github.com/gitbundle/modules@v0.0.0-20231025071548-85b91c5c3b01/log/stack.go (about)

     1  // Copyright 2023 The GitBundle Inc. All rights reserved.
     2  // Copyright 2017 The Gitea Authors. All rights reserved.
     3  // Use of this source code is governed by a MIT-style
     4  // license that can be found in the LICENSE file.
     5  
     6  package log
     7  
     8  import (
     9  	"bytes"
    10  	"fmt"
    11  	"os"
    12  	"runtime"
    13  )
    14  
    15  var unknown = []byte("???")
    16  
    17  // Stack will skip back the provided number of frames and return a stack trace with source code.
    18  // Although we could just use debug.Stack(), this routine will return the source code and
    19  // skip back the provided number of frames - i.e. allowing us to ignore preceding function calls.
    20  // A skip of 0 returns the stack trace for the calling function, not including this call.
    21  // If the problem is a lack of memory of course all this is not going to work...
    22  func Stack(skip int) string {
    23  	buf := new(bytes.Buffer)
    24  
    25  	// Store the last file we opened as its probable that the preceding stack frame
    26  	// will be in the same file
    27  	var lines [][]byte
    28  	var lastFilename string
    29  	for i := skip + 1; ; i++ { // Skip over frames
    30  		programCounter, filename, lineNumber, ok := runtime.Caller(i)
    31  		// If we can't retrieve the information break - basically we're into go internals at this point.
    32  		if !ok {
    33  			break
    34  		}
    35  
    36  		// Print equivalent of debug.Stack()
    37  		fmt.Fprintf(buf, "%s:%d (0x%x)\n", filename, lineNumber, programCounter)
    38  		// Now try to print the offending line
    39  		if filename != lastFilename {
    40  			data, err := os.ReadFile(filename)
    41  			if err != nil {
    42  				// can't read this sourcefile
    43  				// likely we don't have the sourcecode available
    44  				continue
    45  			}
    46  			lines = bytes.Split(data, []byte{'\n'})
    47  			lastFilename = filename
    48  		}
    49  		fmt.Fprintf(buf, "\t%s: %s\n", functionName(programCounter), source(lines, lineNumber))
    50  	}
    51  	return buf.String()
    52  }
    53  
    54  // functionName converts the provided programCounter into a function name
    55  func functionName(programCounter uintptr) []byte {
    56  	function := runtime.FuncForPC(programCounter)
    57  	if function == nil {
    58  		return unknown
    59  	}
    60  	name := []byte(function.Name())
    61  
    62  	// Because we provide the filename we can drop the preceding package name.
    63  	if lastslash := bytes.LastIndex(name, []byte("/")); lastslash >= 0 {
    64  		name = name[lastslash+1:]
    65  	}
    66  	// And the current package name.
    67  	if period := bytes.Index(name, []byte(".")); period >= 0 {
    68  		name = name[period+1:]
    69  	}
    70  	// And we should just replace the interpunct with a dot
    71  	name = bytes.ReplaceAll(name, []byte("ยท"), []byte("."))
    72  	return name
    73  }
    74  
    75  // source returns a space-trimmed slice of the n'th line.
    76  func source(lines [][]byte, n int) []byte {
    77  	n-- // in stack trace, lines are 1-indexed but our array is 0-indexed
    78  	if n < 0 || n >= len(lines) {
    79  		return unknown
    80  	}
    81  	return bytes.TrimSpace(lines[n])
    82  }