Documentation
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Overview ¶
Package xpathleaf lets a host package inside this module mark a function it registers with package xpath as a leaf, without adding exported API to xpath. A leaf never calls back into user code, never keeps the context past its return and never writes to it, so a call to one counts recursion depth on the caller's context in place instead of copying it (see xpath's Function.leaf). host.go carries the other hooks a host needs on the same terms.
Index ¶
Constants ¶
This section is empty.
Variables ¶
var ( GetHost func(ctx any) *Host WithHost func(ctx any, h *Host) any SetHost func(ctx any, h *Host) WithFocusHost func(ctx any, item xdm.Item, pos, size int, h *Host) any )
Package xpath sets these in its init. ctx is a *xpath.Context; WithHost and WithFocusHost return a copy of it, SetHost writes in place and is only for a context the caller has just made and not yet shared.
BindHost, set by the host, is consulted when package xpath turns the library function name into a function item (a named function reference, fn:function-lookup, or a partial application) at ctx, a *xpath.Context. A non-nil result maps the context of each later call of the item to the one the function runs under, putting back the host state it read at ctx: an XSLT function such as key() keeps answering for the transformation the item was made in, as it did when each transformation built its own library.
var Mark func(fn any)
Mark marks fn, which must be a *xpath.Function, as a leaf. Package xpath sets it in its init, so it is non-nil wherever xpath is linked in.
var NewStepMemo func() any
NewStepMemo returns an empty memo for a StepMemoHost. Package xpath sets it in its init.
Functions ¶
This section is empty.
Types ¶
type Host ¶
type Host struct {
// Runtime is the host's own state (XSLT: the transform runtime).
Runtime any
// Current is what fn:current() returns, a single item or, cleared, nil.
// CurrentSet says it is bound at all. A sequence rather than the item, so
// that current() returns it without allocating.
Current xdm.Sequence
CurrentSet bool
// Absent is set across a dynamic function call, where fn:current()
// behaves as if the context item were absent (XSLT XTDE1360).
Absent bool
// Unbound holds host-defined bits of context components this context is
// known to have cleared (XSLT: grouping, merge, regex captures).
Unbound uint8
}
Host is a host language's dynamic state, carried on an xpath.Context in one unexported field and copied with it, as the focus is. XSLT keeps its transform runtime and fn:current() here rather than in variable bindings, whose every lookup walked the whole binding chain.
A Host on a context is never written: a change makes a new one.
type StableLibrary ¶
type StableLibrary interface {
// WrappedLibrary returns the xpath.FunctionLibrary the wrapper consults.
WrappedLibrary() any
}
StableLibrary is implemented by a host's xpath.FunctionLibrary wrapper whose answers depend only on its own comparable fields, the library it wraps and Context.StaticHost. Package xpath caches a call site's resolution through such a wrapper, keyed on the wrapper's value; a wrapper that does not implement it is looked up on every call.
type StepMemoHost ¶
type StepMemoHost interface{ StepMemo() any }
StepMemoHost is implemented by a Host.Runtime that gives package xpath somewhere to remember step walks over parsed trees for as long as the runtime lives (see xpath's stepMemo). StepMemo returns what NewStepMemo made for it. A host that implements it promises not to change a parsed tree while that runtime evaluates.
Source Files