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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>
Practical BPF examples
This git repository contains a diverse set of practical BPF examples that solve (or demonstrate) a specific use-case using BPF.
It is meant to ease doing rapid prototyping and development, writing C-code BPF programs using libbpf. The goal is to make is easier for developers to get started coding.
Many developers struggle to get a working BPF build environment. The repo enviroment makes it easy to build/compile BPF programs by doing the necessary libbpf setup transparently and detect missing compile dependencies (via the (configure)[configure] script). It is a declared goal to make BPF programming more consumable by detecting and reporting issues (when possible).