// 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.

// Buffered reading and decoding of DWARF data streams.

package dwarf

import (
	
	
	
)

// Data buffer being decoded.
type buf struct {
	dwarf  *Data
	order  binary.ByteOrder
	format dataFormat
	name   string
	off    Offset
	data   []byte
	err    error
}

// Data format, other than byte order. This affects the handling of
// certain field formats.
type dataFormat interface {
	// DWARF version number. Zero means unknown.
	version() int

	// 64-bit DWARF format?
	dwarf64() (dwarf64 bool, isKnown bool)

	// Size of an address, in bytes. Zero means unknown.
	addrsize() int
}

// Some parts of DWARF have no data format, e.g., abbrevs.
type unknownFormat struct{}

func ( unknownFormat) () int {
	return 0
}

func ( unknownFormat) () (bool, bool) {
	return false, false
}

func ( unknownFormat) () int {
	return 0
}

func makeBuf( *Data,  dataFormat,  string,  Offset,  []byte) buf {
	return buf{, .order, , , , , nil}
}

func ( *buf) () uint8 {
	if len(.data) < 1 {
		.error("underflow")
		return 0
	}
	 := .data[0]
	.data = .data[1:]
	.off++
	return 
}

func ( *buf) ( int) []byte {
	if len(.data) <  {
		.error("underflow")
		return nil
	}
	 := .data[0:]
	.data = .data[:]
	.off += Offset()
	return 
}

func ( *buf) ( int) { .bytes() }

func ( *buf) () string {
	 := bytes.IndexByte(.data, 0)
	if  < 0 {
		.error("underflow")
		return ""
	}

	 := string(.data[0:])
	.data = .data[+1:]
	.off += Offset( + 1)
	return 
}

func ( *buf) () uint16 {
	 := .bytes(2)
	if  == nil {
		return 0
	}
	return .order.Uint16()
}

func ( *buf) () uint32 {
	 := .bytes(3)
	if  == nil {
		return 0
	}
	if .dwarf.bigEndian {
		return uint32([2]) | uint32([1])<<8 | uint32([0])<<16
	} else {
		return uint32([0]) | uint32([1])<<8 | uint32([2])<<16
	}
}

func ( *buf) () uint32 {
	 := .bytes(4)
	if  == nil {
		return 0
	}
	return .order.Uint32()
}

func ( *buf) () uint64 {
	 := .bytes(8)
	if  == nil {
		return 0
	}
	return .order.Uint64()
}

// Read a varint, which is 7 bits per byte, little endian.
// the 0x80 bit means read another byte.
func ( *buf) () ( uint64,  uint) {
	for  := 0;  < len(.data); ++ {
		 := .data[]
		 |= uint64(&0x7F) << 
		 += 7
		if &0x80 == 0 {
			.off += Offset( + 1)
			.data = .data[+1:]
			return , 
		}
	}
	return 0, 0
}

// Unsigned int is just a varint.
func ( *buf) () uint64 {
	,  := .varint()
	return 
}

// Signed int is a sign-extended varint.
func ( *buf) () int64 {
	,  := .varint()
	 := int64()
	if &(1<<(-1)) != 0 {
		 |= -1 << 
	}
	return 
}

// Address-sized uint.
func ( *buf) () uint64 {
	switch .format.addrsize() {
	case 1:
		return uint64(.uint8())
	case 2:
		return uint64(.uint16())
	case 4:
		return uint64(.uint32())
	case 8:
		return .uint64()
	}
	.error("unknown address size")
	return 0
}

func ( *buf) () ( Offset,  bool) {
	 = Offset(.uint32())
	if  == 0xffffffff {
		 = true
		 = Offset(.uint64())
	} else if  >= 0xfffffff0 {
		.error("unit length has reserved value")
	}
	return
}

func ( *buf) ( string) {
	if .err == nil {
		.data = nil
		.err = DecodeError{.name, .off, }
	}
}

type DecodeError struct {
	Name   string
	Offset Offset
	Err    string
}

func ( DecodeError) () string {
	return "decoding dwarf section " + .Name + " at offset 0x" + strconv.FormatInt(int64(.Offset), 16) + ": " + .Err
}