switch to multi-module project structure

1 files changed, 92 insertions, 0 deletions

diff --git a/lib/src/main/kotlin/FilePermissions.kt b/lib/src/main/kotlin/FilePermissions.kt
new file mode 100644
index 0000000..84a7944
--- /dev/null
+++ b/lib/src/main/kotlin/FilePermissions.kt
@@ -0,0 +1,92 @@
+/**
+ * The permissions of a newly created file.
+ */
+class FilePermissions {
+
+    /**
+     * The permissions for the file's owning user.
+     */
+    val userPerms: Permissions
+
+    /**
+     * The permissions for the file's owning group.
+     */
+    val groupPerms: Permissions
+
+    /**
+     * The permissions for everyone else.
+     */
+    val elsePerms: Permissions
+
+    /**
+     * Is the file a directory? If not, it's a regular file.
+     */
+    val isDirectory: Boolean
+
+    private val DMDIR: UInt = 0x80000000u
+
+    /**
+     * Constructor for file permissions with separate fields.
+     *
+     * @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.
+     */
+    constructor(userPerms: Permissions, groupPerms: Permissions, elsePerms: Permissions, isDirectory: Boolean) {
+        this.userPerms = userPerms
+        this.groupPerms = groupPerms
+        this.elsePerms = elsePerms
+        this.isDirectory = isDirectory
+    }
+
+    /**
+     * Constructor for raw file permission data. Only the first 4 elements are read.
+     *
+     * @param raw The raw file permission data.
+     * @throws IllegalArgumentException if [raw] does not have at least 4 elements.
+     */
+    constructor(raw: List<UByte>) {
+        require(raw.size >= 4)
+        val raw = raw.slice(0..4)
+        val dirValue = raw[0].toUInt().xor(this.DMDIR)
+        this.isDirectory = dirValue > 0u
+        this.userPerms = Permissions.fromByte(raw[1])
+        this.groupPerms = Permissions.fromByte(raw[2])
+        this.elsePerms = Permissions.fromByte(raw[3])
+    }
+
+    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)));
+
+        companion object {
+            /**
+             * Obtain a [Permissions] instance by matching its value.
+             *
+             * @throws NoSuchElementException if no such element has the provided value.
+             */
+            fun fromByte(bits: UByte) = Permissions.entries.first { it.bits == 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(this.DMDIR)
+        }
+        return perms
+    }
+}
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