Import BSDDB 4.7.25 (as of svn r89086)

examples_c/ex_apprec/ex_apprec_template

@@ -0,0 +1,70 @@
+#include "db.h"
+
+/*
+ * ex_apprec_mkdir_recover --
+ *	Recovery function for mkdir.
+ *
+ * PUBLIC: int ex_apprec_mkdir_recover
+ * PUBLIC:   __P((dbenv *, DBT *, DB_LSN *, db_recops));
+ */
+int
+ex_apprec_mkdir_recover(dbenv, dbtp, lsnp, op)
+	dbenv *dbenv;
+	DBT *dbtp;
+	DB_LSN *lsnp;
+	db_recops op;
+{
+	ex_apprec_mkdir_args *argp;
+	int cmp_n, cmp_p, modified, ret;
+
+#ifdef DEBUG_RECOVER
+	(void)ex_apprec_mkdir_print(dbenv, dbtp, lsnp, op);
+#endif
+	argp = NULL;
+	if ((ret = ex_apprec_mkdir_read(dbenv, dbtp->data, &argp)) != 0)
+		goto out;
+
+	modified = 0;
+	cmp_n = 0;
+	cmp_p = 0;
+
+	/*
+	 * The function now needs to calculate cmp_n and cmp_p based
+	 * on whatever is in argp (usually an LSN representing the state
+	 * of an object BEFORE the operation described in this record was
+	 * applied) and whatever other information the function needs,
+	 * e.g., the LSN of the object as it exists now.
+	 *
+	 * cmp_p should be set to 0 if the current state of the object
+	 * is believed to be same as the state of the object BEFORE the
+	 * described operation was applied.  For example, if you had an
+	 * LSN in the log record (argp->prevlsn) and a current LSN of the
+	 * object (curlsn), you might want to do:
+	 *
+	 * cmp_p = log_compare(curlsn, argp->prevlsn);
+	 *
+	 * Similarly, cmp_n should be set to 0 if the current state
+	 * of the object reflects the object AFTER this operation has
+	 * been applied.  Thus, if you can figure out an object's current
+	 * LSN, yo might set cmp_n as:
+	 *
+	 * cmp_n = log_compare(lsnp, curlsn);
+	 */
+	if (cmp_p == 0 && DB_REDO(op)) {
+		/* Need to redo update described. */
+		modified = 1;
+	} else if (cmp_n == 0 && !DB_REDO(op)) {
+		/* Need to undo update described. */
+		modified = 1;
+	}
+
+	/* Allow for following LSN pointers through a transaction. */
+	*lsnp = argp->prev_lsn;
+	ret = 0;
+
+out:	if (argp != NULL)
+		free(argp);
+
+	return (ret);
+}
+