Add some bitfield helper methods from 2.4

Change-Id: Ib9bb549602f71a451d2107fb04de17877553860e

src/google/protobuf/compiler/javanano/javanano_helpers.cc

@@ -407,6 +407,83 @@ string DefaultValue(const Params& params, const FieldDescriptor* field) {
   return "";
 }
 
+
+static const char* kBitMasks[] = {
+  "0x00000001",
+  "0x00000002",
+  "0x00000004",
+  "0x00000008",
+  "0x00000010",
+  "0x00000020",
+  "0x00000040",
+  "0x00000080",
+
+  "0x00000100",
+  "0x00000200",
+  "0x00000400",
+  "0x00000800",
+  "0x00001000",
+  "0x00002000",
+  "0x00004000",
+  "0x00008000",
+
+  "0x00010000",
+  "0x00020000",
+  "0x00040000",
+  "0x00080000",
+  "0x00100000",
+  "0x00200000",
+  "0x00400000",
+  "0x00800000",
+
+  "0x01000000",
+  "0x02000000",
+  "0x04000000",
+  "0x08000000",
+  "0x10000000",
+  "0x20000000",
+  "0x40000000",
+  "0x80000000",
+};
+
+string GetBitFieldName(int index) {
+  string var_name = "bitField";
+  var_name += SimpleItoa(index);
+  var_name += "_";
+  return var_name;
+}
+
+string GetBitFieldNameForBit(int bit_index) {
+  return GetBitFieldName(bit_index / 32);
+}
+
+string GenerateGetBit(int bit_index) {
+  string var_name = GetBitFieldNameForBit(bit_index);
+  int bit_in_var_index = bit_index % 32;
+
+  string mask = kBitMasks[bit_in_var_index];
+  string result = "((" + var_name + " & " + mask + ") == " + mask + ")";
+  return result;
+}
+
+string GenerateSetBit(int bit_index) {
+  string var_name = GetBitFieldNameForBit(bit_index);
+  int bit_in_var_index = bit_index % 32;
+
+  string mask = kBitMasks[bit_in_var_index];
+  string result = var_name + " |= " + mask;
+  return result;
+}
+
+string GenerateClearBit(int bit_index) {
+  string var_name = GetBitFieldNameForBit(bit_index);
+  int bit_in_var_index = bit_index % 32;
+
+  string mask = kBitMasks[bit_in_var_index];
+  string result = var_name + " = (" + var_name + " & ~" + mask + ")";
+  return result;
+}
+
 }  // namespace javanano
 }  // namespace compiler
 }  // namespace protobuf

src/google/protobuf/compiler/javanano/javanano_helpers.h

@@ -138,6 +138,31 @@ string EmptyArrayName(const Params& params, const FieldDescriptor* field);
 
 string DefaultValue(const Params& params, const FieldDescriptor* field);
 
+
+// Methods for shared bitfields.
+
+// Gets the name of the shared bitfield for the given index.
+string GetBitFieldName(int index);
+
+// Gets the name of the shared bitfield for the given bit index.
+// Effectively, GetBitFieldName(bit_index / 32)
+string GetBitFieldNameForBit(int bit_index);
+
+// Generates the java code for the expression that returns the boolean value
+// of the bit of the shared bitfields for the given bit index.
+// Example: "((bitField1_ & 0x04) == 0x04)"
+string GenerateGetBit(int bit_index);
+
+// Generates the java code for the expression that sets the bit of the shared
+// bitfields for the given bit index.
+// Example: "bitField1_ = (bitField1_ | 0x04)"
+string GenerateSetBit(int bit_index);
+
+// Generates the java code for the expression that clears the bit of the shared
+// bitfields for the given bit index.
+// Example: "bitField1_ = (bitField1_ & ~0x04)"
+string GenerateClearBit(int bit_index);
+
 }  // namespace javanano
 }  // namespace compiler
 }  // namespace protobuf