Add endian parameter to the get/set functions in ByteData.

sdk/lib/typeddata/typeddata.dart

Index: sdk/lib/typeddata/typeddata.dart
===================================================================
--- sdk/lib/typeddata/typeddata.dart	(revision 21661)
+++ sdk/lib/typeddata/typeddata.dart	(working copy)
@@ -49,6 +49,23 @@
 
 
 /**
+ * Describes endianness to be used when accessing or updating a
+ * sequence of bytes.
+ */
+class Endianness {
+  const Endianness(this.little_endian);

[Mads Ager (google), 2013/04/18 08:10:44]

Maybe we should make sure that the user cannot create extra values of this type
by making the constructor private?

const Endianness._(this._littleEndian);

Since the value is a boolean it doesn't really matter in this case though.

[siva, 2013/04/18 17:17:47]

Done.

+
+  static const Endianness BIG_ENDIAN = const Endianness(false);
+  static const Endianness LITTLE_ENDIAN = const Endianness(true);
+  static final Endianness HOST_ENDIAN =
+    (new ByteData.view(new Uint16List.fromList([1]).buffer)).getInt8(0) == 1 ?
+    LITTLE_ENDIAN : BIG_ENDIAN;
+
+  final bool little_endian;

[vsm, 2013/04/18 04:06:56]

Can we make this private?  Also, standard Dart style would be _littleEndian.

[siva, 2013/04/18 17:17:47]

Done.

+}
+
+
+/**
  * A fixed-length, random-access sequence of bytes that also provides random
  * and unaligned access to the fixed-width integers and floating point
  * numbers represented by those bytes.
@@ -141,7 +158,7 @@
    * Throws [RangeError] if [byteOffset] is negative, or
    * `byteOffset + 2` is greater than the length of this object.
    */
-  int getInt16(int byteOffset);
+  int getInt16(int byteOffset, [Endianness endian = Endianness.BIG_ENDIAN]);

[Søren Gjesse, 2013/04/18 07:04:36]

How about adding a property endianess to ByteData to set the default endianess
used?

Then

ByteData bd = ...
db.endianess = Endianness.LITTLE_ENDIAN;
db.setInt16(1);
db.setInt32(2);
db.setInt64(1);

would be equal to

ByteData bd = ...
db.setInt16(1, Endianness.LITTLE_ENDIAN);
db.setInt32(2, Endianness.LITTLE_ENDIAN);
db.setInt64(1, Endianness.LITTLE_ENDIAN);

The default value for the endian argument should then just be null, and if null
pick the value from the endianess property which should default to
Endianness.BIG_ENDIAN.

When not using BIG_ENDIAN this would save writing Endianness.LITTLE_ENDIAN all
over the place.

[siva, 2013/04/18 17:17:47]

Seems like a good idea. I will defer this proposal to another CL. Maybe first
get feedback to see if dart2js will not have any issues implementing it this
way.

On 2013/04/18 07:04:36, Søren Gjesse wrote:

 
   /**
    * Sets the two bytes starting at the specified [byteOffset] in this
@@ -152,7 +169,9 @@
    * Throws [RangeError] if [byteOffset] is negative, or
    * `byteOffset + 2` is greater than the length of this object.
    */
-  void setInt16(int byteOffset, int value);
+  void setInt16(int byteOffset,
+                int value,
+                [Endianness endian = Endianness.BIG_ENDIAN]);
 
   /**
    * Returns the positive integer represented by the two bytes starting
@@ -163,7 +182,7 @@
    * Throws [RangeError] if [byteOffset] is negative, or
    * `byteOffset + 2` is greater than the length of this object.
    */
-  int getUint16(int byteOffset);
+  int getUint16(int byteOffset, [Endianness endian = Endianness.BIG_ENDIAN]);
 
   /**
    * Sets the two bytes starting at the specified [byteOffset] in this object
@@ -174,7 +193,9 @@
    * Throws [RangeError] if [byteOffset] is negative, or
    * `byteOffset + 2` is greater than the length of this object.
    */
-  void setUint16(int byteOffset, int value);
+  void setUint16(int byteOffset,
+                 int value,
+                 [Endianness endian = Endianness.BIG_ENDIAN]);
 
   /**
    * Returns the (possibly negative) integer represented by the four bytes at
@@ -186,7 +207,7 @@
    * Throws [RangeError] if [byteOffset] is negative, or
    * `byteOffset + 4` is greater than the length of this object.
    */
-  int getInt32(int byteOffset);
+  int getInt32(int byteOffset, [Endianness endian = Endianness.BIG_ENDIAN]);
 
