comparison osx/include/capnp/endian.h @ 49:3ab5a40c4e3b

Add Capnp and KJ builds for OSX

+// Copyright (c) 2013-2014 Sandstorm Development Group, Inc. and contributors
+// Licensed under the MIT License:
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+
+#ifndef CAPNP_ENDIAN_H_
+#define CAPNP_ENDIAN_H_
+
+#if defined(__GNUC__) && !defined(CAPNP_HEADER_WARNINGS)
+#pragma GCC system_header
+#endif
+
+#include "common.h"
+#include <inttypes.h>
+#include <string.h>  // memcpy
+
+namespace capnp {
+namespace _ {  // private
+
+// WireValue
+//
+// Wraps a primitive value as it appears on the wire.  Namely, values are little-endian on the
+// wire, because little-endian is the most common endianness in modern CPUs.
+//
+// Note:  In general, code that depends cares about byte ordering is bad.  See:
+//     http://commandcenter.blogspot.com/2012/04/byte-order-fallacy.html
+//   Cap'n Proto is special because it is essentially doing compiler-like things, fussing over
+//   allocation and layout of memory, in order to squeeze out every last drop of performance.
+
+#if _MSC_VER
+// Assume Windows is little-endian.
+//
+// TODO(msvc): This is ugly. Maybe refactor later checks to be based on CAPNP_BYTE_ORDER or
+//   CAPNP_SWAP_BYTES or something, and define that in turn based on _MSC_VER or the GCC
+//   intrinsics.
+
+#ifndef __ORDER_BIG_ENDIAN__
+#define __ORDER_BIG_ENDIAN__ 4321
+#endif
+#ifndef __ORDER_LITTLE_ENDIAN__
+#define __ORDER_LITTLE_ENDIAN__ 1234
+#endif
+#ifndef __BYTE_ORDER__
+#define __BYTE_ORDER__ __ORDER_LITTLE_ENDIAN__
+#endif
+#endif
+
+#if CAPNP_REVERSE_ENDIAN
+#define CAPNP_WIRE_BYTE_ORDER __ORDER_BIG_ENDIAN__
+#define CAPNP_OPPOSITE_OF_WIRE_BYTE_ORDER __ORDER_LITTLE_ENDIAN__
+#else
+#define CAPNP_WIRE_BYTE_ORDER __ORDER_LITTLE_ENDIAN__
+#define CAPNP_OPPOSITE_OF_WIRE_BYTE_ORDER __ORDER_BIG_ENDIAN__
+#endif
+
+#if defined(__BYTE_ORDER__) && \
+    __BYTE_ORDER__ == CAPNP_WIRE_BYTE_ORDER && \
+    !CAPNP_DISABLE_ENDIAN_DETECTION
+// CPU is little-endian.  We can just read/write the memory directly.
+
+template <typename T>
+class DirectWireValue {
+public:
+  KJ_ALWAYS_INLINE(T get() const) { return value; }
+  KJ_ALWAYS_INLINE(void set(T newValue)) { value = newValue; }
+
+private:
+  T value;
+};
+
+template <typename T>
+using WireValue = DirectWireValue<T>;
+// To prevent ODR problems when endian-test, endian-reverse-test, and endian-fallback-test are
+// linked together, we define each implementation with a different name and define an alias to the
+// one we want to use.
+
+#elif defined(__BYTE_ORDER__) && \
+      __BYTE_ORDER__ == CAPNP_OPPOSITE_OF_WIRE_BYTE_ORDER && \
+      defined(__GNUC__) && !CAPNP_DISABLE_ENDIAN_DETECTION
+// Big-endian, but GCC's __builtin_bswap() is available.
+
+// TODO(perf):  Use dedicated instructions to read little-endian data on big-endian CPUs that have
+//   them.
+
+// TODO(perf):  Verify that this code optimizes reasonably.  In particular, ensure that the
+//   compiler optimizes away the memcpy()s and keeps everything in registers.
+
+template <typename T, size_t size = sizeof(T)>
+class SwappingWireValue;
+
+template <typename T>
+class SwappingWireValue<T, 1> {
+public:
+  KJ_ALWAYS_INLINE(T get() const) { return value; }
+  KJ_ALWAYS_INLINE(void set(T newValue)) { value = newValue; }
+
+private:
+  T value;
+};
+
+template <typename T>
+class SwappingWireValue<T, 2> {
+public:
+  KJ_ALWAYS_INLINE(T get() const) {
+    // Not all platforms have __builtin_bswap16() for some reason.  In particular, it is missing
+    // on gcc-4.7.3-cygwin32 (but present on gcc-4.8.1-cygwin64).
+    uint16_t swapped = (value << 8) | (value >> 8);
+    T result;
+    memcpy(&result, &swapped, sizeof(T));
+    return result;
+  }
+  KJ_ALWAYS_INLINE(void set(T newValue)) {
+    uint16_t raw;
+    memcpy(&raw, &newValue, sizeof(T));
+    // Not all platforms have __builtin_bswap16() for some reason.  In particular, it is missing
+    // on gcc-4.7.3-cygwin32 (but present on gcc-4.8.1-cygwin64).
