UTHASH(3)

NAME
uthash - C macros to add, find and delete items from a hash

SYNOPSIS
HASH_ADD        (hh_name, head, keyfield_name, key_len, item_ptr)
HASH_ADD_KEYPTR (hh_name, head, key_ptr, key_len, item_ptr)
HASH_FIND       (hh_name, head, key_ptr, key_len, item_ptr)
HASH_DELETE     (hh_name, head, item_ptr)
HASH_SORT       (head, cmp)
HASH_ADD_INT    (head, keyfield_name, item_ptr)
HASH_FIND_INT   (head, key_ptr, item_ptr)
HASH_ADD_STR    (head, keyfield_name, item_ptr)
HASH_FIND_STR   (head, key_ptr, item_ptr)
HASH_DEL        (head, item_ptr)

DESCRIPTION
These macros add, find, delete and sort items in a hash. The first five generalized macros work with keys of any data type and fields of any name. The latter five convenience macros do the same thing, but take fewer arguments. (In order to use the convenience macros, the structure's UT_hash_handle field must be named hh, and the key field must be of type int or char[]). The arguments are summarized below. Refer to the User Guide: http://uthash.sourceforge.net/userguide.html for a full explanation of the usage of these macros.

ARGUMENTS

hh_name
    name of the UT_hash_handle field in the structure. Conventionally called hh.

head
    the structure pointer variable which acts as the "head" of the hash. So named because it points to the first item which is added to the hash.

keyfield_name
    the name of the key field in the structure. (In the case of a multi-field key, this is the first field of the key). If you're new to macros, it might seem strange to pass the name of a structure field as a parameter. Rest assured the macros expand to valid C code.

key_len
    the length of the key field in bytes. E.g. for an integer key, this is sizeof(int), while for a string key it's strlen(key). (For a multi-field key, see the notes in the User Guide on calculating key length).

key_ptr
    for HASH_FIND, this is a pointer to the key to look up in the hash (since it's a pointer, you can't directly pass a literal value here). For HASH_ADD_KEYPTR, this is the address of the key of the item being added.

item_ptr
    pointer to the structure being added, deleted or looked up. This is an input parameter for HASH_ADD and HASH_DELETE macros, and an output parameter for HASH_FIND.

cmp pointer to comparison function which accepts two arguments (pointers to items to compare) and returns an int specifying whether the first item should sort before, equal to, or after the second item (like strcmp()).

NOTES
HASH_ADD_KEYPTR is used when the structure contains a pointer to the key, rather than the key itself.

AUTHOR
Written by Troy D. Hanson, <thanson@users.sourceforge.net: mailto:thanson@users.sourceforge.net>

RESOURCES
See the uthash web site: http://uthash.sourceforge.net/ for the complete User Guide.