tippecanoe/protozero/pbf_writer.hpp
2016-04-22 17:10:33 -07:00

838 lines
28 KiB
C++

#ifndef PROTOZERO_PBF_WRITER_HPP
#define PROTOZERO_PBF_WRITER_HPP
/*****************************************************************************
protozero - Minimalistic protocol buffer decoder and encoder in C++.
This file is from https://github.com/mapbox/protozero where you can find more
documentation.
*****************************************************************************/
/**
* @file pbf_writer.hpp
*
* @brief Contains the pbf_writer class.
*/
#include <cstddef>
#include <cstdint>
#include <cstring>
#include <iterator>
#include <limits>
#include <string>
#include <protozero/config.hpp>
#include <protozero/types.hpp>
#include <protozero/varint.hpp>
#if PROTOZERO_BYTE_ORDER != PROTOZERO_LITTLE_ENDIAN
# include <protozero/byteswap.hpp>
#endif
namespace protozero {
namespace detail {
template <typename T> class packed_field_varint;
template <typename T> class packed_field_svarint;
template <typename T> class packed_field_fixed;
} // end namespace detail
/**
* The pbf_writer is used to write PBF formatted messages into a buffer.
*
* Almost all methods in this class can throw an std::bad_alloc exception if
* the std::string used as a buffer wants to resize.
*/
class pbf_writer {
// A pointer to a string buffer holding the data already written to the
// PBF message. For default constructed writers or writers that have been
// rolled back, this is a nullptr.
std::string* m_data;
// A pointer to a parent writer object if this is a submessage. If this
// is a top-level writer, it is a nullptr.
pbf_writer* m_parent_writer;
// This is usually 0. If there is an open submessage, this is set in the
// parent to the rollback position, ie. the last position before the
// submessage was started. This is the position where the header of the
// submessage starts.
std::size_t m_rollback_pos = 0;
// This is usually 0. If there is an open submessage, this is set in the
// parent to the position where the data of the submessage is written to.
std::size_t m_pos = 0;
inline void add_varint(uint64_t value) {
protozero_assert(m_pos == 0 && "you can't add fields to a parent pbf_writer if there is an existing pbf_writer for a submessage");
protozero_assert(m_data);
write_varint(std::back_inserter(*m_data), value);
}
inline void add_field(pbf_tag_type tag, pbf_wire_type type) {
protozero_assert(((tag > 0 && tag < 19000) || (tag > 19999 && tag <= ((1 << 29) - 1))) && "tag out of range");
uint32_t b = (tag << 3) | uint32_t(type);
add_varint(b);
}
inline void add_tagged_varint(pbf_tag_type tag, uint64_t value) {
add_field(tag, pbf_wire_type::varint);
add_varint(value);
}
template <typename T>
inline void add_fixed(T value) {
protozero_assert(m_pos == 0 && "you can't add fields to a parent pbf_writer if there is an existing pbf_writer for a submessage");
protozero_assert(m_data);
#if PROTOZERO_BYTE_ORDER == PROTOZERO_LITTLE_ENDIAN
m_data->append(reinterpret_cast<const char*>(&value), sizeof(T));
#else
auto size = m_data->size();
m_data->resize(size + sizeof(T));
byteswap<sizeof(T)>(reinterpret_cast<const char*>(&value), const_cast<char*>(m_data->data() + size));
#endif
}
template <typename T, typename It>
inline void add_packed_fixed(pbf_tag_type tag, It first, It last, std::input_iterator_tag) {
if (first == last) {
return;
}
pbf_writer sw(*this, tag);
while (first != last) {
sw.add_fixed<T>(*first++);
}
}
template <typename T, typename It>
inline void add_packed_fixed(pbf_tag_type tag, It first, It last, std::forward_iterator_tag) {
if (first == last) {
return;
}
auto length = std::distance(first, last);
add_length_varint(tag, sizeof(T) * pbf_length_type(length));
reserve(sizeof(T) * std::size_t(length));
while (first != last) {
add_fixed<T>(*first++);
}
}
template <typename It>
inline void add_packed_varint(pbf_tag_type tag, It first, It last) {
if (first == last) {
return;
}
pbf_writer sw(*this, tag);
while (first != last) {
sw.add_varint(uint64_t(*first++));
}
}
template <typename It>
inline void add_packed_svarint(pbf_tag_type tag, It first, It last) {
if (first == last) {
return;
}
pbf_writer sw(*this, tag);
while (first != last) {
sw.add_varint(encode_zigzag64(*first++));
}
}
// The number of bytes to reserve for the varint holding the length of
// a length-delimited field. The length has to fit into pbf_length_type,
// and a varint needs 8 bit for every 7 bit.