   /**
    * Sets the four bytes starting at the specified [byteOffset] in this
@@ -197,7 +218,9 @@
    * Throws [RangeError] if [byteOffset] is negative, or
    * `byteOffset + 4` is greater than the length of this object.
    */
-  void setInt32(int byteOffset, int value);
+  void setInt32(int byteOffset,
+                int value,
+                [Endianness endian = Endianness.BIG_ENDIAN]);
 
   /**
    * Returns the positive integer represented by the four bytes starting
@@ -206,7 +229,7 @@
    * The return value will be between 0 and  2<sup>32</sup> - 1, inclusive.
    *
    */
-  int getUint32(int byteOffset);
+  int getUint32(int byteOffset, [Endianness endian = Endianness.BIG_ENDIAN]);
 
   /**
    * Sets the four bytes starting at the specified [byteOffset] in this object
@@ -217,7 +240,9 @@
    * Throws [RangeError] if [byteOffset] is negative, or
    * `byteOffset + 4` is greater than the length of this object.
    */
-  void setUint32(int byteOffset, int value);
+  void setUint32(int byteOffset,
+                 int value,
+                 [Endianness endian = Endianness.BIG_ENDIAN]);
 
   /**
    * Returns the (possibly negative) integer represented by the eight bytes at
@@ -229,7 +254,7 @@
    * Throws [RangeError] if [byteOffset] is negative, or
    * `byteOffset + 8` is greater than the length of this object.
    */
-  int getInt64(int byteOffset);
+  int getInt64(int byteOffset, [Endianness endian = Endianness.BIG_ENDIAN]);
 
   /**
    * Sets the eight bytes starting at the specified [byteOffset] in this
@@ -240,7 +265,9 @@
    * Throws [RangeError] if [byteOffset] is negative, or
    * `byteOffset + 8` is greater than the length of this object.
    */
-  void setInt64(int byteOffset, int value);
+  void setInt64(int byteOffset,
+                int value,
+                [Endianness endian = Endianness.BIG_ENDIAN]);
 
   /**
    * Returns the positive integer represented by the eight bytes starting
@@ -251,7 +278,7 @@
    * Throws [RangeError] if [byteOffset] is negative, or
    * `byteOffset + 8` is greater than the length of this object.
    */
-  int getUint64(int byteOffset);
+  int getUint64(int byteOffset, [Endianness endian = Endianness.BIG_ENDIAN]);
 
   /**
    * Sets the eight bytes starting at the specified [byteOffset] in this object
@@ -262,7 +289,9 @@
    * Throws [RangeError] if [byteOffset] is negative, or
    * `byteOffset + 8` is greater than the length of this object.
    */
-  void setUint64(int byteOffset, int value);
+  void setUint64(int byteOffset,
+                 int value,
+                 [Endianness endian = Endianness.BIG_ENDIAN]);
 
   /**
    * Returns the floating point number represented by the four bytes at
@@ -272,7 +301,8 @@
    * Throws [RangeError] if [byteOffset] is negative, or
    * `byteOffset + 4` is greater than the length of this object.
    */
-  double getFloat32(int byteOffset);
+  double getFloat32(int byteOffset,
+                    [Endianness endian = Endianness.BIG_ENDIAN]);
 
   /**
    * Sets the four bytes starting at the specified [byteOffset] in this
@@ -291,7 +321,9 @@
    * Throws [RangeError] if [byteOffset] is negative, or
    * `byteOffset + 4` is greater than the length of this object.
    */
-  void setFloat32(int byteOffset, double value);
+  void setFloat32(int byteOffset,
+                  double value,
+                  [Endianness endian = Endianness.BIG_ENDIAN]);
 
   /**
    * Returns the floating point number represented by the eight bytes at
@@ -301,7 +333,8 @@
    * Throws [RangeError] if [byteOffset] is negative, or
    * `byteOffset + 8` is greater than the length of this object.
    */
-  double getFloat64(int byteOffset);
+  double getFloat64(int byteOffset,
+                    [Endianness endian = Endianness.BIG_ENDIAN]);
 
   /**
    * Sets the eight bytes starting at the specified [byteOffset] in this
@@ -311,7 +344,9 @@
    * Throws [RangeError] if [byteOffset] is negative, or
    * `byteOffset + 8` is greater than the length of this object.
    */
-  void setFloat64(int byteOffset, double value);
+  void setFloat64(int byteOffset,
+                  double value,
+                  [Endianness endian = Endianness.BIG_ENDIAN]);
 }