1//===- Endian.h - Utilities for IO with endian specific data ----*- C++ -*-===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// This file declares generic functions to read and write endian specific data.
11//
12//===----------------------------------------------------------------------===//
13
14#ifndef LLVM_SUPPORT_ENDIAN_H
15#define LLVM_SUPPORT_ENDIAN_H
16
17#include "llvm/Support/AlignOf.h"
18#include "llvm/Support/Compiler.h"
19#include "llvm/Support/Host.h"
20#include "llvm/Support/SwapByteOrder.h"
21#include <cassert>
22#include <cstddef>
23#include <cstdint>
24#include <cstring>
25#include <type_traits>
26
27namespace llvm {
28namespace support {
29
30enum endianness {big, little, native};
31
32// These are named values for common alignments.
33enum {aligned = 0, unaligned = 1};
34
35namespace detail {
36
37/// \brief ::value is either alignment, or alignof(T) if alignment is 0.
38template<class T, int alignment>
39struct PickAlignment {
40 enum { value = alignment == 0 ? alignof(T) : alignment };
41};
42
43} // end namespace detail
44
45namespace endian {
46
47constexpr endianness system_endianness() {
48  return sys::IsBigEndianHost ? big : little;
49}
50
51template <typename value_type>
52inline value_type byte_swap(value_type value, endianness endian) {
53  if ((endian != native) && (endian != system_endianness()))
54    sys::swapByteOrder(value);
55  return value;
56}
57
58/// Swap the bytes of value to match the given endianness.
59template<typename value_type, endianness endian>
60inline value_type byte_swap(value_type value) {
61  return byte_swap(value, endian);
62}
63
64/// Read a value of a particular endianness from memory.
65template <typename value_type, std::size_t alignment>
66inline value_type read(const void *memory, endianness endian) {
67  value_type ret;
68
69  memcpy(&ret,
70         LLVM_ASSUME_ALIGNED(
71             memory, (detail::PickAlignment<value_type, alignment>::value)),
72         sizeof(value_type));
73  return byte_swap<value_type>(ret, endian);
74}
75
76template<typename value_type,
77         endianness endian,
78         std::size_t alignment>
79inline value_type read(const void *memory) {
80  return read<value_type, alignment>(memory, endian);
81}
82
83/// Read a value of a particular endianness from a buffer, and increment the
84/// buffer past that value.
85template <typename value_type, std::size_t alignment, typename CharT>
86inline value_type readNext(const CharT *&memory, endianness endian) {
87  value_type ret = read<value_type, alignment>(memory, endian);
88  memory += sizeof(value_type);
89  return ret;
90}
91
92template<typename value_type, endianness endian, std::size_t alignment,
93         typename CharT>
94inline value_type readNext(const CharT *&memory) {
95  return readNext<value_type, alignment, CharT>(memory, endian);
96}
97
98/// Write a value to memory with a particular endianness.
99template <typename value_type, std::size_t alignment>
100inline void write(void *memory, value_type value, endianness endian) {
101  value = byte_swap<value_type>(value, endian);
102  memcpy(LLVM_ASSUME_ALIGNED(
103             memory, (detail::PickAlignment<value_type, alignment>::value)),
104         &value, sizeof(value_type));
105}
106
107template<typename value_type,
108         endianness endian,
109         std::size_t alignment>
110inline void write(void *memory, value_type value) {
111  write<value_type, alignment>(memory, value, endian);
112}
113
114template <typename value_type>
115using make_unsigned_t = typename std::make_unsigned<value_type>::type;
116
117/// Read a value of a particular endianness from memory, for a location
118/// that starts at the given bit offset within the first byte.
119template <typename value_type, endianness endian, std::size_t alignment>
120inline value_type readAtBitAlignment(const void *memory, uint64_t startBit) {
121  assert(startBit < 8);
122  if (startBit == 0)
123    return read<value_type, endian, alignment>(memory);
124  else {
125    // Read two values and compose the result from them.
