nxt_min()
nxt_max()
    Return the minimum/maximum of two values.

nxt_swap()
    Swap the values of two variables passed by their addresses.

nxt_sizeof_array()
    Return the size (in bytes) of an array.

nxt_nitems()
    Return the number of elements in an array.

nxt_memberof()
    Expand to a member of a structure.  It uses a compound literal for
    the object.

nxt_sizeof_incomplete()
    Calculate the size of an incomplete type, as if sizeof() could be
    applied to it.

nxt_sizeof_fam0()
    Calculate the size of each element of a FAM of a structure.

nxt_sizeof_fam()
    Calculate the size of a FAM of a structure.

nxt_offsetof_fam()
    Calculate the offset of the nth element of the FAM from the start of
    the containing structure.

nxt_sizeof_struct()
    Calculate the total size of a structure containing a FAM.  This
    value is the one that should be used for allocating the structure.

    Suggested-by: Andrew Clayton <[email protected]>

nxt_is_near_end()
    Evaluate to true if the member is near the end of a structure.  This
    is only designed to be used with FAMs, to make sure that the FAM is
    near the end of the structure (a zero-length array near the end of
    the structure would still pass this test, but it's a reasonable
    assertion to do.

    Suggested-by: David Laight <[email protected]>

nxt_is_zero_sizeof()
    Evaluate to true if the size of 'x' is 0.

nxt_is_same_type()
    Evaluate to true if the both arguments are compatible types.

nxt_is_same_typeof()
    Evaluate to true if the types of both arguments are compatible.

nxt_is_array()
    Evaluate to true if the argument is an array.

nxt_must_be()
    It's like static_assert(3), but implemented as an expression.  It's
    necessary for writing the must_be_array() macro.  It's always
    evaluates to (int) 0.

nxt_must_be_array()
    Statically assert that the argument is an array.  It is an
    expression that always evaluates to (int) 0.

nxt_must_be_zero_sizeof()
    Statically assert that the argument has a size of 0.

nxt_must_be_near_end()
    Statically assert that a member of a structure is near the end of
    it.

    Suggested-by: David Laight <[email protected]>

nxt_must_be_fam()
    Statically assert that the argument is a flexible array member
    (FAM).  It's an expression that always evaluates to (int) 0.

Link: <https://gustedt.wordpress.com/2011/03/14/flexible-array-member/>
Link: <https://lore.kernel.org/lkml/202308161913.91369D4A@keescook/T/>
Link: <https://inbox.sourceware.org/gcc/[email protected]/T/>
Link: <https://stackoverflow.com/a/57537491>
Link: <shadow-maint/shadow#762>
Cc: Andrew Clayton <[email protected]>
Cc: Zhidao Hong <[email protected]>
Signed-off-by: Alejandro Colomar <[email protected]>

This will allow sending the header from a totally different point, since
the data for the call is present in the request, which is available
everywhere.

It will also allow consulting in a filter if there is a body_handler
installed.  The gzip filter will need this, as it should be a no-op if
there is no body handler installed.

Signed-off-by: Alejandro Colomar <[email protected]>

Filter handlers are a new handler that takes place when a buffer is
about to be sent.  It filters (modifies) the contents of the buffer
in-place, so that the new contents will be sent.  Several filters can be
applied in a loop.

Signed-off-by: Alejandro Colomar <[email protected]>

There are still no supported encodings.  This is just infrastructure for
the next commits, which will add gzip compression.

Signed-off-by: Alejandro Colomar <[email protected]>

Signed-off-by: Alejandro Colomar <[email protected]>

Signed-off-by: Alejandro Colomar <[email protected]>

Related to:

    HTTP: compress: gzip

Signed-off-by: Alejandro Colomar <[email protected]>

They're really more inspired in the API of BSD's strto[iu](3), but use
long just to keep it simple, instead of intmax_t, and since they wrap
strtol(3), I called them like it.

Signed-off-by: Alejandro Colomar <[email protected]>

With this, short responses, that is, responses with a body of up to
content_length_threshold bytes, won't be compressed.  The default value
is 20, as in NGINX.

Signed-off-by: Alejandro Colomar <[email protected]>

Signed-off-by: Alejandro Colomar <[email protected]>

Signed-off-by: Alejandro Colomar <[email protected]>

These are based on C23's <stdbit.h>.

Signed-off-by: Alejandro Colomar <[email protected]>

When the content length is small, optimize zlib for low memory usage.
Conversely, when the content length is large, use a similar amount of
memory within zlib, as it will improve compression, and won't hurt
significantly.

Signed-off-by: Alejandro Colomar <[email protected]>