locate go source

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方便定位 go 源码内容, 比如

1
go build -gcflags -m 2>&1 | grep escapes | codeloc
  • main.go
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    package main

    import (
    	"bufio"
    	"bytes"
    	"fmt"
    	"io"
    	"io/ioutil"
    	"os"
    	"strconv"
    	"strings"
    )

    var filecaches = map[string][]byte{}

    func getfiledata(file string) []byte {
    	data := filecaches[file]
    	if data == nil {
    		var err error
    		data, err = ioutil.ReadFile(file)
    		if err != nil {
    			return nil
    		}
    		filecaches[file] = data
    	}
    	return data
    }

    func main() {
    	cin := bufio.NewReader(os.Stdin)
    	for {
    		s, err := cin.ReadString('\n')
    		s = strings.TrimSpace(s)
    		if s == "" && err != nil {
    			if err == io.EOF {
    				break
    			}
    			os.Exit(1)
    		}

    		info := strings.SplitN(s, ":", 3)
    		if len(info) != 3 {
    			continue
    		}
    		ln, err := strconv.Atoi(info[1])
    		if err != nil {
    			continue
    		}
    		data := getfiledata(info[0])
    		if data == nil {
    			continue
    		}

    		// locate line
    		fail := false
    		p := 0
    		n := 1
    		for n < ln {
    			nln := bytes.IndexByte(data[p:], '\n')
    			if nln == -1 {
    				fail = true
    				break
    			}
    			p = p + nln + 1
    			n++
    		}
    		if fail {
    			fmt.Fprintf(os.Stderr, "%s:%d: no such line\n", info[0], ln)
    			continue
    		}

    		nln := bytes.IndexByte(data[p:], '\n')
    		if nln == -1 {
    			nln = len(data) - p
    		}
    		code := string(data[p : p+nln])

    		// replace indent
    		tabs := 0
    		for i := 0; i < len(code); i++ {
    			if code[i] == '\t' {
    				tabs++
    			} else {
    				break
    			}
    		}
    		code = code[tabs:]
    		fmt.Printf("%s\n%s\n\n", s, strings.Repeat("    ", tabs)+code)
    	}
    }