126    value_type val[2];
127    memcpy(&val[0],
128           LLVM_ASSUME_ALIGNED(
129               memory, (detail::PickAlignment<value_type, alignment>::value)),
130           sizeof(value_type) * 2);
131    val[0] = byte_swap<value_type, endian>(val[0]);
132    val[1] = byte_swap<value_type, endian>(val[1]);
133
134    // Shift bits from the lower value into place.
135    make_unsigned_t<value_type> lowerVal = val[0] >> startBit;
136    // Mask off upper bits after right shift in case of signed type.
137    make_unsigned_t<value_type> numBitsFirstVal =
138        (sizeof(value_type) * 8) - startBit;
139    lowerVal &= ((make_unsigned_t<value_type>)1 << numBitsFirstVal) - 1;
140
141    // Get the bits from the upper value.
142    make_unsigned_t<value_type> upperVal =
143        val[1] & (((make_unsigned_t<value_type>)1 << startBit) - 1);
144    // Shift them in to place.
145    upperVal <<= numBitsFirstVal;
146
147    return lowerVal | upperVal;
148  }
149}
150
151/// Write a value to memory with a particular endianness, for a location
152/// that starts at the given bit offset within the first byte.
153template <typename value_type, endianness endian, std::size_t alignment>
154inline void writeAtBitAlignment(void *memory, value_type value,
155                                uint64_t startBit) {
156  assert(startBit < 8);
157  if (startBit == 0)
158    write<value_type, endian, alignment>(memory, value);
159  else {
160    // Read two values and shift the result into them.
161    value_type val[2];
162    memcpy(&val[0],
163           LLVM_ASSUME_ALIGNED(
164               memory, (detail::PickAlignment<value_type, alignment>::value)),
165           sizeof(value_type) * 2);
166    val[0] = byte_swap<value_type, endian>(val[0]);
167    val[1] = byte_swap<value_type, endian>(val[1]);
168
169    // Mask off any existing bits in the upper part of the lower value that
170    // we want to replace.
171    val[0] &= ((make_unsigned_t<value_type>)1 << startBit) - 1;
172    make_unsigned_t<value_type> numBitsFirstVal =
173        (sizeof(value_type) * 8) - startBit;
174    make_unsigned_t<value_type> lowerVal = value;
175    if (startBit > 0) {
176      // Mask off the upper bits in the new value that are not going to go into
177      // the lower value. This avoids a left shift of a negative value, which
178      // is undefined behavior.
179      lowerVal &= (((make_unsigned_t<value_type>)1 << numBitsFirstVal) - 1);
180      // Now shift the new bits into place
181      lowerVal <<= startBit;
182    }
183    val[0] |= lowerVal;
184
185    // Mask off any existing bits in the lower part of the upper value that
186    // we want to replace.
187    val[1] &= ~(((make_unsigned_t<value_type>)1 << startBit) - 1);
188    // Next shift the bits that go into the upper value into position.
189    make_unsigned_t<value_type> upperVal = value >> numBitsFirstVal;
190    // Mask off upper bits after right shift in case of signed type.
191    upperVal &= ((make_unsigned_t<value_type>)1 << startBit) - 1;
192    val[1] |= upperVal;
193
194    // Finally, rewrite values.
