Adding upstream version 1.21.8.upstream/1.21.8

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 136 insertions, 0 deletions

diff --git a/src/internal/coverage/decodemeta/decode.go b/src/internal/coverage/decodemeta/decode.go
new file mode 100644
index 0000000..fa047c7
--- /dev/null
+++ b/src/internal/coverage/decodemeta/decode.go
@@ -0,0 +1,136 @@
+// Copyright 2021 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 decodemeta
+
+// This package contains APIs and helpers for decoding a single package's
+// meta data "blob" emitted by the compiler when coverage instrumentation
+// is turned on.
+
+import (
+	"encoding/binary"
+	"fmt"
+	"internal/coverage"
+	"internal/coverage/slicereader"
+	"internal/coverage/stringtab"
+	"io"
+	"os"
+)
+
+// See comments in the encodecovmeta package for details on the format.
+
+type CoverageMetaDataDecoder struct {
+	r      *slicereader.Reader
+	hdr    coverage.MetaSymbolHeader
+	strtab *stringtab.Reader
+	tmp    []byte
+	debug  bool
+}
+
+func NewCoverageMetaDataDecoder(b []byte, readonly bool) (*CoverageMetaDataDecoder, error) {
+	slr := slicereader.NewReader(b, readonly)
+	x := &CoverageMetaDataDecoder{
+		r:   slr,
+		tmp: make([]byte, 0, 256),
+	}
+	if err := x.readHeader(); err != nil {
+		return nil, err
+	}
+	if err := x.readStringTable(); err != nil {
+		return nil, err
+	}
+	return x, nil
+}
+
+func (d *CoverageMetaDataDecoder) readHeader() error {
+	if err := binary.Read(d.r, binary.LittleEndian, &d.hdr); err != nil {
+		return err
+	}
+	if d.debug {
+		fmt.Fprintf(os.Stderr, "=-= after readHeader: %+v\n", d.hdr)
+	}
+	return nil
+}
+
+func (d *CoverageMetaDataDecoder) readStringTable() error {
+	// Seek to the correct location to read the string table.
+	stringTableLocation := int64(coverage.CovMetaHeaderSize + 4*d.hdr.NumFuncs)
+	if _, err := d.r.Seek(stringTableLocation, io.SeekStart); err != nil {
+		return err
+	}
+
+	// Read the table itself.
+	d.strtab = stringtab.NewReader(d.r)
+	d.strtab.Read()
+	return nil
+}
+
+func (d *CoverageMetaDataDecoder) PackagePath() string {
+	return d.strtab.Get(d.hdr.PkgPath)
+}
+
+func (d *CoverageMetaDataDecoder) PackageName() string {
+	return d.strtab.Get(d.hdr.PkgName)
+}
+
+func (d *CoverageMetaDataDecoder) ModulePath() string {
+	return d.strtab.Get(d.hdr.ModulePath)
+}
+
+func (d *CoverageMetaDataDecoder) NumFuncs() uint32 {
+	return d.hdr.NumFuncs
+}
+
+// ReadFunc reads the coverage meta-data for the function with index
+// 'findex', filling it into the FuncDesc pointed to by 'f'.
+func (d *CoverageMetaDataDecoder) ReadFunc(fidx uint32, f *coverage.FuncDesc) error {
+	if fidx >= d.hdr.NumFuncs {
+		return fmt.Errorf("illegal function index")
+	}
+
+	// Seek to the correct location to read the function offset and read it.
+	funcOffsetLocation := int64(coverage.CovMetaHeaderSize + 4*fidx)
+	if _, err := d.r.Seek(funcOffsetLocation, io.SeekStart); err != nil {
+		return err
+	}
+	foff := d.r.ReadUint32()
+
+	// Check assumptions
+	if foff < uint32(funcOffsetLocation) || foff > d.hdr.Length {
+		return fmt.Errorf("malformed func offset %d", foff)
+	}
+
+	// Seek to the correct location to read the function.
+	floc := int64(foff)
+	if _, err := d.r.Seek(floc, io.SeekStart); err != nil {
+		return err
+	}
+
+	// Preamble containing number of units, file, and function.
+	numUnits := uint32(d.r.ReadULEB128())
+	fnameidx := uint32(d.r.ReadULEB128())
+	fileidx := uint32(d.r.ReadULEB128())
+
+	f.Srcfile = d.strtab.Get(fileidx)
+	f.Funcname = d.strtab.Get(fnameidx)
+
+	// Now the units
+	f.Units = f.Units[:0]
+	if cap(f.Units) < int(numUnits) {
+		f.Units = make([]coverage.CoverableUnit, 0, numUnits)
+	}
+	for k := uint32(0); k < numUnits; k++ {
+		f.Units = append(f.Units,
+			coverage.CoverableUnit{
+				StLine:  uint32(d.r.ReadULEB128()),
+				StCol:   uint32(d.r.ReadULEB128()),
+				EnLine:  uint32(d.r.ReadULEB128()),
+				EnCol:   uint32(d.r.ReadULEB128()),
+				NxStmts: uint32(d.r.ReadULEB128()),
+			})
+	}
+	lit := d.r.ReadULEB128()
+	f.Lit = lit != 0
+	return nil
+}