0ad/source/lib/byte_order.cpp
2009-04-18 17:51:05 +00:00

231 lines
3.7 KiB
C++

/* Copyright (C) 2009 Wildfire Games.
* This file is part of 0 A.D.
*
* 0 A.D. is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 2 of the License, or
* (at your option) any later version.
*
* 0 A.D. is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with 0 A.D. If not, see <http://www.gnu.org/licenses/>.
*/
/*
* byte order (endianness) support routines.
*/
#include "precompiled.h"
#include "byte_order.h"
#include "bits.h"
#ifndef swap16
u16 swap16(const u16 x)
{
return (u16)(((x & 0xff) << 8) | (x >> 8));
}
u32 swap32(const u32 x)
{
return (x << 24) |
(x >> 24) |
((x << 8) & 0x00ff0000) |
((x >> 8) & 0x0000ff00);
}
u64 swap64(const u64 x)
{
const u32 lo = (u32)(x & 0xFFFFFFFF);
const u32 hi = (u32)(x >> 32);
u64 ret = swap32(lo);
ret <<= 32;
// careful: must shift var of type u64, not u32
ret |= swap32(hi);
return ret;
}
#endif // #ifndef swap16
//-----------------------------------------------------------------------------
u16 to_le16(u16 x)
{
#if BYTE_ORDER == BIG_ENDIAN
return swap16(x);
#else
return x;
#endif
}
u32 to_le32(u32 x)
{
#if BYTE_ORDER == BIG_ENDIAN
return swap32(x);
#else
return x;
#endif
}
u64 to_le64(u64 x)
{
#if BYTE_ORDER == BIG_ENDIAN
return swap64(x);
#else
return x;
#endif
}
u16 to_be16(u16 x)
{
#if BYTE_ORDER == BIG_ENDIAN
return x;
#else
return swap16(x);
#endif
}
u32 to_be32(u32 x)
{
#if BYTE_ORDER == BIG_ENDIAN
return x;
#else
return swap32(x);
#endif
}
u64 to_be64(u64 x)
{
#if BYTE_ORDER == BIG_ENDIAN
return x;
#else
return swap64(x);
#endif
}
u16 read_le16(const void* p)
{
return to_le16(*(u16*)p);
}
u32 read_le32(const void* p)
{
return to_le32(*(u32*)p);
}
u64 read_le64(const void* p)
{
return to_le64(*(u64*)p);
}
u16 read_be16(const void* p)
{
return to_be16(*(u16*)p);
}
u32 read_be32(const void* p)
{
return to_be32(*(u32*)p);
}
u64 read_be64(const void* p)
{
return to_be64(*(u64*)p);
}
void write_le16(void* p, u16 x)
{
*(u16*)p = to_le16(x);
}
void write_le32(void* p, u32 x)
{
*(u32*)p = to_le32(x);
}
void write_le64(void* p, u64 x)
{
*(u64*)p = to_le64(x);
}
void write_be16(void* p, u16 x)
{
*(u16*)p = to_be16(x);
}
void write_be32(void* p, u32 x)
{
*(u32*)p = to_be32(x);
}
void write_be64(void* p, u64 x)
{
*(u64*)p = to_be64(x);
}
u64 movzx_le64(const u8* p, size_t size_bytes)
{
u64 number = 0;
for(size_t i = 0; i < std::min(size_bytes, (size_t)8u); i++)
number |= ((u64)p[i]) << (i*8);
return number;
}
u64 movzx_be64(const u8* p, size_t size_bytes)
{
u64 number = 0;
for(size_t i = 0; i < std::min(size_bytes, (size_t)8u); i++)
{
number <<= 8;
number |= p[i];
}
return number;
}
static inline i64 SignExtend(u64 bits, size_t size_bytes)
{
// no point in sign-extending if >= 8 bytes were requested
if(size_bytes < 8)
{
const u64 sign_bit = Bit<u64>((size_bytes*8)-1);
// number would be negative in the smaller type,
// so sign-extend, i.e. set all more significant bits.
if(bits & sign_bit)
{
const u64 valid_bit_mask = (sign_bit+sign_bit)-1;
bits |= ~valid_bit_mask;
}
}
const i64 number = static_cast<i64>(bits);
return number;
}
i64 movsx_le64(const u8* p, size_t size_bytes)
{
const u64 number = movzx_le64(p, size_bytes);
return SignExtend(number, size_bytes);
}
i64 movsx_be64(const u8* p, size_t size_bytes)
{
const u64 number = movzx_be64(p, size_bytes);
return SignExtend(number, size_bytes);
}