195    val[0] = byte_swap<value_type, endian>(val[0]);
196    val[1] = byte_swap<value_type, endian>(val[1]);
197    memcpy(LLVM_ASSUME_ALIGNED(
198               memory, (detail::PickAlignment<value_type, alignment>::value)),
199           &val[0], sizeof(value_type) * 2);
200  }
201}
202
203} // end namespace endian
204
205namespace detail {
206
207template<typename value_type,
208         endianness endian,
209         std::size_t alignment>
210struct packed_endian_specific_integral {
211  packed_endian_specific_integral() = default;
212
213  explicit packed_endian_specific_integral(value_type val) { *this = val; }
214
215  operator value_type() const {
216    return endian::read<value_type, endian, alignment>(
217      (const void*)Value.buffer);
218  }
219
220  void operator=(value_type newValue) {
221    endian::write<value_type, endian, alignment>(
222      (void*)Value.buffer, newValue);
223  }
224
225  packed_endian_specific_integral &operator+=(value_type newValue) {
226    *this = *this + newValue;
227    return *this;
228  }
229
230  packed_endian_specific_integral &operator-=(value_type newValue) {
231    *this = *this - newValue;
232    return *this;
233  }
234
235  packed_endian_specific_integral &operator|=(value_type newValue) {
236    *this = *this | newValue;
237    return *this;
238  }
239
240  packed_endian_specific_integral &operator&=(value_type newValue) {
241    *this = *this & newValue;
242    return *this;
243  }
244
245private:
246  AlignedCharArray<PickAlignment<value_type, alignment>::value,
247                   sizeof(value_type)> Value;
248
249public:
250  struct ref {
251    explicit ref(void *Ptr) : Ptr(Ptr) {}
252
253    operator value_type() const {
254      return endian::read<value_type, endian, alignment>(Ptr);
255    }
256
257    void operator=(value_type NewValue) {
258      endian::write<value_type, endian, alignment>(Ptr, NewValue);
259    }
260
261  private:
262    void *Ptr;
263  };
264};
265
266} // end namespace detail
267
268using ulittle16_t =
269    detail::packed_endian_specific_integral<uint16_t, little, unaligned>;
270using ulittle32_t =
271    detail::packed_endian_specific_integral<uint32_t, little, unaligned>;
272using ulittle64_t =
273    detail::packed_endian_specific_integral<uint64_t, little, unaligned>;
274
275using little16_t =
276    detail::packed_endian_specific_integral<int16_t, little, unaligned>;
277using little32_t =
278    detail::packed_endian_specific_integral<int32_t, little, unaligned>;
279using little64_t =
280    detail::packed_endian_specific_integral<int64_t, little, unaligned>;
281
282using aligned_ulittle16_t =
283    detail::packed_endian_specific_integral<uint16_t, little, aligned>;
284using aligned_ulittle32_t =
285    detail::packed_endian_specific_integral<uint32_t, little, aligned>;
286using aligned_ulittle64_t =
287    detail::packed_endian_specific_integral<uint64_t, little, aligned>;
288
289using aligned_little16_t =
290    detail::packed_endian_specific_integral<int16_t, little, aligned>;
291using aligned_little32_t =
292    detail::packed_endian_specific_integral<int32_t, little, aligned>;
293using aligned_little64_t =
294    detail::packed_endian_specific_integral<int64_t, little, aligned>;
295
296using ubig16_t =
297    detail::packed_endian_specific_integral<uint16_t, big, unaligned>;
298using ubig32_t =
299    detail::packed_endian_specific_integral<uint32_t, big, unaligned>;
300using ubig64_t =
301    detail::packed_endian_specific_integral<uint64_t, big, unaligned>;
302
303using big16_t =
304    detail::packed_endian_specific_integral<int16_t, big, unaligned>;
305using big32_t =
306    detail::packed_endian_specific_integral<int32_t, big, unaligned>;
307using big64_t =
308    detail::packed_endian_specific_integral<int64_t, big, unaligned>;
309
310using aligned_ubig16_t =
311    detail::packed_endian_specific_integral<uint16_t, big, aligned>;
312using aligned_ubig32_t =