static const int reserve_bytes = sizeof(pbf_length_type) * 8 / 7 + 1;
// If m_rollpack_pos is set to this special value, it means that when
// the submessage is closed, nothing needs to be done, because the length
// of the submessage has already been written correctly.
static const std::size_t size_is_known = std::numeric_limits<std::size_t>::max();
inline void open_submessage(pbf_tag_type tag, std::size_t size) {
protozero_assert(m_pos == 0);
protozero_assert(m_data);
if (size == 0) {
m_rollback_pos = m_data->size();
add_field(tag, pbf_wire_type::length_delimited);
m_data->append(std::size_t(reserve_bytes), '\0');
} else {
m_rollback_pos = size_is_known;
add_length_varint(tag, pbf_length_type(size));
reserve(size);
}
m_pos = m_data->size();
}
inline void rollback_submessage() {
protozero_assert(m_pos != 0);
protozero_assert(m_rollback_pos != size_is_known);
protozero_assert(m_data);
m_data->resize(m_rollback_pos);
m_pos = 0;
}
inline void commit_submessage() {
protozero_assert(m_pos != 0);
protozero_assert(m_rollback_pos != size_is_known);
protozero_assert(m_data);
auto length = pbf_length_type(m_data->size() - m_pos);
protozero_assert(m_data->size() >= m_pos - reserve_bytes);
auto n = write_varint(m_data->begin() + long(m_pos) - reserve_bytes, length);
m_data->erase(m_data->begin() + long(m_pos) - reserve_bytes + n, m_data->begin() + long(m_pos));
m_pos = 0;
}
inline void close_submessage() {
protozero_assert(m_data);
if (m_pos == 0 || m_rollback_pos == size_is_known) {
return;
}
if (m_data->size() - m_pos == 0) {
rollback_submessage();
} else {
commit_submessage();
}
}
inline void add_length_varint(pbf_tag_type tag, pbf_length_type length) {
add_field(tag, pbf_wire_type::length_delimited);
add_varint(length);
}
public:
/**
* Create a writer using the given string as a data store. The pbf_writer
* stores a reference to that string and adds all data to it. The string
* doesn't have to be empty. The pbf_writer will just append data.
*/
inline explicit pbf_writer(std::string& data) noexcept :
m_data(&data),
m_parent_writer(nullptr),
m_pos(0) {
}
/**
* Create a writer without a data store. In this form the writer can not
* be used!
*/
inline pbf_writer() noexcept :
m_data(nullptr),
m_parent_writer(nullptr),
m_pos(0) {
}
/**
* Construct a pbf_writer for a submessage from the pbf_writer of the
* parent message.
*
* @param parent_writer The pbf_writer
* @param tag Tag (field number) of the field that will be written
* @param size Optional size of the submessage in bytes (use 0 for unknown).
* Setting this allows some optimizations but is only possible in
* a few very specific cases.
*/
inline pbf_writer(pbf_writer& parent_writer, pbf_tag_type tag, std::size_t size=0) :
m_data(parent_writer.m_data),
m_parent_writer(&parent_writer),
m_pos(0) {
m_parent_writer->open_submessage(tag, size);
}
/// A pbf_writer object can be copied
pbf_writer(const pbf_writer&) noexcept = default;
/// A pbf_writer object can be copied
pbf_writer& operator=(const pbf_writer&) noexcept = default;
/// A pbf_writer object can be moved
inline pbf_writer(pbf_writer&&) noexcept = default;
/// A pbf_writer object can be moved
inline pbf_writer& operator=(pbf_writer&&) noexcept = default;
inline ~pbf_writer() {
if (m_parent_writer) {
m_parent_writer->close_submessage();
}
}
/**
* Reserve size bytes in the underlying message store in addition to
* whatever the message store already holds. So unlike
* the `std::string::reserve()` method this is not an absolute size,
* but additional memory that should be reserved.