+    value = (raw << 8) | (raw >> 8);
+  }
+
+private:
+  uint16_t value;
+};
+
+template <typename T>
+class SwappingWireValue<T, 4> {
+public:
+  KJ_ALWAYS_INLINE(T get() const) {
+    uint32_t swapped = __builtin_bswap32(value);
+    T result;
+    memcpy(&result, &swapped, sizeof(T));
+    return result;
+  }
+  KJ_ALWAYS_INLINE(void set(T newValue)) {
+    uint32_t raw;
+    memcpy(&raw, &newValue, sizeof(T));
+    value = __builtin_bswap32(raw);
+  }
+
+private:
+  uint32_t value;
+};
+
+template <typename T>
+class SwappingWireValue<T, 8> {
+public:
+  KJ_ALWAYS_INLINE(T get() const) {
+    uint64_t swapped = __builtin_bswap64(value);
+    T result;
+    memcpy(&result, &swapped, sizeof(T));
+    return result;
+  }
+  KJ_ALWAYS_INLINE(void set(T newValue)) {
+    uint64_t raw;
+    memcpy(&raw, &newValue, sizeof(T));
+    value = __builtin_bswap64(raw);
+  }
+
+private:
+  uint64_t value;
+};
+
+template <typename T>
+using WireValue = SwappingWireValue<T>;
+// To prevent ODR problems when endian-test, endian-reverse-test, and endian-fallback-test are
+// linked together, we define each implementation with a different name and define an alias to the
+// one we want to use.
+
+#else
+// Unknown endianness.  Fall back to bit shifts.
+
+#if !CAPNP_DISABLE_ENDIAN_DETECTION
+#if _MSC_VER
+#pragma message("Couldn't detect endianness of your platform.  Using unoptimized fallback implementation.")
+#pragma message("Consider changing this code to detect your platform and send us a patch!")
+#else
+#warning "Couldn't detect endianness of your platform.  Using unoptimized fallback implementation."
+#warning "Consider changing this code to detect your platform and send us a patch!"
+#endif
+#endif  // !CAPNP_DISABLE_ENDIAN_DETECTION
+
+template <typename T, size_t size = sizeof(T)>
+class ShiftingWireValue;
+
+template <typename T>
+class ShiftingWireValue<T, 1> {
+public:
+  KJ_ALWAYS_INLINE(T get() const) { return value; }
+  KJ_ALWAYS_INLINE(void set(T newValue)) { value = newValue; }
+
+private:
+  T value;
+};
+
+template <typename T>
+class ShiftingWireValue<T, 2> {
+public:
+  KJ_ALWAYS_INLINE(T get() const) {
+    uint16_t raw = (static_cast<uint16_t>(bytes[0])     ) |
+                   (static_cast<uint16_t>(bytes[1]) << 8);
+    T result;
+    memcpy(&result, &raw, sizeof(T));
+    return result;
+  }
+  KJ_ALWAYS_INLINE(void set(T newValue)) {
+    uint16_t raw;
+    memcpy(&raw, &newValue, sizeof(T));
+    bytes[0] = raw;
+    bytes[1] = raw >> 8;
+  }
+
+private:
+  union {
+    byte bytes[2];
+    uint16_t align;
+  };
+};
+
+template <typename T>
+class ShiftingWireValue<T, 4> {
+public:
+  KJ_ALWAYS_INLINE(T get() const) {
+    uint32_t raw = (static_cast<uint32_t>(bytes[0])      ) |
+                   (static_cast<uint32_t>(bytes[1]) <<  8) |
+                   (static_cast<uint32_t>(bytes[2]) << 16) |
+                   (static_cast<uint32_t>(bytes[3]) << 24);
+    T result;
+    memcpy(&result, &raw, sizeof(T));
+    return result;
+  }
+  KJ_ALWAYS_INLINE(void set(T newValue)) {
+    uint32_t raw;
+    memcpy(&raw, &newValue, sizeof(T));
+    bytes[0] = raw;
+    bytes[1] = raw >> 8;
+    bytes[2] = raw >> 16;
+    bytes[3] = raw >> 24;
+  }
+
+private:
+  union {
+    byte bytes[4];
+    uint32_t align;
+  };
+};
+
+template <typename T>
+class ShiftingWireValue<T, 8> {
+public:
+  KJ_ALWAYS_INLINE(T get() const) {
+    uint64_t raw = (static_cast<uint64_t>(bytes[0])      ) |
+                   (static_cast<uint64_t>(bytes[1]) <<  8) |
+                   (static_cast<uint64_t>(bytes[2]) << 16) |
+                   (static_cast<uint64_t>(bytes[3]) << 24) |
+                   (static_cast<uint64_t>(bytes[4]) << 32) |
+                   (static_cast<uint64_t>(bytes[5]) << 40) |
+                   (static_cast<uint64_t>(bytes[6]) << 48) |
+                   (static_cast<uint64_t>(bytes[7]) << 56);
+    T result;
+    memcpy(&result, &raw, sizeof(T));
+    return result;
+  }
+  KJ_ALWAYS_INLINE(void set(T newValue)) {
+    uint64_t raw;
+    memcpy(&raw, &newValue, sizeof(T));
+    bytes[0] = raw;
+    bytes[1] = raw >> 8;
+    bytes[2] = raw >> 16;
+    bytes[3] = raw >> 24;
+    bytes[4] = raw >> 32;
+    bytes[5] = raw >> 40;
+    bytes[6] = raw >> 48;
+    bytes[7] = raw >> 56;
+  }
+
+private:
+  union {
+    byte bytes[8];
+    uint64_t align;
+  };
+};
+
+template <typename T>
+using WireValue = ShiftingWireValue<T>;
+// To prevent ODR problems when endian-test, endian-reverse-test, and endian-fallback-test are
+// linked together, we define each implementation with a different name and define an alias to the
+// one we want to use.
+
+#endif
+
+}  // namespace _ (private)
+}  // namespace capnp
+
+#endif  // CAPNP_ENDIAN_H_