1/*
2 *
3 * (C) Copyright IBM Corp. 1998-2011 - All Rights Reserved
4 *
5 */
6
7#ifndef __LESWAPS_H
8#define __LESWAPS_H
9
10#include "LETypes.h"
11
12/**
13 * \file
14 * \brief C++ API: Endian independent access to data for LayoutEngine
15 */
16
17U_NAMESPACE_BEGIN
18
19/**
20 * A convenience macro which invokes the swapWord member function
21 * from a concise call.
22 *
23 * @stable ICU 2.8
24 */
25#define SWAPW(value) LESwaps::swapWord((le_uint16)(value))
26
27/**
28 * A convenience macro which invokes the swapLong member function
29 * from a concise call.
30 *
31 * @stable ICU 2.8
32 */
33#define SWAPL(value) LESwaps::swapLong((le_uint32)(value))
34
35/**
36 * This class is used to access data which stored in big endian order
37 * regardless of the conventions of the platform.
38 *
39 * All methods are static and inline in an attempt to induce the compiler
40 * to do most of the calculations at compile time.
41 *
42 * @stable ICU 2.8
43 */
44class U_LAYOUT_API LESwaps /* not : public UObject because all methods are static */ {
45public:
46
47    /**
48     * Reads a big-endian 16-bit word and returns a native-endian value.
49     * No-op on a big-endian platform, byte-swaps on a little-endian platform.
50     *
51     * @param value - the word to be byte swapped
52     *
53     * @return the byte swapped word
54     *
55     * @stable ICU 2.8
56     */
57    static le_uint16 swapWord(le_uint16 value)
58    {
59#if (defined(U_IS_BIG_ENDIAN) && U_IS_BIG_ENDIAN) || \
60    (defined(BYTE_ORDER) && defined(BIG_ENDIAN) && (BYTE_ORDER == BIG_ENDIAN)) || \
61    defined(__BIG_ENDIAN__)
62        // Fastpath when we know that the platform is big-endian.
63        return value;
64#else
65        // Reads a big-endian value on any platform.
66        const le_uint8 *p = reinterpret_cast<const le_uint8 *>(&value);
67        return (le_uint16)((p[0] << 8) | p[1]);
68#endif
69    };
70
71    /**
72     * Reads a big-endian 32-bit word and returns a native-endian value.
73     * No-op on a big-endian platform, byte-swaps on a little-endian platform.
74     *
75     * @param value - the long to be byte swapped
76     *
77     * @return the byte swapped long
78     *
79     * @stable ICU 2.8
80     */
81    static le_uint32 swapLong(le_uint32 value)
82    {
83#if (defined(U_IS_BIG_ENDIAN) && U_IS_BIG_ENDIAN) || \
84    (defined(BYTE_ORDER) && defined(BIG_ENDIAN) && (BYTE_ORDER == BIG_ENDIAN)) || \
85    defined(__BIG_ENDIAN__)
86        // Fastpath when we know that the platform is big-endian.
87        return value;
88#else
89        // Reads a big-endian value on any platform.
90        const le_uint8 *p = reinterpret_cast<const le_uint8 *>(&value);
91        return (le_uint32)((p[0] << 24) | (p[1] << 16) | (p[2] << 8) | p[3]);
92#endif
93    };
94
95private:
96    LESwaps() {} // private - forbid instantiation
97};
98
99U_NAMESPACE_END
100#endif
101