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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-16 19:19:13 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-16 19:19:13 +0000 |
commit | ccd992355df7192993c666236047820244914598 (patch) | |
tree | f00fea65147227b7743083c6148396f74cd66935 /src/internal/coverage/encodecounter | |
parent | Initial commit. (diff) | |
download | golang-1.21-ccd992355df7192993c666236047820244914598.tar.xz golang-1.21-ccd992355df7192993c666236047820244914598.zip |
Adding upstream version 1.21.8.upstream/1.21.8
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'src/internal/coverage/encodecounter')
-rw-r--r-- | src/internal/coverage/encodecounter/encode.go | 297 |
1 files changed, 297 insertions, 0 deletions
diff --git a/src/internal/coverage/encodecounter/encode.go b/src/internal/coverage/encodecounter/encode.go new file mode 100644 index 0000000..5958673 --- /dev/null +++ b/src/internal/coverage/encodecounter/encode.go @@ -0,0 +1,297 @@ +// 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 encodecounter + +import ( + "bufio" + "encoding/binary" + "fmt" + "internal/coverage" + "internal/coverage/slicewriter" + "internal/coverage/stringtab" + "internal/coverage/uleb128" + "io" + "os" + "sort" +) + +// This package contains APIs and helpers for encoding initial portions +// of the counter data files emitted at runtime when coverage instrumentation +// is enabled. Counter data files may contain multiple segments; the file +// header and first segment are written via the "Write" method below, and +// additional segments can then be added using "AddSegment". + +type CoverageDataWriter struct { + stab *stringtab.Writer + w *bufio.Writer + csh coverage.CounterSegmentHeader + tmp []byte + cflavor coverage.CounterFlavor + segs uint32 + debug bool +} + +func NewCoverageDataWriter(w io.Writer, flav coverage.CounterFlavor) *CoverageDataWriter { + r := &CoverageDataWriter{ + stab: &stringtab.Writer{}, + w: bufio.NewWriter(w), + + tmp: make([]byte, 64), + cflavor: flav, + } + r.stab.InitWriter() + r.stab.Lookup("") + return r +} + +// CounterVisitor describes a helper object used during counter file +// writing; when writing counter data files, clients pass a +// CounterVisitor to the write/emit routines, then the expectation is +// that the VisitFuncs method will then invoke the callback "f" with +// data for each function to emit to the file. +type CounterVisitor interface { + VisitFuncs(f CounterVisitorFn) error +} + +// CounterVisitorFn describes a callback function invoked when writing +// coverage counter data. +type CounterVisitorFn func(pkid uint32, funcid uint32, counters []uint32) error + +// Write writes the contents of the count-data file to the writer +// previously supplied to NewCoverageDataWriter. Returns an error +// if something went wrong somewhere with the write. +func (cfw *CoverageDataWriter) Write(metaFileHash [16]byte, args map[string]string, visitor CounterVisitor) error { + if err := cfw.writeHeader(metaFileHash); err != nil { + return err + } + return cfw.AppendSegment(args, visitor) +} + +func padToFourByteBoundary(ws *slicewriter.WriteSeeker) error { + sz := len(ws.BytesWritten()) + zeros := []byte{0, 0, 0, 0} + rem := uint32(sz) % 4 + if rem != 0 { + pad := zeros[:(4 - rem)] + if nw, err := ws.Write(pad); err != nil { + return err + } else if nw != len(pad) { + return fmt.Errorf("error: short write") + } + } + return nil +} + +func (cfw *CoverageDataWriter) patchSegmentHeader(ws *slicewriter.WriteSeeker) error { + // record position + off, err := ws.Seek(0, io.SeekCurrent) + if err != nil { + return fmt.Errorf("error seeking in patchSegmentHeader: %v", err) + } + // seek back to start so that we can update the segment header + if _, err := ws.Seek(0, io.SeekStart); err != nil { + return fmt.Errorf("error seeking in patchSegmentHeader: %v", err) + } + if cfw.debug { + fmt.Fprintf(os.Stderr, "=-= writing counter segment header: %+v", cfw.csh) + } + if err := binary.Write(ws, binary.LittleEndian, cfw.csh); err != nil { + return err + } + // ... and finally return to the original offset. + if _, err := ws.Seek(off, io.SeekStart); err != nil { + return fmt.Errorf("error seeking in patchSegmentHeader: %v", err) + } + return nil +} + +func (cfw *CoverageDataWriter) writeSegmentPreamble(args map[string]string, ws *slicewriter.WriteSeeker) error { + if err := binary.Write(ws, binary.LittleEndian, cfw.csh); err != nil { + return err + } + hdrsz := uint32(len(ws.BytesWritten())) + + // Write