neoneo-go/pkg/vm/README.md
Anthony De Meulemeester 4bd5b2812e
Optimisations and API changes for smart contracts (#67)
* support VM to pass method and arguments to a script.

* added support for type assertions in smartcontracts.

* added native vm support for print.

* moved VM API packages to vm -> API

* reverted the native Print opcode in favor of runtime.Log

* added support for registering custom interop hooks in the VM.

* Updated README

* Updated compiler with @OPTIMIZE tags

* Moved more tests to VM package.

* optimized and refactored compiler and vm API

* updated README with new smartcontract apis

* bumped version
2018-04-10 11:45:31 +02:00

223 lines
4.7 KiB
Markdown

# NEO-GO-VM
A cross platform virtual machine implementation for `avm` compatible programs.
# Installation
## With neo-go
Install dependencies.
`neo-go` uses [dep](https://github.com/golang/dep) as its dependency manager. After installing `deps` you can run:
```
make deps
```
Build the `neo-go` cli:
```
make build
```
Start the virtual machine:
```
./bin/neo-go vm
```
```
_ ____________ __________ _ ____ ___
/ | / / ____/ __ \ / ____/ __ \ | | / / |/ /
/ |/ / __/ / / / /_____/ / __/ / / /____| | / / /|_/ /
/ /| / /___/ /_/ /_____/ /_/ / /_/ /_____/ |/ / / / /
/_/ |_/_____/\____/ \____/\____/ |___/_/ /_/
NEO-GO-VM >
```
## Standalone
More information about standalone installation coming soon.
# Usage
```
_ ____________ __________ _ ____ ___
/ | / / ____/ __ \ / ____/ __ \ | | / / |/ /
/ |/ / __/ / / / /_____/ / __/ / / /____| | / / /|_/ /
/ /| / /___/ /_/ /_____/ /_/ / /_/ /_____/ |/ / / / /
/_/ |_/_____/\____/ \____/\____/ |___/_/ /_/
NEO-GO-VM > help
COMMAND USAGE
astack show alt stack details
break place a breakpoint (> break 1)
cont continue execution of the current loaded script
estack show evaluation stack details
exit exit the VM prompt
help show available commands
ip show the current instruction
istack show invocation stack details
loadavm load an avm script into the VM (> load /path/to/script.avm)
loadgo compile and load a .go file into the VM (> load /path/to/file.go)
loadhex load a hex string into the VM (> loadhex 006166 )
ops show the opcodes of the current loaded program
run execute the current loaded script
step step (n) instruction in the program (> step 10)
```
### Loading in your script
To load an avm script into the VM:
```
NEO-GO-VM > loadavm ../contract.avm
READY: loaded 36 instructions
```
Run the script:
```
NEO-GO-VM > run
[
{
"value": 1,
"type": "BigInteger"
}
]
```
You can also directly compile and load `.go` files:
```
NEO-GO-VM > loadgo ../contract.go
READY: loaded 36 instructions
```
To make it even more complete, you can directly load hex strings into the VM:
```
NEO-GO-VM > loadhex 54c56b006c766b00527ac46c766b00c391640b006203005a616c756662030000616c7566
READY: loaded 36 instructions
NEO-GO-VM > run
[
{
"value": 10,
"type": "BigInteger"
}
]
```
### Running programs with arguments
You can invoke smart contracts with arguments. Take the following ***roll the dice*** smartcontract as example.
```
package rollthedice
import "github.com/CityOfZion/neo-go/pkg/vm/api/runtime"
func Main(method string, args []interface{}) int {
if method == "rollDice" {
// args parameter is always of type []interface, hence we need to
// cast it to an int.
rollDice(args[0].(int))
}
return 0
}
func rollDice(number int) {
if number == 0 {
runtime.Log("you rolled 0, better luck next time!")
}
if number == 1 {
runtime.Log("you rolled 1, still better then 0!")
}
if number == 2 {
runtime.Log("you rolled 2, coming closer..")
}
if number == 3 {
runtime.Log("Sweet you rolled 3. This dice has only 3 sides o_O")
}
}
```
To invoke this contract we need to specify both the method and the arguments.
The first parameter (called method or operation) is always of type string. Notice that arguments can have different types, to make the VM aware of the type we need to specify it when calling `run`:
```
NEO-GO-VM > run rollDice int:1
```
> The method is always of type string, hence we don't need to specify the type.
To add more then 1 argument:
```
NEO-GO-VM > run someMethod int:1 int:2 string:foo string:bar
```
Current supported types:
- `int (int:1 int:100)`
- `string (string:foo string:this is a string)`
### Debugging
The `neo-go-vm` provides a debugger to inspect your program in-depth.
Step 4 instructions.
```
NEO-GO-VM > step 4
at breakpoint 4 (Opush4)
NEO-GO-VM 4 >
```
Using just `step` will execute 1 instruction at a time.
```
NEO-GO-VM > step
instruction pointer at 5 (Odup)
NEO-GO-VM 5 >
```
To place breakpoints:
```
NEO-GO-VM > break 10
breakpoint added at instruction 10
NEO-GO-VM > cont
at breakpoint 10 (Osetitem)
NEO-GO-VM 10 > cont
```
Inspecting the evaluation stack:
```
NEO-GO-VM > estack
[
{
"value": [
null,
null,
null,
null,
null,
null,
null
],
"type": "Array"
},
{
"value": 4,
"type": "BigInteger"
}
]
```
There are more stacks that you can inspect.
- `astack` alt stack
- `istack` invocation stack