313    detail::packed_endian_specific_integral<uint32_t, big, aligned>;
314using aligned_ubig64_t =
315    detail::packed_endian_specific_integral<uint64_t, big, aligned>;
316
317using aligned_big16_t =
318    detail::packed_endian_specific_integral<int16_t, big, aligned>;
319using aligned_big32_t =
320    detail::packed_endian_specific_integral<int32_t, big, aligned>;
321using aligned_big64_t =
322    detail::packed_endian_specific_integral<int64_t, big, aligned>;
323
324using unaligned_uint16_t =
325    detail::packed_endian_specific_integral<uint16_t, native, unaligned>;
326using unaligned_uint32_t =
327    detail::packed_endian_specific_integral<uint32_t, native, unaligned>;
328using unaligned_uint64_t =
329    detail::packed_endian_specific_integral<uint64_t, native, unaligned>;
330
331using unaligned_int16_t =
332    detail::packed_endian_specific_integral<int16_t, native, unaligned>;
333using unaligned_int32_t =
334    detail::packed_endian_specific_integral<int32_t, native, unaligned>;
335using unaligned_int64_t =
336    detail::packed_endian_specific_integral<int64_t, native, unaligned>;
337
338namespace endian {
339
340template <typename T> inline T read(const void *P, endianness E) {
341  return read<T, unaligned>(P, E);
342}
343
344template <typename T, endianness E> inline T read(const void *P) {
345  return *(const detail::packed_endian_specific_integral<T, E, unaligned> *)P;
346}
347
348inline uint16_t read16(const void *P, endianness E) {
349  return read<uint16_t>(P, E);
350}
351inline uint32_t read32(const void *P, endianness E) {
352  return read<uint32_t>(P, E);
353}
354inline uint64_t read64(const void *P, endianness E) {
355  return read<uint64_t>(P, E);
356}
357
358template <endianness E> inline uint16_t read16(const void *P) {
359  return read<uint16_t, E>(P);
360}
361template <endianness E> inline uint32_t read32(const void *P) {
362  return read<uint32_t, E>(P);
363}
364template <endianness E> inline uint64_t read64(const void *P) {
365  return read<uint64_t, E>(P);
366}
367
368inline uint16_t read16le(const void *P) { return read16<little>(P); }
369inline uint32_t read32le(const void *P) { return read32<little>(P); }
370inline uint64_t read64le(const void *P) { return read64<little>(P); }
371inline uint16_t read16be(const void *P) { return read16<big>(P); }
372inline uint32_t read32be(const void *P) { return read32<big>(P); }
373inline uint64_t read64be(const void *P) { return read64<big>(P); }
374
375template <typename T> inline void write(void *P, T V, endianness E) {
376  write<T, unaligned>(P, V, E);
377}
378
379template <typename T, endianness E> inline void write(void *P, T V) {
380  *(detail::packed_endian_specific_integral<T, E, unaligned> *)P = V;
381}
382
383inline void write16(void *P, uint16_t V, endianness E) {
384  write<uint16_t>(P, V, E);
385}
386inline void write32(void *P, uint32_t V, endianness E) {
387  write<uint32_t>(P, V, E);
388}
389inline void write64(void *P, uint64_t V, endianness E) {
390  write<uint64_t>(P, V, E);
391}
392
393template <endianness E> inline void write16(void *P, uint16_t V) {
394  write<uint16_t, E>(P, V);
395}
396template <endianness E> inline void write32(void *P, uint32_t V) {
397  write<uint32_t, E>(P, V);
398}
399template <endianness E> inline void write64(void *P, uint64_t V) {
400  write<uint64_t, E>(P, V);
401}
402
403inline void write16le(void *P, uint16_t V) { write16<little>(P, V); }
404inline void write32le(void *P, uint32_t V) { write32<little>(P, V); }
405inline void write64le(void *P, uint64_t V) { write64<little>(P, V); }
406inline void write16be(void *P, uint16_t V) { write16<big>(P, V); }
407inline void write32be(void *P, uint32_t V) { write32<big>(P, V); }
408inline void write64be(void *P, uint64_t V) { write64<big>(P, V); }
409
410} // end namespace endian
411
412} // end namespace support
413} // end namespace llvm
414
415#endif // LLVM_SUPPORT_ENDIAN_H
416