string table and args to a byte slice (since we need + // to capture offsets at various points), then emit the slice + // once we are done. + cfw.stab.Freeze() + if err := cfw.stab.Write(ws); err != nil { + return err + } + cfw.csh.StrTabLen = uint32(len(ws.BytesWritten())) - hdrsz + + akeys := make([]string, 0, len(args)) + for k := range args { + akeys = append(akeys, k) + } + sort.Strings(akeys) + + wrULEB128 := func(v uint) error { + cfw.tmp = cfw.tmp[:0] + cfw.tmp = uleb128.AppendUleb128(cfw.tmp, v) + if _, err := ws.Write(cfw.tmp); err != nil { + return err + } + return nil + } + + // Count of arg pairs. + if err := wrULEB128(uint(len(args))); err != nil { + return err + } + // Arg pairs themselves. + for _, k := range akeys { + ki := uint(cfw.stab.Lookup(k)) + if err := wrULEB128(ki); err != nil { + return err + } + v := args[k] + vi := uint(cfw.stab.Lookup(v)) + if err := wrULEB128(vi); err != nil { + return err + } + } + if err := padToFourByteBoundary(ws); err != nil { + return err + } + cfw.csh.ArgsLen = uint32(len(ws.BytesWritten())) - (cfw.csh.StrTabLen + hdrsz) + + return nil +} + +// AppendSegment appends a new segment to a counter data, with a new +// args section followed by a payload of counter data clauses. +func (cfw *CoverageDataWriter) AppendSegment(args map[string]string, visitor CounterVisitor) error { + cfw.stab = &stringtab.Writer{} + cfw.stab.InitWriter() + cfw.stab.Lookup("") + + var err error + for k, v := range args { + cfw.stab.Lookup(k) + cfw.stab.Lookup(v) + } + + ws := &slicewriter.WriteSeeker{} + if err = cfw.writeSegmentPreamble(args, ws); err != nil { + return err + } + if err = cfw.writeCounters(visitor, ws); err != nil { + return err + } + if err = cfw.patchSegmentHeader(ws); err != nil { + return err + } + if err := cfw.writeBytes(ws.BytesWritten()); err != nil { + return err + } + if err = cfw.writeFooter(); err != nil { + return err + } + if err := cfw.w.Flush(); err != nil { + return fmt.Errorf("write error: %v", err) + } + cfw.stab = nil + return nil +} + +func (cfw *CoverageDataWriter) writeHeader(metaFileHash [16]byte) error { + // Emit file header. + ch := coverage.CounterFileHeader{ + Magic: coverage.CovCounterMagic, + Version: coverage.CounterFileVersion, + MetaHash: metaFileHash, + CFlavor: cfw.cflavor, + BigEndian: false, + } + if err := binary.Write(cfw.w, binary.LittleEndian, ch); err != nil { + return err + } + return nil +} + +func (cfw *CoverageDataWriter) writeBytes(b []byte) error { + if len(b) == 0 { + return nil + } + nw, err := cfw.w.Write(b) + if err != nil { + return fmt.Errorf("error writing counter data: %v", err) + } + if len(b) != nw { + return fmt.Errorf("error writing counter data: short write") + } + return nil +} + +func (cfw *CoverageDataWriter) writeCounters(visitor CounterVisitor, ws *slicewriter.WriteSeeker) error { + // Notes: + // - this version writes everything little-endian, which means + // a call is needed to encode every value (expensive) + // - we may want to move to a model in which we just blast out + // all counters, or possibly mmap the file and do the write + // implicitly. + ctrb := make([]byte, 4) + wrval := func(val uint32) error { + var buf []byte + var towr int + if cfw.cflavor == coverage.CtrRaw { + binary.LittleEndian.PutUint32(ctrb, val) + buf = ctrb + towr = 4 + } else if cfw.cflavor == coverage.CtrULeb128 { + cfw.tmp = cfw.tmp[:0] + cfw.tmp = uleb128.AppendUleb128(cfw.tmp, uint(val)) + buf = cfw.tmp + towr = len(buf) + } else { + panic("internal error: bad counter flavor") + } + if sz, err := ws.Write(buf); err != nil { + return err + } else if sz != towr { + return fmt.Errorf("writing counters: short write") + } + return nil + } + + // Write out entries for each live function. + emitter := func(pkid uint32, funcid uint32, counters []uint32) error { + cfw.csh.FcnEntries++ + if err := wrval(uint32(len(counters))); err != nil { + return err + } + + if err := wrval(pkid); err != nil { + return err + } + + if err := wrval(funcid); err != nil { + return err + } + for _, val := range counters { + if err := wrval(val); err != nil { + return err + } + } + return nil + } + if err := visitor.VisitFuncs(emitter); err != nil { + return err + } + return nil +} + +func (cfw *CoverageDataWriter) writeFooter() error { + cfw.segs++ + cf := coverage.CounterFileFooter{ + Magic: coverage.CovCounterMagic, + NumSegments: cfw.segs, + } + if err := binary.Write(cfw.w, binary.LittleEndian, cf); err != nil { + return err + } + return nil +} |