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 45* `show_all_errors` tells whether to stop at the first error or not. 46 47Initializing 48------------ 49 50`init_tree_desc`:: 51 52 Initialize a `tree_desc` and decode its first entry. The buffer and 53 size parameters are assumed to be the same as the buffer and size 54 members of `struct tree`. 55 56`fill_tree_descriptor`:: 57 58 Initialize a `tree_desc` and decode its first entry given the sha1 of 59 a tree. Returns the `buffer` member if the sha1 is a valid tree 60 identifier and NULL otherwise. 61 62`setup_traverse_info`:: 63 64 Initialize a `traverse_info` given the pathname of the tree to start 65 traversing from. The `base` argument is assumed to be the `path` 66 member of the `name_entry` being recursed into unless the tree is a 67 top-level tree in which case the empty string ("") is used. 68 69Walking 70------- 71 72`tree_entry`:: 73 74 Visit the next entry in a tree. Returns 1 when there are more entries 75 left to visit and 0 when all entries have been visited. This is 76 commonly used in the test of a while loop. 77 78`tree_entry_len`:: 79 80 Calculate the length of a tree entry's pathname. This utilizes the 81 memory structure of a tree entry to avoid the overhead of using a 82 generic strlen(). 83 84`update_tree_entry`:: 85 86 Walk to the next entry in a tree. This is commonly used in conjunction 87 with `tree_entry_extract` to inspect the current entry. 88 89`tree_entry_extract`:: 90 91 Decode the entry currently being visited (the one pointed to by 92 `tree_desc's` `entry` member) and return the sha1 of the entry. The 93 `pathp` and `modep` arguments are set to the entry's pathname and mode 94 respectively. 95 96`get_tree_entry`:: 97 98 Find an entry in a tree given a pathname and the sha1 of a tree to 99 search. Returns 0 if the entry is found and -1 otherwise. The third 100 and fourth parameters are set to the entry's sha1 and mode 101 respectively. 102 103Traversing 104---------- 105 106`traverse_trees`:: 107 108 Traverse `n` number of trees in parallel. The `fn` callback member of 109 `traverse_info` is called once for each tree entry. 110 111`traverse_callback_t`:: 112 The arguments passed to the traverse callback are as follows: 113+ 114* `n` counts the number of trees being traversed. 115 116* `mask` has its nth bit set if something exists in the nth entry. 117 118* `dirmask` has its nth bit set if the nth tree's entry is a directory. 119 120* `entry` is an array of size `n` where the nth entry is from the nth tree. 121 122* `info` maintains the state of the traversal. 123 124+ 125Returning a negative value will terminate the traversal. Otherwise the 126return value is treated as an update mask. If the nth bit is set the nth tree 127will be updated and if the bit is not set the nth tree entry will be the 128same in the next callback invocation. 129 130`make_traverse_path`:: 131 132 Generate the full pathname of a tree entry based from the root of the 133 traversal. For example, if the traversal has recursed into another 134 tree named "bar" the pathname of an entry "baz" in the "bar" 135 tree would be "bar/baz". 136 137`traverse_path_len`:: 138 139 Calculate the length of a pathname returned by `make_traverse_path`. 140 This utilizes the memory structure of a tree entry to avoid the 141 overhead of using a generic strlen(). 142 143Authors 144------- 145 146Written by Junio C Hamano <gitster@pobox.com> and Linus Torvalds 147<torvalds@linux-foundation.org>