+++ /dev/null
-Interface differences between TDB and NTDB.
-
-- ntdb shares 'struct TDB_DATA' with tdb, but TDB defines the TDB_DATA
- typedef, whereas ntdb defines NTDB_DATA (ie. both are compatible).
- If you include both ntdb.h and tdb.h, #include tdb.h first,
- otherwise you'll get a compile error when tdb.h re-defined struct
- TDB_DATA.
-
- Example:
- #include <tdb.h>
- #include <ntdb.h>
-
-- ntdb functions return NTDB_SUCCESS (ie 0) on success, and a negative
- error on failure, whereas tdb functions returned 0 on success, and
- -1 on failure. tdb then used tdb_error() to determine the error;
- this API is nasty if we ever want to support threads, so is not supported.
-
- Example:
- #include <tdb.h>
- #include <ntdb.h>
-
- void tdb_example(struct tdb_context *tdb, TDB_DATA key, TDB_DATA d)
- {
- if (tdb_store(tdb, key, d) == -1) {
- printf("store failed: %s\n", tdb_errorstr(tdb));
- }
- }
-
- void ntdb_example(struct ntdb_context *ntdb, NTDB_DATA key, NTDB_DATA d)
- {
- enum NTDB_ERROR e;
-
- e = ntdb_store(ntdb, key, d);
- if (e) {
- printf("store failed: %s\n", ntdb_errorstr(e));
- }
- }
-
-- ntdb's ntdb_fetch() returns an error, tdb's returned the data directly
- (or tdb_null, and you were supposed to check tdb_error() to find out why).
-
- Example:
- #include <tdb.h>
- #include <ntdb.h>
-
- void tdb_example(struct tdb_context *tdb, TDB_DATA key)
- {
- TDB_DATA data;
-
- data = tdb_fetch(tdb, key);
- if (!data.dptr) {
- printf("fetch failed: %s\n", tdb_errorstr(tdb));
- }
- }
-
- void ntdb_example(struct ntdb_context *ntdb, NTDB_DATA key)
- {
- NTDB_DATA data;
- enum NTDB_ERROR e;
-
- e = ntdb_fetch(ntdb, key, &data);
- if (e) {
- printf("fetch failed: %s\n", ntdb_errorstr(e));
- }
- }
-
-- ntdb's ntdb_nextkey() frees the old key's dptr, in tdb you needed to do
- this manually.
-
- Example:
- #include <tdb.h>
- #include <ntdb.h>
-
- void tdb_example(struct tdb_context *tdb)
- {
- TDB_DATA key, next, data;
-
- for (key = tdb_firstkey(tdb); key.dptr; key = next) {
- printf("Got key!\n");
- next = tdb_nextkey(tdb, key);
- free(key.dptr);
- }
- }
-
-
- void ntdb_example(struct ntdb_context *ntdb)
- {
- NTDB_DATA k, data;
- enum NTDB_ERROR e;
-
- for (e = ntdb_firstkey(ntdb,&k); !e; e = ntdb_nextkey(ntdb,&k))
- printf("Got key!\n");
- }
-
-- Unlike tdb_open/tdb_open_ex, ntdb_open does not allow NULL names,
- even for NTDB_INTERNAL dbs, and thus ntdb_name() never returns NULL.
-
- Example:
- #include <tdb.h>
- #include <ntdb.h>
-
- struct tdb_context *tdb_example(void)
- {
- return tdb_open(NULL, 0, TDB_INTERNAL, O_RDWR, 0);
- }
-
- struct ntdb_context *ntdb_example(void)
- {
- return ntdb_open("example", NTDB_INTERNAL, O_RDWR, 0);
- }
-
-- ntdb uses a linked list of attribute structures to implement logging and
- alternate hashes. tdb used tdb_open_ex, which was not extensible.
