXCL); + } else { + tent_flags = flags; + } if (NULL==(lf=H5FD_open(name, tent_flags, fapl_id, HADDR_UNDEF))) { + if (tent_flags == flags) { + HGOTO_ERROR(H5E_FILE, H5E_CANTOPENFILE, NULL, + "unable to open file"); + } H5E_clear(); tent_flags = flags; if (NULL==(lf=H5FD_open(name, tent_flags, fapl_id, HADDR_UNDEF))) { @@ -1223,10 +1255,7 @@ H5F_open(const char *name, uintn flags, hid_t fcpl_id, hid_t fapl_id) ret_value = file; done: - if (!ret_value) { - if (file) H5F_dest(file); - if (lf) H5FD_close(lf); - } + if (!ret_value && file) H5F_dest(file); FUNC_LEAVE(ret_value); } |