github.com/varialus/godfly@v0.0.0-20130904042352-1934f9f095ab/src/pkg/debug/dwarf/unit.go (about)

     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
     6  
     7  import "strconv"
     8  
     9  // DWARF debug info is split into a sequence of compilation units.
    10  // Each unit has its own abbreviation table and address size.
    11  
    12  type unit struct {
    13  	base   Offset // byte offset of header within the aggregate info
    14  	off    Offset // byte offset of data within the aggregate info
    15  	data   []byte
    16  	atable abbrevTable
    17  	asize  int
    18  	vers   int
    19  	is64   bool // True for 64-bit DWARF format
    20  }
    21  
    22  // Implement the dataFormat interface.
    23  
    24  func (u *unit) version() int {
    25  	return u.vers
    26  }
    27  
    28  func (u *unit) dwarf64() (bool, bool) {
    29  	return u.is64, true
    30  }
    31  
    32  func (u *unit) addrsize() int {
    33  	return u.asize
    34  }
    35  
    36  func (d *Data) parseUnits() ([]unit, error) {
    37  	// Count units.
    38  	nunit := 0
    39  	b := makeBuf(d, unknownFormat{}, "info", 0, d.info)
    40  	for len(b.data) > 0 {
    41  		len := b.uint32()
    42  		if len == 0xffffffff {
    43  			len64 := b.uint64()
    44  			if len64 != uint64(uint32(len64)) {
    45  				b.error("unit length overflow")
    46  				break
    47  			}
    48  			len = uint32(len64)
    49  		}
    50  		b.skip(int(len))
    51  		nunit++
    52  	}
    53  	if b.err != nil {
    54  		return nil, b.err
    55  	}
    56  
    57  	// Again, this time writing them down.
    58  	b = makeBuf(d, unknownFormat{}, "info", 0, d.info)
    59  	units := make([]unit, nunit)
    60  	for i := range units {
    61  		u := &units[i]
    62  		u.base = b.off
    63  		n := b.uint32()
    64  		if n == 0xffffffff {
    65  			u.is64 = true
    66  			n = uint32(b.uint64())
    67  		}
    68  		vers := b.uint16()
    69  		if vers != 2 && vers != 3 {
    70  			b.error("unsupported DWARF version " + strconv.Itoa(int(vers)))
    71  			break
    72  		}
    73  		u.vers = int(vers)
    74  		atable, err := d.parseAbbrev(b.uint32())
    75  		if err != nil {
    76  			if b.err == nil {
    77  				b.err = err
    78  			}
    79  			break
    80  		}
    81  		u.atable = atable
    82  		u.asize = int(b.uint8())
    83  		u.off = b.off
    84  		u.data = b.bytes(int(n - (2 + 4 + 1)))
    85  	}
    86  	if b.err != nil {
    87  		return nil, b.err
    88  	}
    89  	return units, nil
    90  }