*
* @param size Number of bytes to reserve in underlying message store.
*/
void reserve(std::size_t size) {
protozero_assert(m_data);
m_data->reserve(m_data->size() + size);
}
inline void rollback() {
protozero_assert(m_parent_writer && "you can't call rollback() on a pbf_writer without a parent");
protozero_assert(m_pos == 0 && "you can't call rollback() on a pbf_writer that has an open nested submessage");
m_parent_writer->rollback_submessage();
m_data = nullptr;
}
///@{
/**
* @name Scalar field writer functions
*/
/**
* Add "bool" field to data.
*
* @param tag Tag (field number) of the field
* @param value Value to be written
*/
inline void add_bool(pbf_tag_type tag, bool value) {
add_field(tag, pbf_wire_type::varint);
protozero_assert(m_pos == 0 && "you can't add fields to a parent pbf_writer if there is an existing pbf_writer for a submessage");
protozero_assert(m_data);
m_data->append(1, value);
}
/**
* Add "enum" field to data.
*
* @param tag Tag (field number) of the field
* @param value Value to be written
*/
inline void add_enum(pbf_tag_type tag, int32_t value) {
add_tagged_varint(tag, uint64_t(value));
}
/**
* Add "int32" field to data.
*
* @param tag Tag (field number) of the field
* @param value Value to be written
*/
inline void add_int32(pbf_tag_type tag, int32_t value) {
add_tagged_varint(tag, uint64_t(value));
}
/**
* Add "sint32" field to data.
*
* @param tag Tag (field number) of the field
* @param value Value to be written
*/
inline void add_sint32(pbf_tag_type tag, int32_t value) {
add_tagged_varint(tag, encode_zigzag32(value));
}
/**
* Add "uint32" field to data.
*
* @param tag Tag (field number) of the field
* @param value Value to be written
*/
inline void add_uint32(pbf_tag_type tag, uint32_t value) {
add_tagged_varint(tag, value);
}
/**
* Add "int64" field to data.
*
* @param tag Tag (field number) of the field
* @param value Value to be written
*/
inline void add_int64(pbf_tag_type tag, int64_t value) {
add_tagged_varint(tag, uint64_t(value));
}
/**
* Add "sint64" field to data.
*
* @param tag Tag (field number) of the field
* @param value Value to be written
*/
inline void add_sint64(pbf_tag_type tag, int64_t value) {
add_tagged_varint(tag, encode_zigzag64(value));
}
/**
* Add "uint64" field to data.
*
* @param tag Tag (field number) of the field
* @param value Value to be written
*/
inline void add_uint64(pbf_tag_type tag, uint64_t value) {
add_tagged_varint(tag, value);
}
/**
* Add "fixed32" field to data.
*
* @param tag Tag (field number) of the field
* @param value Value to be written
*/
inline void add_fixed32(pbf_tag_type tag, uint32_t value) {
add_field(tag, pbf_wire_type::fixed32);
add_fixed<uint32_t>(value);
}
/**
* Add "sfixed32" field to data.
*
* @param tag Tag (field number) of the field
* @param value Value to be written
*/
inline void add_sfixed32(pbf_tag_type tag, int32_t value) {
add_field(tag, pbf_wire_type::fixed32);
add_fixed<int32_t>(value);
}
/**
* Add "fixed64" field to data.
*
* @param tag Tag (field number) of the field
* @param value Value to be written
*/
inline void add_fixed64(pbf_tag_type tag, uint64_t value) {
add_field(tag, pbf_wire_type::fixed64);
add_fixed<uint64_t>(value);
}
/**
* Add "sfixed64" field to data.
*
* @param tag Tag (field number) of the field
* @param value Value to be written
*/
inline void add_sfixed64(pbf_tag_type tag, int64_t value) {
add_field(tag, pbf_wire_type::fixed64);
add_fixed<int64_t>(value);
}
/**
* Add "float" field to data.
*
* @param tag Tag (field number) of the field
* @param value Value to be written
*/
inline void add_float(pbf_tag_type tag, float value) {
add_field(tag, pbf_wire_type::fixed32);
add_fixed<float>(value);
}
/**
* Add "double" field to data.
