101 lines
2.7 KiB
Go
101 lines
2.7 KiB
Go
package engine
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import (
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"context"
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"fmt"
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"io"
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"log"
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"git.defalsify.org/festive/resource"
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"git.defalsify.org/festive/state"
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"git.defalsify.org/festive/vm"
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)
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//
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//type Config struct {
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// FlagCount uint32
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// CacheSize uint32
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//}
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// Engine is an execution engine that handles top-level errors when running user inputs against currently exposed bytecode.
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type Engine struct {
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st *state.State
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rs resource.Resource
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}
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// NewEngine creates a new Engine
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func NewEngine(st *state.State, rs resource.Resource) Engine {
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engine := Engine{st, rs}
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return engine
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}
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// Init must be explicitly called before using the Engine instance.
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//
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// It makes sure bootstrapping code has been executed, and that the exposed bytecode is ready for user input.
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func(en *Engine) Init(ctx context.Context) error {
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b := vm.NewLine([]byte{}, vm.MOVE, []string{"root"}, nil, nil)
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var err error
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_, err = vm.Run(b, en.st, en.rs, ctx)
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if err != nil {
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return err
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}
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location := en.st.Where()
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code, err := en.rs.GetCode(location)
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if err != nil {
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return err
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}
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return en.st.AppendCode(code)
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}
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// Exec processes user input against the current state of the virtual machine environment.
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//
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// If successfully executed:
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// - output of the last execution is available using the WriteResult(...) call
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// - Exec(...) may be called again with new input
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//
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// This implementation is in alpha state. That means that any error emitted may have left the system in an undefined state.
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//
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// TODO: Disambiguate errors as critical and resumable errors.
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//
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// Fails if:
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// - input is objectively invalid (too long etc)
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// - no current bytecode is available
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// - input processing against bytcode failed
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func (en *Engine) Exec(input []byte, ctx context.Context) error {
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l := uint8(len(input))
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if l > 255 {
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return fmt.Errorf("input too long (%v)", l)
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}
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input = append([]byte{l}, input...)
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code, err := en.st.GetCode()
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if err != nil {
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return err
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}
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if len(code) == 0 {
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return fmt.Errorf("no code to execute")
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}
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code, err = vm.Apply(input, code, en.st, en.rs, ctx)
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en.st.SetCode(code)
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return err
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}
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// WriteResult writes the output of the last vm execution to the given writer.
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//
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// Fails if
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// - required data inputs to the template are not available.
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// - the template for the given node point is note available for retrieval using the resource.Resource implementer.
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// - the supplied writer fails to process the writes.
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func(en *Engine) WriteResult(w io.Writer) error {
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location := en.st.Where()
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v, err := en.st.Get()
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if err != nil {
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return err
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}
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r, err := en.rs.RenderTemplate(location, v)
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if err != nil {
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return err
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}
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c, err := io.WriteString(w, r)
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log.Printf("%v bytes written as result for %v", c, location)
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return err
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}
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