Andrii Nakryiko e4168200de Import libbpf: resizable non-thread safe internal hashmap ...

This is a copy of the kernels/libbpf hashmap
 tools/lib/bpf/hashmap.{h,c}

The plan is to prototype an AF_XDP/xsk userspace API for accessing
BTF information, that should be moved to libbpf (or libxdp).  Thus,
this hashmap code will become avail if successful.

Original kernel commit 553db8ba73df ("libbpf: add resizable non-thread
safe internal hashmap") (Author: Andrii Nakryiko). Thus, giving Andrii
author credit in this git commit.

Andrii Nakryiko said:

    libbpf: add resizable non-thread safe internal hashmap

    There is a need for fast point lookups inside libbpf for multiple use
    cases (e.g., name resolution for BTF-to-C conversion, by-name lookups in
    BTF for upcoming BPF CO-RE relocation support, etc). This patch
    implements simple resizable non-thread safe hashmap using single linked
    list chains.

    Four different insert strategies are supported:
     - HASHMAP_ADD - only add key/value if key doesn't exist yet;
     - HASHMAP_SET - add key/value pair if key doesn't exist yet; otherwise,
       update value;
     - HASHMAP_UPDATE - update value, if key already exists; otherwise, do
       nothing and return -ENOENT;
     - HASHMAP_APPEND - always add key/value pair, even if key already exists.
       This turns hashmap into a multimap by allowing multiple values to be
       associated with the same key. Most useful read API for such hashmap is
       hashmap__for_each_key_entry() iteration. If hashmap__find() is still
       used, it will return last inserted key/value entry (first in a bucket
       chain).

    For HASHMAP_SET and HASHMAP_UPDATE, old key/value pair is returned, so
    that calling code can handle proper memory management, if necessary.

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>

2021-11-03 11:01:36 +01:00

5.0 KiB

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