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matterbridge/vendor/github.com/google/gops/internal/obj/obj.go

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2017-03-23 22:28:55 +00:00
// Copyright 2009 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 obj
import (
"fmt"
"path/filepath"
"sort"
"strings"
)
// A LineHist records the history of the file input stack, which maps the virtual line number,
// an incrementing count of lines processed in any input file and typically named lineno,
// to a stack of file:line pairs showing the path of inclusions that led to that position.
// The first line directive (//line in Go, #line in assembly) is treated as pushing
// a new entry on the stack, so that errors can report both the actual and translated
// line number.
//
// In typical use, the virtual lineno begins at 1, and file line numbers also begin at 1,
// but the only requirements placed upon the numbers by this code are:
// - calls to Push, Update, and Pop must be monotonically increasing in lineno
// - except as specified by those methods, virtual and file line number increase
// together, so that given (only) calls Push(10, "x.go", 1) and Pop(15),
// virtual line 12 corresponds to x.go line 3.
type LineHist struct {
Top *LineStack // current top of stack
Ranges []LineRange // ranges for lookup
Dir string // directory to qualify relative paths
TrimPathPrefix string // remove leading TrimPath from recorded file names
PrintFilenameOnly bool // ignore path when pretty-printing a line; internal use only
GOROOT string // current GOROOT
}
// A LineStack is an entry in the recorded line history.
// Although the history at any given line number is a stack,
// the record for all line processed forms a tree, with common
// stack prefixes acting as parents.
type LineStack struct {
Parent *LineStack // parent in inclusion stack
Lineno int // virtual line number where this entry takes effect
File string // file name used to open source file, for error messages
AbsFile string // absolute file name, for pcln tables
FileLine int // line number in file at Lineno
Directive bool
Sym *LSym // for linkgetline - TODO(rsc): remove
}
func (stk *LineStack) fileLineAt(lineno int) int {
return stk.FileLine + lineno - stk.Lineno
}
// The span of valid linenos in the recorded line history can be broken
// into a set of ranges, each with a particular stack.
// A LineRange records one such range.
type LineRange struct {
Start int // starting lineno
Stack *LineStack // top of stack for this range
}
// startRange starts a new range with the given top of stack.
func (h *LineHist) startRange(lineno int, top *LineStack) {
h.Top = top
h.Ranges = append(h.Ranges, LineRange{top.Lineno, top})
}
// setFile sets stk.File = file and also derives stk.AbsFile.
func (h *LineHist) setFile(stk *LineStack, file string) {
// Note: The exclusion of stk.Directive may be wrong but matches what we've done before.
// The check for < avoids putting a path prefix on "<autogenerated>".
abs := file
if h.Dir != "" && !filepath.IsAbs(file) && !strings.HasPrefix(file, "<") && !stk.Directive {
abs = filepath.Join(h.Dir, file)
}
// Remove leading TrimPathPrefix, or else rewrite $GOROOT to literal $GOROOT.
if h.TrimPathPrefix != "" && hasPathPrefix(abs, h.TrimPathPrefix) {
if abs == h.TrimPathPrefix {
abs = ""
} else {
abs = abs[len(h.TrimPathPrefix)+1:]
}
} else if hasPathPrefix(abs, h.GOROOT) {
abs = "$GOROOT" + abs[len(h.GOROOT):]
}
if abs == "" {
abs = "??"
}
abs = filepath.Clean(abs)
stk.AbsFile = abs
if file == "" {
file = "??"
}
stk.File = file
}
// Does s have t as a path prefix?
// That is, does s == t or does s begin with t followed by a slash?
// For portability, we allow ASCII case folding, so that hasPathPrefix("a/b/c", "A/B") is true.
// Similarly, we allow slash folding, so that hasPathPrefix("a/b/c", "a\\b") is true.
// We do not allow full Unicode case folding, for fear of causing more confusion
// or harm than good. (For an example of the kinds of things that can go wrong,
// see http://article.gmane.org/gmane.linux.kernel/1853266.)
func hasPathPrefix(s string, t string) bool {
if len(t) > len(s) {
return false
}
var i int
for i = 0; i < len(t); i++ {
cs := int(s[i])
ct := int(t[i])
if 'A' <= cs && cs <= 'Z' {
cs += 'a' - 'A'
}
if 'A' <= ct && ct <= 'Z' {
ct += 'a' - 'A'
}
if cs == '\\' {
cs = '/'
}
if ct == '\\' {
ct = '/'
}
if cs != ct {
return false
}
}
return i >= len(s) || s[i] == '/' || s[i] == '\\'
}
// Push records that at that lineno a new file with the given name was pushed onto the input stack.
func (h *LineHist) Push(lineno int, file string) {
stk := &LineStack{
Parent: h.Top,
Lineno: lineno,
FileLine: 1,
}
h.setFile(stk, file)
h.startRange(lineno, stk)
}
// Pop records that at lineno the current file was popped from the input stack.
func (h *LineHist) Pop(lineno int) {
top := h.Top
if top == nil {
return
}
if top.Directive && top.Parent != nil { // pop #line level too
top = top.Parent
}
next := top.Parent
if next == nil {
h.Top = nil
h.Ranges = append(h.Ranges, LineRange{lineno, nil})
return
}
// Popping included file. Update parent offset to account for
// the virtual line number range taken by the included file.
