128 lines
3.0 KiB
Go
128 lines
3.0 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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//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 loads and executes code for the start node.
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func(en *Engine) Init(sym string, ctx context.Context) error {
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err := en.st.SetInput([]byte{})
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if err != nil {
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return err
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}
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b := vm.NewLine(nil, vm.MOVE, []string{sym}, nil, nil)
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b, 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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en.st.SetCode(b)
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return nil
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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, output of the last execution is available using the WriteResult call.
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//
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// A bool return valus of false indicates that execution should be terminated. Calling Exec again has undefined effects.
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//
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// Fails if:
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// - input is formally 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) (bool, error) {
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err := vm.ValidInput(input)
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if err != nil {
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return true, err
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}
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err = en.st.SetInput(input)
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if err != nil {
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return false, err
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}
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log.Printf("new execution with input '%s' (0x%x)", input, input)
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code, err := en.st.GetCode()
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if err != nil {
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return false, err
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}
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if len(code) == 0 {
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return false, fmt.Errorf("no code to execute")
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}
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code, err = vm.Run(code, en.st, en.rs, ctx)
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if err != nil {
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return false, err
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}
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v, err := en.st.MatchFlag(state.FLAG_TERMINATE, false)
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if err != nil {
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return false, err
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}
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if v {
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if len(code) > 0 {
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log.Printf("terminated with code remaining: %x", code)
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}
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return false, nil
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}
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en.st.SetCode(code)
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if len(code) == 0 {
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log.Printf("runner finished with no remaining code")
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return false, nil
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}
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return true, nil
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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, idx := 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, idx, nil)
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if err != nil {
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return err
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}
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m, err := en.rs.RenderMenu(idx)
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if err != nil {
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return err
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}
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if len(m) > 0 {
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r += "\n" + m
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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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