github.com/bir3/gocompiler@v0.9.2202/extra/compress/huff0/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 huff0
     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  // Int32 returns a little endian int32 starting at current offset.
    24  func (b byteReader) Int32() int32 {
    25  	v3 := int32(b.b[b.off+3])
    26  	v2 := int32(b.b[b.off+2])
    27  	v1 := int32(b.b[b.off+1])
    28  	v0 := int32(b.b[b.off])
    29  	return (v3 << 24) | (v2 << 16) | (v1 << 8) | v0
    30  }
    31  
    32  // Uint32 returns a little endian uint32 starting at current offset.
    33  func (b byteReader) Uint32() uint32 {
    34  	v3 := uint32(b.b[b.off+3])
    35  	v2 := uint32(b.b[b.off+2])
    36  	v1 := uint32(b.b[b.off+1])
    37  	v0 := uint32(b.b[b.off])
    38  	return (v3 << 24) | (v2 << 16) | (v1 << 8) | v0
    39  }
    40  
    41  // remain will return the number of bytes remaining.
    42  func (b byteReader) remain() int {
    43  	return len(b.b) - b.off
    44  }