add FilePermissions

1 files changed, 34 insertions, 0 deletions

diff --git a/src/main/kotlin/FilePermissions.kt b/src/main/kotlin/FilePermissions.kt
new file mode 100644
index 0000000..04561fe
--- /dev/null
+++ b/src/main/kotlin/FilePermissions.kt
@@ -0,0 +1,34 @@
+/**
+ * The permissions of a newly created file.
+ *
+ * @param userPerms The permissions for the file's owning user.
+ * @param groupPerms The permissions for the file's owning group.
+ * @param elsePerms The permissions for everyone else.
+ * @param isDirectory Is the file a directory? If not, it's a regular file.
+ */
+class FilePermissions(val userPerms: Permissions, val groupPerms: Permissions, val elsePerms: Permissions, val isDirectory: Boolean) {
+    enum class Permissions(val bits: UByte) {
+        READ(0x4u),
+        WRITE(0x2u),
+        EXECUTE(0x1u),
+        READ_WRITE(READ.bits.or(WRITE.bits)),
+        READ_EXECUTE(READ.bits.or(EXECUTE.bits)),
+        WRITE_EXECUTE(WRITE.bits.or(EXECUTE.bits)),
+        READ_WRITE_EXECUTE(READ.bits.or(WRITE.bits.or(EXECUTE.bits)))
+    }
+
+    /**
+     * Turn the permissions described by the [FilePermissions] fields into a permission integer (4 bytes).
+     */
+    fun toPermissionInt(): UInt {
+        val permFileds = listOf(userPerms, groupPerms, elsePerms)
+        val perms: UInt = 0u
+        for (i in 0..permFileds.size) {
+            perms.or(permFileds[i].bits.toUInt().shl(8 * (permFileds.size - 1 - i)))
+        }
+        if (isDirectory) {
+            perms.or(0x80000000u)
+        }
+        return perms
+    }
+}
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