207 lines
6.5 KiB
C++
207 lines
6.5 KiB
C++
/*******************************************************************************
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Copyright(C) Jonas 'Sortie' Termansen 2013.
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This file is part of the Sortix C Library.
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The Sortix C Library is free software: you can redistribute it and/or modify
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it under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation, either version 3 of the License, or (at your
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option) any later version.
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The Sortix C Library is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
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License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with the Sortix C Library. If not, see <http://www.gnu.org/licenses/>.
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__/endian.h
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Convert byte ordering of integers.
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*******************************************************************************/
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#ifndef INCLUDE____ENDIAN_H
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#define INCLUDE____ENDIAN_H
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#include <sys/cdefs.h>
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#include <__/byteswap.h>
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__BEGIN_DECLS
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/* The compiler provides the type constants. */
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#define __LITTLE_ENDIAN __ORDER_LITTLE_ENDIAN__
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#define __PDP_ENDIAN __ORDER_PDP_ENDIAN__
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#define __BIG_ENDIAN __ORDER_BIG_ENDIAN__
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/* The compiler also provides the local endianness as one of the above. */
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#define __BYTE_ORDER __BYTE_ORDER__
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/* Declare conversion macros to allow easy endian conversion. */
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#if __BYTE_ORDER == __LITTLE_ENDIAN
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#define __htobe16(x) __bswap_16(x)
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#define __htole16(x) (x)
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#define __be16toh(x) __bswap_16(x)
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#define __le16toh(x) (x)
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#define __htobe32(x) __bswap_32(x)
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#define __htole32(x) (x)
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#define __be32toh(x) __bswap_32(x)
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#define __le32toh(x) (x)
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#define __htobe64(x) __bswap_64(x)
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#define __htole64(x) (x)
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#define __be64toh(x) __bswap_64(x)
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#define __le64toh(x) (x)
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#elif __BYTE_ORDER == __BIG_ENDIAN
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#define __htobe16(x) (x)
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#define __htole16(x) __bswap_16(x)
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#define __be16toh(x) (x)
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#define __le16toh(x) __bswap_16(x)
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#define __htobe32(x) (x)
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#define __htole32(x) __bswap_32(x)
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#define __be32toh(x) (x)
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#define __le32toh(x) __bswap_32(x)
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#define __htobe64(x) (x)
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#define __htole64(x) __bswap_64(x)
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#define __be64toh(x) (x)
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#define __le64toh(x) __bswap_64(x)
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#else
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#error Your processor uses a weird endian, please add support.
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#endif
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__END_DECLS
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/* Sortix specific extensions only available in C++. */
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#if defined(__cplusplus)
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#include <__/stdint.h>
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/* This template allows creating data types that are stored with a specific
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endianness, but can automatically be used as a normal variable. For instance,
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it allows the creation of a big_uint32_t that is an unsigned 32-bit integer
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stored in big endian format. Any assignments to it will automatically be
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converted to big endian and any reads will automatically be converted to the
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host endian. The template even supports volatile objects, so you can create a
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struct with such data types and then use a volatile pointer to such a struct
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and do memory mapped IO easily and correctly. */
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template <typename T, int endianness>
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class __endian_base
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{
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private:
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T representation;
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static T swap(const T& arg)
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{
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/* No need to swap if we already have the correct endianness. */
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if ( __BYTE_ORDER == endianness )
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return arg;
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/* Use the optimized macros from byteswap.h for small objects. */
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if ( sizeof(arg) == 1 )
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return arg;
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else if ( sizeof(arg) == 2 )
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return (T) __bswap_16((__uint16_t) arg);
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else if ( sizeof(arg) == 4 )
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return (T) __bswap_32((__uint32_t) arg);
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else if ( sizeof(arg) == 8 )
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return (T) __bswap_64((__uint64_t) arg);
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/* Convert the input as a byte buffer. */
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union { T input; __uint8_t input_buf[sizeof(T)]; };
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union { T output; __uint8_t output_buf[sizeof(T)]; };
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input = arg;
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for ( unsigned long i = 0; i < sizeof(T); i++ )
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output_buf[i] = input_buf[sizeof(T)-(i+1)];
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return output;
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}
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public:
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__endian_base() { }
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__endian_base(const T& t) : representation(swap(t)) { }
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operator T() const { return swap(representation); }
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operator T() const volatile { return swap((const T) representation); }
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__endian_base& operator=(const T& rhs)
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{
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representation = swap(rhs);
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return *this;
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}
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__endian_base& operator=(const __endian_base& rhs)
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{
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/* Self-assignment doesn't do any harm here. */
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representation = rhs.representation;
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return *this;
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}
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/* TODO: According to the G++ documentation:
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"When using a reference to volatile, G++ does not treat equivalent
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expressions as accesses to volatiles, but instead issues a warning
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that no volatile is accessed."
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This is problematic in our case as we do want to return a volatile
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reference that isn't implicitly accessed, so that stuff such as
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a = b = c works as intended and with volatile semantics.
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The outcommented code does work, but we get a warning when doing a = b,
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and this warning cannot be disabled. For that reason, we revert to the
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unsafe semantics hoping that a = b = c isn't used. */
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#if defined(ACCEPTS_VOLATILE_IMPLICIT_ACCESS_WARNING)
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volatile __endian_base& operator=(const T& rhs) volatile
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{
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representation = swap(rhs);
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return *this;
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}
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volatile __endian_base& operator=(const __endian_base& rhs) volatile
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{
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/* Self-assignment does the right thing in this case. */
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representation = rhs.representation;
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return *this;
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}
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#else
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__endian_base& operator=(const T& rhs) volatile
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{
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representation = swap(rhs);
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return *(__endian_base*) this;
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}
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__endian_base& operator=(const __endian_base& rhs) volatile
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{
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/* Self-assignment does the right thing in this case. */
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representation = rhs.representation;
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return *(__endian_base*) this;
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}
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#endif
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/* TODO: It could be useful to overload ++, --, and other assignment
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operators here. */
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} __attribute__((packed));
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/* Create big-endian versions of the stdint.h exact size data types. */
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typedef __endian_base<__uint8_t, __BIG_ENDIAN> __big_uint8_t;
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typedef __endian_base<__uint16_t, __BIG_ENDIAN> __big_uint16_t;
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typedef __endian_base<__uint32_t, __BIG_ENDIAN> __big_uint32_t;
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typedef __endian_base<__uint64_t, __BIG_ENDIAN> __big_uint64_t;
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/* Create little-endian versions of the stdint.h exact size data types. */
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typedef __endian_base<__uint8_t, __LITTLE_ENDIAN> __little_uint8_t;
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typedef __endian_base<__uint16_t, __LITTLE_ENDIAN> __little_uint16_t;
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typedef __endian_base<__uint32_t, __LITTLE_ENDIAN> __little_uint32_t;
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typedef __endian_base<__uint64_t, __LITTLE_ENDIAN> __little_uint64_t;
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#endif
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#endif
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