banan-os/BAN/include/BAN/UTF8.h

83 lines
2.2 KiB
C++

#pragma once
#include <stddef.h>
#include <stdint.h>
namespace BAN::UTF8
{
static constexpr uint32_t invalid = 0xFFFFFFFF;
constexpr uint32_t byte_length(uint8_t first_byte)
{
if ((first_byte & 0x80) == 0x00)
return 1;
if ((first_byte & 0xE0) == 0xC0)
return 2;
if ((first_byte & 0xF0) == 0xE0)
return 3;
if ((first_byte & 0xF8) == 0xF0)
return 4;
return 0;
}
template<typename T> requires (sizeof(T) == 1)
constexpr uint32_t to_codepoint(const T* bytes)
{
uint32_t length = byte_length(bytes[0]);
for (uint32_t i = 1; i < length; i++)
if (((uint8_t)bytes[i] & 0xC0) != 0x80)
return UTF8::invalid;
switch (length)
{
case 1: return (((uint8_t)bytes[0] & 0x80) != 0x00) ? UTF8::invalid : (uint8_t)bytes[0];
case 2: return (((uint8_t)bytes[0] & 0xE0) != 0xC0) ? UTF8::invalid : (((uint8_t)bytes[0] & 0x1F) << 6) | ((uint8_t)bytes[1] & 0x3F);
case 3: return (((uint8_t)bytes[0] & 0xF0) != 0xE0) ? UTF8::invalid : (((uint8_t)bytes[0] & 0x0F) << 12) | (((uint8_t)bytes[1] & 0x3F) << 6) | ((uint8_t)bytes[2] & 0x3F);
case 4: return (((uint8_t)bytes[0] & 0xF8) != 0xF0) ? UTF8::invalid : (((uint8_t)bytes[0] & 0x07) << 18) | (((uint8_t)bytes[1] & 0x3F) << 12) | (((uint8_t)bytes[2] & 0x3F) << 6) | ((uint8_t)bytes[3] & 0x3F);
}
return UTF8::invalid;
}
template<typename T>
constexpr bool from_codepoints(const T* codepoints, size_t count, char* out)
{
uint8_t* ptr = (uint8_t*)out;
for (size_t i = 0; i < count; i++)
{
if (codepoints[i] < 0x80)
{
*ptr++ = codepoints[i];
}
else if (codepoints[i] < 0x800)
{
*ptr++ = 0xC0 | ((codepoints[i] >> 6) & 0x1F);
*ptr++ = 0x80 | ((codepoints[i] >> 0) & 0x3F);
}
else if (codepoints[i] < 0x10000)
{
*ptr++ = 0xE0 | ((codepoints[i] >> 12) & 0x0F);
*ptr++ = 0x80 | ((codepoints[i] >> 6) & 0x3F);
*ptr++ = 0x80 | ((codepoints[i] >> 0) & 0x3F);
}
else if (codepoints[i] < 0x110000)
{
*ptr++ = 0xF0 | ((codepoints[i] >> 18) & 0x07);
*ptr++ = 0x80 | ((codepoints[i] >> 12) & 0x3F);
*ptr++ = 0x80 | ((codepoints[i] >> 6) & 0x3F);
*ptr++ = 0x80 | ((codepoints[i] >> 0) & 0x3F);
}
else
{
return false;
}
}
return true;
}
}