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/*************************************************************************
*
* Copyright 2016 Realm Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
**************************************************************************/
#ifndef REALM_UTIL_UTF8_HPP
#define REALM_UTIL_UTF8_HPP
#include <cstdint>
#include <string>
#include <realm/util/safe_int_ops.hpp>
#include <realm/string_data.hpp>
#include <realm/util/features.h>
#include <realm/utilities.hpp>
namespace realm {
namespace util {
/// Transcode between UTF-8 and UTF-16.
///
/// \tparam Char16 Must be an integral type with at least 16 bits.
///
/// \tparam Traits16 Must define to_int_type() and to_char_type() for
/// \a Char16.
template <class Char16, class Traits16 = std::char_traits<Char16>>
struct Utf8x16 {
/// Transcode as much as possible of the specified UTF-8 input, to
/// UTF-16. Returns true if all input characters were transcoded, or
/// transcoding stopped because the next character did not fit into the
/// output buffer. Returns false if transcoding stopped due to invalid
/// input. It is not specified whether this function returns true or false
/// if invalid input occurs at the same time as the output buffer runs
/// full. In any case, upon return, \a in_begin and \a out_begin are
/// advanced to the position where transcoding stopped.
///
/// Throws only if Traits16::to_char_type() throws.
static bool to_utf16(const char*& in_begin, const char* in_end, Char16*& out_begin, Char16* out_end);
/// Same as to_utf16(), but in reverse.
///
/// Throws only if Traits16::to_int_type() throws.
static bool to_utf8(const Char16*& in_begin, const Char16* in_end, char*& out_begin, char* out_end);
/// Summarize the number of UTF-16 elements needed to hold the result of
/// transcoding the specified UTF-8 string. Upon return, if \a in_begin !=
/// \a in_end, then the summation stopped due to invalid UTF-8 input. The
/// returned size then reflects the number of UTF-16 elements needed to hold
/// the result of transcoding the part of the input that was examined. This
/// function will only detect a few UTF-8 validity issues, and can therefore
/// not be used for general UTF-8 validation.
static size_t find_utf16_buf_size(const char*& in_begin, const char* in_end);
/// Summarize the number of UTF-8 bytes needed to hold the result of
/// transcoding the specified UTF-16 string. Upon return, if \a in_begin !=
/// \a in_end, then the summation stopped due to invalid UTF-16 input, or to
/// prevent the returned \c size_t value from overflowing. The returned size
/// then reflects the number of UTF-8 bytes needed to hold the result of
/// transcoding the part of the input that was examined. This function will
/// only detect a few UTF-16 validity issues, and can therefore not be used
/// for general UTF-16 validation.
static size_t find_utf8_buf_size(const Char16*& in_begin, const Char16* in_end);
};
// Implementation:
// Adapted from reference implementation.
