+// Utility to write an integer (signed or unsigned, any size)
+// to a stream in little-endian order. We swap the byte order before the write if
+// necessary to always write in little endian order, independently of the byte
+// ordering of the compiling machine.
+template<typename IntType>
+inline void write_little_endian(std::ostream& stream, IntType value) {
+
+ if (IsLittleEndian)
+ stream.write(reinterpret_cast<const char*>(&value), sizeof(IntType));
+ else
+ {
+ std::uint8_t u[sizeof(IntType)];
+ std::make_unsigned_t<IntType> v = value;
+
+ std::size_t i = 0;
+ // if constexpr to silence the warning about shift by 8
+ if constexpr (sizeof(IntType) > 1)
+ {
+ for (; i + 1 < sizeof(IntType); ++i)
+ {
+ u[i] = std::uint8_t(v);
+ v >>= 8;
+ }
+ }
+ u[i] = std::uint8_t(v);
+
+ stream.write(reinterpret_cast<char*>(u), sizeof(IntType));
+ }
+}
+
+
+// Read integers in bulk from a little indian stream.
+// This reads N integers from stream s and put them in array out.
+template<typename IntType>
+inline void read_little_endian(std::istream& stream, IntType* out, std::size_t count) {
+ if (IsLittleEndian)
+ stream.read(reinterpret_cast<char*>(out), sizeof(IntType) * count);
+ else
+ for (std::size_t i = 0; i < count; ++i)
+ out[i] = read_little_endian<IntType>(stream);
+}
+
+
+// Write integers in bulk to a little indian stream.
+// This takes N integers from array values and writes them on stream s.
+template<typename IntType>
+inline void write_little_endian(std::ostream& stream, const IntType* values, std::size_t count) {
+ if (IsLittleEndian)
+ stream.write(reinterpret_cast<const char*>(values), sizeof(IntType) * count);
+ else
+ for (std::size_t i = 0; i < count; ++i)
+ write_little_endian<IntType>(stream, values[i]);
+}
+
+
+// Read N signed integers from the stream s, putting them in
+// the array out. The stream is assumed to be compressed using the signed LEB128 format.
+// See https://en.wikipedia.org/wiki/LEB128 for a description of the compression scheme.
+template<typename IntType>
+inline void read_leb_128(std::istream& stream, IntType* out, std::size_t count) {
+
+ // Check the presence of our LEB128 magic string
+ char leb128MagicString[Leb128MagicStringSize];
+ stream.read(leb128MagicString, Leb128MagicStringSize);
+ assert(strncmp(Leb128MagicString, leb128MagicString, Leb128MagicStringSize) == 0);
+
+ static_assert(std::is_signed_v<IntType>, "Not implemented for unsigned types");
+
+ const std::uint32_t BUF_SIZE = 4096;
+ std::uint8_t buf[BUF_SIZE];
+
+ auto bytes_left = read_little_endian<std::uint32_t>(stream);
+
+ std::uint32_t buf_pos = BUF_SIZE;
+ for (std::size_t i = 0; i < count; ++i)
+ {
+ IntType result = 0;
+ size_t shift = 0;
+ do
+ {
+ if (buf_pos == BUF_SIZE)
+ {
+ stream.read(reinterpret_cast<char*>(buf), std::min(bytes_left, BUF_SIZE));
+ buf_pos = 0;
+ }
+
+ std::uint8_t byte = buf[buf_pos++];
+ --bytes_left;
+ result |= (byte & 0x7f) << shift;
+ shift += 7;
+
+ if ((byte & 0x80) == 0)
+ {
+ out[i] = (sizeof(IntType) * 8 <= shift || (byte & 0x40) == 0)
+ ? result
+ : result | ~((1 << shift) - 1);
+ break;
+ }
+ } while (shift < sizeof(IntType) * 8);
+ }
+
+ assert(bytes_left == 0);
+}
+
+
+// Write signed integers to a stream with LEB128 compression.
+// This takes N integers from array values, compress them with the LEB128 algorithm and
+// writes the result on the stream s.
+// See https://en.wikipedia.org/wiki/LEB128 for a description of the compression scheme.
+template<typename IntType>
+inline void write_leb_128(std::ostream& stream, const IntType* values, std::size_t count) {
+
+ // Write our LEB128 magic string
+ stream.write(Leb128MagicString, Leb128MagicStringSize);
+
+ static_assert(std::is_signed_v<IntType>, "Not implemented for unsigned types");
+
+ std::uint32_t byte_count = 0;
+ for (std::size_t i = 0; i < count; ++i)
+ {
+ IntType value = values[i];
+ std::uint8_t byte;
+ do
+ {
+ byte = value & 0x7f;
+ value >>= 7;
+ ++byte_count;
+ } while ((byte & 0x40) == 0 ? value != 0 : value != -1);
+ }
+
+ write_little_endian(stream, byte_count);
+
+ const std::uint32_t BUF_SIZE = 4096;
+ std::uint8_t buf[BUF_SIZE];
+ std::uint32_t buf_pos = 0;
+
+ auto flush = [&]() {
+ if (buf_pos > 0)
+ {
+ stream.write(reinterpret_cast<char*>(buf), buf_pos);
+ buf_pos = 0;
+ }
+ };
+
+ auto write = [&](std::uint8_t byte) {
+ buf[buf_pos++] = byte;
+ if (buf_pos == BUF_SIZE)
+ flush();
+ };
+
+ for (std::size_t i = 0; i < count; ++i)
+ {
+ IntType value = values[i];
+ while (true)
+ {
+ std::uint8_t byte = value & 0x7f;
+ value >>= 7;
+ if ((byte & 0x40) == 0 ? value == 0 : value == -1)
+ {
+ write(byte);
+ break;
+ }
+ write(byte | 0x80);
+ }
+ }
+
+ flush();
+}