utils: floating-point number support in size-to-bytes conversion

[Meetp369]

This PR addresses an issue, which is that the flb_utils_size_to_bytes function is only processing non-floating numbers even after providing a floating-number in configuration.

It would address one aspect of the performance issues (Ref: #8673)

---

• Consider a case where the input plugin is winevtlog and the output plugin is stdout.

1. If read_limit_per_cycle is set to 1.8 M,

• Configuration file for the above scenario

[SERVICE]
    flush        1
    daemon       Off
    log_level    debug
    parsers_file parsers.conf
    plugins_file plugins.con
    http_server  Off
    http_listen  0.0.0.0
    http_port    2020
    storage.metrics on

[INPUT]
    Name         winevtlog
    Channels     Setup,Windows PowerShell
    Interval_Sec 60
    read_existing_events true
    render_event_as_xml true
    read_limit_per_cycle 1.8M

[OUTPUT]
    name  stdout
    match *

• Output for the above configuration in debug mode to check, which value is set up for the read_limit_per_cycle parameter.

[2024/04/23 18:34:22] [debug] [input:winevtlog:winevtlog.0] read limit per cycle is set up as 976.6K

• It only sets 976.6k (human_readable_size) as the read_limit_per_cycle parameter value, but it should be 1.7M (human_readable_size).

2. If read_limit_per_cycle is set to 1.2M

• Output for the above configuration in debug mode to check which value is set up for the read_limit_per_cycle parameter if read_limit_per_cycle is set to 1.2M

[2024/04/23 18:42:00] [debug] [input:winevtlog:winevtlog.0] read limit per cycle is set up as 976.6K

• In this case also, the read_limit_per_cycle parameter value sets 976.6k (human_readable_size), but it should be 1.1M (human_readable_size).

---

Enter [N/A] in the box, if an item is not applicable to your change.

Testing
Before we can approve your change; please submit the following in a comment:

• Example configuration file for the change
• Debug log output from testing the change

• [N/A] Attached Valgrind output that shows no leaks or memory corruption was found

If this is a change to packaging of containers or native binaries then please confirm it works for all targets.

• [N/A] Run local packaging test showing all targets (including any new ones) build.
• [N/A] Set ok-package-test label to test for all targets (requires maintainer to do).

Documentation

• [N/A] Documentation required for this feature

Backporting

• [N/A] Backport to latest stable release.

---

Fluent Bit is licensed under Apache 2.0, by submitting this pull request I understand that this code will be released under the terms of that license.

[cosmo0920]

Basically, the change looks attractive. But, is there any chance to add unit tests to verify whether this change is effective or not?
You can add your adding test(s) in https://github.com/fluent/fluent-bit/blob/master/tests/internal/utils.c.

[Meetp369]

Basically, the change looks attractive. But, is there any chance to add unit tests to verify whether this change is effective or not? You can add your adding test(s) in https://github.com/fluent/fluent-bit/blob/master/tests/internal/utils.c.

Okay, I've added a unit test for the change!!

[cosmo0920]

Looks attractive. 👍