vise/engine/loop.go

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1.2 KiB
Go
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package engine
import (
"bufio"
"context"
"fmt"
"io"
"log"
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"strings"
)
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// Loop starts an engine execution loop with the given symbol as the starting node.
//
// The root reads inputs from the provided reader, one line at a time.
//
// It will execute until running out of bytecode in the buffer.
//
// Any error not handled by the engine will terminate the oop and return an error.
//
// Rendered output is written to the provided writer.
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func Loop(en *Engine, reader io.Reader, writer io.Writer, ctx context.Context) error {
var err error
_, err = en.WriteResult(writer, ctx)
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if err != nil {
return err
}
writer.Write([]byte{0x0a})
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running := true
bufReader := bufio.NewReader(reader)
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for running {
in, err := bufReader.ReadString('\n')
if err == io.EOF {
log.Printf("EOF found, that's all folks")
return nil
}
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if err != nil {
return fmt.Errorf("cannot read input: %v\n", err)
}
in = strings.TrimSpace(in)
running, err = en.Exec([]byte(in), ctx)
if err != nil {
return fmt.Errorf("unexpected termination: %v\n", err)
}
_, err = en.WriteResult(writer, ctx)
if err != nil {
return err
}
writer.Write([]byte{0x0a})
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}
return nil
}