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utf.cpp
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utf.cpp
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#include "r-tech1/utf.h"
#include <string>
#include <sstream>
using std::string;
using std::ostringstream;
namespace Utf{
/* utf8 decoding. reads a utf8 string and returns a unicode code point.
* position should be a pointer to an integer that stores the current
* place in the input string where the next character is to be read.
* FIXME: handle the case when `position' runs out of bytes
*/
long readUtf8CodePoint(const std::string & input, unsigned int * position){
unsigned char byte1 = (unsigned char) input[*position];
/* one byte - ascii */
if (byte1 >> 7 == 0){
return byte1;
}
if (byte1 >> 5 == 6){
*position += 1;
if (*position >= input.size()){
return 0;
}
unsigned char byte2 = (unsigned char) input[*position];
int top = byte1 & 31;
int bottom = byte2 & 63;
return (top << 6) + bottom;
}
if (byte1 >> 4 == 14){
*position += 1;
if (*position >= input.size()){
return 0;
}
unsigned char byte2 = (unsigned char) input[*position];
*position += 1;
if (*position >= input.size()){
return 0;
}
unsigned char byte3 = (unsigned char) input[*position];
int top4 = byte1 & 15;
int middle6 = byte2 & 63;
int bottom6 = byte3 & 63;
return (top4 << (6+6)) + (middle6 << 6) + bottom6;
}
if (byte1 >> 3 == 30){
*position += 1;
if (*position >= input.size()){
return 0;
}
unsigned char byte2 = (unsigned char) input[*position];
*position += 1;
if (*position >= input.size()){
return 0;
}
unsigned char byte3 = (unsigned char) input[*position];
*position += 1;
if (*position >= input.size()){
return 0;
}
unsigned char byte4 = (unsigned char) input[*position];
int unit1 = byte1 & 7;
int unit2 = byte2 & 63;
int unit3 = byte3 & 63;
int unit4 = byte4 & 63;
return (unit1 << 18) + (unit2 << 12) + (unit3 << 6) + unit4;
}
return 0;
}
string codePointToUtf8(long unicode){
ostringstream out;
if (unicode <= 0x7f){
out << (char) unicode;
} else if (unicode <= 0x7ff){
/* 110xxxxx 10xxxxxx */
unsigned char byte1 = ((unicode >> (1 * 6)) & 0x1f) | (6 << 5);
unsigned char byte2 = (unicode & 0x3f) | (2 << 6);
out << byte1 << byte2;
} else if (unicode <= 0xffff){
/* 1110xxxx 10xxxxxx 10xxxxxx */
unsigned char byte1 = ((unicode >> (2 * 6)) & 0xf) | (0xe << 4);
unsigned char byte2 = ((unicode >> (1 * 6)) & 0x3f) | (2 << 6);
unsigned char byte3 = (unicode & 0x3f) | (2 << 6);
out << byte1 << byte2 << byte3;
} else if (unicode <= 0x1fffff){
/* 11110xxx 10xxxxxx 10xxxxxx 10xxxxxx */
unsigned char byte1 = ((unicode >> (3 * 6)) & 0x7) | (0x1e << 3);
unsigned char byte2 = ((unicode >> (2 * 6)) & 0x3f) | (2 << 6);
unsigned char byte3 = ((unicode >> (1 * 6)) & 0x3f) | (2 << 6);
unsigned char byte4 = (unicode & 0x3f) | (2 << 6);
out << byte1 << byte2 << byte3 << byte4;
} else if (unicode <= 0x3ffffff){
/* 111110xx 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx */
unsigned char byte1 = ((unicode >> (4 * 6)) & 0x3) | (0x3e << 2);
unsigned char byte2 = ((unicode >> (3 * 6)) & 0x3f) | (2 << 6);
unsigned char byte3 = ((unicode >> (2 * 6)) & 0x3f) | (2 << 6);
unsigned char byte4 = ((unicode >> (1 * 6)) & 0x3f) | (2 << 6);
unsigned char byte5 = (unicode & 0x3f) | (2 << 6);
out << byte1 << byte2 << byte3 << byte4 << byte5;
} else if (unicode <= 0x7fffffff){
/* 1111110x 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx */
unsigned char byte1 = ((unicode >> (5 * 6)) & 0x1) | (0x7e << 1);
unsigned char byte2 = ((unicode >> (4 * 6)) & 0x3f) | (2 << 6);
unsigned char byte3 = ((unicode >> (3 * 6)) & 0x3f) | (2 << 6);
unsigned char byte4 = ((unicode >> (2 * 6)) & 0x3f) | (2 << 6);
unsigned char byte5 = ((unicode >> (1 * 6)) & 0x3f) | (2 << 6);
unsigned char byte6 = (unicode & 0x3f) | (2 << 6);
out << byte1 << byte2 << byte3 << byte4 << byte5 << byte6;
}
return out.str();
}
/* Reads a code point from a utf16 string made up of uint16_t integers */
/* FIXME: add length for input */
long readUtf16CodePoint(const uint16_t * input, unsigned int * position){
uint16_t word1 = input[*position];
*position += 1;
/* 1) If W1 < 0xD800 or W1 > 0xDFFF, the character value U is the value
* of W1. Terminate.
*/
if (word1 < 0xd800 || word1 > 0xdfff){
return word1;
}
/* 2) Determine if W1 is between 0xD800 and 0xDBFF. If not, the sequence
* is in error and no valid character can be obtained using W1.
* Terminate.
*/
if (word1 >= 0xd800 && word1 <= 0xdbff){
/* 3) If there is no W2 (that is, the sequence ends with W1), or if W2
* is not between 0xDC00 and 0xDFFF, the sequence is in error.
* Terminate.
*/
uint16_t word2 = input[*position];
if (word2 >= 0xdc00 && word2 <= 0xdfff){
*position += 1;
/* 4) Construct a 20-bit unsigned integer U', taking the 10 low-order
* bits of W1 as its 10 high-order bits and the 10 low-order bits of
* W2 as its 10 low-order bits.
*/
/* 5) Add 0x10000 to U' to obtain the character value U. Terminate. */
return (((word1 & 0x3ff) << 10) |
(word2 & 0x3ff)) + 0x10000;
}
}
return 0;
}
std::string utf16_to_utf8(const uint16_t * utf16){
ostringstream out;
unsigned int position = 0;
while (utf16[position] != 0){
out << codePointToUtf8(readUtf16CodePoint(utf16, &position));
}
return out.str();
}
}

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