bubbler

README

Bubbler

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Bubbler is a proto generator optimized for IoT devices. It compiles the .bb proto file and generates the output in the specified target language.

Bubbler's proto powerful, and can be non-byte-aligned, which is useful for IoT devices with limited resources. Explained below.

Also, You may need syntax highlighting for .bb files, see bubbler-vscode, or install it from VSCode Marketplace.

Warning: Bubbler is still in development and is not ready for production use.

Installation

git clone https://github.com/xaxys/bubbler.git
cd bubbler
make

Usage

bubbler [options] <input file>

Options

• -t <target>: Target language
• -o <output>: Output Path
• -inner: Generate Inner Class (Nested Struct)
• -single: Generate Single File (Combine all definitions into one file, instead of one generated file per source file)
• -minimal: Generate Minimal Code (Usually without default getter/setter methods)
• -decnum: Force Generate Decimal Format for Constant Value (Translate 0xFF to 255, 0b1111 to 15, etc.)
• -signext <method>: Sign Extension Method used for Integer Field (Options: shift, arith)

Examples

bubbler -t c -minimal -o output/ example.bb
bubbler -t c -single -o gen.hpp example.bb
bubbler -t py -decnum -signext=arith -o output example.bb

Target Languages

Run bubbler to see the list of supported target languages.

Targets:
  c
  python [py]
  java

When selecting the target language, you can use the aliases inside []. For example, python can be abbreviated as py.

• dump: Output the parse tree (intermediate representation) of the .bb file.

• c: C language, output one .bb.h file and one .bb.c file for each .bb file.

  • With -single: Output one file that includes all definitions for all .bb files. The output file name (including the extension) is determined by the -o option.
  • With -minimal: No generation of getter/setter methods for fields.

• python: Python language, output one _bb.py file for each .bb file.

  • With -single: Output one file that includes all definitions for all .bb files. The output file name (including the extension) is determined by the -o option.

• java: Java language, output one .java file for each structure defined in each .bb file.

Protocol Syntax

Bubbler uses a concise syntax to define data structures and enumeration types.

See examples in the example directory.

Package Statements

Use the package keyword to define the package name. For example:

package com.example.rovlink;

The package name is used to generate the output file name. For example, if the package name is com.example.rovlink, the output file name is rovlink.xxx and is placed in the ${Output Path}/com/example/ directory.

Only one package statement is allowed in a .bb file, and it can not be duplicated globally.

Option Statements

Use the option keyword to define options. For example:

option omit_empty = true;
option go_package = "example.com/rovlink";
option cpp_namespace = "com::example::rovlink";

The option statement cannot be duplicated in a .bb file.

Warning will be reported if a option is unknown.

Supported Options

omit_empty

If omit_empty is set to true, the generated code will not generate files without typedefs.

package all;

option omit_empty = true;

import "rovlink.bb";
import "control.bb";
import "excomponent.bb";
import "excontrol.bb";
import "exdata.bb";
import "host.bb";
import "mode.bb";
import "sensor.bb";

In this example, the omit_empty option is set to true, and this .bb file will not generate as all.xxx file.

You can use this option to generate multiple .bb files at once, without writing a external script to do multiple bubbler calls.

go_package

If go_package is set, the generated code will use the specified package name in the generated Go code.

cpp_namespace

If cpp_namespace is set, the generated code will use the specified namespace in the generated C++ code.

csharp_namespace

If csharp_namespace is set, the generated code will use the specified namespace in the generated C# code.

java_package

If java_package is set, the generated code will use the specified package name in the generated Java code.

Import Statements

Use the import keyword to import other Bubbler protocol files. For example:

import "control.bb";
import "a.bb";

Enumeration Types

Use the enum keyword to define enumeration types. The definition of an enumeration type includes the enumeration name and enumeration values. For example:

enum FrameType[1] {
    SENSOR_PRESS = 0x00,
    SENSOR_HUMID = 0x01,
    CURRENT_SERVO_A = 0xA0,
    CURRENT_SERVO_B = 0xA1,
};

In this example, FrameType is an enumeration type with four enumeration values: SENSOR_PRESS, SENSOR_HUMID, CURRENT_SERVO_A, and CURRENT_SERVO_B.

Enumeration values cannot be negative (tentatively), and if the value is not filled in, the default value of the enumeration value is the previous enumeration value plus 1.

The number in the square brackets after the enumeration type name indicates the width of the enumeration type, for example, [1] indicates 1 byte. You can also use the # symbol to represent bytes and bits, for example, #1 represents 1 bit, #2 represents 2 bits. You can also use them in combination, for example, 1#4 represents 1 byte 4 bits, that is, 12 bits.

