// Copyright 2009 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 dwarf

import "strconv"

// DWARF debug info is split into a sequence of compilation units.
// Each unit has its own abbreviation table and address size.

type unit struct {
	base     Offset // byte offset of header within the aggregate info
	off      Offset // byte offset of data within the aggregate info
	lineoff  Offset // byte offset of data within the line info
	data     []byte
	atable   abbrevTable
	addrsize int
	version  int
	dwarf64  bool // True for 64-bit DWARF format
	dir      string
	pc       []addrRange   // PC ranges in this compilation unit
	lines    []mapLineInfo // PC -> line mapping
}

// A range is an address range.
type addrRange struct {
	low  uint64
	high uint64
}

func (d *Data) parseUnits() ([]unit, error) {
	// Count units.
	nunit := 0
	b := makeBuf(d, nil, "info", 0, d.info)
	for len(b.data) > 0 {
		len := b.uint32()
		if len == 0xffffffff {
			len64 := b.uint64()
			if len64 != uint64(int(len64)) {
				b.error("unit length overflow")
				break
			}
			len = uint32(len64)
		}
		b.skip(int(len))
		nunit++
	}
	if b.err != nil {
		return nil, b.err
	}

	// Again, this time writing them down.
	b = makeBuf(d, nil, "info", 0, d.info)
	units := make([]unit, nunit)
	for i := range units {
		u := &units[i]
		u.base = b.off
		n := b.uint32()
		if n == 0xffffffff {
			u.dwarf64 = true
			n = uint32(b.uint64())
		}
		vers := b.uint16()
		if vers < 2 || vers > 4 {
			b.error("unsupported DWARF version " + strconv.Itoa(int(vers)))
			break
		}
		atable, err := d.parseAbbrev(b.uint32())
		if err != nil {
			if b.err == nil {
				b.err = err
			}
			break
		}
		u.version = int(vers)
		u.atable = atable
		u.addrsize = int(b.uint8())
		u.off = b.off
		u.data = b.bytes(int(n - (2 + 4 + 1)))
	}
	if b.err != nil {
		return nil, b.err
	}
	return units, nil
}