1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538
// Copyright 2018 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 protowire parses and formats the raw wire encoding.
// See https://developers.google.com/protocol-buffers/docs/encoding.
//
// For marshaling and unmarshaling entire protobuf messages,
// use the "google.golang.org/protobuf/proto" package instead.
package protowire

import (
	"io"
	"math"
	"math/bits"

	"google.golang.org/protobuf/internal/errors"
)

// Number represents the field number.
type Number int32

const (
	MinValidNumber      Number = 1
	FirstReservedNumber Number = 19000
	LastReservedNumber  Number = 19999
	MaxValidNumber      Number = 1<<29 - 1
)

// IsValid reports whether the field number is semantically valid.
//
// Note that while numbers within the reserved range are semantically invalid,
// they are syntactically valid in the wire format.
// Implementations may treat records with reserved field numbers as unknown.
func (n Number) IsValid() bool {
	return MinValidNumber <= n && n < FirstReservedNumber || LastReservedNumber < n && n <= MaxValidNumber
}

// Type represents the wire type.
type Type int8

const (
	VarintType     Type = 0
	Fixed32Type    Type = 5
	Fixed64Type    Type = 1
	BytesType      Type = 2
	StartGroupType Type = 3
	EndGroupType   Type = 4
)

const (
	_ = -iota
	errCodeTruncated
	errCodeFieldNumber
	errCodeOverflow
	errCodeReserved
	errCodeEndGroup
)

var (
	errFieldNumber = errors.New("invalid field number")
	errOverflow    = errors.New("variable length integer overflow")
	errReserved    = errors.New("cannot parse reserved wire type")
	errEndGroup    = errors.New("mismatching end group marker")
	errParse       = errors.New("parse error")
)

// ParseError converts an error code into an error value.
// This returns nil if n is a non-negative number.
func ParseError(n int) error {
	if n >= 0 {
		return nil
	}
	switch n {
	case errCodeTruncated:
		return io.ErrUnexpectedEOF
	case errCodeFieldNumber:
		return errFieldNumber
	case errCodeOverflow:
		return errOverflow
	case errCodeReserved:
		return errReserved
	case errCodeEndGroup:
		return errEndGroup
	default:
		return errParse
	}
}

// ConsumeField parses an entire field record (both tag and value) and returns
// the field number, the wire type, and the total length.
// This returns a negative length upon an error (see ParseError).
//
// The total length includes the tag header and the end group marker (if the
// field is a group).
func ConsumeField(b []byte) (Number, Type, int) {
	num, typ, n := ConsumeTag(b)
	if n < 0 {
		return 0, 0, n // forward error code
	}
	m := ConsumeFieldValue(num, typ, b[n:])
	if m < 0 {
		return 0, 0, m // forward error code
	}
	return num, typ, n + m
}

// ConsumeFieldValue parses a field value and returns its length.
// This assumes that the field Number and wire Type have already been parsed.
// This returns a negative length upon an error (see ParseError).
//
// When parsing a group, the length includes the end group marker and
// the end group is verified to match the starting field number.
func ConsumeFieldValue(num Number, typ Type, b []byte) (n int) {
	switch typ {
	case VarintType:
		_, n = ConsumeVarint(b)
		return n
	case Fixed32Type:
		_, n = ConsumeFixed32(b)
		return n
	case Fixed64Type:
		_, n = ConsumeFixed64(b)
		return n
	case BytesType:
		_, n = ConsumeBytes(b)
		return n
	case StartGroupType:
		n0 := len(b)
		for {
			num2, typ2, n := ConsumeTag(b)
			if n < 0 {
				return n // forward error code
			}
			b = b[n:]
			if typ2 == EndGroupType {
				if num != num2 {
					return errCodeEndGroup
				}
				return n0 - len(b)
			}

			n = ConsumeFieldValue(num2, typ2, b)
			if n < 0 {
				return n // forward error code
			}
			b = b[n:]
		}
	case EndGroupType:
		return errCodeEndGroup
	default:
		return errCodeReserved
	}
}

// AppendTag encodes num and typ as a varint-encoded tag and appends it to b.
func AppendTag(b []byte, num Number, typ Type) []byte {
	return AppendVarint(b, EncodeTag(num, typ))
}

