Current File : //usr/local/go119/src/cmd/internal/src/xpos.go
// Copyright 2016 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.
// This file implements the compressed encoding of source
// positions using a lookup table.
package src
// XPos is a more compact representation of Pos.
type XPos struct {
index int32
lico
}
// NoXPos is a valid unknown position.
var NoXPos XPos
// IsKnown reports whether the position p is known.
// XPos.IsKnown() matches Pos.IsKnown() for corresponding
// positions.
func (p XPos) IsKnown() bool {
return p.index != 0 || p.Line() != 0
}
// Before reports whether the position p comes before q in the source.
// For positions with different bases, ordering is by base index.
func (p XPos) Before(q XPos) bool {
n, m := p.index, q.index
return n < m || n == m && p.lico < q.lico
}
// SameFile reports whether p and q are positions in the same file.
func (p XPos) SameFile(q XPos) bool {
return p.index == q.index
}
// SameFileAndLine reports whether p and q are positions on the same line in the same file.
func (p XPos) SameFileAndLine(q XPos) bool {
return p.index == q.index && p.lico.SameLine(q.lico)
}
// After reports whether the position p comes after q in the source.
// For positions with different bases, ordering is by base index.
func (p XPos) After(q XPos) bool {
n, m := p.index, q.index
return n > m || n == m && p.lico > q.lico
}
// WithNotStmt returns the same location to be marked with DWARF is_stmt=0
func (p XPos) WithNotStmt() XPos {
p.lico = p.lico.withNotStmt()
return p
}
// WithDefaultStmt returns the same location with undetermined is_stmt
func (p XPos) WithDefaultStmt() XPos {
p.lico = p.lico.withDefaultStmt()
return p
}
// WithIsStmt returns the same location to be marked with DWARF is_stmt=1
func (p XPos) WithIsStmt() XPos {
p.lico = p.lico.withIsStmt()
return p
}
// WithBogusLine returns a bogus line that won't match any recorded for the source code.
// Its use is to disrupt the statements within an infinite loop so that the debugger
// will not itself loop infinitely waiting for the line number to change.
// gdb chooses not to display the bogus line; delve shows it with a complaint, but the
// alternative behavior is to hang.
func (p XPos) WithBogusLine() XPos {
if p.index == 0 {
// See #35652
panic("Assigning a bogus line to XPos with no file will cause mysterious downstream failures.")
}
p.lico = makeBogusLico()
return p
}
// WithXlogue returns the same location but marked with DWARF function prologue/epilogue
func (p XPos) WithXlogue(x PosXlogue) XPos {
p.lico = p.lico.withXlogue(x)
return p
}
// LineNumber returns a string for the line number, "?" if it is not known.
func (p XPos) LineNumber() string {
if !p.IsKnown() {
return "?"
}
return p.lico.lineNumber()
}
// FileIndex returns a smallish non-negative integer corresponding to the
// file for this source position. Smallish is relative; it can be thousands
// large, but not millions.
func (p XPos) FileIndex() int32 {
return p.index
}
func (p XPos) LineNumberHTML() string {
if !p.IsKnown() {
return "?"
}
return p.lico.lineNumberHTML()
}
// AtColumn1 returns the same location but shifted to column 1.
func (p XPos) AtColumn1() XPos {
p.lico = p.lico.atColumn1()
return p
}
// A PosTable tracks Pos -> XPos conversions and vice versa.
// Its zero value is a ready-to-use PosTable.
type PosTable struct {
baseList []*PosBase
indexMap map[*PosBase]int
nameMap map[string]int // Maps file symbol name to index for debug information.
}
// XPos returns the corresponding XPos for the given pos,
// adding pos to t if necessary.
func (t *PosTable) XPos(pos Pos) XPos {
m := t.indexMap
if m == nil {
// Create new list and map and populate with nil
// base so that NoPos always gets index 0.
t.baseList = append(t.baseList, nil)
m = map[*PosBase]int{nil: 0}
t.indexMap = m
t.nameMap = make(map[string]int)
}
i, ok := m[pos.base]
if !ok {
i = len(t.baseList)
t.baseList = append(t.baseList, pos.base)
t.indexMap[pos.base] = i
if _, ok := t.nameMap[pos.base.symFilename]; !ok {
t.nameMap[pos.base.symFilename] = len(t.nameMap)
}
}
return XPos{int32(i), pos.lico}
}
// Pos returns the corresponding Pos for the given p.
// If p cannot be translated via t, the function panics.
func (t *PosTable) Pos(p XPos) Pos {
var base *PosBase
if p.index != 0 {
base = t.baseList[p.index]
}
return Pos{base, p.lico}
}
// FileIndex returns the index of the given filename(symbol) in the PosTable, or -1 if not found.
func (t *PosTable) FileIndex(filename string) int {
if v, ok := t.nameMap[filename]; ok {
return v
}
return -1
}
// FileTable returns a slice of all files used to build this package.
func (t *PosTable) FileTable() []string {
// Create a LUT of the global package level file indices. This table is what
// is written in the debug_lines header, the file[N] will be referenced as
// N+1 in the debug_lines table.
fileLUT := make([]string, len(t.nameMap))
for str, i := range t.nameMap {
fileLUT[i] = str
}
return fileLUT
}
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