diff options
Diffstat (limited to 'lib')
| -rw-r--r-- | lib/endians2.nim | 186 |
1 files changed, 0 insertions, 186 deletions
diff --git a/lib/endians2.nim b/lib/endians2.nim deleted file mode 100644 index c9a39144..00000000 --- a/lib/endians2.nim +++ /dev/null @@ -1,186 +0,0 @@ -# Copyright (c) 2018-2019 Status Research & Development GmbH -# Licensed and distributed under either of -# * MIT license (license terms in the root directory or at http://opensource.org/licenses/MIT). -# * Apache v2 license (license terms in the root directory or at http://www.apache.org/licenses/LICENSE-2.0). -# at your option. This file may not be copied, modified, or distributed except according to those terms. - -# Endian conversion operations for unsigned integers, suitable for serializing -# and deserializing data. The operations are only defined for unsigned -# integers - if you wish to encode signed integers, convert / cast them to -# unsigned first! -# -# Although it would be possible to enforce correctness with endians in the type -# (`BigEndian[uin64]`) this seems like overkill. That said, some -# static analysis tools allow you to annotate fields with endianness - perhaps -# an idea for the future, akin to `TaintedString`? -# -# Keeping the above in mind, it's generally safer to use `array[N, byte]` to -# hold values of specific endianness and read them out with `fromBytes` when the -# integer interpretation of the bytes is needed. - -{.push raises: [].} - -type - SomeEndianInt* = uint8|uint16|uint32|uint64 - ## types that we support endian conversions for - uint8 is there for - ## for syntactic / generic convenience. Other candidates: - ## * int/uint - uncertain size, thus less suitable for binary interop - ## * intX - over and underflow protection in nim might easily cause issues - - ## need to consider before adding here - -const - useBuiltins = not defined(noIntrinsicsEndians) - -when (defined(gcc) or defined(llvm_gcc) or defined(clang)) and useBuiltins: - func swapBytesBuiltin(x: uint8): uint8 = x - func swapBytesBuiltin(x: uint16): uint16 {. - importc: "__builtin_bswap16", nodecl.} - - func swapBytesBuiltin(x: uint32): uint32 {. - importc: "__builtin_bswap32", nodecl.} - - func swapBytesBuiltin(x: uint64): uint64 {. - importc: "__builtin_bswap64", nodecl.} - -elif defined(icc) and useBuiltins: - func swapBytesBuiltin(x: uint8): uint8 = x - func swapBytesBuiltin(a: uint16): uint16 {.importc: "_bswap16", nodecl.} - func swapBytesBuiltin(a: uint32): uint32 {.importc: "_bswap", nodec.} - func swapBytesBuiltin(a: uint64): uint64 {.importc: "_bswap64", nodecl.} - -elif defined(vcc) and useBuiltins: - func swapBytesBuiltin(x: uint8): uint8 = x - func swapBytesBuiltin(a: uint16): uint16 {. - importc: "_byteswap_ushort", cdecl, header: "<intrin.h>".} - - func swapBytesBuiltin(a: uint32): uint32 {. - importc: "_byteswap_ulong", cdecl, header: "<intrin.h>".} - - func swapBytesBuiltin(a: uint64): uint64 {. - importc: "_byteswap_uint64", cdecl, header: "<intrin.h>".} - -func swapBytesNim(x: uint8): uint8 = x -func swapBytesNim(x: uint16): uint16 = (x shl 8) or (x shr 8) - -func swapBytesNim(x: uint32): uint32 = - let v = (x shl 16) or (x shr 16) - - ((v shl 8) and 0xff00ff00'u32) or ((v shr 8) and 0x00ff00ff'u32) - -func swapBytesNim(x: uint64): uint64 = - var v = (x shl 32) or (x shr 32) - v = - ((v and 0x0000ffff0000ffff'u64) shl 16) or - ((v and 0xffff0000ffff0000'u64) shr 16) - - ((v and 0x00ff00ff00ff00ff'u64) shl 8) or - ((v and 0xff00ff00ff00ff00'u64) shr 8) - -func swapBytes*[T: SomeEndianInt](x: T): T {.inline.} = - ## Reverse the bytes within an integer, such that the most significant byte - ## changes place with the least significant one, etc - ## - ## Example: - ## doAssert swapBytes(0x01234567'u32) == 0x67452301 - when nimvm: - swapBytesNim(x) - else: - when declared(swapBytesBuiltin): - swapBytesBuiltin(x) - else: - swapBytesNim(x) - -func toBytes*(x: SomeEndianInt, endian: Endianness = system.cpuEndian): - array[sizeof(x), byte] {.noinit, inline.