protoscan – github.com/paulmach/protoscan Index | Examples | Files | Directories

package protoscan

import "github.com/paulmach/protoscan"

Example (Count)

ExampleCount demonstrates some basics of using the library by counting elements in a larger customer message without fully decoding it.

Code:play  

package main

import (
	"fmt"

	"github.com/paulmach/protoscan"
	"github.com/paulmach/protoscan/internal/testmsg"
	"google.golang.org/protobuf/proto"
)

func main() {
	c := &testmsg.Customer{
		Id:       proto.Int64(123),
		Username: proto.String("name"),
		Orders: []*testmsg.Order{
			{
				Id:   proto.Int64(1),
				Open: proto.Bool(true),
				Items: []*testmsg.Item{
					{Id: proto.Int64(1)},
					{Id: proto.Int64(2)},
					{Id: proto.Int64(3)},
				},
			},
			{
				Id:   proto.Int64(2),
				Open: proto.Bool(false),
				Items: []*testmsg.Item{
					{Id: proto.Int64(1)},
					{Id: proto.Int64(2)},
				},
			},
			{
				Id:   proto.Int64(3),
				Open: proto.Bool(true),
				Items: []*testmsg.Item{
					{Id: proto.Int64(1)},
				},
			},
		},
		FavoriteIds: []int64{1, 2, 3, 4, 5, 6, 7, 8},
	}
	data, _ := proto.Marshal(c)

	// start the decoding
	openCount := 0
	itemCount := 0
	favoritesCount := 0

	customer := protoscan.New(data)
	for customer.Next() {
		switch customer.FieldNumber() {
		case 1: // id
			id, err := customer.Int64()
			if err != nil {
				panic(err)
			}
			_ = id // do something or skip this case if not needed

		case 2: // username
			username, err := customer.String()
			if err != nil {
				panic(err)
			}
			_ = username // do something or skip this case if not needed

		case 3: // orders
			open := false
			count := 0

			orderData, _ := customer.MessageData()
			order := protoscan.New(orderData)
			for order.Next() {
				switch order.FieldNumber() {
				case 2: // open
					v, _ := order.Bool()
					open = v
				case 3: // item
					count++

					// we're not reading the data but we still need to skip it.
					order.Skip()
				default:
					// required to move past unneeded fields
					order.Skip()
				}
			}

			if open {
				openCount++
				itemCount += count
			}
		case 4: // favorite ids
			iter, err := customer.Iterator(nil)
			if err != nil {
				panic(err)
			}

			// Typically this section would only be run once but it is valid
			// protobuf to contain multiple sections of repeated fields that should
			// be concatenated together.
			favoritesCount += iter.Count(protoscan.WireTypeVarint)
		default:
			// unread fields must be skipped
			customer.Skip()
		}
	}

	if customer.Err() != nil {
		panic(customer.Err())
	}

	fmt.Printf("Open Orders: %d\n", openCount)
	fmt.Printf("Items:       %d\n", itemCount)
	fmt.Printf("Favorites:   %d\n", favoritesCount)

}

Output:

Open Orders: 2
Items:       4
Favorites:   8

Index

Examples

Constants 

const (
	WireTypeVarint          = 0
	WireType64bit           = 1
	WireTypeLengthDelimited = 2
	WireTypeStartGroup      = 3 // deprecated by protobuf, not supported
	WireTypeEndGroup        = 4 // deprecated by protobuf, not supported
	WireType32bit           = 5
)

The WireType describes the encoding method for the next value in the stream.

Variables 

var ErrIntOverflow = errors.New("protoscan: integer overflow")

ErrIntOverflow is returned when scanning an integer with varint encoding and the value is too long for the integer type. 

var ErrInvalidLength = errors.New("protoscan: invalid length")

ErrInvalidLength is returned when a length is not valid, usually resulting from scanning the incorrect type.

