Download the NDK in Bazel

README.md

@@ -28,12 +28,31 @@ To use the Android NDK rules, add the following to your `WORKSPACE` file:
         sha256 = RULES_ANDROID_NDK_SHA,
         strip_prefix = "rules_android_ndk-%s" % RULES_ANDROID_NDK_COMMIT,
     )
-    load("@rules_android_ndk//:rules.bzl", "android_ndk_repository")
-    android_ndk_repository(name = "androidndk")
 
-Then, set the `ANDROID_NDK_HOME` environment variable or the `path` attribute of
-`android_ndk_repository` to the path of the local Android NDK installation
-directory.
+    load("@rules_android_ndk//:rules.bzl", "android_ndk_repository")
+    android_ndk_repository(name = "androidndk", version = "r25c")
+
+    # either register the toolchains, or use `--extra_toolchains` when invoking Bazel
+    register_toolchains("@androidndk//:all")
+
+You can also customize the `base_url` attribute if, for example, you mirror the NDK archives
+on a private server.
+
+Some sha256 checksums are included in this repository, but these might not be up to date,
+if you want to use a version of the NDK that's not included, you can also specify the `sha256sums`
+attribute which maps platforms to checksums, like so:
+
+```
+android_ndk_repository(
+    name = "androidndk",
+    version = "r25c"
+    sha256sums = {
+        "windows": "f70093964f6cbbe19268f9876a20f92d3a593db3ad2037baadd25fd8d71e84e2",
+        "darwin": "b01bae969a5d0bfa0da18469f650a1628dc388672f30e0ba231da5c74245bc92",
+        "linux": "769ee342ea75f80619d985c2da990c48b3d8eaf45f48783a2d48870d04b46108",
+    }
+)
+```
 
 The `api_level` attribute can also be used to set the Android API level to build
 against.

rules.bzl

@@ -14,46 +14,72 @@
 
 """A repository rule for integrating the Android NDK."""
 
+load(":sha256sums.bzl", "ndk_sha256")
+
+def _ndk_platform(ctx):
+    os_name = ctx.os.name.lower()
+    if os_name == "linux":
+        return "linux"
+    elif os_name.startswith("mac os"):
+        return "darwin"
+    elif os_name.startswith("windows"):
+        return "windows"
+    else:
+        fail("Unsupported platform for the Android NDK: {}", ctx.os.name)
+
 def _android_ndk_repository_impl(ctx):
-    """Install the Android NDK files.
+    """Download and extract the Android NDK files.
 
     Args:
         ctx: An implementation context.
 
     Returns:
         A final dict of configuration attributes and values.
     """
-    ndk_path = ctx.attr.path or ctx.os.environ.get("ANDROID_NDK_HOME", None)
-    if not ndk_path:
-        fail("Either the ANDROID_NDK_HOME environment variable or the " +
-             "path attribute of android_ndk_repository must be set.")
 
-    if ctx.os.name == "linux":
+    ndk_version = ctx.attr.version
+    ndk_platform = _ndk_platform(ctx)
+    ndk_url = "{base_url}/android-ndk-{version}-{platform}.zip".format(
+        base_url = ctx.attr.base_url,
+        version = ndk_version,
+        platform = ndk_platform,
+    )
+
+    filename = ndk_url.split("/")[-1]
+    sha256 = ndk_sha256(filename, ctx)
+    prefix = "android-ndk-{}".format(ndk_version)
+
+    result = ctx.download_and_extract(url = ndk_url, sha256 = sha256, stripPrefix = prefix)
+    if not result.success:
+        fail("Failed to download NDK archive", ndk_url)
+
+    if ndk_platform == "linux":
         clang_directory = "toolchains/llvm/prebuilt/linux-x86_64"
-    elif ctx.os.name == "mac os x":
+    elif ndk_platform == "darwin":
         # Note: darwin-x86_64 does indeed contain fat binaries with arm64 slices, too.
         clang_directory = "toolchains/llvm/prebuilt/darwin-x86_64"
+    elif ndk_platform == "windows":
+        clang_directory = "toolchains/llvm/prebuilt/windows-x86_64"
     else:
-        fail("Unsupported operating system: " + ctx.os.name)
+        fail("Unsupported NDK platform", ndk_platform)
 
     sysroot_directory = "%s/sysroot" % clang_directory
 
-    _create_symlinks(ctx, ndk_path, clang_directory, sysroot_directory)
+    # TODO(#32): Remove this hack
+    ctx.symlink("sources", "ndk/sources")
 
