UTF8 to CP1252

utf8to1252.c

// Copyright (c) 2008-2009 Bjoern Hoehrmann <bjoern@hoehrmann.de>
// See http://bjoern.hoehrmann.de/utf-8/decoder/dfa/ for details.
// Copyright (c) 2017 ZephRay <zephray@outlook.com>
//
// utf8to1252 - almost equivalent to iconv -f utf-8 -t windows-1252, but better
//
// What this program can do?
// Sometimes you would encounter some "double utf-8 encoded file", most cases
// from a MySQL dump. If this happens, you may find some luck use this program
// to fix your file!

// What does this program do?
// In my case, I stored something in UTF-8 in my database, for example the
// Chinese character '检', it was encoded into UTF-8 sequence 0xe3 0xa3 0x80.
// Then when it was exported, it was encoded with UTF-8 again! Actually it 
// consists two steps, the first step is to Unicode Code Point (convert charset)
// then to UTF-8 (encoding). I am not sure why MySQL picked CP1252 rather than
// ISO-8859 (which make more sense since it's compatiable with Unicode), but
// this is what happend. So, 0xe3 0xa3 was converted to 0x00e3 and 0x00a3,
// respectively. 0x80 is tricky, 0x80 in CP1252 is converted to 0x20ac in the
// unicode. And finally, 0x00e3 0x00a3 0x20ac was encoded into UTF-8 : 0xc3
// 0xa6 0xc2 0xa3 0xe2 0x82 0xac.
// So, in short, the MySQL treated the UTF-8 encoded string as a CP1252 ANSI
// string and encoded it with UTF-8 again. To recover that, simply do a UTF-8 to
// CP1252 convertion and we should be fine. But I found iconv's Windows-1252
// charset will not handle all 256 characters correctly(actually not characters,
// just UTF-8 encoded byte sequence), so I wrote this to fix that.
// So as you can see, this program would read a file, then decode it from UTF-8
// to Unicode, then it tries to convert the decoded Unicode Code Point to CP1252
// char, which could fill the whole 0x00-0xFF space. Then the double-encoded
// UTF-8 file is now single-encoded, problem solved.

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

#define UTF8_ACCEPT 0
#define UTF8_REJECT 1

static const uint8_t utf8d[] = {
	0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, // 00..1f
	0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, // 20..3f
	0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, // 40..5f
	0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, // 60..7f
	1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9, // 80..9f
	7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7, // a0..bf
	8,8,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2, // c0..df
	0xa,0x3,0x3,0x3,0x3,0x3,0x3,0x3,0x3,0x3,0x3,0x3,0x3,0x4,0x3,0x3, // e0..ef
	0xb,0x6,0x6,0x6,0x5,0x8,0x8,0x8,0x8,0x8,0x8,0x8,0x8,0x8,0x8,0x8, // f0..ff
	0x0,0x1,0x2,0x3,0x5,0x8,0x7,0x1,0x1,0x1,0x4,0x6,0x1,0x1,0x1,0x1, // s0..s0
	1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,0,1,1,1,1,1,0,1,0,1,1,1,1,1,1, // s1..s2
	1,2,1,1,1,1,1,2,1,2,1,1,1,1,1,1,1,1,1,1,1,1,1,2,1,1,1,1,1,1,1,1, // s3..s4
	1,2,1,1,1,1,1,1,1,2,1,1,1,1,1,1,1,1,1,1,1,1,1,3,1,3,1,1,1,1,1,1, // s5..s6
	1,3,1,1,1,1,1,3,1,3,1,1,1,1,1,1,1,3,1,1,1,1,1,1,1,1,1,1,1,1,1,1, // s7..s8
};

uint32_t decode(uint32_t* state, uint32_t* codep, uint32_t byte) {
	uint32_t type = utf8d[byte];

	*codep = (*state != UTF8_ACCEPT) ?
		(byte & 0x3fu) | (*codep << 6) :
		(0xff >> type) & (byte);

	*state = utf8d[256 + *state*16 + type];
	return *state;
}

long fileLoad(const char * filename, unsigned char * * buffer) {
		FILE * pFile;
		long lSize;
	
		pFile = fopen(filename, "rb");
		if (pFile != NULL) {
				fseek(pFile, 0, SEEK_END);
				lSize = ftell(pFile);
				rewind(pFile);
				*buffer = (unsigned char *)malloc(lSize);
				if (buffer != NULL) {
						return fread(*buffer, 1, lSize, pFile);
				}
				fclose(pFile);
		}
		return 0;
}

uint8_t UNICODEtoCP1252(uint16_t chr) {
	if (chr <= 0xff)
		return (chr&0xff);
	else {
		switch(chr) {
			case 0x20ac: return 0x80; break;
			case 0x201a: return 0x82; break;
			case 0x0192: return 0x83; break;
			case 0x201e: return 0x84; break;
			case 0x2026: return 0x85; break;
			case 0x2020: return 0x86; break;
			case 0x2021: return 0x87; break;
			case 0x02c6: return 0x88; break;
			case 0x2030: return 0x89; break;
			case 0x0160: return 0x8a; break;
			case 0x2039: return 0x8b; break;
			case 0x0152: return 0x8c; break;
			case 0x017d: return 0x8e; break;
			case 0x2018: return 0x91; break;
			case 0x2019: return 0x92; break;
			case 0x201c: return 0x93; break;
			case 0x201d: return 0x94; break;
			case 0x2022: return 0x95; break;
			case 0x2013: return 0x96; break;
			case 0x2014: return 0x97; break;
			case 0x02dc: return 0x98; break;
			case 0x2122: return 0x99; break;
			case 0x0161: return 0x9a; break;
			case 0x203a: return 0x9b; break;
			case 0x0153: return 0x9c; break;
			case 0x017e: return 0x9e; break;
			case 0x0178: return 0x9f; break;
			default: 
				printf(stderr, "Your file is probably NOT a UTF-8 encoded CP1251 file.\n"); 
				return 0x00; break;
		}
	}
}

int main(int argc, char* argv[]) {
	uint32_t codepoint;
	uint32_t state = 0;
	uint8_t *s;
	uint8_t chr;
	long size, pos;
	FILE *fp;

	if (argc != 2) {
		printf("utf8to1251 input.file\n");
		return 0;
	}

	size = fileLoad(argv[1], &s);

	for (pos=0; pos<size; pos++) {
		if (!decode(&state, &codepoint, *s)) {			
			chr = UNICODEtoCP1252(codepoint);
			printf("%c", chr);
		}
		s++;
	}

	if (state != UTF8_ACCEPT)
		printf(stderr, "Your file is probably NOT encoded in UTF-8.\n");

	return 0;
}