diff --git a/DataStructures/radix-tree.md b/DataStructures/radix-tree.md index 73c4b79..49d7e55 100644 --- a/DataStructures/radix-tree.md +++ b/DataStructures/radix-tree.md @@ -41,9 +41,9 @@ Lets talk about what a `radix tree` is. Radix tree is a `compressed trie` where                             +-----------+ ``` -So in this example, we can see the `trie` with keys, `go` and `cat`. A compressed trie or `radix tree` differs from a `trie` in that all intermediates nodes which have only one child are removed. +So in this example, we can see the `trie` with keys, `go` and `cat`. The compressed trie or `radix tree` differs from `trie` in that all intermediates nodes which have only one child are removed. -Radix tree in linux kernel is the data structure which maps values to the integer key. It is represented by the following structures from the file [include/linux/radix-tree.h](https://github.com/torvalds/linux/blob/master/include/linux/radix-tree.h): +Radix tree in linux kernel is the datastructure which maps values to integer keys. It is represented by the following structures from the file [include/linux/radix-tree.h](https://github.com/torvalds/linux/blob/master/include/linux/radix-tree.h): ```C struct radix_tree_root { @@ -56,14 +56,20 @@ struct radix_tree_root { This structure presents the root of a radix tree and contains three fields: * `height` - height of the tree; -* `gfp_mask` - tells how memory allocations are to be performed; +* `gfp_mask` - tells how memory allocations will be performed; * `rnode` - pointer to the child node. -The first structure we will discuss is `gfp_mask`: +The first field we will discuss is `gfp_mask`: Low-level kernel memory allocation functions take a set of flags as - `gfp_mask`, which describes how that allocation is to be performed. These `GFP_` flags which control the allocation process can have following values: (`GF_NOIO` flag) means sleep and wait for memory, (`__GFP_HIGHMEM` flag) means high memory can be used, (`GFP_ATOMIC` flag) means the allocation process has high-priority and can't sleep etc. -The next structure is `rnode`: +* `GFP_NOIO` - can sleep and wait for memory; +* `__GFP_HIGHMEM` - high memory can be used; +* `GFP_ATOMIC` - allocation process is high-priority and can't sleep; + +etc. + +The next field is `rnode`: ```C struct radix_tree_node { @@ -83,7 +89,7 @@ struct radix_tree_node { }; ``` -This structure contains information about the offset in a parent and height from the bottom, count of the child nodes and fields for accessing and freeing a node. The fields are described below: +This structure contains information about the offset in a parent and height from the bottom, count of the child nodes and fields for accessing and freeing a node. This fields are described below: * `path` - offset in parent & height from the bottom; * `count` - count of the child nodes; @@ -99,7 +105,7 @@ Now that we know about radix tree structure, it is time to look on its API. Linux kernel radix tree API --------------------------------------------------------------------------------- -We start from the data structure intialization. There are two ways to initialize new radix tree. The first is to use `RADIX_TREE` macro: +We start from the datastructure initialization. There are two ways to initialize a new radix tree. The first is to use `RADIX_TREE` macro: ```C RADIX_TREE(name, gfp_mask); @@ -140,10 +146,10 @@ do { \ makes the same initialziation with default values as it does `RADIX_TREE_INIT` macro. -The next are two functions for the inserting and deleting records to/from a radix tree: +The next are two functions for inserting and deleting records to/from a radix tree: * `radix_tree_insert`; -* `radix_tree_delete`. +* `radix_tree_delete`; The first `radix_tree_insert` function takes three parameters: @@ -173,7 +179,7 @@ unsigned int radix_tree_gang_lookup(struct radix_tree_root *root, unsigned int max_items); ``` -and returns number of records, sorted by the keys, starting from the first index. Number of the returned records will be not greater than `max_items` value. +and returns number of records, sorted by the keys, starting from the first index. Number of the returned records will not be greater than `max_items` value. And the last `radix_tree_lookup_slot` function will return the slot which will contain the data.