+
+ // read_leb_128(s, out, N) : 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_leb_128(s, values, N) : 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();
+ }
+