75 lines
1.8 KiB
Go
75 lines
1.8 KiB
Go
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package wasm
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import (
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"context"
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"github.com/tetratelabs/wazero/api"
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"github.com/tetratelabs/wazero/experimental"
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)
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type snapshotskey struct{}
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// withSetjmpLongjmp updates the context to contain wazero/experimental.Snapshotter{} support,
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// and embeds the necessary snapshots map required for later calls to Setjmp() / Longjmp().
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func withSetjmpLongjmp(ctx context.Context) context.Context {
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snapshots := make(map[uint32]experimental.Snapshot, 10)
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ctx = experimental.WithSnapshotter(ctx)
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ctx = context.WithValue(ctx, snapshotskey{}, snapshots)
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return ctx
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}
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func getSnapshots(ctx context.Context) map[uint32]experimental.Snapshot {
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v, _ := ctx.Value(snapshotskey{}).(map[uint32]experimental.Snapshot)
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return v
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}
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// setjmp implements the C function: setjmp(env jmp_buf)
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func setjmp(ctx context.Context, mod api.Module, stack []uint64) {
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// Input arguments.
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envptr := api.DecodeU32(stack[0])
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// Take snapshot of current execution environment.
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snapshotter := experimental.GetSnapshotter(ctx)
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snapshot := snapshotter.Snapshot()
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// Get stored snapshots map.
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snapshots := getSnapshots(ctx)
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if snapshots == nil {
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panic("setjmp / longjmp not supported")
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}
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// Set latest snapshot in map.
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snapshots[envptr] = snapshot
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// Set return.
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stack[0] = 0
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}
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// longjmp implements the C function: int longjmp(env jmp_buf, value int)
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func longjmp(ctx context.Context, mod api.Module, stack []uint64) {
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// Input arguments.
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envptr := api.DecodeU32(stack[0])
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// val := stack[1]
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// Get stored snapshots map.
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snapshots := getSnapshots(ctx)
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if snapshots == nil {
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panic("setjmp / longjmp not supported")
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}
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// Get snapshot stored in map.
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snapshot := snapshots[envptr]
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if snapshot == nil {
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panic("must first call setjmp")
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}
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// Set return.
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stack[0] = 0
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// Restore execution and
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// return passed value arg.
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snapshot.Restore(stack[1:])
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}
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