1tree walking API 2================ 3 4The tree walking API is used to traverse and inspect trees. 5 6Data Structures 7--------------- 8 9`struct name_entry`:: 10 11 An entry in a tree. Each entry has a sha1 identifier, pathname, and 12 mode. 13 14`struct tree_desc`:: 15 16 A semi-opaque data structure used to maintain the current state of the 17 walk. 18+ 19* `buffer` is a pointer into the memory representation of the tree. It always 20points at the current entry being visited. 21 22* `size` counts the number of bytes left in the `buffer`. 23 24* `entry` points to the current entry being visited. 25 26`struct traverse_info`:: 27 28 A structure used to maintain the state of a traversal. 29+ 30* `prev` points to the traverse_info which was used to descend into the 31current tree. If this is the top-level tree `prev` will point to 32a dummy traverse_info. 33 34* `name` is the entry for the current tree (if the tree is a subtree). 35 36* `pathlen` is the length of the full path for the current tree. 37 38* `conflicts` can be used by callbacks to maintain directory-file conflicts. 39 40* `fn` is a callback called for each entry in the tree. See Traversing for more 41information. 42 43* `data` can be anything the `fn` callback would want to use. 44 45Initializing 46------------ 47 48`init_tree_desc`:: 49 50 Initialize a `tree_desc` and decode its first entry. The buffer and 51 size parameters are assumed to be the same as the buffer and size 52 members of `struct tree`. 53 54`fill_tree_descriptor`:: 55 56 Initialize a `tree_desc` and decode its first entry given the sha1 of 57 a tree. Returns the `buffer` member if the sha1 is a valid tree 58 identifier and NULL otherwise. 59 60`setup_traverse_info`:: 61 62 Initialize a `traverse_info` given the pathname of the tree to start 63 traversing from. The `base` argument is assumed to be the `path` 64 member of the `name_entry` being recursed into unless the tree is a 65 top-level tree in which case the empty string ("") is used. 66 67Walking 68------- 69 70`tree_entry`:: 71 72 Visit the next entry in a tree. Returns 1 when there are more entries 73 left to visit and 0 when all entries have been visited. This is 74 commonly used in the test of a while loop. 75 76`tree_entry_len`:: 77 78 Calculate the length of a tree entry's pathname. This utilizes the 79 memory structure of a tree entry to avoid the overhead of using a 80 generic strlen(). 81 82`update_tree_entry`:: 83 84 Walk to the next entry in a tree. This is commonly used in conjunction 85 with `tree_entry_extract` to inspect the current entry. 86 87`tree_entry_extract`:: 88 89 Decode the entry currently being visited (the one pointed to by 90 `tree_desc's` `entry` member) and return the sha1 of the entry. The 91 `pathp` and `modep` arguments are set to the entry's pathname and mode 92 respectively. 93 94`get_tree_entry`:: 95 96 Find an entry in a tree given a pathname and the sha1 of a tree to 97 search. Returns 0 if the entry is found and -1 otherwise. The third 98 and fourth parameters are set to the entry's sha1 and mode 99 respectively. 100 101Traversing 102---------- 103 104`traverse_trees`:: 105 106 Traverse `n` number of trees in parallel. The `fn` callback member of 107 `traverse_info` is called once for each tree entry. 108 109`traverse_callback_t`:: 110 The arguments passed to the traverse callback are as follows: 111+ 112* `n` counts the number of trees being traversed. 113 114* `mask` has its nth bit set if something exists in the nth entry. 115 116* `dirmask` has its nth bit set if the nth tree's entry is a directory. 117 118* `entry` is an array of size `n` where the nth entry is from the nth tree. 119 120* `info` maintains the state of the traversal. 121 122+ 123Returning a negative value will terminate the traversal. Otherwise the 124return value is treated as an update mask. If the nth bit is set the nth tree 125will be updated and if the bit is not set the nth tree entry will be the 126same in the next callback invocation. 127 128`make_traverse_path`:: 129 130 Generate the full pathname of a tree entry based from the root of the 131 traversal. For example, if the traversal has recursed into another 132 tree named "bar" the pathname of an entry "baz" in the "bar" 133 tree would be "bar/baz". 134 135`traverse_path_len`:: 136 137 Calculate the length of a pathname returned by `make_traverse_path`. 138 This utilizes the memory structure of a tree entry to avoid the 139 overhead of using a generic strlen(). 140 141Authors 142------- 143 144Written by Junio C Hamano <gitster@pobox.com> and Linus Torvalds 145<torvalds@linux-foundation.org>