// http://www.unicode.org/resources/utf8.html
// http://www.bsdua.org/files/unicode.tar.gz
template <class Char16, class Traits16>
inline bool Utf8x16<Char16, Traits16>::to_utf16(const char*& in_begin, const char* const in_end, Char16*& out_begin,
Char16* const out_end)
{
typedef std::char_traits<char> traits8;
bool invalid = false;
const char* in = in_begin;
Char16* out = out_begin;
while (in != in_end) {
if (REALM_UNLIKELY(out == out_end)) {
break; // Need space in output buffer
}
REALM_ASSERT(&in[0] >= in_begin && &in[0] < in_end);
uint_fast16_t v1 = uint_fast16_t(traits8::to_int_type(in[0]));
if (REALM_LIKELY(v1 < 0x80)) { // One byte
// UTF-8 layout: 0xxxxxxx
*out++ = Traits16::to_char_type(v1);
in += 1;
continue;
}
if (REALM_UNLIKELY(v1 < 0xC0)) {
invalid = true;
break; // Invalid first byte of UTF-8 sequence
}
if (REALM_LIKELY(v1 < 0xE0)) { // Two bytes
if (REALM_UNLIKELY(in_end - in < 2)) {
invalid = true;
break; // Incomplete UTF-8 sequence
}
REALM_ASSERT(&in[1] >= in_begin && &in[1] < in_end);
uint_fast16_t v2 = uint_fast16_t(traits8::to_int_type(in[1]));
// UTF-8 layout: 110xxxxx 10xxxxxx
if (REALM_UNLIKELY((v2 & 0xC0) != 0x80)) {
invalid = true;
break; // Invalid continuation byte
}
uint_fast16_t v = uint_fast16_t(((v1 & 0x1F) << 6) | ((v2 & 0x3F) << 0));
if (REALM_UNLIKELY(v < 0x80)) {
invalid = true;
break; // Overlong encoding is invalid
}
*out++ = Traits16::to_char_type(v);
in += 2;
continue;
}
if (REALM_LIKELY(v1 < 0xF0)) { // Three bytes
if (REALM_UNLIKELY(in_end - in < 3)) {
invalid = true;
break; // Incomplete UTF-8 sequence
}
REALM_ASSERT(&in[1] >= in_begin && &in[2] < in_end);
uint_fast16_t v2 = uint_fast16_t(traits8::to_int_type(in[1]));
uint_fast16_t v3 = uint_fast16_t(traits8::to_int_type(in[2]));
// UTF-8 layout: 1110xxxx 10xxxxxx 10xxxxxx
if (REALM_UNLIKELY((v2 & 0xC0) != 0x80 || (v3 & 0xC0) != 0x80)) {
invalid = true;
break; // Invalid continuation byte
}
uint_fast16_t v = uint_fast16_t(((v1 & 0x0F) << 12) | ((v2 & 0x3F) << 6) | ((v3 & 0x3F) << 0));
if (REALM_UNLIKELY(v < 0x800)) {
invalid = true;
break; // Overlong encoding is invalid
}
if (REALM_UNLIKELY(0xD800 <= v && v < 0xE000)) {
invalid = true;
break; // Illegal code point range (reserved for UTF-16 surrogate pairs)
}
*out++ = Traits16::to_char_type(v);
in += 3;
continue;
}
if (REALM_UNLIKELY(out + 1 == out_end)) {
break; // Need space in output buffer for surrogate pair
}
if (REALM_LIKELY(v1 < 0xF8)) { // Four bytes
if (REALM_UNLIKELY(in_end - in < 4)) {
invalid = true;
break; // Incomplete UTF-8 sequence
}
uint_fast32_t w1 = uint_fast32_t(v1); // 16 bit -> 32 bit
REALM_ASSERT(&in[1] >= in_begin && &in[3] < in_end);
uint_fast32_t v2 = uint_fast32_t(traits8::to_int_type(in[1])); // 32 bit intended
uint_fast16_t v3 = uint_fast16_t(traits8::to_int_type(in[2])); // 16 bit intended
uint_fast16_t v4 = uint_fast16_t(traits8::to_int_type(in[3])); // 16 bit intended
// UTF-8 layout: 11110xxx 10xxxxxx 10xxxxxx 10xxxxxx
if (REALM_UNLIKELY((v2 & 0xC0) != 0x80 || (v3 & 0xC0) != 0x80 || (v4 & 0xC0) != 0x80)) {
invalid = true;