-
- Example:
- #include <tdb.h>
- #include <ntdb.h>
-
- /* Custom hash function */
- static unsigned int my_tdb_hash_func(TDB_DATA *key)
- {
- return key->dsize;
- }
-
- struct tdb_context *tdb_example(void)
- {
- return tdb_open_ex("example.tdb", 0, TDB_DEFAULT,
- O_CREAT|O_RDWR, 0600, NULL, my_hash_func);
- }
-
- /* Custom hash function */
- static unsigned int my_ntdb_hash_func(const void *key, size_t len,
- uint32_t seed, void *data)
- {
- return len;
- }
-
- struct ntdb_context *ntdb_example(void)
- {
- union ntdb_attribute hash;
-
- hash.base.attr = NTDB_ATTRIBUTE_HASH;
- hash.base.next = NULL;
- hash.hash.fn = my_ntdb_hash_func;
- return ntdb_open("example.ntdb", NTDB_DEFAULT,
- O_CREAT|O_RDWR, 0600, &hash);
- }
-
-- tdb's tdb_open/tdb_open_ex took an explicit hash size, defaulting to
- 131. ntdb's uses an attribute for this, defaulting to 8192.
-
- Example:
- #include <tdb.h>
- #include <ntdb.h>
-
- struct tdb_context *tdb_example(void)
- {
- return tdb_open("example.tdb", 10007, TDB_DEFAULT,
- O_CREAT|O_RDWR, 0600);
- }
-
- struct ntdb_context *ntdb_example(void)
- {
- union ntdb_attribute hashsize;
-
- hashsize.base.attr = NTDB_ATTRIBUTE_HASHSIZE;
- hashsize.base.next = NULL;
- hashsize.hashsize.size = 16384;
- return ntdb_open("example.ntdb", NTDB_DEFAULT,
- O_CREAT|O_RDWR, 0600, &hashsize);
- }
-
-- ntdb's log function is simpler than tdb's log function. The string
- is already formatted, is not terminated by a '\n', and it takes an
- enum ntdb_log_level not a tdb_debug_level, and which has only three
- values: NTDB_LOG_ERROR, NTDB_LOG_USE_ERROR and NTDB_LOG_WARNING.
-
- #include <tdb.h>
- #include <ntdb.h>
-
- static void tdb_log(struct tdb_context *tdb,
- enum tdb_debug_level level, const char *fmt, ...)
- {
- va_list ap;
- const char *name;
-
- switch (level) {
- case TDB_DEBUG_FATAL:
- fprintf(stderr, "FATAL: ");
- break;
- case TDB_DEBUG_ERROR:
- fprintf(stderr, "ERROR: ");
- break;
- case TDB_DEBUG_WARNING:
- fprintf(stderr, "WARNING: ");
- break;
- case TDB_DEBUG_TRACE:
- /* Don't print out tracing. */
- return;
- }
-
- name = tdb_name(tdb);
- if (!name) {
- name = "unnamed";
- }
-
- fprintf(stderr, "tdb(%s):", name);
-
- va_start(ap, fmt);
- vfprintf(stderr, fmt, ap);
- va_end(ap);
- }
-
- struct tdb_context *tdb_example(void)
- {
- struct tdb_logging_context lctx;
-
- lctx.log_fn = tdb_log;
- return tdb_open_ex("example.tdb", 0, TDB_DEFAULT,
- O_CREAT|O_RDWR, 0600, &lctx, NULL);
- }
-
- static void ntdb_log(struct ntdb_context *ntdb,
- enum ntdb_log_level level,
- enum NTDB_ERROR ecode,
- const char *message,
- void *data)
- {
- switch (level) {
- case NTDB_LOG_ERROR:
- fprintf(stderr, "ERROR: ");
- break;
- case NTDB_LOG_USE_ERROR:
- /* We made a mistake, so abort. */
- abort();
- break;
- case NTDB_LOG_WARNING:
- fprintf(stderr, "WARNING: ");
- break;
- }
-
- fprintf(stderr, "ntdb(%s):%s:%s\n",
- ntdb_name(ntdb), ntdb_errorstr(ecode), message);
- }
-
- struct ntdb_context *ntdb_example(void)
- {
- union ntdb_attribute log;
-
- log.base.attr = NTDB_ATTRIBUTE_LOG;
- log.base.next = NULL;
- log.log.fn = ntdb_log;
- return ntdb_open("example.ntdb", NTDB_DEFAULT,
- O_CREAT|O_RDWR, 0600, &log);
- }
-
-- ntdb provides ntdb_deq() for comparing two NTDB_DATA, and ntdb_mkdata() for
- creating an NTDB_DATA.
