Encoded file is a concatenation of keys and value pairs.

Key indicates which field is written to and what type to read off the wire.

Value is the data on the wire.

Integers

Read bytes as long as the highest bit is set.

Clear flag bits from each byte read.

Reverse the bytes.

Bit shuffling to concatenate the 7-bit chunks together.

Wire types

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

Keys

An integer naming the field mixed with the wire type.

Encoded as varint((typecode << 3) | wire_type).

ZigZag encoding

• ZigZag encoding

Fixed size

4 bytes or 8 bytes of the type blitted in to the stream

Length-delimited

Integer holding size of payload followed by raw payload in bytes.

Optional

If a field is optional then it may not appear in binary at all.

Repeating

If you encounter a key in a repeating field, push the value to the array for that field.

If you encounter a key in a non-repeating field, overwrite the value for that field.

Packed

In 2.1.0 and beyond allow a packed format for varints, 32 and 64-bit fixed length.

Packed encoding is length of payload followed by each number in its wire format.