break; // Invalid continuation byte
}
uint_fast32_t v = uint_fast32_t(((w1 & 0x07) << 18) | // Parenthesis is 32 bit partial result
((v2 & 0x3F) << 12) | // Parenthesis is 32 bit partial result
((v3 & 0x3F) << 6) | // Parenthesis is 16 bit partial result
((v4 & 0x3F) << 0)); // Parenthesis is 16 bit partial result
if (REALM_UNLIKELY(v < 0x10000)) {
invalid = true;
break; // Overlong encoding is invalid
}
if (REALM_UNLIKELY(0x110000 <= v)) {
invalid = true;
break; // Code point too big for UTF-16
}
v -= 0x10000l;
*out++ = Traits16::to_char_type(0xD800 + (v / 0x400));
*out++ = Traits16::to_char_type(0xDC00 + (v % 0x400));
in += 4;
continue;
}
// Invalid first byte of UTF-8 sequence, or code point too big for UTF-16
invalid = true;
break;
}
REALM_ASSERT(in >= in_begin && in <= in_end);
REALM_ASSERT(out >= out_begin && out <= out_end);
in_begin = in;
out_begin = out;
return !invalid;
}
template <class Char16, class Traits16>
inline size_t Utf8x16<Char16, Traits16>::find_utf16_buf_size(const char*& in_begin, const char* const in_end)
{
typedef std::char_traits<char> traits8;
size_t num_out = 0;
const char* in = in_begin;
while (in != in_end) {
REALM_ASSERT(&in[0] >= in_begin && &in[0] < in_end);
uint_fast16_t v1 = uint_fast16_t(traits8::to_int_type(in[0]));
if (REALM_LIKELY(v1 < 0x80)) { // One byte
num_out += 1;
in += 1;
continue;
}
if (REALM_UNLIKELY(v1 < 0xC0)) {
break; // Invalid first byte of UTF-8 sequence
}
if (REALM_LIKELY(v1 < 0xE0)) { // Two bytes
if (REALM_UNLIKELY(in_end - in < 2)) {
break; // Incomplete UTF-8 sequence
}
num_out += 1;
in += 2;
continue;
}
if (REALM_LIKELY(v1 < 0xF0)) { // Three bytes
if (REALM_UNLIKELY(in_end - in < 3)) {
break; // Incomplete UTF-8 sequence
}
num_out += 1;
in += 3;
continue;
}
if (REALM_LIKELY(v1 < 0xF8)) { // Four bytes
if (REALM_UNLIKELY(in_end - in < 4)) {
break; // Incomplete UTF-8 sequence
}
num_out += 2; // Surrogate pair
in += 4;
continue;
}
// Invalid first byte of UTF-8 sequence, or code point too big for UTF-16
break;
}
REALM_ASSERT(in >= in_begin && in <= in_end);
in_begin = in;
return num_out;
}
// Adapted from reference implementation.
// http://www.unicode.org/resources/utf8.html
// http://www.bsdua.org/files/unicode.tar.gz
template <class Char16, class Traits16>
inline bool Utf8x16<Char16, Traits16>::to_utf8(const Char16*& in_begin, const Char16* const in_end, char*& out_begin,
char* const out_end)
{
typedef std::char_traits<char> traits8;
typedef typename traits8::int_type traits8_int_type;
bool invalid = false;
const Char16* in = in_begin;
char* out = out_begin;
while (in != in_end) {
REALM_ASSERT(&in[0] >= in_begin && &in[0] < in_end);
uint_fast16_t v1 = uint_fast16_t(Traits16::to_int_type(in[0]));
if (REALM_LIKELY(v1 < 0x80)) {
if (REALM_UNLIKELY(out == out_end)) {
break; // Not enough output buffer space
}
// UTF-8 layout: 0xxxxxxx
REALM_ASSERT(out >= out_begin && out < out_end);
*out++ = traits8::to_char_type(traits8_int_type(v1));
in += 1;
continue;
}
if (REALM_LIKELY(v1 < 0x800)) {
if (REALM_UNLIKELY(out_end - out < 2)) {