} = - ## Convert integer to its corresponding byte sequence using the chosen - ## endianness. By default, native endianness is used which is not portable! - let v = - if endian == system.cpuEndian: x - else: swapBytes(x) - - when nimvm: # No copyMem in vm - for i in 0..<sizeof(result): - result[i] = byte((v shr (i * 8)) and 0xff) - else: - copyMem(addr result, unsafeAddr v, sizeof(result)) - -func toBytesLE*(x: SomeEndianInt): - array[sizeof(x), byte] {.inline.} = - ## Convert a native endian integer to a little endian byte sequence - toBytes(x, littleEndian) - -func toBytesBE*(x: SomeEndianInt): - array[sizeof(x), byte] {.inline.} = - ## Convert a native endian integer to a native endian byte sequence - toBytes(x, bigEndian) - -func fromBytes*( - T: typedesc[SomeEndianInt], - x: openArray[byte], - endian: Endianness = system.cpuEndian): T {.inline.} = - ## Read bytes and convert to an integer according to the given endianness. - ## - ## Note: The default value of `system.cpuEndian` is not portable across - ## machines. - ## - ## Panics when `x.len < sizeof(T)` - for shorter buffers, copy the data to - ## an `array` first using `arrayops.initCopyFrom`, taking care to zero-fill - ## at the right end - usually the beginning for big endian and the end for - ## little endian, but this depends on the serialization of the bytes. - - # This check gets optimized away when the compiler can prove that the length - # is large enough - passing in an `array` or using a construct like - # ` toOpenArray(pos, pos + sizeof(T) - 1)` are two ways that this happens - doAssert x.len >= sizeof(T), "Not enough bytes for endian conversion" - - when nimvm: # No copyMem in vm - for i in 0..<sizeof(result): - result = result or (T(x[i]) shl (i * 8)) - else: - # `copyMem` helps compilers optimize the copy into a single instruction, when - # alignment etc permits - copyMem(addr result, unsafeAddr x[0], sizeof(result)) - - if endian != system.cpuEndian: - # The swap is turned into a CPU-specific instruction and/or combined with - # the copy above, again when conditions permit it - for example, on X86 - # fromBytesBE gets compiled into a single `MOVBE` instruction - result = swapBytes(result) - -func fromBytesBE*( - T: typedesc[SomeEndianInt], - x: openArray[byte]): T {.inline.} = - ## Read big endian bytes and convert to an integer. At runtime, v must contain - ## at least sizeof(T) bytes. By default, native endianness is used which is - ## not portable! - fromBytes(T, x, bigEndian) - -func toBE*[T: SomeEndianInt](x: T): T {.inline.} = - ## Convert a native endian value to big endian. Consider toBytesBE instead - ## which may prevent some confusion. - if cpuEndian == bigEndian: x - else: x.swapBytes - -func fromBE*[T: SomeEndianInt](x: T): T {.inline.} = - ## Read a big endian value and return the corresponding native endian - # there's no difference between this and toBE, except when reading the code - toBE(x) - -func fromBytesLE*( - T: typedesc[SomeEndianInt], - x: openArray[byte]): T {.inline.} = - ## Read little endian bytes and convert to an integer. At runtime, v must - ## contain at least sizeof(T) bytes. By default, native endianness is used - ## which is not portable! - fromBytes(T, x, littleEndian) - -func toLE*[T: SomeEndianInt](x: T): T {.inline.} = - ## Convert a native endian value to little endian. Consider toBytesLE instead - ## which may prevent some confusion. - if cpuEndian == littleEndian: x - else: x.swapBytes - -func fromLE*[T: SomeEndianInt](x: T): T {.inline.} = - ## Read a little endian value and return the corresponding native endian - # there's no difference between this and toLE, except when reading the code - toLE(x) |