Initialize module and dependencies

vendor/golang.org/x/telemetry/internal/counter/parse.go

@@ -0,0 +1,82 @@
+// Copyright 2023 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package counter
+
+import (
+	"bytes"
+	"fmt"
+	"strings"
+	"unsafe"
+
+	"golang.org/x/telemetry/internal/mmap"
+)
+
+type File struct {
+	Meta  map[string]string
+	Count map[string]uint64
+}
+
+func Parse(filename string, data []byte) (*File, error) {
+	if !bytes.HasPrefix(data, []byte(hdrPrefix)) || len(data) < pageSize {
+		if len(data) < pageSize {
+			return nil, fmt.Errorf("%s: file too short (%d<%d)", filename, len(data), pageSize)
+		}
+		return nil, fmt.Errorf("%s: wrong hdr (not %q)", filename, hdrPrefix)
+	}
+	corrupt := func() (*File, error) {
+		// TODO(rfindley): return a useful error message.
+		return nil, fmt.Errorf("%s: corrupt counter file", filename)
+	}
+
+	f := &File{
+		Meta:  make(map[string]string),
+		Count: make(map[string]uint64),
+	}
+	np := round(len(hdrPrefix), 4)
+	hdrLen := *(*uint32)(unsafe.Pointer(&data[np]))
+	if hdrLen > pageSize {
+		return corrupt()
+	}
+	meta := data[np+4 : hdrLen]
+	if i := bytes.IndexByte(meta, 0); i >= 0 {
+		meta = meta[:i]
+	}
+	m := &mappedFile{
+		meta:    string(meta),
+		hdrLen:  hdrLen,
+		mapping: &mmap.Data{Data: data},
+	}
+
+	lines := strings.Split(m.meta, "\n")
+	for _, line := range lines {
+		if line == "" {
+			continue
+		}
+		k, v, ok := strings.Cut(line, ": ")
+		if !ok {
+			return corrupt()
+		}
+		f.Meta[k] = v
+	}
+
+	for i := uint32(0); i < numHash; i++ {
+		headOff := hdrLen + hashOff + i*4
+		head := m.load32(headOff)
+		off := head
+		for off != 0 {
+			ename, next, v, ok := m.entryAt(off)
+			if !ok {
+				return corrupt()
+			}
+			if _, ok := f.Count[string(ename)]; ok {
+				return corrupt()
+			}
+			ctrName := DecodeStack(string(ename))
+			f.Count[ctrName] = v.Load()
+			off = next
+		}
+	}
+	return f, nil
+}