Double-precision floating point numbers. It is desirable that this type be at least equal in range and precision to the IEEE double-precision type.

Single-precision floating point numbers. It is desirable that this type be at least equal in range and precision to the IEEE single-precision type.

The Maybe type encapsulates an optional value. A value of type Maybe a either contains a value of type a (represented as Just a), or it is empty (represented as Nothing). Using Maybe is a good way to deal with errors or exceptional cases without resorting to drastic measures such as error.

The Maybe type is also a monad. It is a simple kind of error monad, where all errors are represented by Nothing. A richer error monad can be built using the Data.Either.Either type.

General-purpose finite sequences.

Utf8 is used to mark ByteString values that (should) contain valud utf8 encoded strings. This type is used to represent TYPE_STRING values.

A space-efficient representation of a Word8 vector, supporting many efficient operations. A ByteString contains 8-bit characters only.

Instances of Eq, Ord, Read, Show, Data, Typeable

32-bit signed integer type

64-bit signed integer type

32-bit unsigned integer type

64-bit unsigned integer type

WireTag is the 32 bit value with the upper 29 bits being the FieldId and the lower 3 bits being the WireType

FieldId is the field number which can be in the range 1 to 2^29-1 but the value from 19000 to 19999 are forbidden (so sayeth Google).

WireType is the 3 bit wire encoding value, and is currently in the range 0 to 5, leaving 6 and 7 currently invalid.

• 0 Varint : int32, int64, uint32, uint64, sint32, sint64, bool, enum
• 1 64-bit : fixed64, sfixed64, double
• 2 Length-delimited : string, bytes, embedded messages
• 3 Start group : groups (deprecated)
• 4 End group : groups (deprecated)
• 5 32-bit : fixed32, sfixed32, float

FieldType is the integer associated with the FieldDescriptorProto's Type. The allowed range is currently 1 to 18, as shown below (excerpt from descritor.proto)

    // 0 is reserved for errors.
    // Order is weird for historical reasons.
    TYPE_DOUBLE         = 1;
    TYPE_FLOAT          = 2;
    TYPE_INT64          = 3;   // Not ZigZag encoded.  Negative numbers
                               // take 10 bytes.  Use TYPE_SINT64 if negative
                               // values are likely.
    TYPE_UINT64         = 4;
    TYPE_INT32          = 5;   // Not ZigZag encoded.  Negative numbers
                               // take 10 bytes.  Use TYPE_SINT32 if negative
                               // values are likely.
    TYPE_FIXED64        = 6;
    TYPE_FIXED32        = 7;
    TYPE_BOOL           = 8;
    TYPE_STRING         = 9;
    TYPE_GROUP          = 10;  // Tag-delimited aggregate.
    TYPE_MESSAGE        = 11;  // Length-delimited aggregate.

    // New in version 2.
    TYPE_BYTES          = 12;
    TYPE_UINT32         = 13;
    TYPE_ENUM           = 14;
    TYPE_SFIXED32       = 15;
    TYPE_SFIXED64       = 16;
    TYPE_SINT32         = 17;  // Uses ZigZag encoding.
    TYPE_SINT64         = 18;  // Uses ZigZag encoding.

EnumCode is the Int32 assoicated with a EnumValueDescriptorProto and is in the range 0 to 2^31-1.

WireSize is the Int64 size type associate with the lazy bytestrings used in the Put and Get monads.

The Mergeable class is not a Monoid, mergeEmpty is not a left or right unit like mempty. The default mergeAppend is to take the second parameter and discard the first one. The mergeConcat defaults to foldl associativity.

The Default class has the default-default values of types. See http://code.google.com/apis/protocolbuffers/docs/proto.html#optional and also note that Enum types have a defaultValue that is the first one in the .proto file (there is always at least one value). Instances of this for messages hold any default value defined in the .proto file. defaultValue is where the MessageAPI function getVal looks when an optional field is not set.

The Wire class is for internal use, and may change. If there is a mis-match between the FieldType and the type of b then you will get a failure at runtime.

Users should stick to the message functions defined in Text.ProtocolBuffers.WireMessage and exported to use user by Text.ProtocolBuffers. These are less likely to change.