Introduce SetLink on profiles (#13223)

<!--Ex. Fixing a bug - Describe the bug and how this fixes the issue.
Ex. Adding a feature - Explain what this achieves.-->
#### Description

This is part of
#13106
It introduces a new `SetLink` method, which allows setting a sample's
link based on a specific dictionary.

Related:
#13197

---------

Co-authored-by: Pablo Baeyens <[email protected]>

Author: dmathieu

.chloggen/link-equal.yaml

@@ -0,0 +1,23 @@
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: enhancement
+
+# The name of the component, or a single word describing the area of concern, (e.g. otlpreceiver)
+component: pdata/pprofile
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Introduce `Equal` method on the `Link` type
+
+# One or more tracking issues or pull requests related to the change
+issues: [13223]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext:
+
+# Optional: The change log or logs in which this entry should be included.
+# e.g. '[user]' or '[user, api]'
+# Include 'user' if the change is relevant to end users.
+# Include 'api' if there is a change to a library API.
+# Default: '[user]'
+change_logs: [api]

.chloggen/set-link.yaml

@@ -0,0 +1,25 @@
+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: enhancement
+
+# The name of the component, or a single word describing the area of concern, (e.g. otlpreceiver)
+component: pdata/pprofile
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Add new helper method `SetLink` to set a new link on a sample.
+
+# One or more tracking issues or pull requests related to the change
+issues: [13223]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext:
+
+# Optional: The change log or logs in which this entry should be included.
+# e.g. '[user]' or '[user, api]'
+# Include 'user' if the change is relevant to end users.
+# Include 'api' if there is a change to a library API.
+# Default: '[user]'
+change_logs: [api]

pdata/pprofile/link.go

@@ -0,0 +1,10 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package pprofile // import "go.opentelemetry.io/collector/pdata/pprofile"
+
+// Equal checks equality with another Link
+func (l Link) Equal(val Link) bool {
+	return l.TraceID() == val.TraceID() &&
+		l.SpanID() == val.SpanID()
+}

pdata/pprofile/link_test.go

@@ -0,0 +1,79 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package pprofile
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+
+	"go.opentelemetry.io/collector/pdata/pcommon"
+)
+
+func TestLinkEqual(t *testing.T) {
+	for _, tt := range []struct {
+		name string
+		orig Link
+		dest Link
+		want bool
+	}{
+		{
+			name: "empty links",
+			orig: NewLink(),
+			dest: NewLink(),
+			want: true,
+		},
+		{
+			name: "non-empty identical links",
+			orig: buildLink(
+				pcommon.TraceID([16]byte{1, 2, 3, 4, 5, 6, 7, 8, 8, 7, 6, 5, 4, 3, 2, 1}),
+				pcommon.SpanID([8]byte{1, 2, 3, 4, 5, 6, 7, 8}),
+			),
+			dest: buildLink(
+				pcommon.TraceID([16]byte{1, 2, 3, 4, 5, 6, 7, 8, 8, 7, 6, 5, 4, 3, 2, 1}),
+				pcommon.SpanID([8]byte{1, 2, 3, 4, 5, 6, 7, 8}),
+			),
+			want: true,
+		},
+		{
+			name: "with different trace IDs",
+			orig: buildLink(
+				pcommon.TraceID([16]byte{1, 2, 3, 4, 5, 6, 7, 8, 8, 7, 6, 5, 4, 3, 2, 1}),
+				pcommon.SpanID([8]byte{1, 2, 3, 4, 5, 6, 7, 8}),
+			),
+			dest: buildLink(
+				pcommon.TraceID([16]byte{8, 7, 6, 5, 4, 3, 2, 1, 1, 2, 3, 4, 5, 6, 7, 8}),
+				pcommon.SpanID([8]byte{1, 2, 3, 4, 5, 6, 7, 8}),
+			),
+			want: false,
+		},
+		{
+			name: "with different span IDs",
+			orig: buildLink(
+				pcommon.TraceID([16]byte{1, 2, 3, 4, 5, 6, 7, 8, 8, 7, 6, 5, 4, 3, 2, 1}),
+				pcommon.SpanID([8]byte{1, 2, 3, 4, 5, 6, 7, 8}),
+			),
+			dest: buildLink(
+				pcommon.TraceID([16]byte{1, 2, 3, 4, 5, 6, 7, 8, 8, 7, 6, 5, 4, 3, 2, 1}),
+				pcommon.SpanID([8]byte{8, 7, 6, 5, 4, 3, 2, 1}),
+			),
+			want: false,
+		},
+	} {
+		t.Run(tt.name, func(t *testing.T) {
+			if tt.want {
+				assert.True(t, tt.orig.Equal(tt.dest))
+			} else {
+				assert.False(t, tt.orig.Equal(tt.dest))
+			}
+		})
+	}
+}
+
+func buildLink(traceID pcommon.TraceID, spanID pcommon.SpanID) Link {
+	l := NewLink()
+	l.SetTraceID(traceID)
+	l.SetSpanID(spanID)
+	return l
+}