// ConsumeTag parses b as a varint-encoded tag, reporting its length.
// This returns a negative length upon an error (see ParseError).
func ConsumeTag(b []byte) (Number, Type, int) {
	v, n := ConsumeVarint(b)
	if n < 0 {
		return 0, 0, n // forward error code
	}
	num, typ := DecodeTag(v)
	if num < MinValidNumber {
		return 0, 0, errCodeFieldNumber
	}
	return num, typ, n
}

func SizeTag(num Number) int {
	return SizeVarint(EncodeTag(num, 0)) // wire type has no effect on size
}

// AppendVarint appends v to b as a varint-encoded uint64.
func AppendVarint(b []byte, v uint64) []byte {
	switch {
	case v < 1<<7:
		b = append(b, byte(v))
	case v < 1<<14:
		b = append(b,
			byte((v>>0)&0x7f|0x80),
			byte(v>>7))
	case v < 1<<21:
		b = append(b,
			byte((v>>0)&0x7f|0x80),
			byte((v>>7)&0x7f|0x80),
			byte(v>>14))
	case v < 1<<28:
		b = append(b,
			byte((v>>0)&0x7f|0x80),
			byte((v>>7)&0x7f|0x80),
			byte((v>>14)&0x7f|0x80),
			byte(v>>21))
	case v < 1<<35:
		b = append(b,
			byte((v>>0)&0x7f|0x80),
			byte((v>>7)&0x7f|0x80),
			byte((v>>14)&0x7f|0x80),
			byte((v>>21)&0x7f|0x80),
			byte(v>>28))
	case v < 1<<42:
		b = append(b,
			byte((v>>0)&0x7f|0x80),
			byte((v>>7)&0x7f|0x80),
			byte((v>>14)&0x7f|0x80),
			byte((v>>21)&0x7f|0x80),
			byte((v>>28)&0x7f|0x80),
			byte(v>>35))
	case v < 1<<49:
		b = append(b,
			byte((v>>0)&0x7f|0x80),
			byte((v>>7)&0x7f|0x80),
			byte((v>>14)&0x7f|0x80),
			byte((v>>21)&0x7f|0x80),
			byte((v>>28)&0x7f|0x80),
			byte((v>>35)&0x7f|0x80),
			byte(v>>42))
	case v < 1<<56:
		b = append(b,
			byte((v>>0)&0x7f|0x80),
			byte((v>>7)&0x7f|0x80),
			byte((v>>14)&0x7f|0x80),
			byte((v>>21)&0x7f|0x80),
			byte((v>>28)&0x7f|0x80),
			byte((v>>35)&0x7f|0x80),
			byte((v>>42)&0x7f|0x80),
			byte(v>>49))
	case v < 1<<63:
		b = append(b,
			byte((v>>0)&0x7f|0x80),
			byte((v>>7)&0x7f|0x80),
			byte((v>>14)&0x7f|0x80),
			byte((v>>21)&0x7f|0x80),
			byte((v>>28)&0x7f|0x80),
			byte((v>>35)&0x7f|0x80),
			byte((v>>42)&0x7f|0x80),
			byte((v>>49)&0x7f|0x80),
			byte(v>>56))
	default:
		b = append(b,
			byte((v>>0)&0x7f|0x80),
			byte((v>>7)&0x7f|0x80),
			byte((v>>14)&0x7f|0x80),
			byte((v>>21)&0x7f|0x80),
			byte((v>>28)&0x7f|0x80),
			byte((v>>35)&0x7f|0x80),
			byte((v>>42)&0x7f|0x80),
			byte((v>>49)&0x7f|0x80),
			byte((v>>56)&0x7f|0x80),
			1)
	}
	return b
}