*
* @param tag Tag (field number) of the field
* @param value Value to be written
*/
inline void add_double(pbf_tag_type tag, double value) {
add_field(tag, pbf_wire_type::fixed64);
add_fixed<double>(value);
}
/**
* Add "bytes" field to data.
*
* @param tag Tag (field number) of the field
* @param value Pointer to value to be written
* @param size Number of bytes to be written
*/
inline void add_bytes(pbf_tag_type tag, const char* value, std::size_t size) {
protozero_assert(m_pos == 0 && "you can't add fields to a parent pbf_writer if there is an existing pbf_writer for a submessage");
protozero_assert(m_data);
protozero_assert(size <= std::numeric_limits<pbf_length_type>::max());
add_length_varint(tag, pbf_length_type(size));
m_data->append(value, size);
}
/**
* Add "bytes" field to data.
*
* @param tag Tag (field number) of the field
* @param value Value to be written
*/
inline void add_bytes(pbf_tag_type tag, const std::string& value) {
add_bytes(tag, value.data(), value.size());
}
/**
* Add "string" field to data.
*
* @param tag Tag (field number) of the field
* @param value Pointer to value to be written
* @param size Number of bytes to be written
*/
inline void add_string(pbf_tag_type tag, const char* value, std::size_t size) {
add_bytes(tag, value, size);
}
/**
* Add "string" field to data.
*
* @param tag Tag (field number) of the field
* @param value Value to be written
*/
inline void add_string(pbf_tag_type tag, const std::string& value) {
add_bytes(tag, value.data(), value.size());
}
/**
* Add "string" field to data. Bytes from the value are written until
* a null byte is encountered. The null byte is not added.
*
* @param tag Tag (field number) of the field
* @param value Pointer to value to be written
*/
inline void add_string(pbf_tag_type tag, const char* value) {
add_bytes(tag, value, std::strlen(value));
}
/**
* Add "message" field to data.
*
* @param tag Tag (field number) of the field
* @param value Pointer to message to be written
* @param size Length of the message
*/
inline void add_message(pbf_tag_type tag, const char* value, std::size_t size) {
add_bytes(tag, value, size);
}
/**
* Add "message" field to data.
*
* @param tag Tag (field number) of the field
* @param value Value to be written. The value must be a complete message.
*/
inline void add_message(pbf_tag_type tag, const std::string& value) {
add_bytes(tag, value.data(), value.size());
}
///@}
///@{
/**
* @name Repeated packed field writer functions
*/
/**
* Add "repeated packed bool" field to data.
*
* @tparam InputIterator An type satisfying the InputIterator concept.
* Dereferencing the iterator must yield a type assignable to bool.
* @param tag Tag (field number) of the field
* @param first Iterator pointing to the beginning of the data
* @param last Iterator pointing one past the end of data
*/
template <typename InputIterator>
inline void add_packed_bool(pbf_tag_type tag, InputIterator first, InputIterator last) {
add_packed_varint(tag, first, last);
}
/**
* Add "repeated packed enum" field to data.
*
* @tparam InputIterator An type satisfying the InputIterator concept.
* Dereferencing the iterator must yield a type assignable to int32_t.
* @param tag Tag (field number) of the field
* @param first Iterator pointing to the beginning of the data
* @param last Iterator pointing one past the end of data
*/
template <typename InputIterator>
inline void add_packed_enum(pbf_tag_type tag, InputIterator first, InputIterator last) {
add_packed_varint(tag, first, last);
}
/**
* Add "repeated packed int32" field to data.
*
* @tparam InputIterator An type satisfying the InputIterator concept.
* Dereferencing the iterator must yield a type assignable to int32_t.
* @param tag Tag (field number) of the field
* @param first Iterator pointing to the beginning of the data
* @param last Iterator pointing one past the end of data
*/
template <typename InputIterator>
inline void add_packed_int32(pbf_tag_type tag, InputIterator first, InputIterator last) {
add_packed_varint(tag, first, last);
}
/**
* Add "repeated packed sint32" field to data.
*
* @tparam InputIterator An type satisfying the InputIterator concept.
* Dereferencing the iterator must yield a type assignable to int32_t.
* @param tag Tag (field number) of the field
* @param first Iterator pointing to the beginning of the data
* @param last Iterator pointing one past the end of data
*/
template <typename InputIterator>
inline void add_packed_sint32(pbf_tag_type tag, InputIterator first, InputIterator last) {
add_packed_svarint(tag, first, last);
}
/**
* Add "repeated packed uint32" field to data.
