reader_buf.go 7.8 KB
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
// 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 pool

import (
	"bufio"
	"bytes"
	"io"
)

const defaultBufSize = 65536

type BufReader struct {
	Columns [][]byte

	rd io.Reader // reader provided by the client

	buf       []byte
	r, w      int // buf read and write positions
	lastByte  int
	bytesRead int64
	err       error

	available int         // bytes available for reading
	bytesRd   BytesReader // reusable bytes reader
}

func NewBufReader(rd io.Reader) *BufReader {
	return &BufReader{
		rd:        rd,
		buf:       make([]byte, defaultBufSize),
		available: -1,
	}
}

func (b *BufReader) BytesReader(n int) *BytesReader {
	if b.Buffered() < n {
		return nil
	}
	buf := b.buf[b.r : b.r+n]
	b.r += n
	b.bytesRd.Reset(buf)
	return &b.bytesRd
}

func (b *BufReader) SetAvailable(n int) {
	b.available = n
}

func (b *BufReader) Available() int {
	return b.available
}

func (b *BufReader) changeAvailable(n int) {
	if b.available != -1 {
		b.available += n
	}
}

func (b *BufReader) Reset(rd io.Reader) {
	b.rd = rd
	b.r, b.w = 0, 0
	b.err = nil
}

// Buffered returns the number of bytes that can be read from the current buffer.
func (b *BufReader) Buffered() int {
	d := b.w - b.r
	if b.available != -1 && d > b.available {
		return b.available
	}
	return d
}

func (b *BufReader) Bytes() []byte {
	if b.available == -1 {
		return b.buf[b.r:b.w]
	}
	w := b.r + b.available
	if w > b.w {
		w = b.w
	}
	return b.buf[b.r:w]
}

func (b *BufReader) flush() []byte {
	if b.available == -1 {
		buf := b.buf[b.r:b.w]
		b.r = b.w
		return buf
	}

	w := b.r + b.available
	if w > b.w {
		w = b.w
	}
	buf := b.buf[b.r:w]
	b.r = w
	b.changeAvailable(-len(buf))
	return buf
}

// fill reads a new chunk into the buffer.
func (b *BufReader) fill() {
	// Slide existing data to beginning.
	if b.r > 0 {
		copy(b.buf, b.buf[b.r:b.w])
		b.w -= b.r
		b.r = 0
	}

	if b.w >= len(b.buf) {
		panic("bufio: tried to fill full buffer")
	}
	if b.available == 0 {
		b.err = io.EOF
		return
	}

	// Read new data: try a limited number of times.
	const maxConsecutiveEmptyReads = 100
	for i := maxConsecutiveEmptyReads; i > 0; i-- {
		n, err := b.readDirectly(b.buf[b.w:])
		b.w += n
		if err != nil {
			b.err = err
			return
		}
		if n > 0 {
			return
		}
	}
	b.err = io.ErrNoProgress
}

func (b *BufReader) readErr() error {
	err := b.err
	b.err = nil
	return err
}

func (b *BufReader) Read(p []byte) (n int, err error) {
	if len(p) == 0 {
		return 0, b.readErr()
	}

	if b.available != -1 {
		if b.available == 0 {
			return 0, io.EOF
		}
		if len(p) > b.available {
			p = p[:b.available]
		}
	}

	if b.r == b.w {
		if b.err != nil {
			return 0, b.readErr()
		}

		if len(p) >= len(b.buf) {
			// Large read, empty buffer.
			// Read directly into p to avoid copy.
			n, err = b.readDirectly(p)
			if n > 0 {
				b.changeAvailable(-n)
				b.lastByte = int(p[n-1])
			}
			return n, err
		}

		// One read.
		// Do not use b.fill, which will loop.
		b.r = 0
		b.w = 0
		n, b.err = b.readDirectly(b.buf)
		if n == 0 {
			return 0, b.readErr()
		}
		b.w += n
	}

	// copy as much as we can
	n = copy(p, b.Bytes())
	b.r += n
	b.changeAvailable(-n)
	b.lastByte = int(b.buf[b.r-1])
	return n, nil
}

// ReadSlice reads until the first occurrence of delim in the input,
// returning a slice pointing at the bytes in the buffer.
// The bytes stop being valid at the next read.
// If ReadSlice encounters an error before finding a delimiter,
// it returns all the data in the buffer and the error itself (often io.EOF).
// ReadSlice fails with error ErrBufferFull if the buffer fills without a delim.
// Because the data returned from ReadSlice will be overwritten
// by the next I/O operation, most clients should use
// ReadBytes or ReadString instead.
// ReadSlice returns err != nil if and only if line does not end in delim.
func (b *BufReader) ReadSlice(delim byte) (line []byte, err error) {
	for {
		// Search buffer.
		if i := bytes.IndexByte(b.Bytes(), delim); i >= 0 {
			i++
			line = b.buf[b.r : b.r+i]
			b.r += i
			b.changeAvailable(-i)
			break
		}