pdata/pprofile/links.go

@@ -0,0 +1,47 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package pprofile // import "go.opentelemetry.io/collector/pdata/pprofile"
+
+import (
+	"errors"
+	"fmt"
+	"math"
+)
+
+var errTooManyLinkTableEntries = errors.New("too many entries in LinkTable")
+
+// SetLink updates a LinkTable and a Sample's LinkIndex to
+// add or update a link.
+func SetLink(table LinkSlice, record Sample, li Link) error {
+	idx := int(record.LinkIndex())
+	if idx > 0 {
+		if idx >= table.Len() {
+			return fmt.Errorf("index value %d out of range for LinkIndex", idx)
+		}
+		mapAt := table.At(idx)
+		if mapAt.Equal(li) {
+			// Link already exists, nothing to do.
+			return nil
+		}
+	}
+
+	for j, l := range table.All() {
+		if l.Equal(li) {
+			if j > math.MaxInt32 {
+				return errTooManyLinkTableEntries
+			}
+			// Add the index of the existing link to the indices.
+			record.SetLinkIndex(int32(j)) //nolint:gosec // G115 overflow checked
+			return nil
+		}
+	}
+
+	if table.Len() >= math.MaxInt32 {
+		return errTooManyLinkTableEntries
+	}
+
+	li.CopyTo(table.AppendEmpty())
+	record.SetLinkIndex(int32(table.Len() - 1)) //nolint:gosec // G115 overflow checked
+	return nil
+}

pdata/pprofile/links_test.go

@@ -0,0 +1,124 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package pprofile
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"go.opentelemetry.io/collector/pdata/pcommon"
+)
+
+func TestSetLink(t *testing.T) {
+	table := NewLinkSlice()
+	l := NewLink()
+	l.SetTraceID(pcommon.TraceID([16]byte{1, 2, 3, 4, 5, 6, 7, 8, 8, 7, 6, 5, 4, 3, 2, 1}))
+	l2 := NewLink()
+	l.SetTraceID(pcommon.TraceID([16]byte{2, 2, 3, 4, 5, 6, 7, 8, 8, 7, 6, 5, 4, 3, 2, 2}))
+	smpl := NewSample()
+
+	// Put a first link
+	require.NoError(t, SetLink(table, smpl, l))
+	assert.Equal(t, 1, table.Len())
+	assert.Equal(t, int32(0), smpl.LinkIndex())
+
+	// Put the same link
+	// This should be a no-op.
+	require.NoError(t, SetLink(table, smpl, l))
+	assert.Equal(t, 1, table.Len())
+	assert.Equal(t, int32(0), smpl.LinkIndex())
+
+	// Set a new link
+	// This sets the index and adds to the table.
+	require.NoError(t, SetLink(table, smpl, l2))
+	assert.Equal(t, 2, table.Len())
+	assert.Equal(t, int32(table.Len()-1), smpl.LinkIndex()) //nolint:gosec // G115
+
+	// Set an existing link
+	require.NoError(t, SetLink(table, smpl, l))
+	assert.Equal(t, 2, table.Len())
+	assert.Equal(t, int32(0), smpl.LinkIndex())
+	// Set another existing link
+	require.NoError(t, SetLink(table, smpl, l2))
+	assert.Equal(t, 2, table.Len())
+	assert.Equal(t, int32(table.Len()-1), smpl.LinkIndex()) //nolint:gosec // G115
+}
+
+func TestSetLinkCurrentTooHigh(t *testing.T) {
+	table := NewLinkSlice()
+	smpl := NewSample()
+	smpl.SetLinkIndex(42)
+
+	err := SetLink(table, smpl, NewLink())
+	require.Error(t, err)
+	assert.Equal(t, 0, table.Len())
+	assert.Equal(t, int32(42), smpl.LinkIndex())
+}
+
+func BenchmarkSetLink(b *testing.B) {
+	for _, bb := range []struct {
+		name string
+		link Link
+
+		runBefore func(*testing.B, LinkSlice, Sample)
+	}{
+		{
+			name: "with a new link",
+			link: NewLink(),
+		},
+		{
+			name: "with an existing link",
+			link: func() Link {
+				l := NewLink()
+				l.SetTraceID(pcommon.NewTraceIDEmpty())
+				return l
+			}(),
+
+			runBefore: func(_ *testing.B, table LinkSlice, _ Sample) {
+				l := table.AppendEmpty()
+				l.SetTraceID(pcommon.NewTraceIDEmpty())
+			},
+		},
+		{
+			name: "with a duplicate link",
+			link: NewLink(),
+
+			runBefore: func(_ *testing.B, table LinkSlice, obj Sample) {
+				require.NoError(b, SetLink(table, obj, NewLink()))
+			},
+		},
+		{
+			name: "with a hundred links to loop through",
+			link: func() Link {
+				l := NewLink()
+				l.SetTraceID(pcommon.NewTraceIDEmpty())
+				return l
+			}(),
+
+			runBefore: func(_ *testing.B, table LinkSlice, _ Sample) {
+				for range 100 {
+					table.AppendEmpty()
+				}
+			},
+		},
+	} {
+		b.Run(bb.name, func(b *testing.B) {
+			table := NewLinkSlice()
+			obj := NewSample()
+
+			if bb.runBefore != nil {
+				bb.runBefore(b, table, obj)
+			}
+
+			b.ResetTimer()
+			b.ReportAllocs()
+
+			for range b.N {
+				_ = SetLink(table, obj, bb.link)
+			}
+		})
+	}
+}