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Endian.h
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1 /* GRAPHITE2 LICENSING
2 
3  Copyright 2011, SIL International
4  All rights reserved.
5 
6  This library is free software; you can redistribute it and/or modify
7  it under the terms of the GNU Lesser General Public License as published
8  by the Free Software Foundation; either version 2.1 of License, or
9  (at your option) any later version.
10 
11  This program is distributed in the hope that it will be useful,
12  but WITHOUT ANY WARRANTY; without even the implied warranty of
13  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14  Lesser General Public License for more details.
15 
16  You should also have received a copy of the GNU Lesser General Public
17  License along with this library in the file named "LICENSE".
18  If not, write to the Free Software Foundation, 51 Franklin Street,
19  Suite 500, Boston, MA 02110-1335, USA or visit their web page on the
20  internet at http://www.fsf.org/licenses/lgpl.html.
21 
22 Alternatively, the contents of this file may be used under the terms of the
23 Mozilla Public License (http://mozilla.org/MPL) or the GNU General Public
24 License, as published by the Free Software Foundation, either version 2
25 of the License or (at your option) any later version.
26 */
27 
28 /*
29 Description:
30  A set of fast template based decoders for decoding values of any C integer
31  type up to long int size laid out with most significant byte first or least
32  significant byte first (aka big endian or little endian). These are CPU
33  byte order agnostic and will function the same regardless of the CPUs native
34  byte order.
35 
36  Being template based means if the either le or be class is not used then
37  template code of unused functions will not be instantiated by the compiler
38  and thus shouldn't cause any overhead.
39 */
40 
41 #include <cstddef>
42 
43 #pragma once
44 
45 
46 class be
47 {
48  template<int S>
49  inline static unsigned long int _peek(const unsigned char * p) {
50  return _peek<S/2>(p) << (S/2)*8 | _peek<S/2>(p+S/2);
51  }
52 public:
53  template<typename T>
54  inline static T peek(const void * p) {
55  return T(_peek<sizeof(T)>(static_cast<const unsigned char *>(p)));
56  }
57 
58  template<typename T>
59  inline static T read(const unsigned char * &p) {
60  const T r = T(_peek<sizeof(T)>(p));
61  p += sizeof r;
62  return r;
63  }
64 
65  template<typename T>
66  inline static T swap(const T x) {
67  return T(_peek<sizeof(T)>(reinterpret_cast<const unsigned char *>(&x)));
68  }
69 
70  template<typename T>
71  inline static void skip(const unsigned char * &p, size_t n=1) {
72  p += sizeof(T)*n;
73  }
74 };
75 
76 template<>
77 inline unsigned long int be::_peek<1>(const unsigned char * p) { return *p; }
78 
79 
80 class le
81 {
82  template<int S>
83  inline static unsigned long int _peek(const unsigned char * p) {
84  return _peek<S/2>(p) | _peek<S/2>(p+S/2) << (S/2)*8;
85  }
86 public:
87  template<typename T>
88  inline static T peek(const void * p) {
89  return T(_peek<sizeof(T)>(static_cast<const unsigned char *>(p)));
90  }
91 
92  template<typename T>
93  inline static T read(const unsigned char * &p) {
94  const T r = T(_peek<sizeof(T)>(p));
95  p += sizeof r;
96  return r;
97  }
98 
99  template<typename T>
100  inline static T swap(const T x) {
101  return T(_peek<sizeof(T)>(reinterpret_cast<const unsigned char *>(&x)));
102  }
103 
104  template<typename T>
105  inline static void skip(const unsigned char * &p, size_t n=1) {
106  p += sizeof(T)*n;
107  }
108 };
109 
110 template<>
111 inline unsigned long int le::_peek<1>(const unsigned char * p) { return *p; }
Definition: Endian.h:47
static unsigned long int _peek(const unsigned char *p)
Definition: Endian.h:49
static T peek(const void *p)
Definition: Endian.h:54
static T swap(const T x)
Definition: Endian.h:66
static T read(const unsigned char *&p)
Definition: Endian.h:59
static void skip(const unsigned char *&p, size_t n=1)
Definition: Endian.h:71
Definition: Endian.h:81
static unsigned long int _peek(const unsigned char *p)
Definition: Endian.h:83
static T swap(const T x)
Definition: Endian.h:100
static T read(const unsigned char *&p)
Definition: Endian.h:93
static void skip(const unsigned char *&p, size_t n=1)
Definition: Endian.h:105
static T peek(const void *p)
Definition: Endian.h:88
#define n
Definition: t4ht.c:1290
#define T
Definition: fmt.h:20
small capitals from c petite p
Definition: afcover.h:72
float x
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int r
Definition: ppmqvga.c:68
@ S
Definition: ubidiimp.h:53