Merge pull request #189 from andyjgf/bazel_doc

Add Bazel build instructions.

Bazel.md

@@ -0,0 +1,100 @@
+# Use as a Bazel Dependency
+
+To use libcbor in your
+[Baze](https://bazel.build/)
+project, first add the following section to your project's `WORKSPACE` file.
+Note the location of the `third_party/libcbor.BUILD` file - you may use a
+different location if you wish, but you the file must be make available to
+`WORKSPACE`.
+
+## WORKSPACE
+
+Note, this imports version `0.8.0` - you may need to update the version and
+the sha256 hash.
+
+```python
+# libcbor
+http_archive(
+    name = "libcbor",
+    build_file = "//third_party:libcbor.BUILD",
+    sha256 = "dd04ea1a7df484217058d389e027e7a0143a4f245aa18a9f89a5dd3e1a4fcc9a",
+    strip_prefix = "libcbor-0.8.0",
+    urls = ["https://github.com/PJK/libcbor/archive/refs/tags/v0.8.0.zip"],
+)
+```
+
+## third_party/libcbor.BUILD
+
+Bazel will unzip the libcbor zip file, then copy this file in as `BUILD`.
+Bazel will then use this file to compile libcbor.
+[Cmake](https://cmake.org/)
+is used in two passes: to create the Makefiles, and then to invoke Make to build
+the `libcbor.a` static library. `libcbor.a` and the `.h` files are then made
+available for other packages to use.
+
+```python
+genrule(
+  name = "cbor_cmake",
+  srcs = glob(["**"]),
+  outs = ["libcbor.a", "cbor.h", "cbor/arrays.h", "cbor/bytestrings.h",
+          "cbor/callbacks.h", "cbor/cbor_export.h", "cbor/common.h", "cbor/configuration.h", "cbor/data.h",
+          "cbor/encoding.h", "cbor/floats_ctrls.h", "cbor/ints.h", "cbor/maps.h",
+          "cbor/serialization.h", "cbor/streaming.h", "cbor/strings.h", "cbor/tags.h"],
+  cmd = " && ".join([
+    # Remember where output should go.
+    "INITIAL_WD=`pwd`",
+    # Build libcbor library.
+    "cd `dirname $(location CMakeLists.txt)`",
+    "cmake -DCMAKE_BUILD_TYPE=Release -DCBOR_CUSTOM_ALLOC=ON .",
+    "cmake --build .",
+    # Export the .a and .h files for cbor rule, below.
+    "cp src/libcbor.a src/cbor.h $$INITIAL_WD/$(RULEDIR)",
+    "cp src/cbor/*h cbor/configuration.h $$INITIAL_WD/$(RULEDIR)/cbor"]),
+  visibility = ["//visibility:private"],
+)
+
+cc_import(
+  name = "cbor",
+  hdrs = ["cbor.h", "cbor/arrays.h", "cbor/bytestrings.h",
+          "cbor/callbacks.h", "cbor/cbor_export.h", "cbor/common.h", "cbor/configuration.h", "cbor/data.h",
+          "cbor/encoding.h", "cbor/floats_ctrls.h", "cbor/ints.h", "cbor/maps.h",
+          "cbor/serialization.h", "cbor/streaming.h", "cbor/strings.h", "cbor/tags.h"],
+  static_library = "libcbor.a",
+  visibility = ["//visibility:public"],
+)
+```
+
+## third_party/BUILD
+
+The `libcbor.BUILD` file must be make available to the top-level `WORKSPACE`
+file:
+
+```python
+exports_files(["libcbor.BUILD"]))
+```
+
+## Your BUILD File
+
+Add libcbor dependency to your package's `BUILD` file like so:
+
+```python
+cc_library(
+    name = "...",
+    srcs = [ ... ],
+    hdrs = [ ... ],
+    deps = [
+        ...
+        "@libcbor//:cbor",
+    ],
+)
+```
+
+## Your C File
+
+Now you may simply include `cbor.h`:
+
+```c
+#include "cbor.h"
+
+static const uint8_t version = cbor_major_version;
+```