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Diffstat (limited to 'doc/encoding.n')
| -rw-r--r-- | doc/encoding.n | 48 |
1 files changed, 35 insertions, 13 deletions
diff --git a/doc/encoding.n b/doc/encoding.n index 1c0bfa9..5782199 100644 --- a/doc/encoding.n +++ b/doc/encoding.n @@ -12,19 +12,30 @@ encoding \- Manipulate encodings .SH SYNOPSIS \fBencoding \fIoption\fR ?\fIarg arg ...\fR? .BE - .SH INTRODUCTION .PP -Strings in Tcl are encoded using 16-bit Unicode characters. Different -operating system interfaces or applications may generate strings in -other encodings such as Shift-JIS. The \fBencoding\fR command helps -to bridge the gap between Unicode and these other formats. +Strings in Tcl are logically a sequence of 16-bit Unicode characters. +These strings are represented in memory as a sequence of bytes that +may be in one of several encodings: modified UTF\-8 (which uses 1 to 3 +bytes per character), 16-bit +.QW Unicode +(which uses 2 bytes per character, with an endianness that is +dependent on the host architecture), and binary (which uses a single +byte per character but only handles a restricted range of characters). +Tcl does not guarantee to always use the same encoding for the same +string. +.PP +Different operating system interfaces or applications may generate +strings in other encodings such as Shift\-JIS. The \fBencoding\fR +command helps to bridge the gap between Unicode and these other +formats. .SH DESCRIPTION .PP Performs one of several encoding related operations, depending on \fIoption\fR. The legal \fIoption\fRs are: .TP \fBencoding convertfrom\fR ?\fIencoding\fR? \fIdata\fR +. Convert \fIdata\fR to Unicode from the specified \fIencoding\fR. The characters in \fIdata\fR are treated as binary data where the lower 8-bits of each character is taken as a single byte. The resulting @@ -33,14 +44,16 @@ sequence of bytes is treated as a string in the specified system encoding is used. .TP \fBencoding convertto\fR ?\fIencoding\fR? \fIstring\fR +. Convert \fIstring\fR from Unicode to the specified \fIencoding\fR. The result is a sequence of bytes that represents the converted string. Each byte is stored in the lower 8-bits of a Unicode -character. If \fIencoding\fR is not specified, the current -system encoding is used. +character (indeed, the resulting string is a binary string as far as +Tcl is concerned, at least initially). If \fIencoding\fR is not +specified, the current system encoding is used. .TP \fBencoding dirs\fR ?\fIdirectoryList\fR? -.VS 8.5 +. Tcl can load encoding data files from the file system that describe additional encodings for it to work with. This command sets the search path for \fB*.enc\fR encoding data files to the list of directories @@ -50,13 +63,19 @@ search path. It is an error for \fIdirectoryList\fR to not be a valid list. If, when a search for an encoding data file is happening, an element in \fIdirectoryList\fR does not refer to a readable, searchable directory, that element is ignored. -.VE 8.5 .TP \fBencoding names\fR +. Returns a list containing the names of all of the encodings that are currently available. +The encodings +.QW utf-8 +and +.QW iso8859-1 +are guaranteed to be present in the list. .TP \fBencoding system\fR ?\fIencoding\fR? +. Set the system encoding to \fIencoding\fR. If \fIencoding\fR is omitted then the command returns the current system encoding. The system encoding is used whenever Tcl passes strings to system calls. @@ -71,7 +90,7 @@ However, because the \fBsource\fR command always reads files using the current system encoding, Tcl will only source such files correctly when the encoding used to write the file is the same. This tends not to be true in an internationalized setting. For example, if such a -file was sourced in North America (where the ISO8859-1 is normally +file was sourced in North America (where the ISO8859\-1 is normally used), each byte in the file would be treated as a separate character that maps to the 00 page in Unicode. The resulting Tcl strings will not contain the expected Japanese characters. Instead, they will @@ -79,15 +98,18 @@ contain a sequence of Latin-1 characters that correspond to the bytes of the original string. The \fBencoding\fR command can be used to convert this string to the expected Japanese Unicode characters. For example, +.PP .CS set s [\fBencoding convertfrom\fR euc-jp "\exA4\exCF"] .CE +.PP would return the Unicode string .QW "\eu306F" , which is the Hiragana letter HA. - .SH "SEE ALSO" Tcl_GetEncoding(3) - .SH KEYWORDS -encoding +encoding, unicode +.\" Local Variables: +.\" mode: nroff +.\" End: |