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		addrsize    int
    28		order       binary.ByteOrder
    29		typeCache   map[Offset]Type
    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		}
    54	
    55		// Sniff .debug_info to figure out byte order.
    56		// bytes 4:6 are the version, a tiny 16-bit number (1, 2, 3).
    57		if len(d.info) < 6 {
    58			return nil, DecodeError{"info", Offset(len(d.info)), "too short"}
    59		}
    60		x, y := d.info[4], d.info[5]
    61		switch {
    62		case x == 0 && y == 0:
    63			return nil, DecodeError{"info", 4, "unsupported version 0"}
    64		case x == 0:
    65			d.order = binary.BigEndian
    66		case y == 0:
    67			d.order = binary.LittleEndian
    68		default:
    69			return nil, DecodeError{"info", 4, "cannot determine byte order"}
    70		}
    71	
    72		u, err := d.parseUnits()
    73		if err != nil {
    74			return nil, err
    75		}
    76		d.unit = u
    77		return d, nil
    78	}

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