Build state

Twofold binding to libsodium, a modern, portable, easy to use crypto library; support of current libsodium version v1.0.18, released May 31, 2019.

subPackage deimos: The "import-only" C header's declarations.
subPackage wrapper: The content of deimos + some 'D-friendly' stuff, predominantly overloaded functions and unittests.

The dependency name is either sodium:deimos or sodium:wrapper (for dub build|test simply: :deimos or :wrapper)

IMPORTANT NOTICE
deimos/dub.json and wrapper/dub.json set as default: "versions": ["bin_v1_0_18", "SODIUM_LIBRARY_MINIMAL"]

1. If the binary to link against is not compiled with ./configure --enable-minimal and You want to use the low-level functions, then remove
   , "SODIUM_LIBRARY_MINIMAL"
   from "versions".
2. If not linking against v1.0.18 binary libsodium.so/.dll/.dylib, it's required to specify/change that in deimos/dub.json and wrapper/dub.json:
   In the past while I maintained this binding, it was kind of independent from binary libsodium versions: The last binding release supporting headers of libsodium 1.016 could be used with a binary versioned e.g. 1.014, 1.016 (or probably 1.018, actually not possible), because in C headers (so far) only functions where added, and the compiler/linker would complain, if (new) functions not available from the (older) binary/import library should be called. This also holds for Windows, if You don't trick the compiler with a non-associated pair of import .lib/binary .dll.
   Now for the first time (since v1.0.17) a constant changed it's value as well as a struct size change occured and the easy times are gone.
   This is solved by conditional compilation, which is guided by the following version identifiers, one of which - the correct one matching the binary - must be used: bin_v1_0_18, bin_v1_0_17 or bin_v1_0_16 (bin_v1_0_16 subsumes any libsodium binary version lower than v1.0.16 as well). The dub.json s set bin_v1_0_18 as default, stating the binary version v1.0.18 expected to link against.

A version mismatch of binding-adaption and libsodium binary can do any harm as undefined behavior can do, like memory corruption or worse, a SIGSEGV in the best case.

(The versioning of this binding doesn't matter here, but to make things more intuitive, it'll change to reflect the latest (libsodium C source) header version covered, the next/this will be something like 1.0.18-alpha.1).

wrapper is based on DIP1008/compiler switch -dip1008; this rules out the gdc compiler currently (I didn't find any info about that). dmd/ldc support it since 2.078.3.
DIP1008 is the enabling feature used for @nogc exceptions, implemented via dependency package nogc.
wrapper also supports usage of -dip1000 (includes -dip25). dub build|test :wrapper --config=travis uses that but it's not set as default for any other configuration.
END_NOTICE

wrapper aims at providing at least the same functionality as deimos and provide @trusted @nogc (possibly also pure nothrow) 'D-friendly' alternatives, that are hard to use in a wrong way; [WIP]:
a) 'wrapper' is a superset of 'deimos' in that everything from 'deimos' is reachable, but deliberately not all at your fingertips.
b) all new functions with 'deimos-functionality' have the same name as their 'deimos'-cousins and call them, building either overload sets to choose from, or for parameter-less functions, 'substituting' their cousins.
c) all new functions calculating a variable-length output are restrictive referring to the size of the output-buffer offered, if the required size can be easily known/computed in advance, throwing (a NoGcException) in case of wrong-sized buffers.
This way, if a function succeeds, all output-buffer.length bytes are meaningful and no additional/'deimos'-like function out parameter carrying the meaningful length information is required.
d) Exceptions thrown while checking valid function arguments are NOT allocated by GC, enabling @nobc attribue usage.
e) No need to explicitely call sodium_init() up-front (wrapper.sodium.core:shared static this() calls it).
f) A few functions with int return type expressing true or false have bool return type in 'wrapper'.
g) Usage of 'wrapper' isn't possible, if function randombytes_set_implementation shall be used.

The unittests of subPackage 'wrapper' include a lot of function usage examples; the next is a simple application example, using rdmd and file cmdfile, suitable as is for Linux with libsodium.so available (otherwise example/source/cmdfile and/or first line of app.d might need adaption):

$ cd example/source && chmod +x app.d && ./app.d

Expected output (byte values within brackets differing of course):

Unpredictable sequence of 8 bytes: [52, 225, 21, 245, 74, 66, 192, 247]
crypto_aead_aes256gcm_is_available
ciphertext: [76, 18, 112, 219, 144, 230, 206, 219, 40, 255, 78, 43, 172, 49, 129, 175, 4, 235, 81, 224]

Heap allocations: Quoting the Sodium-manual: "Cryptographic operations in Sodium (C binary) never allocate memory on the heap (malloc, calloc, etc.) with the obvious exceptions of crypto_pwhash and sodium_malloc."
The same holds, if usage is restricted to sodium:deimos and also holds for many (@nogc) functions of sodium:wrapper.