*
* @tparam InputIterator An type satisfying the InputIterator concept.
* Dereferencing the iterator must yield a type assignable to uint32_t.
* @param tag Tag (field number) of the field
* @param first Iterator pointing to the beginning of the data
* @param last Iterator pointing one past the end of data
*/
template <typename InputIterator>
inline void add_packed_uint32(pbf_tag_type tag, InputIterator first, InputIterator last) {
add_packed_varint(tag, first, last);
}
/**
* Add "repeated packed int64" field to data.
*
* @tparam InputIterator An type satisfying the InputIterator concept.
* Dereferencing the iterator must yield a type assignable to int64_t.
* @param tag Tag (field number) of the field
* @param first Iterator pointing to the beginning of the data
* @param last Iterator pointing one past the end of data
*/
template <typename InputIterator>
inline void add_packed_int64(pbf_tag_type tag, InputIterator first, InputIterator last) {
add_packed_varint(tag, first, last);
}
/**
* Add "repeated packed sint64" field to data.
*
* @tparam InputIterator An type satisfying the InputIterator concept.
* Dereferencing the iterator must yield a type assignable to int64_t.
* @param tag Tag (field number) of the field
* @param first Iterator pointing to the beginning of the data
* @param last Iterator pointing one past the end of data
*/
template <typename InputIterator>
inline void add_packed_sint64(pbf_tag_type tag, InputIterator first, InputIterator last) {
add_packed_svarint(tag, first, last);
}
/**
* Add "repeated packed uint64" field to data.
*
* @tparam InputIterator An type satisfying the InputIterator concept.
* Dereferencing the iterator must yield a type assignable to uint64_t.
* @param tag Tag (field number) of the field
* @param first Iterator pointing to the beginning of the data
* @param last Iterator pointing one past the end of data
*/
template <typename InputIterator>
inline void add_packed_uint64(pbf_tag_type tag, InputIterator first, InputIterator last) {
add_packed_varint(tag, first, last);
}
/**
* Add "repeated packed fixed32" field to data.
*
* @tparam InputIterator An type satisfying the InputIterator concept.
* Dereferencing the iterator must yield a type assignable to uint32_t.
* @param tag Tag (field number) of the field
* @param first Iterator pointing to the beginning of the data
* @param last Iterator pointing one past the end of data
*/
template <typename InputIterator>
inline void add_packed_fixed32(pbf_tag_type tag, InputIterator first, InputIterator last) {
add_packed_fixed<uint32_t, InputIterator>(tag, first, last,
typename std::iterator_traits<InputIterator>::iterator_category());
}
/**
* Add "repeated packed sfixed32" field to data.
*
* @tparam InputIterator An type satisfying the InputIterator concept.
* Dereferencing the iterator must yield a type assignable to int32_t.
* @param tag Tag (field number) of the field
* @param first Iterator pointing to the beginning of the data
* @param last Iterator pointing one past the end of data
*/
template <typename InputIterator>
inline void add_packed_sfixed32(pbf_tag_type tag, InputIterator first, InputIterator last) {
add_packed_fixed<int32_t, InputIterator>(tag, first, last,
typename std::iterator_traits<InputIterator>::iterator_category());
}
/**
* Add "repeated packed fixed64" field to data.
*
* @tparam InputIterator An type satisfying the InputIterator concept.
* Dereferencing the iterator must yield a type assignable to uint64_t.
* @param tag Tag (field number) of the field
* @param first Iterator pointing to the beginning of the data
* @param last Iterator pointing one past the end of data
*/
template <typename InputIterator>
inline void add_packed_fixed64(pbf_tag_type tag, InputIterator first, InputIterator last) {
add_packed_fixed<uint64_t, InputIterator>(tag, first, last,
typename std::iterator_traits<InputIterator>::iterator_category());
}
/**
* Add "repeated packed sfixed64" field to data.
*
* @tparam InputIterator An type satisfying the InputIterator concept.
* Dereferencing the iterator must yield a type assignable to int64_t.
