Co-authored-by: Alejandro Colomar <alx@kernel.org>
Signed-off-by: Alejandro Colomar <alx@kernel.org>
Signed-off-by: Andrew Clayton <a.clayton@nginx.com>

Signed-off-by: Andrew Clayton <a.clayton@nginx.com>

This adds two helper function that will be used in subsequent commits.

nxt_http_comp_compress() does the actual compression.

nxt_http_comp_bound() returns the maximum compressed size for the given
size.

Signed-off-by: Andrew Clayton <a.clayton@nginx.com>

This exposes a new "settings.http.compression" configuration object.

Under which are types & compressors objects.

types is used to specify what MIME types should be considered
compressible.

compressors is used to configure an array of compressors that are
available. For each of these, you specify the encoding, e.g gzip and
optional level and min_length parameters. Where level is what
compression level to use and min_length is the minimum length of data
that should be compressed.

By default the default compression level for the specified compressor is
used and there is no minimum data length considered for compression.

It may look something like

    "settings": {
        "http": {
            "server_version": true,
            "static": {
                "mime_types": {
                    "text/x-c": [
                        ".c",
                        ".h"
                    ]
                }
            },
            "compression": {
                "types": [
                    "text/*"
                ],
                "compressors": [
                    {
                        "encoding": "gzip",
                        "level": 3,
                        "min_length": 2048
                    },
                    {
                        "encoding": "deflate",
                        "min_length": 1024
                    },
                    {
                        "encoding": "zstd",
                        "min_length": 2048
                    },
                    {
                        "encoding": "br",
                        "min_length": 256
                    }
                ]
            }
        }
    },

Currently this is a global option that will effect both static and
application responses.

In future it should be possible to add per-application (and perhaps even
per-static) configuration.

Signed-off-by: Andrew Clayton <a.clayton@nginx.com>

This allows to actually build unit with support fro zlib, zstd and
brotli compression.

Any or all can be specified. E.g.

  $ ./configure --zlib ...

  $ ./configure --zlib --zstd --brotli ...

During configure you will see if support for the requested compressions
has been found and what version of the library is being used.

E.g.

  ...
  checking for zlib ... found
   + zlib version: 1.3.1.zlib-ng
  checking for zstd ... found
   + zstd version: 1.5.6
  checking for brotli ... found
   + brotli version: 1.1.0
  ...
  Unit configuration summary:
  ...
    zlib support: .............. YES
    zstd support: .............. YES
    brotli support: ............ YES
  ...

Co-authored-by: Alejandro Colomar <alx@kernel.org>
Signed-off-by: Alejandro Colomar <alx@kernel.org>
Signed-off-by: Andrew Clayton <a.clayton@nginx.com>

Signed-off-by: Andrew Clayton <a.clayton@nginx.com>

Signed-off-by: Andrew Clayton <a.clayton@nginx.com>

This adds support for both deflate & gzip compressors.

Signed-off-by: Andrew Clayton <a.clayton@nginx.com>

This is the initial step to enabling HTTP compression on both static and
application responses.

This code itself doesn't do any actual compression, that will come in
subsequent commits. It just contains the core functions for initialising
structures that describe the available compressors and functions for
checking if compression should be done depending on various criteria.

Signed-off-by: Andrew Clayton <a.clayton@nginx.com>