Data Structures

Use the struct keyword to define data structures. The definition of a data structure includes the structure name and a series of fields. For example:

struct Frame[20] {
    FrameType opcode;
    struct some_embed[1] {
        bool valid[#1];
        bool error[#1];
        uint8 source[#3];
        uint8 target[#3];
    };
    uint8<18> payload;
};

In this example, Frame is a data structure with three fields: opcode, some_embed, and payload. opcode is of type FrameType, some_embed is an anonymous embedded data structure, and payload is of type uint8.

Please note that Bubbler does not have the concept of scope (to accommodate the C language), so the names Frame and some_embed as data structure names are not allowed to be duplicated globally, even if some_embed is an anonymous embedded data structure.

Field Types

The Bubbler protocol supports four types of fields: regular fields, anonymous embedded fields, constant fields, and empty fields.

• Regular fields: Consist of a type name, field name, and field width (optional).
• Anonymous embedded fields: An anonymous field, which can be a struct definition or a defined struct name, its internal subfields will be promoted and expanded into the parent structure.
• Constant fields: A field with a fixed value, its value is determined at the time of definition and cannot be modified. The field name is optional. If there is a field name, the corresponding field will be generated. When encoding, the value of the constant field will be ignored. When decoding, the value of the constant field will be checked. If it does not match, an error will be reported.
• Empty fields: A field without a name and type, only width, used for placeholders.

Regular Fields

Regular fields consist of a type name, field name, and field width. For example:

struct Frame {
    RovlinkFrameType opcode;
};

In this example, opcode is a regular field, its type is RovlinkFrameType.

The field width is optional. If the width is not filled in, the field width is the width of the type.

The field width can be less than the width of the type, for example:

struct Frame[20] {
    int64 myInt48[6];
};

In this example, myInt48 is a 6-byte field, its type is int64, but its width is 6 bytes, so it will only occupy 6 bytes of space when encoding.

However, for fields of struct type, the field width must be equal to the width of the type (tentatively)

Anonymous Embedded Fields

Anonymous embedded fields are nameless data structures that can contain multiple subfields. For example:

struct Frame {
    int64 myInt48[6];
    struct some_embed[1] {
        bool valid[#1];
        bool error[#1];
        uint8 source[#3];
        uint8 target[#3];
    };
};

In this example, some_embed is an anonymous embedded field, it contains four subfields: valid, error, source, and target.

The subfields of the anonymous embedded field will be promoted and expanded into the parent structure. The generated structure is as follows:

struct Frame {
    int64_t myInt48;
    bool valid;
    bool error;
    uint8_t source;
    uint8_t target;
};

Anonymous embedded fields can also be a defined data structure, for example:

struct AnotherTest {
    int8<2> arr;
}

struct Frame {
    int64 myInt48[6];
    AnotherTest;
    uint8<18> payload;
};

In this way, the generated structure is as follows:

struct Frame {
    int64_t myInt48;
    int8_t arr[2];
    uint8_t payload;
};

Constant Fields

Constant fields are fields with a fixed value, its value is determined at the time of definition and cannot be modified. For example:

struct Frame {
    uint8 FRAME_HEADER = 0xAA;
};

In this example, FRAME_HEADER is a constant field with a value of 0xAA.

The value of the constant field will be ignored during encoding and checked during decoding. If it does not match, an error will be reported.

Empty Fields

Empty fields are fields without a name and type, they only have a width. Empty fields are often used for padding or aligning data structures. For example:

struct Frame {
    void [#2];
};

In this example, void [#2] is an empty field that occupies 2 bits of space.

Field Options

Field options are used to specify additional attributes of a field. For example, you can use the order option to specify the byte order of an array:

struct AnotherTest {
    int8<2> arr [order = "big"];
}

In this example, the byte order of the arr field is set to big-endian.

Custom getter/setter

You can define custom getter and setter methods for a field to perform specific operations when reading or writing field values. For example:

struct SensorTemperatureData {
    uint16 temperature[2] {
        get temperature_display(float64): value / 10 - 40;
        set temperature_display(float64): value == 0 ? 0 : (value + 40) * 10;
        set another_custom_setter(uint8): value == 0 ? 0 : (value + 40) * 10;
    };
}

In this example, the temperature field has a custom getter method and two custom setter methods.

The custom getter named temperature_display returns afloat64 type and calculates the result based on value / 10 - 40. Here,value is filled with the field value and is of type uint16.

The custom setter named temperature_display accepts a float64 type parameter and calculates the result based on value == 0 ? 0 : (value + 40) * 10 to set the field value. Here, value is filled with the parameter value and is of type float64.

The custom setter named another_custom_setter accepts a uint8 type parameter and calculates the result based on value == 0 ? 0 : (value + 40) * 10 to set the field value. Here, value is filled with the parameter value and is of type uint8.

Contributing

Contributions to Bubbler are welcome.

License

MIT License