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Safer UTF-8 decoder

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This commit is contained in:
Clownacy 2019-01-25 11:50:42 +00:00
parent acdf8aa622
commit 414fe76abc
1 changed files with 40 additions and 18 deletions
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58
src/Font.cpp
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@ -38,25 +38,47 @@ static unsigned long UTF8ToCode(const unsigned char *string, unsigned int *bytes
unsigned int length;
unsigned long charcode;
if ((string[0] & 0x80) == 0)
unsigned int zero_bit = 0;
for (unsigned char lead_byte = string[0]; zero_bit < 5 && (lead_byte & 0x80); ++zero_bit, lead_byte <<= 1);
switch (zero_bit)
{
length = 1;
charcode = string[0] & 0x7F;
}
else if ((string[0] & 0xE0) == 0xC0)
{
length = 2;
charcode = ((string[0] & ~0xE0) << 6) | (string[1] & 0x3F);
}
else if ((string[0] & 0xF0) == 0xE0)
{
length = 3;
charcode = ((string[0] & ~0xF0) << (6 * 2)) | ((string[1] & 0x3F) << 6) | (string[2] & 0x3F);
}
else //if (string[0] & 0xF8 == 0xF0)
{
length = 4;
charcode = ((string[0] & ~0xF8) << (6 * 3)) | ((string[1] & 0x3F) << (6 * 2)) | ((string[2] & 0x3F) << 6) | (string[3] & 0x3F);
case 0:
// Single-byte character
length = 1;
charcode = string[0];
break;
case 2:
case 3:
case 4:
length = zero_bit;
charcode = string[0] & (1 << (8 - zero_bit)) - 1;
for (unsigned int i = 1; i < zero_bit; ++i)
{
if ((string[i] & 0xC0) == 0x80)
{
charcode <<= 6;
charcode |= string[i] & ~0xC0;
}
else
{
// Error: Invalid continuation byte
length = 1;
charcode = 0xFFFD;
break;
}
}
break;
default:
// Error: Invalid lead byte
length = 1;
charcode = 0xFFFD;
break;
}
if (bytes_read)