SVML Specification

This page serves as a repository for preliminary specification of a virtual machine code (byte code) format for Virtual Machine implementations of Source.

Assembly code format

The assembly code consists of an array of arrays. Each element array represents one instruction. Each instruction has the opcode in position 0, followed by the arguments, which might include numbers, boolean values or strings, depending on the instruction.

Bytecode format

Header:

• Magic word: 0x5005ACAD
• Version number: 2 bytes for minor, 2 bytes for major
• Constant pool count
• Constant pool
• code

The code is a sequence of bytes, with segments of length 1 to 3 representing individual instructions. The first byte is the opcode, and the following bytes are the arguments.

See here for comparison: https://en.wikipedia.org/wiki/Java_class_file

Instruction set

(click on the link)

Constant pool

Each constant pool entry has:

• 1 byte: Type of constant pool entry
• 2 bytes: Length of constant pool entry in bytes (including 1 + 2)
• remaining bytes: data of constant pool entry (for example the string, in unicode)