// Cannot modify the LineStack directly, or else lookups
// for the earlier line numbers will get the wrong answers,
// so make a new one.
stk := new(LineStack)
*stk = *next
stk.Lineno = lineno
stk.FileLine = next.fileLineAt(top.Lineno)
h.startRange(lineno, stk)
}
// Update records that at lineno the file name and line number were changed using
// a line directive (//line in Go, #line in assembly).
func (h *LineHist) Update(lineno int, file string, line int) {
top := h.Top
if top == nil {
return // shouldn't happen
}
var stk *LineStack
if top.Directive {
// Update existing entry, except make copy to avoid changing earlier history.
stk = new(LineStack)
*stk = *top
} else {
// Push new entry.
stk = &LineStack{
Parent: top,
Directive: true,
}
}
stk.Lineno = lineno
if stk.File != file {
h.setFile(stk, file) // only retain string if needed
}
stk.FileLine = line
h.startRange(lineno, stk)
}
// AddImport adds a package to the list of imported packages.
func (ctxt *Link) AddImport(pkg string) {
ctxt.Imports = append(ctxt.Imports, pkg)
}
// At returns the input stack in effect at lineno.
func (h *LineHist) At(lineno int) *LineStack {
i := sort.Search(len(h.Ranges), func(i int) bool {
return h.Ranges[i].Start > lineno
})
// Found first entry beyond lineno.
if i == 0 {
return nil
}
return h.Ranges[i-1].Stack
}
// LineString returns a string giving the file and line number
// corresponding to lineno, for use in error messages.
func (h *LineHist) LineString(lineno int) string {
stk := h.At(lineno)
if stk == nil {
return "<unknown line number>"
}
filename := stk.File
if h.PrintFilenameOnly {
filename = filepath.Base(filename)
}
text := fmt.Sprintf("%s:%d", filename, stk.fileLineAt(lineno))
if stk.Directive && stk.Parent != nil {
stk = stk.Parent
filename = stk.File
if h.PrintFilenameOnly {
filename = filepath.Base(filename)
}
text += fmt.Sprintf("[%s:%d]", filename, stk.fileLineAt(lineno))
}
const showFullStack = false // was used by old C compilers
if showFullStack {
for stk.Parent != nil {
lineno = stk.Lineno - 1
stk = stk.Parent
text += fmt.Sprintf(" %s:%d", filename, stk.fileLineAt(lineno))
if stk.Directive && stk.Parent != nil {
stk = stk.Parent
text += fmt.Sprintf("[%s:%d]", filename, stk.fileLineAt(lineno))
}
}
}
return text
}
// FileLine returns the file name and line number
// at the top of the stack for the given lineno.
func (h *LineHist) FileLine(lineno int) (file string, line int) {
stk := h.At(lineno)
if stk == nil {
return "??", 0
}
return stk.File, stk.fileLineAt(lineno)
}
// AbsFileLine returns the absolute file name and line number
// at the top of the stack for the given lineno.
func (h *LineHist) AbsFileLine(lineno int) (file string, line int) {
stk := h.At(lineno)
if stk == nil {
return "??", 0
}
return stk.AbsFile, stk.fileLineAt(lineno)
}
// This is a simplified copy of linklinefmt above.
// It doesn't allow printing the full stack, and it returns the file name and line number separately.
// TODO: Unify with linklinefmt somehow.
func linkgetline(ctxt *Link, lineno int32) (f *LSym, l int32) {
stk := ctxt.LineHist.At(int(lineno))
if stk == nil || stk.AbsFile == "" {
return Linklookup(ctxt, "??", HistVersion), 0
}
if stk.Sym == nil {
stk.Sym = Linklookup(ctxt, stk.AbsFile, HistVersion)
}
return stk.Sym, int32(stk.fileLineAt(int(lineno)))
}
func Linkprfile(ctxt *Link, line int) {
fmt.Printf("%s ", ctxt.LineHist.LineString(line))
}
func fieldtrack(ctxt *Link, cursym *LSym) {
p := cursym.Text
if p == nil || p.Link == nil { // handle external functions and ELF section symbols
return
}
ctxt.Cursym = cursym
for ; p != nil; p = p.Link {
if p.As == AUSEFIELD {
r := Addrel(ctxt.Cursym)
r.Off = 0
r.Siz = 0
r.Sym = p.From.Sym
r.Type = R_USEFIELD
}
}
}