github.com/bir3/gocompiler@v0.9.2202/extra/compress/fse/bytereader.go (about)

     1  // Copyright 2018 Klaus Post. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  // Based on work Copyright (c) 2013, Yann Collet, released under BSD License.
     5  
     6  package fse
     7  
     8  // byteReader provides a byte reader that reads
     9  // little endian values from a byte stream.
    10  // The input stream is manually advanced.
    11  // The reader performs no bounds checks.
    12  type byteReader struct {
    13  	b   []byte
    14  	off int
    15  }
    16  
    17  // init will initialize the reader and set the input.
    18  func (b *byteReader) init(in []byte) {
    19  	b.b = in
    20  	b.off = 0
    21  }
    22  
    23  // advance the stream b n bytes.
    24  func (b *byteReader) advance(n uint) {
    25  	b.off += int(n)
    26  }
    27  
    28  // Uint32 returns a little endian uint32 starting at current offset.
    29  func (b byteReader) Uint32() uint32 {
    30  	b2 := b.b[b.off:]
    31  	b2 = b2[:4]
    32  	v3 := uint32(b2[3])
    33  	v2 := uint32(b2[2])
    34  	v1 := uint32(b2[1])
    35  	v0 := uint32(b2[0])
    36  	return v0 | (v1 << 8) | (v2 << 16) | (v3 << 24)
    37  }
    38  
    39  // unread returns the unread portion of the input.
    40  func (b byteReader) unread() []byte {
    41  	return b.b[b.off:]
    42  }
    43  
    44  // remain will return the number of bytes remaining.
    45  func (b byteReader) remain() int {
    46  	return len(b.b) - b.off
    47  }