go posmap 源码
golang posmap 代码
文件路径：/src/cmd/compile/internal/noder/posmap.go
// Copyright 2021 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package noder
import (
"cmd/compile/internal/base"
"cmd/compile/internal/syntax"
"cmd/internal/src"
)
// A posMap handles mapping from syntax.Pos to src.XPos.
type posMap struct {
bases map[*syntax.PosBase]*src.PosBase
cache struct {
last *syntax.PosBase
base *src.PosBase
}
}
type poser interface{ Pos() syntax.Pos }
type ender interface{ End() syntax.Pos }
func (m *posMap) pos(p poser) src.XPos { return m.makeXPos(p.Pos()) }
func (m *posMap) end(p ender) src.XPos { return m.makeXPos(p.End()) }
func (m *posMap) makeXPos(pos syntax.Pos) src.XPos {
// Predeclared objects (e.g., the result parameter for error.Error)
// do not have a position.
if !pos.IsKnown() {
return src.NoXPos
}
posBase := m.makeSrcPosBase(pos.Base())
return base.Ctxt.PosTable.XPos(src.MakePos(posBase, pos.Line(), pos.Col()))
}
// makeSrcPosBase translates from a *syntax.PosBase to a *src.PosBase.
func (m *posMap) makeSrcPosBase(b0 *syntax.PosBase) *src.PosBase {
// fast path: most likely PosBase hasn't changed
if m.cache.last == b0 {
return m.cache.base
}
b1, ok := m.bases[b0]
if !ok {
fn := b0.Filename()
absfn := trimFilename(b0)
if b0.IsFileBase() {
b1 = src.NewFileBase(fn, absfn)
} else {
// line directive base
p0 := b0.Pos()
p0b := p0.Base()
if p0b == b0 {
panic("infinite recursion in makeSrcPosBase")
}
p1 := src.MakePos(m.makeSrcPosBase(p0b), p0.Line(), p0.Col())
b1 = src.NewLinePragmaBase(p1, fn, absfn, b0.Line(), b0.Col())
}
if m.bases == nil {
m.bases = make(map[*syntax.PosBase]*src.PosBase)
}
m.bases[b0] = b1
}
// update cache
m.cache.last = b0
m.cache.base = b1
return b1
}
func (m *posMap) join(other *posMap) {
if m.bases == nil {
m.bases = make(map[*syntax.PosBase]*src.PosBase)
}
for k, v := range other.bases {
if m.bases[k] != nil {
base.Fatalf("duplicate posmap bases")
}
m.bases[k] = v
}
}
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