forked from TrueCloudLab/neoneo-go
56 lines
1.5 KiB
Go
56 lines
1.5 KiB
Go
package stack
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import "errors"
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// Invocation embeds a Random Access stack
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// Providing helper methods for the context object
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type Invocation struct{ RandomAccess }
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//NewInvocation will return a new
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// Invocation stack
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func NewInvocation() *Invocation {
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return &Invocation{
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RandomAccess{
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vals: make([]Item, 0, StackAverageSize),
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},
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}
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}
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func (i *Invocation) peekContext(n uint16) (*Context, error) {
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item, err := i.Peek(n)
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if err != nil {
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return nil, err
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}
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return item.Context()
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}
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// CurrentContext returns the current context on the invocation stack
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func (i *Invocation) CurrentContext() (*Context, error) {
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return i.peekContext(0)
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}
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// RemoveCurrentContext removes the context on the top of the invocation stack
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// This is a convenience method for Pop
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func (i *Invocation) RemoveCurrentContext() error {
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_, err := i.Pop()
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return err
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}
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// CallingContext will return the cntext item
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// that will be called next.
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func (i *Invocation) CallingContext() (*Context, error) {
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if i.Len() < 1 {
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return nil, errors.New("Length of invocation stack is < 1, no calling context")
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}
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return i.peekContext(1)
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}
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// EntryContext will return the context item that
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// started the program
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func (i *Invocation) EntryContext() (*Context, error) {
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// firstItemIndex refers to the first item
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// that was popped on the stack
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firstItemIndex := uint16(i.Len() - 1) // N.B. if this overflows because len is zero, then an error will be returned
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return i.peekContext(firstItemIndex)
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}
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