Types

type Iterator 

type Iterator struct {
	// contains filtered or unexported fields
}

An Iterator allows for moving across a packed repeated field in a 'controlled' fashion.

func (*Iterator) Bool 

func (b *Iterator) Bool() (bool, error)

Bool is encoded as 0x01 or 0x00 plus the field+type prefix byte. 2 bytes total.

func (*Iterator) Count 

func (i *Iterator) Count(wireType int) int

Count returns the total number of values in this repeated field. The answer depends on the type/encoding or the field: double, float, fixed, sfixed are WireType32bit or WireType64bit, all others int, uint, sint types are WireTypeVarint. The function will panic for any other value.

func (*Iterator) Double 

func (b *Iterator) Double() (float64, error)

Double values are encoded as a fixed length of 8 bytes in their IEEE-754 format.

func (*Iterator) FieldNumber 

func (i *Iterator) FieldNumber() int

FieldNumber returns the number for the current repeated field. These numbers are defined in the protobuf definition file used to encode the message.

func (*Iterator) Fixed32 

func (b *Iterator) Fixed32() (uint32, error)

Fixed32 reads a fixed 4 byte value as a uint32. This proto type is more efficient than uint32 if values are often greater than 2^28.

func (*Iterator) Fixed64 

func (b *Iterator) Fixed64() (uint64, error)

Fixed64 reads a fixed 8 byte value as an uint64. This proto type is more efficient than uint64 if values are often greater than 2^56.

func (*Iterator) Float 

func (b *Iterator) Float() (float32, error)

Float values are encoded as a fixed length of 4 bytes in their IEEE-754 format.

func (*Iterator) HasNext 

func (i *Iterator) HasNext() bool

HasNext is used in a 'for' loop to read through all the elements. Returns false when all the items have been read. This method does NOT need to be called, reading a value automatically moves in the index forward. This behavior is different than Message.Next().

func (*Iterator) Int32 

func (b *Iterator) Int32() (int32, error)

Int32 reads a variable-length encoding of up to 4 bytes. This field type is best used if the field only has positive numbers, otherwise use sint32. Note, this field can also by read as an Int64.

func (*Iterator) Int64 

func (b *Iterator) Int64() (int64, error)

Int64 reads a variable-length encoding of up to 8 bytes. This field type is best used if the field only has positive numbers, otherwise use sint64.

func (*Iterator) Sfixed32 

func (b *Iterator) Sfixed32() (int32, error)

Sfixed32 reads a fixed 4 byte value signed value.

func (*Iterator) Sfixed64 

func (b *Iterator) Sfixed64() (int64, error)

Sfixed64 reads a fixed 8 byte signed value.

func (*Iterator) Sint32 

func (b *Iterator) Sint32() (int32, error)

Sint32 uses variable-length encoding with zig-zag encoding for signed values. This field type more efficiently encodes negative numbers than regular int32s.

func (*Iterator) Sint64 

func (b *Iterator) Sint64() (int64, error)

Sint64 uses variable-length encoding with zig-zag encoding for signed values. This field type more efficiently encodes negative numbers than regular int64s.

func (*Iterator) Uint32 

func (b *Iterator) Uint32() (uint32, error)

Uint32 reads a variable-length encoding of up to 4 bytes.

func (*Iterator) Uint64 

func (b *Iterator) Uint64() (uint64, error)

Uint64 reads a variable-length encoding of up to 8 bytes.

func (*Iterator) Varint32 

func (b *Iterator) Varint32() (uint32, error)

Varint32 reads up to 32-bits of variable-length encoded data. Note that negative int32 values could still be encoded as 64-bit varints due to their leading 1s.

func (*Iterator) Varint64 

func (b *Iterator) Varint64() (uint64, error)

Varint64 reads up to 64-bits of variable-length encoded data.

type Message 

type Message struct {
	// contains filtered or unexported fields
}

Message is a container for a protobuf message type that is ready for scanning.