-    api_level = ctx.attr.api_level or 31
+    api_level = ctx.attr.api_level
 
     result = ctx.execute([clang_directory + "/bin/clang", "--print-resource-dir"])
     if result.return_code != 0:
         fail("Failed to execute clang: %s" % result.stderr)
     clang_resource_directory = result.stdout.strip().split(clang_directory)[1].strip("/")
 
-    # Use a label relative to the workspace from which this repository rule came
-    # to get the workspace name.
-    repository_name = Label("//:BUILD").workspace_name
+    repository_name = ctx.attr._build.workspace_name
 
     ctx.template(
-        "BUILD",
-        Label("//:BUILD.ndk_root.tpl"),
+        "BUILD.bazel",
+        ctx.attr._template_ndk_root,
         {
             "{clang_directory}": clang_directory,
         },
@@ -62,15 +88,15 @@ def _android_ndk_repository_impl(ctx):
 
     ctx.template(
         "target_systems.bzl",
-        Label("//:target_systems.bzl.tpl"),
+        ctx.attr._template_target_systems,
         {
         },
         executable = False,
     )
 
     ctx.template(
         "%s/BUILD" % clang_directory,
-        Label("//:BUILD.ndk_clang.tpl"),
+        ctx.attr._template_ndk_clang,
         {
             "{repository_name}": repository_name,
             "{api_level}": str(api_level),
@@ -82,52 +108,24 @@ def _android_ndk_repository_impl(ctx):
 
     ctx.template(
         "%s/BUILD" % sysroot_directory,
-        Label("//:BUILD.ndk_sysroot.tpl"),
+        ctx.attr._template_ndk_sysroot,
         {
             "{api_level}": str(api_level),
         },
         executable = False,
     )
 
-# Manually create a partial symlink tree of the NDK to avoid creating BUILD
-# files in the real NDK directory.
-def _create_symlinks(ctx, ndk_path, clang_directory, sysroot_directory):
-    # Path needs to end in "/" for replace() below to work
-    if not ndk_path.endswith("/"):
-        ndk_path = ndk_path + "/"
-
-    for p in ctx.path(ndk_path + clang_directory).readdir():
-        repo_relative_path = str(p).replace(ndk_path, "")
-
-        # Skip sysroot directory, since it gets its own BUILD file
-        if repo_relative_path != sysroot_directory:
-            ctx.symlink(p, repo_relative_path)
-
-    for p in ctx.path(ndk_path + sysroot_directory).readdir():
-        repo_relative_path = str(p).replace(ndk_path, "")
-        ctx.symlink(p, repo_relative_path)
-
-    ctx.symlink(ndk_path + "sources", "sources")
-
-    # TODO(#32): Remove this hack
-    ctx.symlink(ndk_path + "sources", "ndk/sources")
-
-_android_ndk_repository = repository_rule(
+android_ndk_repository = repository_rule(
     attrs = {
-        "path": attr.string(),
-        "api_level": attr.int(),
+        "api_level": attr.int(default = 31),
+        "version": attr.string(default = "r25b"),
+        "base_url": attr.string(default = "https://dl.google.com/android/repository"),
+        "sha256s": attr.string_dict(),
+        "_build": attr.label(default = ":BUILD", allow_single_file = True),
+        "_template_ndk_root": attr.label(default = ":BUILD.ndk_root.tpl", allow_single_file = True),
+        "_template_target_systems": attr.label(default = ":target_systems.bzl.tpl", allow_single_file = True),
+        "_template_ndk_clang": attr.label(default = ":BUILD.ndk_clang.tpl", allow_single_file = True),
+        "_template_ndk_sysroot": attr.label(default = ":BUILD.ndk_sysroot.tpl", allow_single_file = True),
     },
-    local = True,
     implementation = _android_ndk_repository_impl,
 )
-
-def android_ndk_repository(name, **kwargs):
-    _android_ndk_repository(
-        name = name,
-        **kwargs
-    )
-    native.register_toolchains("@%s//:all" % name)
-    native.bind(
-        name = "android/crosstool",
-        actual = "@%s//:toolchain" % name,
-    )

