77 lines
2.2 KiB
Plaintext
77 lines
2.2 KiB
Plaintext
sha1-array API
|
|
==============
|
|
|
|
The sha1-array API provides storage and manipulation of sets of SHA1
|
|
identifiers. The emphasis is on storage and processing efficiency,
|
|
making them suitable for large lists. Note that the ordering of items is
|
|
not preserved over some operations.
|
|
|
|
Data Structures
|
|
---------------
|
|
|
|
`struct sha1_array`::
|
|
|
|
A single array of SHA1 hashes. This should be initialized by
|
|
assignment from `SHA1_ARRAY_INIT`. The `sha1` member contains
|
|
the actual data. The `nr` member contains the number of items in
|
|
the set. The `alloc` and `sorted` members are used internally,
|
|
and should not be needed by API callers.
|
|
|
|
Functions
|
|
---------
|
|
|
|
`sha1_array_append`::
|
|
Add an item to the set. The sha1 will be placed at the end of
|
|
the array (but note that some operations below may lose this
|
|
ordering).
|
|
|
|
`sha1_array_lookup`::
|
|
Perform a binary search of the array for a specific sha1.
|
|
If found, returns the offset (in number of elements) of the
|
|
sha1. If not found, returns a negative integer. If the array is
|
|
not sorted, this function has the side effect of sorting it.
|
|
|
|
`sha1_array_clear`::
|
|
Free all memory associated with the array and return it to the
|
|
initial, empty state.
|
|
|
|
`sha1_array_for_each_unique`::
|
|
Efficiently iterate over each unique element of the list,
|
|
executing the callback function for each one. If the array is
|
|
not sorted, this function has the side effect of sorting it.
|
|
|
|
Examples
|
|
--------
|
|
|
|
-----------------------------------------
|
|
void print_callback(const unsigned char sha1[20],
|
|
void *data)
|
|
{
|
|
printf("%s\n", sha1_to_hex(sha1));
|
|
}
|
|
|
|
void some_func(void)
|
|
{
|
|
struct sha1_array hashes = SHA1_ARRAY_INIT;
|
|
unsigned char sha1[20];
|
|
|
|
/* Read objects into our set */
|
|
while (read_object_from_stdin(sha1))
|
|
sha1_array_append(&hashes, sha1);
|
|
|
|
/* Check if some objects are in our set */
|
|
while (read_object_from_stdin(sha1)) {
|
|
if (sha1_array_lookup(&hashes, sha1) >= 0)
|
|
printf("it's in there!\n");
|
|
|
|
/*
|
|
* Print the unique set of objects. We could also have
|
|
* avoided adding duplicate objects in the first place,
|
|
* but we would end up re-sorting the array repeatedly.
|
|
* Instead, this will sort once and then skip duplicates
|
|
* in linear time.
|
|
*/
|
|
sha1_array_for_each_unique(&hashes, print_callback, NULL);
|
|
}
|
|
-----------------------------------------
|