com.livecode.byte: Add in-place reverse statement

peter-b · peter-b · commit df8ca5fcfebd · 2017-03-31T11:10:14.000+01:00
Add the ability to reverse a binary string in an LCB program with a
new `reverse tData` statement.
diff --git a/libscript/src/byte.lcb b/libscript/src/byte.lcb
@@ -432,6 +432,37 @@ begin
 	MCDataExecRandomBytes(Count, output)
 end syntax
 
+--
+
+public foreign handler MCDataExecReverseBytesOf(inout Target as Data) \
+		returns nothing binds to "<builtin>"
+
+/**
+Summary:	Reverse binary data
+Target:	A binary data string
+
+Example:
+	variable tForward
+	put 5 random bytes into tForward
+
+	variable tReversed
+	put tForward into tReversed
+	reverse tReversed
+
+	expect that the first byte of tForward is the last byte of tReversed
+	expect that the last byte of tForward is the first byte of tReversed
+
+Description:
+Reverses the order of bytes in the <Target>.
+
+Tags: Binary
+*/
+syntax ReverseBytesOf is statement
+	"reverse" <Target: Expression>
+begin
+	MCDataExecReverseBytesOf(Target)
+end syntax
+
 ----------------------------------------------------------------
 -- Conversion between bytes and numbers
 ----------------------------------------------------------------
diff --git a/libscript/src/module-byte.cpp b/libscript/src/module-byte.cpp
@@ -223,6 +223,21 @@ MCDataExecRandomBytes (uindex_t p_count, MCDataRef & r_data)
 
 ////////////////////////////////////////////////////////////////////////////////
 
+extern "C" MC_DLLEXPORT_DEF void
+MCDataExecReverseBytesOf(MCDataRef &x_data)
+{
+    MCAutoDataRef t_data;
+    if (!MCDataMutableCopy(x_data, &t_data))
+        return;
+    if (!MCDataReverse(*t_data))
+        return;
+    if (!t_data.MakeImmutable())
+        return;
+    MCValueAssign(x_data, *t_data);
+}
+
+////////////////////////////////////////////////////////////////////////////////
+
 extern "C" MC_DLLEXPORT_DEF void
 MCByteEvalByteWithCode (uinteger_t p_value,
                         MCDataRef & r_data)
diff --git a/tests/lcb/stdlib/byte.lcb b/tests/lcb/stdlib/byte.lcb
@@ -272,6 +272,40 @@ return
 
 end handler
 
+----------------------------------------------------------------
+-- Other manipulations
+----------------------------------------------------------------
+
+public handler TestReverse()
+	variable kFOdd
+	put EncodeUTF8("abc") into kFOdd
+	variable kROdd
+	put EncodeUTF8("cba") into kROdd
+	variable kFEven
+	put EncodeUTF8("0123") into kFEven
+	variable kREven
+	put EncodeUTF8("3210") into kREven
+
+	variable tReversed
+
+	put kFOdd into tReversed
+	reverse tReversed
+	test "reverse in-place (odd)" when tReversed is kROdd
+	reverse tReversed
+	test "rereverse in-place (odd)" when tReversed is kFOdd
+
+	put kFEven into tReversed
+	reverse tReversed
+	test "reverse in-place (even)" when tReversed is kREven
+	reverse tReversed
+	test "rereverse in-place (even)" when tReversed is kFEven
+
+	put the empty data into tReversed
+	reverse tReversed
+	test "reverse in-place (empty)" when tReversed is empty
+
+end handler
+
 ----------------------------------------------------------------
 -- Helper functions
 ----------------------------------------------------------------
