The intention of this page is to provide some explanation
of the gedcom parser, to aid development on and with it. First,
@@ -125,7 +123,9 @@ containing a lot of special characters.
test file. Simply cat the file through the lexer on standard input
and you should get all the tokens in the file. Similar tests can be
done using
make lexer_hilo and
-make lexer_lohi (for the unicode lexers). In each of the cases you need to know yourself which of the test files are appropriate to pass through the lexer.
+make lexer_lohi
+ (for the unicode lexers). In each of the cases you need to know
+yourself which of the test files are appropriate to pass through the lexer.
This concludes the testing setup. Now for some explanations...
@@ -151,56 +151,9 @@ the file.
This basic description ignores the problem of character encoding. The next section describes what this problem exactly is.
-
Character encoding
-
The character encoding problem
-
-Developers are usually familiar with the ASCII character set. This
-is a character set that assigns a unique number to some characters, e.g.
-an "A" has ASCII code 65 (or 0x41 in hex), and an "a" has ASCII code 97 (or
-0x61 in hex). Some people may also have used ASCII codes for several
-drawing characters (such as a horizontal bar, a vertical bar, or a top-right
-corner) in the old DOS days, to be able to draw nice windows in text mode.
-
-However, these last characters are strictly spoken not part of the ASCII
-set. The standard ASCII set contains only the character positions from
-0 to 127 (i.e. anything that fits into an integer that is 7 bits wide). An
-example of this table can be found
here. Anything that has an ASCII code between 128 and 255 is in principle undefined.
-
-Now, several systems (including the old DOS) have defined those character
-positions anyway, but usually in totally different ways. Some well
-known extensions are:
-
- - the DOS
- character set, nowadays usually known as Code Page 437, but sometimes also
-named LatinUS, ECS (Extended Character Set) or PC-8; note that the table
-displayed in the link also contains the standard ASCII part
- - the ANSI character set, also known as Code Page 1252, and usually the default on Windows
- - the ISO-8859-1 character set (also called Latin-1), which is an ISO standard for Western European languages, mostly used on various Unices
- - the Adobe Standard Encoding, which is by default used in Postscript, unless overridden
-
-And these are only examples of character sets used in West-European languages.
- For Japanese, Chinese, Korean, Vietnamese, ... there are separate character
-sets in which one byte's meaning can even be influenced by what the previous
-byte was, i.e. these are multi-byte character sets. This is because
-even 256 characters is totally inadequate to represent all characters in
-such languages.
-
-So, summarizing, if a text file contains a byte that has a value 65, it is
-pretty safe to assume that this byte represents an "A", if we ignore the
-multi-byte character sets spoken of before. However, a value 233 cannot
-be interpreted without knowing in which character set the text file is written.
- In Latin-1, it happens to be the character "é", but in another
-character set it can be something totally different (e.g. in the DOS character
-set it is the Greek letter theta).
-
-Vice versa, if you need to write a character "é" to a file, it depends
-on the character set you will use what the numerical value will be in the
-file: in Latin-1 it will be 233, but if you use the DOS character set it
-will be 130.
-
-
Unicode
-Enter the Unicode standard...
-
+
Character encoding
Refer to
this page for some introduction on character encoding...
+
+
TO BE COMPLETED
