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