		// Pending error?
		if b.err != nil {
			line = b.flush()
			err = b.readErr()
			break
		}

		buffered := b.Buffered()

		// Out of available.
		if b.available != -1 && buffered >= b.available {
			line = b.flush()
			err = io.EOF
			break
		}

		// Buffer full?
		if buffered >= len(b.buf) {
			line = b.flush()
			err = bufio.ErrBufferFull
			break
		}

		b.fill() // buffer is not full
	}

	// Handle last byte, if any.
	if i := len(line) - 1; i >= 0 {
		b.lastByte = int(line[i])
	}

	return line, err
}

func (b *BufReader) ReadBytes(fn func(byte) bool) (line []byte, err error) {
	for {
		for i, c := range b.Bytes() {
			if !fn(c) {
				i--
				line = b.buf[b.r : b.r+i] //nolint
				b.r += i
				b.changeAvailable(-i)
				break
			}
		}

		// Pending error?
		if b.err != nil {
			line = b.flush() //nolint
			err = b.readErr()
			break
		}

		buffered := b.Buffered()

		// Out of available.
		if b.available != -1 && buffered >= b.available {
			line = b.flush()
			err = io.EOF
			break
		}

		// Buffer full?
		if buffered >= len(b.buf) {
			line = b.flush()
			err = bufio.ErrBufferFull
			break
		}

		b.fill() // buffer is not full
	}

	// Handle last byte, if any.
	if i := len(line) - 1; i >= 0 {
		b.lastByte = int(line[i])
	}

	return line, err
}

func (b *BufReader) ReadByte() (byte, error) {
	if b.available == 0 {
		return 0, io.EOF
	}
	for b.r == b.w {
		if b.err != nil {
			return 0, b.readErr()
		}
		b.fill() // buffer is empty
	}
	c := b.buf[b.r]
	b.r++
	b.lastByte = int(c)
	b.changeAvailable(-1)
	return c, nil
}

func (b *BufReader) UnreadByte() error {
	if b.lastByte < 0 || b.r == 0 && b.w > 0 {
		return bufio.ErrInvalidUnreadByte
	}
	// b.r > 0 || b.w == 0
	if b.r > 0 {
		b.r--
	} else {
		// b.r == 0 && b.w == 0
		b.w = 1
	}
	b.buf[b.r] = byte(b.lastByte)
	b.lastByte = -1
	b.changeAvailable(+1)
	return nil
}

// Discard skips the next n bytes, returning the number of bytes discarded.
//
// If Discard skips fewer than n bytes, it also returns an error.
// If 0 <= n <= b.Buffered(), Discard is guaranteed to succeed without
// reading from the underlying io.BufReader.
func (b *BufReader) Discard(n int) (discarded int, err error) {
	if n < 0 {
		return 0, bufio.ErrNegativeCount
	}
	if n == 0 {
		return
	}
	remain := n
	for {
		skip := b.Buffered()
		if skip == 0 {
			b.fill()
			skip = b.Buffered()
		}
		if skip > remain {
			skip = remain
		}
		b.r += skip
		b.changeAvailable(-skip)
		remain -= skip
		if remain == 0 {
			return n, nil
		}
		if b.err != nil {
			return n - remain, b.readErr()
		}
	}
}

func (b *BufReader) ReadN(n int) (line []byte, err error) {
	if n < 0 {
		return nil, bufio.ErrNegativeCount
	}
	if n == 0 {
		return
	}

	nn := n
	if b.available != -1 && nn > b.available {
		nn = b.available
	}

	for {
		buffered := b.Buffered()

		if buffered >= nn {
			line = b.buf[b.r : b.r+nn]
			b.r += nn
			b.changeAvailable(-nn)
			if n > nn {
				err = io.EOF
			}
			break
		}

		// Pending error?
		if b.err != nil {
			line = b.flush()
			err = b.readErr()
			break
		}

		// Buffer full?
		if buffered >= len(b.buf) {
			line = b.flush()
			err = bufio.ErrBufferFull
			break
		}

		b.fill() // buffer is not full
	}

	// Handle last byte, if any.
	if i := len(line) - 1; i >= 0 {
		b.lastByte = int(line[i])
	}

	return line, err
}

func (b *BufReader) ReadFull() ([]byte, error) {
	if b.available == -1 {
		panic("not reached")
	}
	buf := make([]byte, b.available)
	_, err := io.ReadFull(b, buf)
	return buf, err
}

func (b *BufReader) ReadFullTemp() ([]byte, error) {
	if b.available == -1 {
		panic("not reached")
	}
	if b.available <= len(b.buf) {
		return b.ReadN(b.available)
	}
	return b.ReadFull()
}

func (b *BufReader) readDirectly(buf []byte) (int, error) {
	n, err := b.rd.Read(buf)
	b.bytesRead += int64(n)
	return n, err
}