* @param tag Tag (field number) of the field
* @param first Iterator pointing to the beginning of the data
* @param last Iterator pointing one past the end of data
*/
template <typename InputIterator>
inline void add_packed_sfixed64(pbf_tag_type tag, InputIterator first, InputIterator last) {
add_packed_fixed<int64_t, InputIterator>(tag, first, last,
typename std::iterator_traits<InputIterator>::iterator_category());
}
/**
* Add "repeated packed float" field to data.
*
* @tparam InputIterator An type satisfying the InputIterator concept.
* Dereferencing the iterator must yield a type assignable to float.
* @param tag Tag (field number) of the field
* @param first Iterator pointing to the beginning of the data
* @param last Iterator pointing one past the end of data
*/
template <typename InputIterator>
inline void add_packed_float(pbf_tag_type tag, InputIterator first, InputIterator last) {
add_packed_fixed<float, InputIterator>(tag, first, last,
typename std::iterator_traits<InputIterator>::iterator_category());
}
/**
* Add "repeated packed double" field to data.
*
* @tparam InputIterator An type satisfying the InputIterator concept.
* Dereferencing the iterator must yield a type assignable to double.
* @param tag Tag (field number) of the field
* @param first Iterator pointing to the beginning of the data
* @param last Iterator pointing one past the end of data
*/
template <typename InputIterator>
inline void add_packed_double(pbf_tag_type tag, InputIterator first, InputIterator last) {
add_packed_fixed<double, InputIterator>(tag, first, last,
typename std::iterator_traits<InputIterator>::iterator_category());
}
///@}
template <typename T> friend class detail::packed_field_varint;
template <typename T> friend class detail::packed_field_svarint;
template <typename T> friend class detail::packed_field_fixed;
}; // class pbf_writer
namespace detail {
class packed_field {
protected:
pbf_writer m_writer;
public:
packed_field(pbf_writer& parent_writer, pbf_tag_type tag) :
m_writer(parent_writer, tag) {
}
packed_field(pbf_writer& parent_writer, pbf_tag_type tag, std::size_t size) :
m_writer(parent_writer, tag, size) {
}
void rollback() {
m_writer.rollback();
}
}; // class packed_field
template <typename T>
class packed_field_fixed : public packed_field {
public:
packed_field_fixed(pbf_writer& parent_writer, pbf_tag_type tag) :
packed_field(parent_writer, tag) {
}
packed_field_fixed(pbf_writer& parent_writer, pbf_tag_type tag, std::size_t size) :
packed_field(parent_writer, tag, size * sizeof(T)) {
}
void add_element(T value) {
m_writer.add_fixed<T>(value);
}
}; // class packed_field_fixed
template <typename T>
class packed_field_varint : public packed_field {
public:
packed_field_varint(pbf_writer& parent_writer, pbf_tag_type tag) :
packed_field(parent_writer, tag) {
}
void add_element(T value) {
m_writer.add_varint(uint64_t(value));
}
}; // class packed_field_varint
template <typename T>
class packed_field_svarint : public packed_field {
public:
packed_field_svarint(pbf_writer& parent_writer, pbf_tag_type tag) :
packed_field(parent_writer, tag) {
}
void add_element(T value) {
m_writer.add_varint(encode_zigzag64(value));
}
}; // class packed_field_svarint
} // end namespace detail
using packed_field_bool = detail::packed_field_varint<bool>;
using packed_field_enum = detail::packed_field_varint<int32_t>;
using packed_field_int32 = detail::packed_field_varint<int32_t>;
using packed_field_sint32 = detail::packed_field_svarint<int32_t>;
using packed_field_uint32 = detail::packed_field_varint<uint32_t>;
using packed_field_int64 = detail::packed_field_varint<int64_t>;
using packed_field_sint64 = detail::packed_field_svarint<int64_t>;
using packed_field_uint64 = detail::packed_field_varint<uint64_t>;
using packed_field_fixed32 = detail::packed_field_fixed<uint32_t>;
using packed_field_sfixed32 = detail::packed_field_fixed<int32_t>;
using packed_field_fixed64 = detail::packed_field_fixed<uint64_t>;
using packed_field_sfixed64 = detail::packed_field_fixed<int64_t>;
using packed_field_float = detail::packed_field_fixed<float>;
using packed_field_double = detail::packed_field_fixed<double>;
} // end namespace protozero
#endif // PROTOZERO_PBF_WRITER_HPP