break; // Not enough output buffer space
}
// UTF-8 layout: 110xxxxx 10xxxxxx
*out++ = traits8::to_char_type(traits8_int_type(0xC0 + v1 / 0x40));
REALM_ASSERT(out >= out_begin && out < out_end);
*out++ = traits8::to_char_type(traits8_int_type(0x80 + v1 % 0x40));
in += 1;
continue;
}
if (REALM_LIKELY(v1 < 0xD800 || 0xE000 <= v1)) {
if (REALM_UNLIKELY(out_end - out < 3)) {
break; // Not enough output buffer space
}
// UTF-8 layout: 1110xxxx 10xxxxxx 10xxxxxx
REALM_ASSERT(out >= out_begin && out + 2 < out_end);
*out++ = traits8::to_char_type(traits8_int_type(0xE0 + v1 / 0x1000));
*out++ = traits8::to_char_type(traits8_int_type(0x80 + v1 / 0x40 % 0x40));
*out++ = traits8::to_char_type(traits8_int_type(0x80 + v1 % 0x40));
in += 1;
continue;
}
// Surrogate pair
if (REALM_UNLIKELY(out_end - out < 4)) {
break; // Not enough output buffer space
}
if (REALM_UNLIKELY(0xDC00 <= v1)) {
invalid = true;
break; // Invalid first half of surrogate pair
}
if (REALM_UNLIKELY(in + 1 == in_end)) {
invalid = true;
break; // Incomplete surrogate pair
}
REALM_ASSERT(&in[1] >= in_begin && &in[1] < in_end);
uint_fast16_t v2 = uint_fast16_t(Traits16::to_int_type(in[1]));
if (REALM_UNLIKELY(v2 < 0xDC00 || 0xE000 <= v2)) {
invalid = true;
break; // Invalid second half of surrogate pair
}
uint_fast32_t v = 0x10000l + (uint_fast32_t(v1 - 0xD800) * 0x400 + (v2 - 0xDC00));
// UTF-8 layout: 11110xxx 10xxxxxx 10xxxxxx 10xxxxxx
REALM_ASSERT(out >= out_begin && out + 3 < out_end);
*out++ = traits8::to_char_type(traits8_int_type(0xF0 + v / 0x40000));
*out++ = traits8::to_char_type(traits8_int_type(0x80 + v / 0x1000 % 0x40));
*out++ = traits8::to_char_type(traits8_int_type(0x80 + v / 0x40 % 0x40));
*out++ = traits8::to_char_type(traits8_int_type(0x80 + v % 0x40));
in += 2;
}
REALM_ASSERT(in >= in_begin && in <= in_end);
REALM_ASSERT(out >= out_begin && out <= out_end);
in_begin = in;
out_begin = out;
return !invalid;
}
template <class Char16, class Traits16>
inline size_t Utf8x16<Char16, Traits16>::find_utf8_buf_size(const Char16*& in_begin, const Char16* const in_end)
{
size_t num_out = 0;
const Char16* in = in_begin;
while (in != in_end) {
REALM_ASSERT(&in[0] >= in_begin && &in[0] < in_end);
uint_fast16_t v = uint_fast16_t(Traits16::to_int_type(in[0]));
if (REALM_LIKELY(v < 0x80)) {
if (REALM_UNLIKELY(int_add_with_overflow_detect(num_out, 1)))
break; // Avoid overflow
in += 1;
}
else if (REALM_LIKELY(v < 0x800)) {
if (REALM_UNLIKELY(int_add_with_overflow_detect(num_out, 2)))
break; // Avoid overflow
in += 1;
}
else if (REALM_LIKELY(v < 0xD800 || 0xE000 <= v)) {
if (REALM_UNLIKELY(int_add_with_overflow_detect(num_out, 3)))
break; // Avoid overflow
in += 1;
}
else {
if (REALM_UNLIKELY(in + 1 == in_end)) {
break; // Incomplete surrogate pair
}
if (REALM_UNLIKELY(int_add_with_overflow_detect(num_out, 4)))
break; // Avoid overflow
in += 2;
}
}
REALM_ASSERT(in >= in_begin && in <= in_end);
in_begin = in;
return num_out;
}
} // namespace util
} // namespace realm
#endif // REALM_UTIL_UTF8_HPP
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