-
- #include <tdb.h>
- #include <ntdb.h>
-
- void tdb_example(struct tdb_context *tdb)
- {
- TDB_DATA data, key;
-
- key.dsize = strlen("hello");
- key.dptr = "hello";
- data = tdb_fetch(tdb, key);
- if (data.dsize == key.dsize
- && !memcmp(data.dptr, key.dptr, key.dsize))
- printf("key is same as data\n");
- }
- free(data.dptr);
- }
-
- void ntdb_example(struct ntdb_context *ntdb)
- {
- NTDB_DATA data, key;
-
- key = ntdb_mkdata("hello", strlen("hello"));
- if (ntdb_fetch(ntdb, key, &data) == NTDB_SUCCESS) {
- if (ntdb_deq(key, data)) {
- printf("key is same as data\n");
- }
- free(data.dptr);
- }
- }
-
-- ntdb's ntdb_parse_record() takes a type-checked callback data
- pointer, not a void * (though a void * pointer still works). The
- callback function is allowed to do read operations on the database,
- or write operations if you first call ntdb_lockall(). TDB's
- tdb_parse_record() did not allow any database access within the
- callback, could crash if you tried.
-
- Example:
- #include <tdb.h>
- #include <ntdb.h>
-
- static int tdb_parser(TDB_DATA key, TDB_DATA data, void *private_data)
- {
- TDB_DATA *expect = private_data;
-
- return data.dsize == expect->dsize
- && !memcmp(data.dptr, expect->dptr, data.dsize);
- }
-
- void tdb_example(struct tdb_context *tdb, TDB_DATA key, NTDB_DATA d)
- {
- switch (tdb_parse_record(tdb, key, tdb_parser, &d)) {
- case -1:
- printf("parse failed: %s\n", tdb_errorstr(tdb));
- break;
- case 0:
- printf("data was different!\n");
- break;
- case 1:
- printf("data was same!\n");
- break;
- }
- }
-
- static int ntdb_parser(TDB_DATA key, TDB_DATA data, TDB_DATA *expect)
- {
- return ntdb_deq(data, *expect);
- }
-
- void ntdb_example(struct ntdb_context *ntdb, NTDB_DATA key, NTDB_DATA d)
- {
- enum NTDB_ERROR e;
-
- e = tdb_parse_record(tdb, key, tdb_parser, &d);
- switch (e) {
- case 0:
- printf("data was different!\n");
- break;
- case 1:
- printf("data was same!\n");
- break;
- default:
- printf("parse failed: %s\n", ntdb_errorstr(e));
- break;
- }
- }
-
-- ntdb does locking on read-only databases (ie. O_RDONLY passed to ntdb_open).
- tdb did not: use the NTDB_NOLOCK flag if you want to suppress locking.
-
- Example:
- #include <tdb.h>
- #include <ntdb.h>
-
- struct tdb_context *tdb_example(void)
- {
- return tdb_open("example.tdb", 0, TDB_DEFAULT, O_RDONLY, 0);
- }
-
- struct ntdb_context *ntdb_example(void)
- {
- return ntdb_open("example.ntdb", NTDB_NOLOCK, O_RDONLY, NULL);
- }
-
-- Failure inside a transaction (such as a lock function failing) does
- not implicitly cancel the transaction; you still need to call
- ntdb_transaction_cancel().
