Define a tool and a static rule to calculate the hash of a directory

The rule will be used in a follow up change that adds a directory in a
provider.

Test: m nothing
Bug: 381104942
Change-Id: I7147dcbc43e19840b2d73380785a01bda6643d85

1 files changed, 14 insertions, 0 deletions

diff --git a/android/defs.go b/android/defs.go
index 9f3fb1ee6..c4e3b995f 100644
--- a/android/defs.go
+++ b/android/defs.go
@@ -102,6 +102,18 @@ var (
 			Description: "concatenate files to $out",
 		})
 
+	// Calculates the hash of a directory and writes to a file.
+	// Note that the directory to calculate the hash is intentionally not listed as an input,
+	// to prevent adding directory as a ninja dependency. Thus, an implicit dependency to a file
+	// is required.
+	WriteDirectoryHash = pctx.AndroidStaticRule("WriteDirectoryHash",
+		blueprint.RuleParams{
+			Command:     "rm -f $out && ${calculateDirectoryHash} $dir $out",
+			CommandDeps: []string{"${calculateDirectoryHash}"},
+			Description: "Calculates the hash of a directory and writes to $out",
+		}, "dir",
+	)
+
 	// Used only when USE_GOMA=true is set, to restrict non-goma jobs to the local parallelism value
 	localPool = blueprint.NewBuiltinPool("local_pool")
 
@@ -118,4 +130,6 @@ func init() {
 	pctx.VariableFunc("RBEWrapper", func(ctx PackageVarContext) string {
 		return ctx.Config().RBEWrapper()
 	})
+
+	pctx.HostBinToolVariable("calculateDirectoryHash", "calculate_directory_hash")
 }