// ConsumeVarint parses b as a varint-encoded uint64, reporting its length.
// This returns a negative length upon an error (see ParseError).
func ConsumeVarint(b []byte) (v uint64, n int) {
	var y uint64
	if len(b) <= 0 {
		return 0, errCodeTruncated
	}
	v = uint64(b[0])
	if v < 0x80 {
		return v, 1
	}
	v -= 0x80

	if len(b) <= 1 {
		return 0, errCodeTruncated
	}
	y = uint64(b[1])
	v += y << 7
	if y < 0x80 {
		return v, 2
	}
	v -= 0x80 << 7

	if len(b) <= 2 {
		return 0, errCodeTruncated
	}
	y = uint64(b[2])
	v += y << 14
	if y < 0x80 {
		return v, 3
	}
	v -= 0x80 << 14

	if len(b) <= 3 {
		return 0, errCodeTruncated
	}
	y = uint64(b[3])
	v += y << 21
	if y < 0x80 {
		return v, 4
	}
	v -= 0x80 << 21

	if len(b) <= 4 {
		return 0, errCodeTruncated
	}
	y = uint64(b[4])
	v += y << 28
	if y < 0x80 {
		return v, 5
	}
	v -= 0x80 << 28

	if len(b) <= 5 {
		return 0, errCodeTruncated
	}
	y = uint64(b[5])
	v += y << 35
	if y < 0x80 {
		return v, 6
	}
	v -= 0x80 << 35

	if len(b) <= 6 {
		return 0, errCodeTruncated
	}
	y = uint64(b[6])
	v += y << 42
	if y < 0x80 {
		return v, 7
	}
	v -= 0x80 << 42

	if len(b) <= 7 {
		return 0, errCodeTruncated
	}
	y = uint64(b[7])
	v += y << 49
	if y < 0x80 {
		return v, 8
	}
	v -= 0x80 << 49

	if len(b) <= 8 {
		return 0, errCodeTruncated
	}
	y = uint64(b[8])
	v += y << 56
	if y < 0x80 {
		return v, 9
	}
	v -= 0x80 << 56

	if len(b) <= 9 {
		return 0, errCodeTruncated
	}
	y = uint64(b[9])
	v += y << 63
	if y < 2 {
		return v, 10
	}
	return 0, errCodeOverflow
}

// SizeVarint returns the encoded size of a varint.
// The size is guaranteed to be within 1 and 10, inclusive.
func SizeVarint(v uint64) int {
	// This computes 1 + (bits.Len64(v)-1)/7.
	// 9/64 is a good enough approximation of 1/7
	return int(9*uint32(bits.Len64(v))+64) / 64
}

// AppendFixed32 appends v to b as a little-endian uint32.
func AppendFixed32(b []byte, v uint32) []byte {
	return append(b,
		byte(v>>0),
		byte(v>>8),
		byte(v>>16),
		byte(v>>24))
}

// ConsumeFixed32 parses b as a little-endian uint32, reporting its length.
// This returns a negative length upon an error (see ParseError).
func ConsumeFixed32(b []byte) (v uint32, n int) {
	if len(b) < 4 {
		return 0, errCodeTruncated
	}
	v = uint32(b[0])<<0 | uint32(b[1])<<8 | uint32(b[2])<<16 | uint32(b[3])<<24
	return v, 4
}

// SizeFixed32 returns the encoded size of a fixed32; which is always 4.
func SizeFixed32() int {
	return 4
}

// AppendFixed64 appends v to b as a little-endian uint64.
func AppendFixed64(b []byte, v uint64) []byte {
	return append(b,
		byte(v>>0),
		byte(v>>8),
		byte(v>>16),
		byte(v>>24),
		byte(v>>32),
		byte(v>>40),
		byte(v>>48),
		byte(v>>56))
}

// ConsumeFixed64 parses b as a little-endian uint64, reporting its length.
// This returns a negative length upon an error (see ParseError).
func ConsumeFixed64(b []byte) (v uint64, n int) {
	if len(b) < 8 {
		return 0, errCodeTruncated
	}
	v = uint64(b[0])<<0 | uint64(b[1])<<8 | uint64(b[2])<<16 | uint64(b[3])<<24 | uint64(b[4])<<32 | uint64(b[5])<<40 | uint64(b[6])<<48 | uint64(b[7])<<56
	return v, 8
}

// SizeFixed64 returns the encoded size of a fixed64; which is always 8.
func SizeFixed64() int {
	return 8
}

// AppendBytes appends v to b as a length-prefixed bytes value.
func AppendBytes(b []byte, v []byte) []byte {
	return append(AppendVarint(b, uint64(len(v))), v...)
}