-
- #include <tdb.h>
- #include <ntdb.h>
-
- void tdb_example(struct tdb_context *tdb, TDB_DATA key, TDB_DATA d)
- {
- if (tdb_transaction_start(tdb) == -1) {
- printf("transaction failed: %s\n", tdb_errorstr(tdb));
- return;
- }
-
- if (tdb_store(tdb, key, d) == -1) {
- printf("store failed: %s\n", tdb_errorstr(tdb));
- return;
- }
- if (tdb_transaction_commit(tdb) == -1) {
- printf("commit failed: %s\n", tdb_errorstr(tdb));
- }
- }
-
- void ntdb_example(struct ntdb_context *ntdb, NTDB_DATA key, NTDB_DATA d)
- {
- enum NTDB_ERROR e;
-
- e = ntdb_transaction_start(ntdb);
- if (e) {
- printf("transaction failed: %s\n", ntdb_errorstr(e));
- return;
- }
-
- e = ntdb_store(ntdb, key, d);
- if (e) {
- printf("store failed: %s\n", ntdb_errorstr(e));
- ntdb_transaction_cancel(ntdb);
- }
-
- e = ntdb_transaction_commit(ntdb);
- if (e) {
- printf("commit failed: %s\n", ntdb_errorstr(e));
- }
- }
-
-- There is no NTDB_CLEAR_IF_FIRST flag; it has severe scalability and
- API problems. If necessary, you can emulate this by using the open
- hook and placing a 1-byte lock at offset 4. If your program forks
- and exits, you will need to place this lock again in the child before
- the parent exits.
-
- Example:
-
- #include <tdb.h>
- #include <ntdb.h>
-
- struct tdb_context *tdb_example(void)
- {
- return tdb_open("example.tdb", 0, TDB_CLEAR_IF_FIRST,
- O_CREAT|O_RDWR, 0600);
- }
-
- static enum NTDB_ERROR clear_if_first(int fd, void *unused)
- {
- /* We hold a lock offset 4 always, so we can tell if
- * anyone else is. */
- struct flock fl;
-
- fl.l_type = F_WRLCK;
- fl.l_whence = SEEK_SET;
- fl.l_start = 4; /* ACTIVE_LOCK */
- fl.l_len = 1;
-
- if (fcntl(fd, F_SETLK, &fl) == 0) {
- /* We must be first ones to open it! Clear it. */
- if (ftruncate(fd, 0) != 0) {
- return NTDB_ERR_IO;
- }
- }
- fl.l_type = F_RDLCK;
- if (fcntl(fd, F_SETLKW, &fl) != 0) {
- return NTDB_ERR_IO;
- }
- return NTDB_SUCCESS;
- }
-
- struct ntdb_context *ntdb_example(void)
- {
- union ntdb_attribute open_attr;
-
- open_attr.openhook.base.attr = NTDB_ATTRIBUTE_OPENHOOK;
- open_attr.openhook.base.next = NULL;
- open_attr.openhook.fn = clear_if_first;
-
- return ntdb_open("example.ntdb", NTDB_DEFAULT,
- O_CREAT|O_RDWR, 0600, &open_attr);
- }
-
-- ntdb traversals are not reliable if the database is changed during
- the traversal, ie your traversal may not cover all elements, or may
- cover elements multiple times. As a special exception, deleting the
- current record within ntdb_traverse() is reliable.
-
-- There is no ntdb_traverse_read, since ntdb_traverse does not hold
- a lock across the entire traversal anyway. If you want to make sure
- that your traversal function does not write to the database, you can
- set and clear the NTDB_RDONLY flag around the traversal.
-
-- ntdb does not need tdb_reopen() or tdb_reopen_all(). If you call
- fork() after during certain operations the child should close the
- ntdb, or complete the operations before continuing to use the tdb:
-
- ntdb_transaction_start(): child must ntdb_transaction_cancel()
- ntdb_lockall(): child must call ntdb_unlockall()
- ntdb_lockall_read(): child must call ntdb_unlockall_read()
- ntdb_chainlock(): child must call ntdb_chainunlock()
- ntdb_parse() callback: child must return from ntdb_parse()
-
-- ntdb will not open a non-ntdb file, even if O_CREAT is specified. tdb
- will overwrite an unknown file in that case.
projects / ccan / blobdiff