Support: Add Endian.h

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@117057 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 228 insertions, 0 deletions

diff --git a/include/llvm/Support/Endian.h b/include/llvm/Support/Endian.h
new file mode 100644
index 0000000000..985c5870dd
--- /dev/null
+++ b/include/llvm/Support/Endian.h
@@ -0,0 +1,228 @@
+//===- Endian.h - Utilities for IO with endian specific data ----*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file declares generic functions to read and write endian specific data.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_SUPPORT_ENDIAN_H
+#define LLVM_SUPPORT_ENDIAN_H
+
+#include "llvm/Config/config.h"
+#include "llvm/System/SwapByteOrder.h"
+#include "llvm/Support/type_traits.h"
+
+namespace llvm {
+namespace support {
+
+enum endianness {big, little};
+enum alignment {unaligned, aligned};
+
+template<typename value_type, int host, int target>
+static typename enable_if_c<host == target, value_type>::type
+SwapByteOrderIfDifferent(value_type value) {
+  // Target endianess is the same as the host. Just pass the value through.
+  return value;
+}
+
+template<typename value_type, int host, int target>
+static typename enable_if_c<host != target, value_type>::type
+SwapByteOrderIfDifferent(value_type value) {
+    return sys::SwapByteOrder<value_type>(value);
+}
+
+namespace detail {
+
+template<typename value_type, alignment align>
+struct alignment_access_helper;
+
+template<typename value_type>
+struct alignment_access_helper<value_type, aligned>
+{
+  value_type val;
+};
+
+// Provides unaligned loads and stores.
+#pragma pack(push)
+#pragma pack(1)
+template<typename value_type>
+struct alignment_access_helper<value_type, unaligned>
+{
+  value_type val;
+};
+#pragma pack(pop)
+
+} // end namespace detail
+
+#if defined(LLVM_IS_TARGET_BIG_ENDIAN) \
+ || defined(_BIG_ENDIAN) || defined(__BIG_ENDIAN__)
+static const endianness host_endianness = big;
+#else
+static const endianness host_endianness = little;
+#endif
+
+struct endian {
+  template<typename value_type, alignment align>
+  static value_type read_le(const void *memory) {
+    return SwapByteOrderIfDifferent<value_type, host_endianness, little>(
+      reinterpret_cast<const detail::alignment_access_helper
+        <value_type, align> *>(memory)->val);
+  }
+
+  template<typename value_type, alignment align>
+  static void write_le(void *memory, value_type value) {
+    reinterpret_cast<detail::alignment_access_helper<value_type, align> *>
+      (memory)->val =
+        SwapByteOrderIfDifferent< value_type
+                                , host_endianness
+                                , little>(value);
+  }
+
+  template<typename value_type, alignment align>
+  static value_type read_be(const void *memory) {
+    return SwapByteOrderIfDifferent<value_type, host_endianness, big>(
+      reinterpret_cast<const detail::alignment_access_helper
+        <value_type, align> *>(memory)->val);
+  }
+
+  template<typename value_type, alignment align>
+  static void write_be(void *memory, value_type value) {
+    reinterpret_cast<detail::alignment_access_helper
+      <value_type, align> *>(memory)->val =
+        SwapByteOrderIfDifferent< value_type
+                                , host_endianness
+                                , big>(value);
+  }
+};
+
+namespace detail {
+
+template<typename value_type,
+         endianness target_endianness,
+         alignment target_alignment>
+class packed_endian_specific_integral;
+
+template<typename value_type>
+class packed_endian_specific_integral<value_type, little, unaligned> {
+public:
+  operator value_type() const {
+    return endian::read_le<value_type, unaligned>(Value);
+  }
+private:
+  uint8_t Value[sizeof(value_type)];
+};
+
+template<typename value_type>
+class packed_endian_specific_integral<value_type, big, unaligned> {
+public:
+  operator value_type() const {
+    return endian::read_be<value_type, unaligned>(Value);
+  }
+private:
+  uint8_t Value[sizeof(value_type)];
+};
+
+template<typename value_type>
+class packed_endian_specific_integral<value_type, little, aligned> {
