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#
#
# Nim's Runtime Library
# (c) Copyright 2012 Andreas Rumpf
#
# See the file "copying.txt", included in this
# distribution, for details about the copyright.
#
## This module contains helpers that deal with different byte orders
## (`endian`:idx:).
when defined(gcc) or defined(llvm_gcc) or defined(clang):
const useBuiltinSwap = true
proc builtin_bswap16(a: uint16): uint16 {.
importc: "__builtin_bswap16", nodecl, nosideeffect.}
proc builtin_bswap32(a: uint32): uint32 {.
importc: "__builtin_bswap32", nodecl, nosideeffect.}
proc builtin_bswap64(a: uint64): uint64 {.
importc: "__builtin_bswap64", nodecl, nosideeffect.}
elif defined(icc):
const useBuiltinSwap = true
proc builtin_bswap16(a: uint16): uint16 {.
importc: "_bswap16", nodecl, nosideeffect.}
proc builtin_bswap32(a: uint32): uint32 {.
importc: "_bswap", nodecl, nosideeffect.}
proc builtin_bswap64(a: uint64): uint64 {.
importc: "_bswap64", nodecl, nosideeffect.}
elif defined(vcc):
const useBuiltinSwap = true
proc builtin_bswap16(a: uint16): uint16 {.
importc: "_byteswap_ushort", nodecl, header: "<intrin.h>", nosideeffect.}
proc builtin_bswap32(a: uint32): uint32 {.
importc: "_byteswap_ulong", nodecl, header: "<intrin.h>", nosideeffect.}
proc builtin_bswap64(a: uint64): uint64 {.
importc: "_byteswap_uint64", nodecl, header: "<intrin.h>", nosideeffect.}
else:
const useBuiltinSwap = false
when useBuiltinSwap:
template swapOpImpl(T: typedesc, op: untyped) =
## We have to use `copyMem` here instead of a simple deference because they
## may point to a unaligned address. A sufficiently smart compiler _should_
## be able to elide them when they're not necessary.
var tmp: T
copyMem(addr tmp, inp, sizeOf(T))
tmp = op(tmp)
copyMem(outp, addr tmp, sizeOf(T))
proc swapEndian64*(outp, inp: pointer) {.inline, nosideeffect.}=
swapOpImpl(uint64, builtin_bswap64)
proc swapEndian32*(outp, inp: pointer) {.inline, nosideeffect.}=
swapOpImpl(uint32, builtin_bswap32)
proc swapEndian16*(outp, inp: pointer) {.inline, nosideeffect.}=
swapOpImpl(uint16, builtin_bswap16)
else:
proc swapEndian64*(outp, inp: pointer) =
## copies `inp` to `outp` swapping bytes. Both buffers are supposed to
## contain at least 8 bytes.
var i = cast[cstring](inp)
var o = cast[cstring](outp)
o[0] = i[7]
o[1] = i[6]
o[2] = i[5]
o[3] = i[4]
o[4] = i[3]
o[5] = i[2]
o[6] = i[1]
o[7] = i[0]
proc swapEndian32*(outp, inp: pointer) =
## copies `inp` to `outp` swapping bytes. Both buffers are supposed to
## contain at least 4 bytes.
var i = cast[cstring](inp)
var o = cast[cstring](outp)
o[0] = i[3]
o[1] = i[2]
o[2] = i[1]
o[3] = i[0]
proc swapEndian16*(outp, inp: pointer) =
## copies `inp` to `outp` swapping bytes. Both buffers are supposed to
## contain at least 2 bytes.
var i = cast[cstring](inp)
var o = cast[cstring](outp)
o[0] = i[1]
o[1] = i[0]
when system.cpuEndian == bigEndian:
proc littleEndian64*(outp, inp: pointer) {.inline.} = swapEndian64(outp, inp)
proc littleEndian32*(outp, inp: pointer) {.inline.} = swapEndian32(outp, inp)
proc littleEndian16*(outp, inp: pointer) {.inline.} = swapEndian16(outp, inp)
proc bigEndian64*(outp, inp: pointer) {.inline.} = copyMem(outp, inp, 8)
proc bigEndian32*(outp, inp: pointer) {.inline.} = copyMem(outp, inp, 4)
proc bigEndian16*(outp, inp: pointer) {.inline.} = copyMem(outp, inp, 2)
else:
proc littleEndian64*(outp, inp: pointer) {.inline.} = copyMem(outp, inp, 8)
proc littleEndian32*(outp, inp: pointer) {.inline.} = copyMem(outp, inp, 4)
proc littleEndian16*(outp, inp: pointer){.inline.} = copyMem(outp, inp, 2)
proc bigEndian64*(outp, inp: pointer) {.inline.} = swapEndian64(outp, inp)
proc bigEndian32*(outp, inp: pointer) {.inline.} = swapEndian32(outp, inp)
proc bigEndian16*(outp, inp: pointer) {.inline.} = swapEndian16(outp, inp)
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