139 lines
3.7 KiB
Go
139 lines
3.7 KiB
Go
package vm
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import (
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"encoding/binary"
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"fmt"
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"context"
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"git.defalsify.org/festive/state"
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"git.defalsify.org/festive/resource"
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)
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type Runner func(instruction []byte, st state.State, rs resource.Fetcher, ctx context.Context) (state.State, []byte, error)
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func Run(instruction []byte, st state.State, rs resource.Fetcher, ctx context.Context) (state.State, []byte, error) {
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var err error
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for len(instruction) > 0 {
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op := binary.BigEndian.Uint16(instruction[:2])
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if op > _MAX {
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return st, instruction, fmt.Errorf("opcode value %v out of range (%v)", op, _MAX)
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}
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switch op {
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case CATCH:
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st, instruction, err = RunCatch(instruction[2:], st, rs, ctx)
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case CROAK:
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st, instruction, err = RunCroak(instruction[2:], st, rs, ctx)
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case LOAD:
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st, instruction, err = RunLoad(instruction[2:], st, rs, ctx)
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case RELOAD:
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st, instruction, err = RunReload(instruction[2:], st, rs, ctx)
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case MAP:
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st, instruction, err = RunMap(instruction[2:], st, rs, ctx)
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case SINK:
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st, instruction, err = RunSink(instruction[2:], st, rs, ctx)
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default:
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err = fmt.Errorf("Unhandled state: %v", op)
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}
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if err != nil {
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return st, instruction, err
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}
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}
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return st, instruction, nil
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}
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func RunMap(instruction []byte, st state.State, rs resource.Fetcher, ctx context.Context) (state.State, []byte, error) {
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head, tail, err := instructionSplit(instruction)
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if err != nil {
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return st, instruction, err
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}
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st.Map(head)
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return st, tail, nil
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}
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func RunSink(instruction []byte, st state.State, rs resource.Fetcher, ctx context.Context) (state.State, []byte, error) {
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return st, nil, nil
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}
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func RunCatch(instruction []byte, st state.State, rs resource.Fetcher, ctx context.Context) (state.State, []byte, error) {
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head, tail, err := instructionSplit(instruction)
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if err != nil {
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return st, instruction, err
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}
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r, err := rs.Get(head)
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if err != nil {
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return st, instruction, err
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}
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st.Add(head, r, uint32(len(r)))
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return st, tail, nil
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}
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func RunCroak(instruction []byte, st state.State, rs resource.Fetcher, ctx context.Context) (state.State, []byte, error) {
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head, tail, err := instructionSplit(instruction)
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if err != nil {
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return st, instruction, err
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}
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_ = head
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st.Reset()
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return st, tail, nil
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}
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func RunLoad(instruction []byte, st state.State, rs resource.Fetcher, ctx context.Context) (state.State, []byte, error) {
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head, tail, err := instructionSplit(instruction)
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if err != nil {
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return st, instruction, err
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}
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if !st.Check(head) {
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return st, instruction, fmt.Errorf("key %v already loaded", head)
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}
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sz := uint32(tail[0])
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tail = tail[1:]
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r, err := refresh(head, tail, rs, ctx)
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if err != nil {
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return st, tail, err
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}
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st.Add(head, r, sz)
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return st, tail, nil
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}
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func RunReload(instruction []byte, st state.State, rs resource.Fetcher, ctx context.Context) (state.State, []byte, error) {
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head, tail, err := instructionSplit(instruction)
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if err != nil {
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return st, instruction, err
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}
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r, err := refresh(head, tail, rs, ctx)
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if err != nil {
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return st, tail, err
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}
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st.Add(head, r, uint32(len(r)))
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return st, tail, nil
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}
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func RunMove(instruction []byte, st state.State, rs resource.Fetcher, ctx context.Context) (state.State, []byte, error) {
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return st, nil, nil
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}
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func refresh(key string, sym []byte, rs resource.Fetcher, ctx context.Context) (string, error) {
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fn, err := rs.FuncFor(key)
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if err != nil {
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return "", err
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}
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return fn(sym, ctx)
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}
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func instructionSplit(b []byte) (string, []byte, error) {
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if len(b) == 0 {
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return "", nil, fmt.Errorf("argument is empty")
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}
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sz := uint8(b[0])
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if sz == 0 {
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return "", nil, fmt.Errorf("zero-length argument")
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}
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tailSz := uint8(len(b))
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if tailSz < sz {
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return "", nil, fmt.Errorf("corrupt instruction, len %v less than symbol length: %v", tailSz, sz)
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}
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r := string(b[1:1+sz])
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return r, b[1+sz:], nil
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}
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