// ConsumeBytes parses b as a length-prefixed bytes value, reporting its length.
// This returns a negative length upon an error (see ParseError).
func ConsumeBytes(b []byte) (v []byte, n int) {
	m, n := ConsumeVarint(b)
	if n < 0 {
		return nil, n // forward error code
	}
	if m > uint64(len(b[n:])) {
		return nil, errCodeTruncated
	}
	return b[n:][:m], n + int(m)
}

// SizeBytes returns the encoded size of a length-prefixed bytes value,
// given only the length.
func SizeBytes(n int) int {
	return SizeVarint(uint64(n)) + n
}

// AppendString appends v to b as a length-prefixed bytes value.
func AppendString(b []byte, v string) []byte {
	return append(AppendVarint(b, uint64(len(v))), v...)
}

// ConsumeString parses b as a length-prefixed bytes value, reporting its length.
// This returns a negative length upon an error (see ParseError).
func ConsumeString(b []byte) (v string, n int) {
	bb, n := ConsumeBytes(b)
	return string(bb), n
}

// AppendGroup appends v to b as group value, with a trailing end group marker.
// The value v must not contain the end marker.
func AppendGroup(b []byte, num Number, v []byte) []byte {
	return AppendVarint(append(b, v...), EncodeTag(num, EndGroupType))
}

// ConsumeGroup parses b as a group value until the trailing end group marker,
// and verifies that the end marker matches the provided num. The value v
// does not contain the end marker, while the length does contain the end marker.
// This returns a negative length upon an error (see ParseError).
func ConsumeGroup(num Number, b []byte) (v []byte, n int) {
	n = ConsumeFieldValue(num, StartGroupType, b)
	if n < 0 {
		return nil, n // forward error code
	}
	b = b[:n]

	// Truncate off end group marker, but need to handle denormalized varints.
	// Assuming end marker is never 0 (which is always the case since
	// EndGroupType is non-zero), we can truncate all trailing bytes where the
	// lower 7 bits are all zero (implying that the varint is denormalized).
	for len(b) > 0 && b[len(b)-1]&0x7f == 0 {
		b = b[:len(b)-1]
	}
	b = b[:len(b)-SizeTag(num)]
	return b, n
}

// SizeGroup returns the encoded size of a group, given only the length.
func SizeGroup(num Number, n int) int {
	return n + SizeTag(num)
}

// DecodeTag decodes the field Number and wire Type from its unified form.
// The Number is -1 if the decoded field number overflows int32.
// Other than overflow, this does not check for field number validity.
func DecodeTag(x uint64) (Number, Type) {
	// NOTE: MessageSet allows for larger field numbers than normal.
	if x>>3 > uint64(math.MaxInt32) {
		return -1, 0
	}
	return Number(x >> 3), Type(x & 7)
}

// EncodeTag encodes the field Number and wire Type into its unified form.
func EncodeTag(num Number, typ Type) uint64 {
	return uint64(num)<<3 | uint64(typ&7)
}

// DecodeZigZag decodes a zig-zag-encoded uint64 as an int64.
//	Input:  {…,  5,  3,  1,  0,  2,  4,  6, …}
//	Output: {…, -3, -2, -1,  0, +1, +2, +3, …}
func DecodeZigZag(x uint64) int64 {
	return int64(x>>1) ^ int64(x)<<63>>63
}

// EncodeZigZag encodes an int64 as a zig-zag-encoded uint64.
//	Input:  {…, -3, -2, -1,  0, +1, +2, +3, …}
//	Output: {…,  5,  3,  1,  0,  2,  4,  6, …}
func EncodeZigZag(x int64) uint64 {
	return uint64(x<<1) ^ uint64(x>>63)
}

// DecodeBool decodes a uint64 as a bool.
//	Input:  {    0,    1,    2, …}
//	Output: {false, true, true, …}
func DecodeBool(x uint64) bool {
	return x != 0
}

// EncodeBool encodes a bool as a uint64.
//	Input:  {false, true}
//	Output: {    0,    1}
func EncodeBool(x bool) uint64 {
	if x {
		return 1
	}
	return 0
}