| 1 | #ifndef BABELTRACE_REF_H |
| 2 | #define BABELTRACE_REF_H |
| 3 | |
| 4 | /* |
| 5 | * BabelTrace: common reference counting |
| 6 | * |
| 7 | * Copyright (c) 2015 EfficiOS Inc. and Linux Foundation |
| 8 | * Copyright (c) 2015 Philippe Proulx <pproulx@efficios.com> |
| 9 | * Copyright (c) 2015 Jérémie Galarneau <jeremie.galarneau@efficios.com> |
| 10 | * |
| 11 | * Permission is hereby granted, free of charge, to any person obtaining a copy |
| 12 | * of this software and associated documentation files (the "Software"), to deal |
| 13 | * in the Software without restriction, including without limitation the rights |
| 14 | * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell |
| 15 | * copies of the Software, and to permit persons to whom the Software is |
| 16 | * furnished to do so, subject to the following conditions: |
| 17 | * |
| 18 | * The above copyright notice and this permission notice shall be included in |
| 19 | * all copies or substantial portions of the Software. |
| 20 | * |
| 21 | * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR |
| 22 | * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, |
| 23 | * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE |
| 24 | * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER |
| 25 | * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, |
| 26 | * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE |
| 27 | * SOFTWARE. |
| 28 | */ |
| 29 | |
| 30 | #ifdef __cplusplus |
| 31 | extern "C" { |
| 32 | #endif |
| 33 | |
| 34 | /* |
| 35 | * BT_PUT: calls bt_put() with a variable, then sets this variable to NULL. |
| 36 | * |
| 37 | * A common action with Babeltrace objects is to create or get one, perform |
| 38 | * an action with it, and then put it. To avoid putting it a second time |
| 39 | * later (if an error occurs, for example), the variable is often reset |
| 40 | * to NULL after putting the object it points to. Since this is so |
| 41 | * common, the BT_PUT() macro can be used to do just that. |
| 42 | * |
| 43 | * It is safe to call this function with a variable containing NULL. |
| 44 | * |
| 45 | * @param obj Variable pointing to a Babeltrace object. |
| 46 | */ |
| 47 | #define BT_PUT(_obj) \ |
| 48 | do { \ |
| 49 | bt_put(_obj); \ |
| 50 | (_obj) = NULL; \ |
| 51 | } while (0) |
| 52 | |
| 53 | /* |
| 54 | * BT_MOVE: transfers the ownership of an object, setting the old owner to NULL. |
| 55 | * |
| 56 | * This macro sets the variable _dst to the value of the variable _src, |
| 57 | * then sets _src to NULL, effectively moving the ownership of an |
| 58 | * object from one variable to the other. |
| 59 | * |
| 60 | * Before assigning _src to _dst, it puts _dst. Therefore it is not safe to |
| 61 | * call this function with an uninitialized value of _dst. |
| 62 | * |
| 63 | * @param _dst Destination variable pointing to a Babeltrace object. |
| 64 | * @param _src Source variable pointing to a Babeltrace object. |
| 65 | */ |
| 66 | #define BT_MOVE(_dst, _src) \ |
| 67 | do { \ |
| 68 | bt_put(_dst); \ |
| 69 | (_dst) = (_src);\ |
| 70 | (_src) = NULL; \ |
| 71 | } while (0) |
| 72 | |
| 73 | /* |
| 74 | * bt_get: increments the reference count of a Babeltrace object. |
| 75 | * |
| 76 | * The same number of bt_get() and bt_put() (plus one extra bt_put() to release |
| 77 | * the initial reference acquired at creation) have to be performed to destroy a |
| 78 | * Babeltrace object. |
| 79 | * |
| 80 | * It is safe to call this function with a NULL object. |
| 81 | * |
| 82 | * @param obj Babeltrace object. |
| 83 | * |
| 84 | * Returns obj. |
| 85 | */ |
| 86 | void *bt_get(void *obj); |
| 87 | |
| 88 | /* |
| 89 | * bt_put: decrements the reference count of a Babeltrace object. |
| 90 | * |
| 91 | * The same number of bt_get() and bt_put() (plus one extra bt_put() to release |
| 92 | * bt_put() to release the initial reference done at creation) have to be |
| 93 | * performed to destroy a Babeltrace object. |
| 94 | * |
| 95 | * The object is freed when its reference count is decremented to 0 by a call to |
| 96 | * bt_put(). |
| 97 | * |
| 98 | * It is safe to call this function with a NULL object. |
| 99 | * |
| 100 | * @param obj Babeltrace object. |
| 101 | */ |
| 102 | void bt_put(void *obj); |
| 103 | |
| 104 | #ifdef __cplusplus |
| 105 | } |
| 106 | #endif |
| 107 | |
| 108 | #endif /* BABELTRACE_REF_H */ |