From 49d74bf6cd4e479c1705fcc9c14c9e3139093559 Mon Sep 17 00:00:00 2001
From: Alexander Vollschwitz <xelalex@gmx.net>
Date: Fri, 26 Jan 2024 10:41:30 +0100
Subject: [PATCH] #101: cross-compile for other architectures

---
 Makefile        | 25 +++++++++++++++----------
 README.md       |  2 ++
 hack/devenvutil | 35 +++++++++++++++++++++++++++++++++++
 3 files changed, 52 insertions(+), 10 deletions(-)

diff --git a/Makefile b/Makefile
index f2e9b30..01f0705 100644
--- a/Makefile
+++ b/Makefile
@@ -18,7 +18,7 @@
 SHELL = /bin/bash
 
 REPO = dregsy
-DREGSY_VERSION = $$(git describe --always --tag --dirty)
+DREGSY_VERSION = $(shell git describe --always --tag --dirty)
 SKOPEO_VERSION = v1.14.1 # https://github.com/containers/skopeo/releases
 
 ROOT = $(shell pwd)
@@ -87,6 +87,8 @@ GOARCH = $(shell ./hack/devenvutil get_architecture)
 #			running ${DIM}make clean${NRM}. That way you can force a clean build/test, where all
 #			dependencies are retrieved & built inside the container.
 #
+#	${ITL}CROSS=y${NRM}		set this to build binaries for various platforms & architectures
+#
 #	${ITL}TEST_ALPINE=n${NRM}	when using this with the test target, tests will not be performed
 #	${ITL}TEST_UBUNTU=n${NRM}	for the respective image (${ITL}Alpine${NRM} or ${ITL}Ubuntu${NRM} based)
 #
@@ -166,15 +168,18 @@ publish:
 dregsy: prep
 #	build the ${ITL}dregsy${NRM} binary
 #
-	echo "os: $(GOOS), arch: $(GOARCH)"
-	docker run --rm --user $(shell id -u):$(shell id -g) \
-		-v $(shell pwd)/$(BINARIES):/go/bin $(CACHE_VOLS) \
-		-v $(shell pwd):/go/src/$(REPO) -w /go/src/$(REPO) \
-		-e CGO_ENABLED=0 -e GOOS=$(GOOS) -e GOARCH=$(GOARCH) \
-		$(GO_IMAGE)@sha256:$(GO_IMAGE_DIGEST_$(GOARCH)) bash -c \
-			"go mod tidy && go build -v -tags netgo -installsuffix netgo \
-			-ldflags \"-w -X main.DregsyVersion=$(DREGSY_VERSION)\" \
-			-o $(BINARIES)/dregsy ./cmd/dregsy/"
+	rm -f $(BINARIES)/dregsy
+ifneq ($(CROSS),y)
+	$(call utils, build_binary dregsy $(GOOS) $(GOARCH) keep)
+else
+	$(call utils, build_binary dregsy linux amd64 keep)
+	$(call utils, build_binary dregsy linux arm64)
+	$(call utils, build_binary dregsy linux arm)
+	$(call utils, build_binary dregsy linux 386)
+endif
+	unzip -q $(BINARIES)/dregsy_*_linux_amd64.zip -d $(BINARIES) 2>/dev/null \
+		|| true
+	cd $(BINARIES); sha256sum dregsy_*.zip > checksums.txt
 
 
 .PHONY: imgdregsy
diff --git a/README.md b/README.md
index 8ab3635..114b862 100644
--- a/README.md
+++ b/README.md
@@ -317,6 +317,8 @@ Logging behavior can be changed with these environment variables:
 | `LOG_METHODS` | include method names in log messages | `true`, `false` |
 
 ### Running Natively
+Pre-built binaries are provided in the release section of this project. Note however that currently, only the `linux_amd64` flavor is tested upon release. All other binaries are untested. Feedback is welcome!
+
 If you run *dregsy* natively on your system, with relay type `docker`, the *Docker* daemon of your system will be used as the relay for all sync tasks, so all synced images will wind up in the *Docker* storage of that daemon.
 
 ### Running Inside a Container
diff --git a/hack/devenvutil b/hack/devenvutil
index fe8984c..1f8932e 100755
--- a/hack/devenvutil
+++ b/hack/devenvutil
@@ -143,6 +143,41 @@ function remove_test_images {
     done
 }
 
+#
+# build command binary
+#
+# $1    command
+# $2    target OS
+# $3    target architecture
+#
+function build_binary {
+
+    local binary="${BINARIES}/$1"
+
+    local extra_env
+    [[ "$3" != "arm" ]] || extra_env="-e GOARM=7"
+    [[ "$3" != "mips" ]] || extra_env="-e GOMIPS=softfloat"
+
+    local digest_ref="GO_IMAGE_DIGEST_${GOARCH}"
+
+    echo -e "building ${binary} for $2/$3, using build image ${GO_IMAGE}@sha256:${!digest_ref}"
+    # shellcheck disable=SC2086
+    docker run --rm --user "$(id -u):$(id -g)" \
+        -v "${ROOT}/${BINARIES}:/go/bin" ${CACHE_VOLS} \
+        -v "${ROOT}:/go/src/${REPO}" -w "/go/src/${REPO}" \
+        -e CGO_ENABLED=0 -e GOOS="$2" -e GOARCH="$3" ${extra_env} \
+        ${GO_IMAGE}@sha256:${!digest_ref} bash -c \
+            "go mod tidy && go build -v -tags netgo -installsuffix netgo \
+            -ldflags \"-w -X main.DregsyVersion=${DREGSY_VERSION}\" \
+            -o \"${binary}\" \"./cmd/$1/\""
+
+    local specifier="_${DREGSY_VERSION}_$2_$3"
+    zip -j "../${binary}${specifier}.zip" "../${binary}"
+    rm -f "../${binary}"
+
+    echo
+}
+
 #
 # $1    test image variant (`alpine` or `ubuntu`)
 #