+public:
+  operator value_type() const {
+    return endian::read_le<value_type, aligned>(&Value);
+  }
+private:
+  value_type Value;
+};
+
+template<typename value_type>
+class packed_endian_specific_integral<value_type, big, aligned> {
+public:
+  operator value_type() const {
+    return endian::read_be<value_type, aligned>(&Value);
+  }
+private:
+  value_type Value;
+};
+
+} // end namespace detail
+
+typedef detail::packed_endian_specific_integral
+                  <uint8_t, little, unaligned>  ulittle8_t;
+typedef detail::packed_endian_specific_integral
+                  <uint16_t, little, unaligned> ulittle16_t;
+typedef detail::packed_endian_specific_integral
+                  <uint32_t, little, unaligned> ulittle32_t;
+typedef detail::packed_endian_specific_integral
+                  <uint64_t, little, unaligned> ulittle64_t;
+
+typedef detail::packed_endian_specific_integral
+                   <int8_t, little, unaligned>  little8_t;
+typedef detail::packed_endian_specific_integral
+                   <int16_t, little, unaligned> little16_t;
+typedef detail::packed_endian_specific_integral
+                   <int32_t, little, unaligned> little32_t;
+typedef detail::packed_endian_specific_integral
+                   <int64_t, little, unaligned> little64_t;
+
+typedef detail::packed_endian_specific_integral
+                    <uint8_t, little, aligned>  aligned_ulittle8_t;
+typedef detail::packed_endian_specific_integral
+                    <uint16_t, little, aligned> aligned_ulittle16_t;
+typedef detail::packed_endian_specific_integral
+                    <uint32_t, little, aligned> aligned_ulittle32_t;
+typedef detail::packed_endian_specific_integral
+                    <uint64_t, little, aligned> aligned_ulittle64_t;
+
+typedef detail::packed_endian_specific_integral
+                     <int8_t, little, aligned>  aligned_little8_t;
+typedef detail::packed_endian_specific_integral
+                     <int16_t, little, aligned> aligned_little16_t;
+typedef detail::packed_endian_specific_integral
+                     <int32_t, little, aligned> aligned_little32_t;
+typedef detail::packed_endian_specific_integral
+                     <int64_t, little, aligned> aligned_little64_t;
+
+typedef detail::packed_endian_specific_integral
+                  <uint8_t, big, unaligned>     ubig8_t;
+typedef detail::packed_endian_specific_integral
+                  <uint16_t, big, unaligned>    ubig16_t;
+typedef detail::packed_endian_specific_integral
+                  <uint32_t, big, unaligned>    ubig32_t;
+typedef detail::packed_endian_specific_integral
+                  <uint64_t, big, unaligned>    ubig64_t;
+
+typedef detail::packed_endian_specific_integral
+                   <int8_t, big, unaligned>     big8_t;
+typedef detail::packed_endian_specific_integral
+                   <int16_t, big, unaligned>    big16_t;
+typedef detail::packed_endian_specific_integral
+                   <int32_t, big, unaligned>    big32_t;
+typedef detail::packed_endian_specific_integral
+                   <int64_t, big, unaligned>    big64_t;
+
+typedef detail::packed_endian_specific_integral
+                    <uint8_t, big, aligned>     aligned_ubig8_t;
+typedef detail::packed_endian_specific_integral
+                    <uint16_t, big, aligned>    aligned_ubig16_t;
+typedef detail::packed_endian_specific_integral
+                    <uint32_t, big, aligned>    aligned_ubig32_t;
+typedef detail::packed_endian_specific_integral
+                    <uint64_t, big, aligned>    aligned_ubig64_t;
+
+typedef detail::packed_endian_specific_integral
+                     <int8_t, big, aligned>     aligned_big8_t;
+typedef detail::packed_endian_specific_integral
+                     <int16_t, big, aligned>    aligned_big16_t;
+typedef detail::packed_endian_specific_integral
+                     <int32_t, big, aligned>    aligned_big32_t;
+typedef detail::packed_endian_specific_integral
+                     <int64_t, big, aligned>    aligned_big64_t;
+
+} // end namespace llvm
+} // end namespace support
+
+#endif