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f951f697c4
Add a new package with APIs for encoding coverage meta-data. This provides support for accumulating information about each function during the compilation process, and then encoding and emitting a payload for a coverage meta-data symbol. Not yet connected to the rest of the coverage machinery (that will appear in a later patch). Updates #51430. Change-Id: I61054ce87f205b25fb1bfedaa740fd7425c34de4 Reviewed-on: https://go-review.googlesource.com/c/go/+/353453 Run-TryBot: Than McIntosh <thanm@google.com> Reviewed-by: David Chase <drchase@google.com> TryBot-Result: Gopher Robot <gobot@golang.org>
89 lines
2.3 KiB
Go
89 lines
2.3 KiB
Go
// Copyright 2022 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package stringtab
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import (
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"fmt"
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"internal/coverage/uleb128"
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"io"
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)
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// This package implements a string table writer utility for use in
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// emitting coverage meta-data and counter-data files.
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type Writer struct {
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stab map[string]uint32
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strs []string
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tmp []byte
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frozen bool
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}
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// InitWriter initializes a stringtab.Writer.
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func (stw *Writer) InitWriter() {
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stw.stab = make(map[string]uint32)
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stw.tmp = make([]byte, 64)
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}
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// Nentries returns the number of strings interned so far.
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func (stw *Writer) Nentries() uint32 {
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return uint32(len(stw.strs))
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}
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// Lookup looks up string 's' in the writer's table, adding
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// a new entry if need be, and returning an index into the table.
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func (stw *Writer) Lookup(s string) uint32 {
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if idx, ok := stw.stab[s]; ok {
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return idx
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}
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idx := uint32(len(stw.strs))
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stw.stab[s] = idx
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stw.strs = append(stw.strs, s)
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return idx
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}
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// Size computes the memory in bytes needed for the serialized
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// version of a stringtab.Writer.
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func (stw *Writer) Size() uint32 {
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rval := uint32(0)
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stw.tmp = stw.tmp[:0]
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stw.tmp = uleb128.AppendUleb128(stw.tmp, uint(len(stw.strs)))
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rval += uint32(len(stw.tmp))
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for _, s := range stw.strs {
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stw.tmp = stw.tmp[:0]
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slen := uint(len(s))
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stw.tmp = uleb128.AppendUleb128(stw.tmp, slen)
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rval += uint32(len(stw.tmp)) + uint32(slen)
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}
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return rval
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}
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// Write writes the string table in serialized form to the specified
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// io.Writer.
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func (stw *Writer) Write(w io.Writer) error {
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wr128 := func(v uint) error {
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stw.tmp = stw.tmp[:0]
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stw.tmp = uleb128.AppendUleb128(stw.tmp, v)
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if nw, err := w.Write(stw.tmp); err != nil {
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return fmt.Errorf("writing string table: %v", err)
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} else if nw != len(stw.tmp) {
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return fmt.Errorf("short write emitting stringtab uleb")
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}
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return nil
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}
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if err := wr128(uint(len(stw.strs))); err != nil {
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return err
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}
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for _, s := range stw.strs {
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if err := wr128(uint(len(s))); err != nil {
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return err
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}
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if nw, err := w.Write([]byte(s)); err != nil {
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return fmt.Errorf("writing string table: %v\n", err)
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} else if nw != len([]byte(s)) {
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return fmt.Errorf("short write emitting stringtab")
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}
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}
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return nil
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}
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