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Source file src/pkg/debug/dwarf/open.go

     1	// Copyright 2009 The Go Authors.  All rights reserved.
     2	// Use of this source code is governed by a BSD-style
     3	// license that can be found in the LICENSE file.
     4	
     5	// Package dwarf provides access to DWARF debugging information loaded from
     6	// executable files, as defined in the DWARF 2.0 Standard at
     7	// http://dwarfstd.org/doc/dwarf-2.0.0.pdf
     8	package dwarf
     9	
    10	import "encoding/binary"
    11	
    12	// Data represents the DWARF debugging information
    13	// loaded from an executable file (for example, an ELF or Mach-O executable).
    14	type Data struct {
    15		// raw data
    16		abbrev   []byte
    17		aranges  []byte
    18		frame    []byte
    19		info     []byte
    20		line     []byte
    21		pubnames []byte
    22		ranges   []byte
    23		str      []byte
    24	
    25		// parsed data
    26		abbrevCache map[uint32]abbrevTable
    27		order       binary.ByteOrder
    28		typeCache   map[Offset]Type
    29		typeSigs    map[uint64]*typeUnit
    30		unit        []unit
    31	}
    32	
    33	// New returns a new Data object initialized from the given parameters.
    34	// Rather than calling this function directly, clients should typically use
    35	// the DWARF method of the File type of the appropriate package debug/elf,
    36	// debug/macho, or debug/pe.
    37	//
    38	// The []byte arguments are the data from the corresponding debug section
    39	// in the object file; for example, for an ELF object, abbrev is the contents of
    40	// the ".debug_abbrev" section.
    41	func New(abbrev, aranges, frame, info, line, pubnames, ranges, str []byte) (*Data, error) {
    42		d := &Data{
    43			abbrev:      abbrev,
    44			aranges:     aranges,
    45			frame:       frame,
    46			info:        info,
    47			line:        line,
    48			pubnames:    pubnames,
    49			ranges:      ranges,
    50			str:         str,
    51			abbrevCache: make(map[uint32]abbrevTable),
    52			typeCache:   make(map[Offset]Type),
    53			typeSigs:    make(map[uint64]*typeUnit),
    54		}
    55	
    56		// Sniff .debug_info to figure out byte order.
    57		// bytes 4:6 are the version, a tiny 16-bit number (1, 2, 3).
    58		if len(d.info) < 6 {
    59			return nil, DecodeError{"info", Offset(len(d.info)), "too short"}
    60		}
    61		x, y := d.info[4], d.info[5]
    62		switch {
    63		case x == 0 && y == 0:
    64			return nil, DecodeError{"info", 4, "unsupported version 0"}
    65		case x == 0:
    66			d.order = binary.BigEndian
    67		case y == 0:
    68			d.order = binary.LittleEndian
    69		default:
    70			return nil, DecodeError{"info", 4, "cannot determine byte order"}
    71		}
    72	
    73		u, err := d.parseUnits()
    74		if err != nil {
    75			return nil, err
    76		}
    77		d.unit = u
    78		return d, nil
    79	}
    80	
    81	// AddTypes will add one .debug_types section to the DWARF data.  A
    82	// typical object with DWARF version 4 debug info will have multiple
    83	// .debug_types sections.  The name is used for error reporting only,
    84	// and serves to distinguish one .debug_types section from another.
    85	func (d *Data) AddTypes(name string, types []byte) error {
    86		return d.parseTypes(name, types)
    87	}
    88	

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