[Bug 14828] com.livecode.byte: Add "the byte with code _".

peter-b · peter-b · commit 52c177acd05d · 2015-03-06T17:22:00.000Z
Add syntax for converting an integer to a single-byte `Data` value.
diff --git a/libscript/src/byte.mlc b/libscript/src/byte.mlc
@@ -56,6 +56,8 @@ public foreign handler MCByteExecDeleteFirstByteOf(inout Target as Data) as unde
 
 public foreign handler MCDataExecRandomBytes(in Count as LCUIndex, out Value as Data) as undefined binds to "<builtin>"
 
+public foreign handler MCByteEvalByteWithCode(in Value as LCUInt, out Result as Data) as undefined binds to "<builtin>"
+
 --
 
 /*
@@ -427,6 +429,25 @@ begin
 	MCDataExecRandomBytes(Count, output)
 end syntax
 
---
+----------------------------------------------------------------
+-- Conversion between bytes and numbers
+----------------------------------------------------------------
+
+/*
+Summary:	Create a 1-byte data value from a number
+
+Value:		The value for the new data value
+
+Description:
+Returns a byte of binary data, created using the given value.  The
+<Value> must be between 0 and 255 (inclusive).
+
+Tags: Binary
+*/
+syntax ByteWithCode is prefix operator with precedence 2
+      "the" "byte" "with" "code" <Value: Expression>
+begin
+	MCByteEvalByteWithCode(Value, output)
+end syntax
 
 end module
diff --git a/libscript/src/module-byte.cpp b/libscript/src/module-byte.cpp
@@ -217,6 +217,25 @@ MCDataExecRandomBytes (uindex_t p_count, MCDataRef & r_data)
 	/* UNCHECKED */ MCSRandomData (p_count, r_data);
 }
 
+////////////////////////////////////////////////////////////////////////////////
+
+extern "C" MC_DLLEXPORT void
+MCByteEvalByteWithCode (uinteger_t p_value,
+                        MCDataRef & r_data)
+{
+	if (p_value > BYTE_MAX)
+	{
+		MCErrorCreateAndThrow (kMCGenericErrorTypeInfo,
+		                       "reason", MCSTR("overflow in byte operation"),
+		                       nil);
+		return;
+	}
+
+	const byte_t t_byte = p_value;
+
+	MCDataCreateWithBytes (&t_byte, 1, r_data);
+}
+
 ////////////////////////////////////////////////////////////////////////////////////////////////////
 
 #ifdef _TEST
diff --git a/tests/lcb/stdlib/byte.lcb b/tests/lcb/stdlib/byte.lcb
@@ -0,0 +1,38 @@
+/*
+Copyright (C) 2015 Runtime Revolution Ltd.
+
+This file is part of LiveCode.
+
+LiveCode is free software; you can redistribute it and/or modify it under
+the terms of the GNU General Public License v3 as published by the Free
+Software Foundation.
+
+LiveCode is distributed in the hope that it will be useful, but WITHOUT ANY
+WARRANTY; without even the implied warranty of MERCHANTABILITY or
+FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+for more details.
+
+You should have received a copy of the GNU General Public License
+along with LiveCode.  If not see <http://www.gnu.org/licenses/>.  */
+
+module com.livecode.foreign.tests
+
+use com.livecode.__INTERNAL._testlib
+
+handler TestByteWithCode_Negative()
+	return the byte with code -1
+end handler
+handler TestByteWithCode_Overflow()
+	return the byte with code 256
+end handler
+public handler TestByteWithCode()
+	variable t
+	put the byte with code 0 into t
+
+	test "code->byte" when the number of bytes in t is 1
+
+	MCUnitTestHandlerThrows(TestByteWithCode_Negative, "code->byte (negative)")
+	MCUnitTestHandlerThrows(TestByteWithCode_Overflow, "code->byte (overflow)")
+end handler
+
+end module
