source.go

package events

import "strings"

// SourceForPC returns the file and line given a program counter address.
// The file path is in the canonical form for Go programs, starting with
// the package path.
func SourceForPC(pc uintptr) (file string, line int) {
	var name string
	file, line, name = fileLineFunc(pc)
	file = trimGOPATH(name, file)
	return
}

// =============================================================================
// From https://github.com/pkg/errors/blob/master/stack.go
//
// Copyright (c) 2015, Dave Cheney <dave@cheney.net>
// All rights reserved.
//
//	Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
//
// * Redistributions of source code must retain the above copyright notice, this
// list of conditions and the following disclaimer.
//
// * Redistributions in binary form must reproduce the above copyright notice,
// this list of conditions and the following disclaimer in the documentation
// and/or other materials provided with the distribution.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
// DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
// FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
// DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
// SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
// CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
// OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
//
func trimGOPATH(name, file string) string {
	// Here we want to get the source file path relative to the compile time
	// GOPATH. As of Go 1.6.x there is no direct way to know the compiled
	// GOPATH at runtime, but we can infer the number of path segments in the
	// GOPATH. We note that fn.Name() returns the function name qualified by
	// the import path, which does not include the GOPATH. Thus we can trim
	// segments from the beginning of the file path until the number of path
	// separators remaining is one more than the number of path separators in
	// the function name. For example, given:
	//
	//    GOPATH     /home/user
	//    file       /home/user/src/pkg/sub/file.go
	//    fn.Name()  pkg/sub.Type.Method
	//
	// We want to produce:
	//
	//    pkg/sub/file.go
	//
	// From this we can easily see that fn.Name() has one less path separator
	// than our desired output. We count separators from the end of the file
	// path until it finds two more than in the function name and then move
	// one character forward to preserve the initial path segment without a
	// leading separator.
	const sep = "/"
	goal := strings.Count(name, sep) + 2
	i := len(file)
	for n := 0; n < goal; n++ {
		i = strings.LastIndex(file[:i], sep)
		if i == -1 {
			// not enough separators found, set i so that the slice expression
			// below leaves file unmodified
			i = -len(sep)
			break
		}
	}
	// get back to 0 or trim the leading separator
	file = file[i+len(sep):]
	return file
}

// =============================================================================