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148 строки
4.3 KiB
Plaintext
148 строки
4.3 KiB
Plaintext
tree walking API
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================
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The tree walking API is used to traverse and inspect trees.
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Data Structures
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---------------
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`struct name_entry`::
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An entry in a tree. Each entry has a sha1 identifier, pathname, and
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mode.
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`struct tree_desc`::
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A semi-opaque data structure used to maintain the current state of the
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walk.
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+
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* `buffer` is a pointer into the memory representation of the tree. It always
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points at the current entry being visited.
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* `size` counts the number of bytes left in the `buffer`.
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* `entry` points to the current entry being visited.
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`struct traverse_info`::
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A structure used to maintain the state of a traversal.
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+
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* `prev` points to the traverse_info which was used to descend into the
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current tree. If this is the top-level tree `prev` will point to
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a dummy traverse_info.
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* `name` is the entry for the current tree (if the tree is a subtree).
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* `pathlen` is the length of the full path for the current tree.
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* `conflicts` can be used by callbacks to maintain directory-file conflicts.
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* `fn` is a callback called for each entry in the tree. See Traversing for more
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information.
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* `data` can be anything the `fn` callback would want to use.
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* `show_all_errors` tells whether to stop at the first error or not.
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Initializing
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------------
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`init_tree_desc`::
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Initialize a `tree_desc` and decode its first entry. The buffer and
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size parameters are assumed to be the same as the buffer and size
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members of `struct tree`.
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`fill_tree_descriptor`::
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Initialize a `tree_desc` and decode its first entry given the
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object ID of a tree. Returns the `buffer` member if the latter
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is a valid tree identifier and NULL otherwise.
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`setup_traverse_info`::
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Initialize a `traverse_info` given the pathname of the tree to start
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traversing from. The `base` argument is assumed to be the `path`
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member of the `name_entry` being recursed into unless the tree is a
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top-level tree in which case the empty string ("") is used.
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Walking
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-------
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`tree_entry`::
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Visit the next entry in a tree. Returns 1 when there are more entries
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left to visit and 0 when all entries have been visited. This is
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commonly used in the test of a while loop.
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`tree_entry_len`::
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Calculate the length of a tree entry's pathname. This utilizes the
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memory structure of a tree entry to avoid the overhead of using a
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generic strlen().
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`update_tree_entry`::
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Walk to the next entry in a tree. This is commonly used in conjunction
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with `tree_entry_extract` to inspect the current entry.
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`tree_entry_extract`::
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Decode the entry currently being visited (the one pointed to by
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`tree_desc's` `entry` member) and return the sha1 of the entry. The
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`pathp` and `modep` arguments are set to the entry's pathname and mode
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respectively.
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`get_tree_entry`::
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Find an entry in a tree given a pathname and the sha1 of a tree to
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search. Returns 0 if the entry is found and -1 otherwise. The third
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and fourth parameters are set to the entry's sha1 and mode
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respectively.
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Traversing
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----------
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`traverse_trees`::
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Traverse `n` number of trees in parallel. The `fn` callback member of
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`traverse_info` is called once for each tree entry.
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`traverse_callback_t`::
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The arguments passed to the traverse callback are as follows:
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+
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* `n` counts the number of trees being traversed.
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* `mask` has its nth bit set if something exists in the nth entry.
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* `dirmask` has its nth bit set if the nth tree's entry is a directory.
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* `entry` is an array of size `n` where the nth entry is from the nth tree.
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* `info` maintains the state of the traversal.
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Returning a negative value will terminate the traversal. Otherwise the
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return value is treated as an update mask. If the nth bit is set the nth tree
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will be updated and if the bit is not set the nth tree entry will be the
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same in the next callback invocation.
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`make_traverse_path`::
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Generate the full pathname of a tree entry based from the root of the
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traversal. For example, if the traversal has recursed into another
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tree named "bar" the pathname of an entry "baz" in the "bar"
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tree would be "bar/baz".
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`traverse_path_len`::
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Calculate the length of a pathname returned by `make_traverse_path`.
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This utilizes the memory structure of a tree entry to avoid the
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overhead of using a generic strlen().
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Authors
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-------
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Written by Junio C Hamano <gitster@pobox.com> and Linus Torvalds
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<torvalds@linux-foundation.org>
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