uni/inf2270/hw3/oppgave.c

#include <stdio.h>
#include <stdlib.h>

typedef unsigned char byte;
typedef unsigned long unicode;

// The minimum value of the first `char` to indicate n bytes
#define C4bytes 0xF0
#define C3bytes 0xE0
#define C2bytes 0xC0

// The minimum value for the vm_var_char for the utf8 equivalent to be n bytes
#define U4bytes 0x10000
#define U3bytes 0x0800
#define U2bytes 0x0080

void writebyte(FILE *f, byte b)
{
	fwrite(&b, 1, 1, f);
}

void writeutf8char(FILE *f, unicode u)
{
	if (u >= U4bytes)
	{
		writebyte(f, 0b11110000 | ((u >> 18) & 0b00000111));
		writebyte(f, 0b10000000 | ((u >> 12) & 0b00111111));
		writebyte(f, 0b10000000 | ((u >> 6) & 0b00111111));
		writebyte(f, 0b10000000 | (u & 0b00111111));
	}
	else if (u >= U3bytes)
	{
		writebyte(f, 0b11100000 | ((u >> 12) & 0b00001111));
		writebyte(f, 0b10000000 | ((u >> 6) & 0b00111111));
		writebyte(f, 0b10000000 | (u & 0b00111111));
	}
	else if (u >= U2bytes)
	{
		writebyte(f, 0b11000000 | ((u >> 6) & 0b00011111));
		writebyte(f, 0b10000000 | (u & 0b00111111));
	}
	else
	{
		writebyte(f, u);
	}
}

int readbyte(FILE *f)
{
	int status;
	byte c;
	status = fread(&c, 1, 1, f);
	if (status <= 0) return -1;
	return (int)c;
}

long readutf8char(FILE *f)
{
	byte first = readbyte(f);
	unicode u = 0;

	if (first >= C4bytes)
	{
		u |= (first & 0b00000111) << 18;
		u |= (readbyte(f) & 0b00111111) << 12;
		u |= (readbyte(f) & 0b00111111) << 6;
		u |= readbyte(f) & 0b00111111;
	}
	else if (first >= C3bytes)
	{
		u |= (first & 0b00001111) << 12;
		u |= (readbyte(f) & 0b00111111) << 6;
		u |= readbyte(f) & 0b00111111;
	}
	else if (first >= C2bytes)
	{
		u |= (first & 0b00011111) << 6;
		u |= readbyte(f) & 0b00111111;
	}
	else
	{
		u |= first;
	}

	return u;
}