sha256sums.bzl

@@ -0,0 +1,34 @@
+"""
+SHA256 checksums for downloaded NDK archives
+"""
+
+_NDK_PACKAGE_SHA256SUMS = {
+    # r26
+    "android-ndk-r26-windows.zip": "a748c6634b96991e15cb8902ffa4a498bba2ec6aa8028526de3c4c9dfcf00663",
+    "android-ndk-r26-darwin.zip": "b2ab2fd17f71e2d2994c8c0ba2e48e99377806e05bf7477093344c26ab71dec0",
+    "android-ndk-r26-linux.zip": "1505c2297a5b7a04ed20b5d44da5665e91bac2b7c0fbcd3ae99b6ccc3a61289a",
+    # r25c
+    "android-ndk-r25c-windows.zip": "f70093964f6cbbe19268f9876a20f92d3a593db3ad2037baadd25fd8d71e84e2",
+    "android-ndk-r25c-darwin.zip": "b01bae969a5d0bfa0da18469f650a1628dc388672f30e0ba231da5c74245bc92",
+    "android-ndk-r25c-linux.zip": "769ee342ea75f80619d985c2da990c48b3d8eaf45f48783a2d48870d04b46108",
+    # r25b
+    "android-ndk-r25b-windows.zip": "c9a72beda4663ab714c9fb3dc06bb9b9f124f2b5199957c86cd6f57eb59fd49a",
+    "android-ndk-r25b-darwin.zip": "7e12f1f809878d4f5d5a901809277aa31546d36c10730fade2036d7d95b3607a",
+    "android-ndk-r25b-linux.zip": "403ac3e3020dd0db63a848dcaba6ceb2603bf64de90949d5c4361f848e44b005",
+}
+
+def ndk_sha256(filename, repository_ctx):
+    """Get the sha256 for a specific NDK release
+
+    Args:
+        filename: the name of the NDK release file (as seen on https://developer.android.com/ndk/downloads)
+        repository_ctx: the repository_rule ctx
+
+    Returns:
+        a sha256sum string to use with ctx.download_and_extract
+    """
+    internal_sha256 = _NDK_PACKAGE_SHA256SUMS.get(filename)
+    external_sha256 = repository_ctx.attr.sha256s.get(filename)
+    if internal_sha256 == None and external_sha256 == None:
+        fail("This NDK version is unsupported, and you haven't supplied a custom sha256sum for", filename)
+    return _NDK_PACKAGE_SHA256SUMS.get(filename)

utils/checksums.sh

@@ -0,0 +1,14 @@
+#!/bin/bash
+# Download a specific release of the NDK for all three platforms and calculate SHA256 checksums
+# to add to the sha256sums.bzl file.
+set -eu
+
+ndk_version=$1
+
+cd "$(mktemp -d)"
+echo "Working in $PWD"
+
+curl -LO "https://dl.google.com/android/repository/android-ndk-${ndk_version}-windows.zip"
+curl -LO "https://dl.google.com/android/repository/android-ndk-${ndk_version}-darwin.zip"
+curl -LO "https://dl.google.com/android/repository/android-ndk-${ndk_version}-linux.zip"
+sha256sum ./*