path: root/lib/pure/endians.nim

#
#
#            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:
  proc swapEndian64*(outp, inp: pointer) {.inline, nosideeffect.}=
    var i = cast[ptr uint64](inp)
    var o = cast[ptr uint64](outp)
    o[] = builtin_bswap64(i[])

  proc swapEndian32*(outp, inp: pointer) {.inline, nosideeffect.}=
    var i = cast[ptr uint32](inp)
    var o = cast[ptr uint32](outp)
    o[] = builtin_bswap32(i[])

  proc swapEndian16*(outp, inp: pointer) {.inline, nosideeffect.}=
    var i = cast[ptr uint16](inp)
    var o = cast[ptr uint16](outp)
    o[] = builtin_bswap16(i[])

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)