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src/univalue/lib/univalue_utffilter.h

// Copyright 2016 Wladimir J. van der Laan // Copyright 2016 Wladimir J. van der Laan
// Distributed under the MIT software license, see the accompanying // Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php. // file COPYING or http://www.opensource.org/licenses/mit-license.php.
#ifndef UNIVALUE_UTFFILTER_H #ifndef UNIVALUE_UTFFILTER_H
#define UNIVALUE_UTFFILTER_H #define UNIVALUE_UTFFILTER_H
#include <string> #include <string>
/** /**
* Filter that generates and validates UTF-8, as well as collates UTF-16 * Filter that generates and validates UTF-8, as well as collates UTF-16
* surrogate pairs as specified in RFC4627. * surrogate pairs as specified in RFC4627.
*/ */
class JSONUTF8StringFilter class JSONUTF8StringFilter
{ {
public: public:
explicit JSONUTF8StringFilter(std::string &s): JSONUTF8StringFilter(std::string &s):
str(s), is_valid(true), codepoint(0), state(0), surpair(0) str(s), is_valid(true), codepoint(0), state(0), surpair(0)
{ {
} }
// Write single 8-bit char (may be part of UTF-8 sequence) // Write single 8-bit char (may be part of UTF-8 sequence)
void push_back(unsigned char ch) void push_back(unsigned char ch)
{ {
if (state == 0) { if (state == 0) {
if (ch < 0x80) // 7-bit ASCII, fast direct pass-through if (ch < 0x80) // 7-bit ASCII, fast direct pass-through
Show All 16 Lines void push_back(unsigned char ch)
is_valid = false; is_valid = false;
state -= 6; state -= 6;
codepoint |= (ch & 0x3f) << state; codepoint |= (ch & 0x3f) << state;
if (state == 0) if (state == 0)
push_back_u(codepoint); push_back_u(codepoint);
} }
} }
// Write codepoint directly, possibly collating surrogate pairs // Write codepoint directly, possibly collating surrogate pairs
void push_back_u(unsigned int codepoint_) void push_back_u(unsigned int codepoint)
{ {
if (state) // Only accept full codepoints in open state if (state) // Only accept full codepoints in open state
is_valid = false; is_valid = false;
if (codepoint_ >= 0xD800 && codepoint_ < 0xDC00) { // First half of surrogate pair if (codepoint >= 0xD800 && codepoint < 0xDC00) { // First half of surrogate pair
if (surpair) // Two subsequent surrogate pair openers - fail if (surpair) // Two subsequent surrogate pair openers - fail
is_valid = false; is_valid = false;
else else
surpair = codepoint_; surpair = codepoint;
} else if (codepoint_ >= 0xDC00 && codepoint_ < 0xE000) { // Second half of surrogate pair } else if (codepoint >= 0xDC00 && codepoint < 0xE000) { // Second half of surrogate pair
if (surpair) { // Open surrogate pair, expect second half if (surpair) { // Open surrogate pair, expect second half
// Compute code point from UTF-16 surrogate pair // Compute code point from UTF-16 surrogate pair
append_codepoint(0x10000 | ((surpair - 0xD800)<<10) | (codepoint_ - 0xDC00)); append_codepoint(0x10000 | ((surpair - 0xD800)<<10) | (codepoint - 0xDC00));
surpair = 0; surpair = 0;
} else // Second half doesn't follow a first half - fail } else // Second half doesn't follow a first half - fail
is_valid = false; is_valid = false;
} else { } else {
if (surpair) // First half of surrogate pair not followed by second - fail if (surpair) // First half of surrogate pair not followed by second - fail
is_valid = false; is_valid = false;
else else
append_codepoint(codepoint_); append_codepoint(codepoint);
} }
} }
// Check that we're in a state where the string can be ended // Check that we're in a state where the string can be ended
// No open sequences, no open surrogate pairs, etc // No open sequences, no open surrogate pairs, etc
bool finalize() bool finalize()
{ {
if (state || surpair) if (state || surpair)
is_valid = false; is_valid = false;
Show All 13 Linesprivate:
// Plane, the character is represented as a twelve-character sequence, // Plane, the character is represented as a twelve-character sequence,
// encoding the UTF-16 surrogate pair. So, for example, a string // encoding the UTF-16 surrogate pair. So, for example, a string
// containing only the G clef character (U+1D11E) may be represented as // containing only the G clef character (U+1D11E) may be represented as
// "\uD834\uDD1E". // "\uD834\uDD1E".
// //
// Two subsequent \u.... may have to be replaced with one actual codepoint. // Two subsequent \u.... may have to be replaced with one actual codepoint.
unsigned int surpair; // First half of open UTF-16 surrogate pair, or 0 unsigned int surpair; // First half of open UTF-16 surrogate pair, or 0
void append_codepoint(unsigned int codepoint_) void append_codepoint(unsigned int codepoint)
{ {
if (codepoint_ <= 0x7f) if (codepoint <= 0x7f)
str.push_back((char)codepoint_); str.push_back((char)codepoint);
else if (codepoint_ <= 0x7FF) { else if (codepoint <= 0x7FF) {
str.push_back((char)(0xC0 | (codepoint_ >> 6))); str.push_back((char)(0xC0 | (codepoint >> 6)));
str.push_back((char)(0x80 | (codepoint_ & 0x3F))); str.push_back((char)(0x80 | (codepoint & 0x3F)));
} else if (codepoint_ <= 0xFFFF) { } else if (codepoint <= 0xFFFF) {
str.push_back((char)(0xE0 | (codepoint_ >> 12))); str.push_back((char)(0xE0 | (codepoint >> 12)));
str.push_back((char)(0x80 | ((codepoint_ >> 6) & 0x3F))); str.push_back((char)(0x80 | ((codepoint >> 6) & 0x3F)));
str.push_back((char)(0x80 | (codepoint_ & 0x3F))); str.push_back((char)(0x80 | (codepoint & 0x3F)));
} else if (codepoint_ <= 0x1FFFFF) { } else if (codepoint <= 0x1FFFFF) {
str.push_back((char)(0xF0 | (codepoint_ >> 18))); str.push_back((char)(0xF0 | (codepoint >> 18)));
str.push_back((char)(0x80 | ((codepoint_ >> 12) & 0x3F))); str.push_back((char)(0x80 | ((codepoint >> 12) & 0x3F)));
str.push_back((char)(0x80 | ((codepoint_ >> 6) & 0x3F))); str.push_back((char)(0x80 | ((codepoint >> 6) & 0x3F)));
str.push_back((char)(0x80 | (codepoint_ & 0x3F))); str.push_back((char)(0x80 | (codepoint & 0x3F)));
} }
} }
}; };
#endif #endif