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javascriptdatabaseutf-8codepages

Properly parsing mixed codepage strings?

I have this weird state that my db got into. Basically, some text is in mixed mode. windows-1252 and miscoded utf-8. Here's a sample:

"donc d'être transparent avec lui et surtout pas de minimiser à l’oral pour le charger à l'écrit".

If I treat the string as utf8, the "’" will correctly become an a apostrophe, but then all the accented e's get converted to some nonsense.

If I treat it as windows-1252, the accented e's stay in place but then the "’" does not become an apostrophe.

Is there some way of explicitly converting only the utf-8 stuff?

Solution
    1. Get windows-1252 codes iterating the string character by character (see function get8bitCodeArray).
    2. Build the output string (myNewStr): seek for utf-8 byte sequences in the array of windows-1252 codes and
    • if found such a sequence of at least 2 bytes, decode it (see TextDecoder) and use the decoded character;
    • otherwise, use the original character.

    const cp1252dict = {'€': 128, '‚': 130, 'ƒ': 131, '„': 132, '…': 133, '†': 134, '‡': 135, 'ˆ': 136, '‰': 137, 'Š': 138, '‹': 139, 'Œ': 140, 'Ž': 142, '‘': 145, '’': 146, '“': 147, '”': 148, '•': 149, '–': 150, '—': 151, '˜': 152, '™': 153, 'š': 154, '›': 155, 'œ': 156, 'ž': 158, 'Ÿ': 159}
function get8bitCodeArray(aString) {
    var auxArr = aString.split('')
    for (var ii = 0; ii < aString.length; ii++) {
        auxChar = auxArr[ii]
        auxCode = auxChar.charCodeAt()
        if ( auxCode < 256 ) {
            auxArr[ii] = auxCode
        }
        else {
            auxArr[ii] = cp1252dict[auxChar]
        }
    }
    return auxArr
}
let decoder = new TextDecoder('utf-8');
var myOldStr = "d'être … à l’oral … à l'écrit"
var mySArray = get8bitCodeArray(myOldStr);
var myNewStr = ""
var arrLength = mySArray.length;
const mask = new Array(128, 224, 240, 248, 192);
const rslt = new Array(0, 192, 224, 240, 128);
for (var ii = 0; ii < arrLength; ii++) {
    //  // console.log(ii, mySArray[ii]);
    if (    (((mySArray[ii+0] & mask[0]) === rslt[0])) ) {
        // console.log(ii, myOldStr.charAt(ii), mySArray[ii], 'ascii');
        myNewStr += myOldStr.charAt(ii);
    }
    else if (((mySArray[ii+0] & mask[+1]) === rslt[+1]) &&
             (ii + 1 <= arrLength) &&
             ((mySArray[ii+1] & mask[4]) === rslt[4]) ) {
        var ui8Arr = new Uint8Array(mySArray.slice(ii, ii+2));
        // console.log(ii, myOldStr.charAt(ii), mySArray[ii], '2');
        myNewStr += decoder.decode(ui8Arr);
        ii += 1;
    }
    else if (((mySArray[ii+0] & mask[+2]) === rslt[+2]) &&
             (ii + 2 <= arrLength) &&
             ((mySArray[ii+1] & mask[4]) === rslt[4]) &&
             ((mySArray[ii+2] & mask[4]) === rslt[4]) ) {
        var ui8Arr = new Uint8Array(mySArray.slice(ii, ii+3));
        // console.log(ii, myOldStr.charAt(ii), mySArray[ii], '3');
        myNewStr += decoder.decode(ui8Arr);
        ii += 2;
    }
    else if (((mySArray[ii+0] & mask[3]) === rslt[3]) &&
             (ii + 3 <= arrLength) &&
             ((mySArray[ii+1] & mask[4]) === rslt[4]) &&
             ((mySArray[ii+2] & mask[4]) === rslt[4]) &&
             ((mySArray[ii+3] & mask[4]) === rslt[4])) {
        var ui8Arr = new Uint8Array(mySArray.slice(ii, ii+4));
        // console.log(ii, myOldStr.charAt(ii), mySArray[ii], '4');
        myNewStr += decoder.decode(ui8Arr);
        ii += 3;
    }
    else {
        // console.log(ii, myOldStr.charAt(ii), mySArray[ii], 'else');
        myNewStr += myOldStr.charAt(ii);
    }
};
console.log(myOldStr);
console.log(myNewStr);

    Sorry, I'm a JavaScript noob so my code could look a bit artless.

    The key parts for above code snippet were computed in Python as follows:

    mask and rslt arrays:

    UTF8_BIN_PATTERNS = [
  '0xxxxxxx', #  U+0000..U+007F
  '110xxxxx', #  U+0080..U+07FF
  '1110xxxx', #  U+0800..U+FFFF
  '11110xxx', # U+10000..U+10FFFF
  '10xxxxxx'  # Continuation bytes
]             # https://en.wikipedia.org/wiki/UTF-8#Encoding
UTF8_BIN_MASKSS = [_.replace( '0', '1')
                    .replace( 'x', '0') for _ in UTF8_BIN_PATTERNS]
UTF8_BIN_VALUES = [_.replace( 'x', '0') for _ in UTF8_BIN_PATTERNS]
INT_MASKSS = [int( _, 2) for _ in UTF8_BIN_MASKSS]
INT_VALUES = [int( _, 2) for _ in UTF8_BIN_VALUES]
# debugging print
# print( UTF8_BIN_PATTERNS, UTF8_BIN_MASKSS, UTF8_BIN_VALUES, sep = '\n')
print( INT_MASKSS, INT_VALUES, sep = '\n')

    [128, 224, 240, 248, 192]
[0, 192, 224, 240, 128]

    cp1252dict dictionary:

    cp1252dict = {}
for ii in range(128,256):
    aux_chr = ii.to_bytes(1, 'big').decode('cp1252', 'replace')
    aux_ord = ord(aux_chr)
    if ( aux_ord > 255 and        # a valid character above 8 bits
         aux_ord != 65533):       # replacement character
        cp1252dict[aux_chr] = ii

cp1252dict


{'€': 128, '‚': 130, 'ƒ': 131, '„': 132, '…': 133, '†': 134, '‡': 135, 'ˆ': 136, '‰': 137, 'Š': 138, '‹': 139, 'Œ': 140, 'Ž': 142, '‘': 145, '’': 146, '“': 147, '”': 148, '•': 149, '–': 150, '—': 151, '˜': 152, '™': 153, 'š': 154, '›': 155, 'œ': 156, 'ž': 158, 'Ÿ': 159}