func New 

func New(data []byte) *Message

New creates a new Message scanner for the given encoded protobuf data.

func (*Message) Bool 

func (b *Message) Bool() (bool, error)

Bool is encoded as 0x01 or 0x00 plus the field+type prefix byte. 2 bytes total.

func (*Message) Bytes 

func (m *Message) Bytes() ([]byte, error)

Bytes returns the encode sequence of bytes. NOTE: this value is NOT copied.

func (*Message) Double 

func (b *Message) Double() (float64, error)

Double values are encoded as a fixed length of 8 bytes in their IEEE-754 format.

func (*Message) Err 

func (m *Message) Err() error

Err will return any errors that were encountered during scanning. Errors could be due to reading the incorrect types or forgetting to skip and unused value.

func (*Message) FieldNumber 

func (m *Message) FieldNumber() int

FieldNumber returns the number for the current value being scanned. These numbers are defined in the protobuf definition file used to encode the message.

func (*Message) Fixed32 

func (b *Message) Fixed32() (uint32, error)

Fixed32 reads a fixed 4 byte value as a uint32. This proto type is more efficient than uint32 if values are often greater than 2^28.

func (*Message) Fixed64 

func (b *Message) Fixed64() (uint64, error)

Fixed64 reads a fixed 8 byte value as an uint64. This proto type is more efficient than uint64 if values are often greater than 2^56.

func (*Message) Float 

func (b *Message) Float() (float32, error)

Float values are encoded as a fixed length of 4 bytes in their IEEE-754 format.

func (*Message) Int32 

func (b *Message) Int32() (int32, error)

Int32 reads a variable-length encoding of up to 4 bytes. This field type is best used if the field only has positive numbers, otherwise use sint32. Note, this field can also by read as an Int64.

func (*Message) Int64 

func (b *Message) Int64() (int64, error)

Int64 reads a variable-length encoding of up to 8 bytes. This field type is best used if the field only has positive numbers, otherwise use sint64.

func (*Message) Iterator 

func (m *Message) Iterator(iter *Iterator) (*Iterator, error)

Iterator will use the current field. The field must be a packed repeated field.

func (*Message) Message 

func (m *Message) Message() (*Message, error)

Message will return a pointer to an embedded message that can then be scanned in kind of a recursive fashion.

func (*Message) MessageData 

func (m *Message) MessageData() ([]byte, error)

MessageData returns the encoded data a message. This data can then be decoded using conventional tools.

func (*Message) Next 

func (m *Message) Next() bool

Next will move the scanner to the next value. This function should be used in a for loop. 

for msg.Next() {
  switch msg.FieldNumber() {
  case 1:
    v, err := msg.Float()
  default:
    msg.Skip()
  }
}

func (*Message) RepeatedBool 

func (m *Message) RepeatedBool(buf []bool) ([]bool, error)

RepeatedBool will append the repeated value(s) to the buffer. This method supports packed or unpacked encoding.

func (*Message) RepeatedDouble 

func (m *Message) RepeatedDouble(buf []float64) ([]float64, error)

RepeatedDouble will append the repeated value(s) to the buffer. This method supports packed or unpacked encoding.

func (*Message) RepeatedFixed32 

func (m *Message) RepeatedFixed32(buf []uint32) ([]uint32, error)

RepeatedFixed32 will append the repeated value(s) to the buffer. This method supports packed or unpacked encoding.

func (*Message) RepeatedFixed64 

func (m *Message) RepeatedFixed64(buf []uint64) ([]uint64, error)

RepeatedFixed64 will append the repeated value(s) to the buffer. This method supports packed or unpacked encoding.

func (*Message) RepeatedFloat 

func (m *Message) RepeatedFloat(buf []float32) ([]float32, error)

RepeatedFloat will append the repeated value(s) to the buffer. This method supports packed or unpacked encoding.

func (*Message) RepeatedInt32 

func (m *Message) RepeatedInt32(buf []int32) ([]int32, error)

