1// Copyright 2014 The Go Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style
3// license that can be found in the LICENSE file.
4
5// Implements methods to remove frames from profiles.
6
7package profile
8
9import (
10	"fmt"
11	"regexp"
12)
13
14// Prune removes all nodes beneath a node matching dropRx, and not
15// matching keepRx. If the root node of a Sample matches, the sample
16// will have an empty stack.
17func (p *Profile) Prune(dropRx, keepRx *regexp.Regexp) {
18	prune := make(map[uint64]bool)
19	pruneBeneath := make(map[uint64]bool)
20
21	for _, loc := range p.Location {
22		var i int
23		for i = len(loc.Line) - 1; i >= 0; i-- {
24			if fn := loc.Line[i].Function; fn != nil && fn.Name != "" {
25				funcName := fn.Name
26				// Account for leading '.' on the PPC ELF v1 ABI.
27				if funcName[0] == '.' {
28					funcName = funcName[1:]
29				}
30				if dropRx.MatchString(funcName) {
31					if keepRx == nil || !keepRx.MatchString(funcName) {
32						break
33					}
34				}
35			}
36		}
37
38		if i >= 0 {
39			// Found matching entry to prune.
40			pruneBeneath[loc.ID] = true
41
42			// Remove the matching location.
43			if i == len(loc.Line)-1 {
44				// Matched the top entry: prune the whole location.
45				prune[loc.ID] = true
46			} else {
47				loc.Line = loc.Line[i+1:]
48			}
49		}
50	}
51
52	// Prune locs from each Sample
53	for _, sample := range p.Sample {
54		// Scan from the root to the leaves to find the prune location.
55		// Do not prune frames before the first user frame, to avoid
56		// pruning everything.
57		foundUser := false
58		for i := len(sample.Location) - 1; i >= 0; i-- {
59			id := sample.Location[i].ID
60			if !prune[id] && !pruneBeneath[id] {
61				foundUser = true
62				continue
63			}
64			if !foundUser {
65				continue
66			}
67			if prune[id] {
68				sample.Location = sample.Location[i+1:]
69				break
70			}
71			if pruneBeneath[id] {
72				sample.Location = sample.Location[i:]
73				break
74			}
75		}
76	}
77}
78
79// RemoveUninteresting prunes and elides profiles using built-in
80// tables of uninteresting function names.
81func (p *Profile) RemoveUninteresting() error {
82	var keep, drop *regexp.Regexp
83	var err error
84
85	if p.DropFrames != "" {
86		if drop, err = regexp.Compile("^(" + p.DropFrames + ")$"); err != nil {
87			return fmt.Errorf("failed to compile regexp %s: %v", p.DropFrames, err)
88		}
89		if p.KeepFrames != "" {
90			if keep, err = regexp.Compile("^(" + p.KeepFrames + ")$"); err != nil {
91				return fmt.Errorf("failed to compile regexp %s: %v", p.KeepFrames, err)
92			}
93		}
94		p.Prune(drop, keep)
95	}
96	return nil
97}
98