939403c10b
This simplifies FunctionListener definition by making it possible to implement both interfaces without intermediate state. Passing the function definition to the before/after callbacks is the key. This also continues efforts towards Go 1.19 doc formatting. Signed-off-by: Adrian Cole <adrian@tetrate.io>
59 lines
2.4 KiB
Go
59 lines
2.4 KiB
Go
package experimental
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import (
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"context"
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"github.com/tetratelabs/wazero/api"
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)
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// FunctionListenerFactoryKey is a context.Context Value key. Its associated value should be a FunctionListenerFactory.
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//
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// Note: This is interpreter-only for now!
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//
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// See https://github.com/tetratelabs/wazero/issues/451
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type FunctionListenerFactoryKey struct{}
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// FunctionListenerFactory returns FunctionListeners to be notified when a
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// function is called.
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type FunctionListenerFactory interface {
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// NewListener returns a FunctionListener for a defined function. If nil is
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// returned, no listener will be notified.
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NewListener(api.FunctionDefinition) FunctionListener
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}
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// FunctionListener can be registered for any function via
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// FunctionListenerFactory to be notified when the function is called.
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type FunctionListener interface {
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// Before is invoked before a function is called. The returned context will
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// be used as the context of this function call.
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//
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// # Params
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//
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// - ctx: the context of the caller function which must be the same
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// instance or parent of the result.
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// - def: the function definition.
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// - paramValues: api.ValueType encoded parameters.
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Before(ctx context.Context, def api.FunctionDefinition, paramValues []uint64) context.Context
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// After is invoked after a function is called.
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//
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// # Params
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//
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// - ctx: the context returned by Before.
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// - def: the function definition.
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// - err: nil if the function didn't err
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// - resultValues: api.ValueType encoded results.
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After(ctx context.Context, def api.FunctionDefinition, err error, resultValues []uint64)
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}
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// TODO: We need to add tests to enginetest to ensure contexts nest. A good test can use a combination of call and call
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// indirect in terms of depth and breadth. The test could show a tree 3 calls deep where the there are a couple calls at
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// each depth under the root. The main thing this can help prevent is accidentally swapping the context internally.
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// TODO: Errors aren't handled, and the After hook should accept one along with the result values.
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// TODO: The context parameter of the After hook is not the same as the Before hook. This means interceptor patterns
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// are awkward. Ex. something like timing is difficult as it requires propagating a stack. Otherwise, nested calls will
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// overwrite each other's "since" time. Propagating a stack is further awkward as the After hook needs to know the
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// position to read from which might be subtle.
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