The API is centered around the Amount
type, which is an immutable monetary value in a specific currency. It is based
on Shopspring's arbitrary-precision Decimal
type, making it suitable for mathematical operations.
Amount provides serialization logic for text, binary, JSON and protocol
buffers formats.
Both the text and binary formats are "lossless" insofar as they can encode any amount that can be represented by the internal arbitrary precision decimal.
The JSON and protocol buffers formats are based on the google.type.Money
"well-known" protocol buffers type, which has a fixed precision of 9 decimal
places.
The JSON representation of an amount is obtained by applying Protocol Buffers'
canonical JSON mapping rules to the
Money type. This encoding is widely used throughout Google's APIs, an example
of which can be seen here.
Dosh also provides the protomoney
package, which can be used to perform comparisons and basic mathematical
operations on google.type.Money values directly, without unmarshaling them to
an Amount.
Google's money package does not include the source .proto file used to
generate the money.Money
type. This makes it difficult to use the Money type in user-defined protocol
buffers messages. For this reason, the original .proto file is included in
Dosh's protomoney package.