RepeatedInt32 will append the repeated value(s) to the buffer. This method supports packed or unpacked encoding.

func (*Message) RepeatedInt64 

func (m *Message) RepeatedInt64(buf []int64) ([]int64, error)

RepeatedInt64 will append the repeated value(s) to the buffer. This method supports packed or unpacked encoding.

func (*Message) RepeatedSfixed32 

func (m *Message) RepeatedSfixed32(buf []int32) ([]int32, error)

RepeatedSfixed32 will append the repeated value(s) to the buffer. This method supports packed or unpacked encoding.

func (*Message) RepeatedSfixed64 

func (m *Message) RepeatedSfixed64(buf []int64) ([]int64, error)

RepeatedSfixed64 will append the repeated value(s) to the buffer. This method supports packed or unpacked encoding.

func (*Message) RepeatedSint32 

func (m *Message) RepeatedSint32(buf []int32) ([]int32, error)

RepeatedSint32 will append the repeated value(s) to the buffer. This method supports packed or unpacked encoding.

func (*Message) RepeatedSint64 

func (m *Message) RepeatedSint64(buf []int64) ([]int64, error)

RepeatedSint64 will append the repeated value(s) to the buffer. This method supports packed or unpacked encoding.

func (*Message) RepeatedUint32 

func (m *Message) RepeatedUint32(buf []uint32) ([]uint32, error)

RepeatedUint32 will append the repeated value(s) to the buffer. This method supports packed or unpacked encoding.

func (*Message) RepeatedUint64 

func (m *Message) RepeatedUint64(buf []uint64) ([]uint64, error)

RepeatedUint64 will append the repeated value(s) to the buffer. This method supports packed or unpacked encoding.

func (*Message) Reset 

func (m *Message) Reset(newData []byte)

Reset will set the index to 0 so the message can be read again. Optionally pass in new data to reuse the Message object.

func (*Message) Sfixed32 

func (b *Message) Sfixed32() (int32, error)

Sfixed32 reads a fixed 4 byte value signed value.

func (*Message) Sfixed64 

func (b *Message) Sfixed64() (int64, error)

Sfixed64 reads a fixed 8 byte signed value.

func (*Message) Sint32 

func (b *Message) Sint32() (int32, error)

Sint32 uses variable-length encoding with zig-zag encoding for signed values. This field type more efficiently encodes negative numbers than regular int32s.

func (*Message) Sint64 

func (b *Message) Sint64() (int64, error)

Sint64 uses variable-length encoding with zig-zag encoding for signed values. This field type more efficiently encodes negative numbers than regular int64s.

func (*Message) Skip 

func (m *Message) Skip()

Skip will move the scanner past the current value if it is not needed. If a value is not parsed this method must be called to move the decoder past the value.

func (*Message) String 

func (m *Message) String() (string, error)

String reads a string type. This data will always contain UTF-8 encoded or 7-bit ASCII text.

func (*Message) Uint32 

func (b *Message) Uint32() (uint32, error)

Uint32 reads a variable-length encoding of up to 4 bytes.

func (*Message) Uint64 

func (b *Message) Uint64() (uint64, error)

Uint64 reads a variable-length encoding of up to 8 bytes.

func (*Message) Varint32 

func (b *Message) Varint32() (uint32, error)

Varint32 reads up to 32-bits of variable-length encoded data. Note that negative int32 values could still be encoded as 64-bit varints due to their leading 1s.

func (*Message) Varint64 

func (b *Message) Varint64() (uint64, error)

Varint64 reads up to 64-bits of variable-length encoded data.

func (*Message) WireType 

func (m *Message) WireType() int

WireType returns the 'type' of the data at the current location.

Source Files

iterator.go message.go repeated.go scalar.go

Directories

PathSynopsis
internal
Version
v0.1.0
Published
Dec 9, 2020
Platform
js/wasm
Imports
4 packages
Last checked
now –

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