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Diffstat (limited to 'doc/fcopy.n')
| -rw-r--r-- | doc/fcopy.n | 93 |
1 files changed, 55 insertions, 38 deletions
diff --git a/doc/fcopy.n b/doc/fcopy.n index 3702f15..d583cf0 100644 --- a/doc/fcopy.n +++ b/doc/fcopy.n @@ -10,54 +10,56 @@ .BS '\" Note: do not modify the .SH NAME line immediately below! .SH NAME -fcopy \- Copy data from one channel to another. +fcopy \- Copy data from one channel to another .SH SYNOPSIS \fBfcopy \fIinchan\fR \fIoutchan\fR ?\fB\-size \fIsize\fR? ?\fB\-command \fIcallback\fR? .BE .SH DESCRIPTION .PP -The \fBfcopy\fP command copies data from one I/O channel, \fIinchan\fR to another I/O channel, \fIoutchan\fR. -The \fBfcopy\fP command leverages the buffering in the Tcl I/O system to +The \fBfcopy\fR command copies data from one I/O channel, \fIinchan\fR to another I/O channel, \fIoutchan\fR. +The \fBfcopy\fR command leverages the buffering in the Tcl I/O system to avoid extra copies and to avoid buffering too much data in main memory when copying large files to slow destinations like network sockets. .PP -The \fBfcopy\fP +The \fBfcopy\fR command transfers data from \fIinchan\fR until end of file -or \fIsize\fP bytes have been -transferred. If no \fB\-size\fP argument is given, +or \fIsize\fR bytes have been +transferred. If no \fB\-size\fR argument is given, then the copy goes until end of file. All the data read from \fIinchan\fR is copied to \fIoutchan\fR. -Without the \fB\-command\fP option, \fBfcopy\fP blocks until the copy is complete +Without the \fB\-command\fR option, \fBfcopy\fR blocks until the copy is complete and returns the number of bytes written to \fIoutchan\fR. .PP -The \fB\-command\fP argument makes \fBfcopy\fP work in the background. -In this case it returns immediately and the \fIcallback\fP is invoked +The \fB\-command\fR argument makes \fBfcopy\fR work in the background. +In this case it returns immediately and the \fIcallback\fR is invoked later when the copy completes. -The \fIcallback\fP is called with +The \fIcallback\fR is called with one or two additional arguments that indicates how many bytes were written to \fIoutchan\fR. If an error occurred during the background copy, the second argument is the error string associated with the error. With a background copy, it is not necessary to put \fIinchan\fR or \fIoutchan\fR into -non-blocking mode; the \fBfcopy\fP command takes care of that automatically. +non-blocking mode; the \fBfcopy\fR command takes care of that automatically. However, it is necessary to enter the event loop by using -the \fBvwait\fP command or by using Tk. +the \fBvwait\fR command or by using Tk. .PP You are not allowed to do other I/O operations with -\fIinchan\fR or \fIoutchan\fR during a background fcopy. +\fIinchan\fR or \fIoutchan\fR during a background \fBfcopy\fR. If either \fIinchan\fR or \fIoutchan\fR get closed while the copy is in progress, the current copy is stopped -and the command callback is \fInot\fP made. +and the command callback is \fInot\fR made. If \fIinchan\fR is closed, then all data already queued for \fIoutchan\fR is written out. .PP Note that \fIinchan\fR can become readable during a background copy. -You should turn off any \fBfileevent\fP handlers during a background +You should turn off any \fBfileevent\fR handlers during a background copy so those handlers do not interfere with the copy. -Any I/O attempted by a \fBfileevent\fP handler will get a "channel busy" error. +Any I/O attempted by a \fBfileevent\fR handler will get a +.QW "channel busy" +error. .PP \fBFcopy\fR translates end-of-line sequences in \fIinchan\fR and \fIoutchan\fR according to the \fB\-translation\fR option @@ -67,30 +69,46 @@ See the manual entry for \fBfconfigure\fR for details on the The translations mean that the number of bytes read from \fIinchan\fR can be different than the number of bytes written to \fIoutchan\fR. Only the number of bytes written to \fIoutchan\fR is reported, -either as the return value of a synchronous \fBfcopy\fP or -as the argument to the callback for an asynchronous \fBfcopy\fP. +either as the return value of a synchronous \fBfcopy\fR or +as the argument to the callback for an asynchronous \fBfcopy\fR. .PP -\fBFcopy\fR obeys the encodings configured for the channels. This +\fBFcopy\fR obeys the encodings and character translations configured +for the channels. This means that the incoming characters are converted internally first UTF-8 and then into the encoding of the channel \fBfcopy\fR writes to. See the manual entry for \fBfconfigure\fR for details on the -\fB\-encoding\fR option. No conversion is done if both channels are -set to encoding "binary". If only the output channel is set to -encoding "binary" the system will write the internal UTF-8 -representation of the incoming characters. If only the input channel -is set to encoding "binary" the system will assume that the incoming +\fB\-encoding\fR and \fB\-translation\fR options. No conversion is +done if both channels are +set to encoding +.QW binary +and have matching translations. If only the output channel is set to encoding +.QW binary +the system will write the internal UTF-8 representation of the incoming +characters. If only the input channel is set to encoding +.QW binary +the system will assume that the incoming bytes are valid UTF-8 characters and convert them according to the output encoding. The behaviour of the system for bytes which are not valid UTF-8 characters is undefined in this case. -.SH EXAMPLE +.SH EXAMPLES .PP -This first example shows how the callback gets +The first example transfers the contents of one channel exactly to +another. Note that when copying one file to another, it is better to +use \fBfile copy\fR which also copies file metadata (e.g. the file +access permissions) where possible. +.CS +fconfigure $in -translation binary +fconfigure $out -translation binary +\fBfcopy\fR $in $out +.CE +.PP +This second example shows how the callback gets passed the number of bytes transferred. It also uses vwait to put the application into the event loop. Of course, this simplified example could be done without the command callback. -.DS +.CS proc Cleanup {in out bytes {error {}}} { global total set total $bytes @@ -102,14 +120,13 @@ proc Cleanup {in out bytes {error {}}} { } set in [open $file1] set out [socket $server $port] -fcopy $in $out -command [list Cleanup $in $out] +\fBfcopy\fR $in $out -command [list Cleanup $in $out] vwait total - -.DE +.CE .PP -The second example copies in chunks and tests for end of file +The third example copies in chunks and tests for end of file in the command callback -.DS +.CS proc CopyMore {in out chunk bytes {error {}}} { global total done incr total $bytes @@ -118,21 +135,21 @@ proc CopyMore {in out chunk bytes {error {}}} { close $in close $out } else { - fcopy $in $out -command [list CopyMore $in $out $chunk] \\ - -size $chunk + \fBfcopy\fR $in $out -size $chunk \e + -command [list CopyMore $in $out $chunk] } } set in [open $file1] set out [socket $server $port] set chunk 1024 set total 0 -fcopy $in $out -command [list CopyMore $in $out $chunk] -size $chunk +\fBfcopy\fR $in $out -size $chunk \e + -command [list CopyMore $in $out $chunk] vwait done - -.DE +.CE .SH "SEE ALSO" -eof(n), fblocked(n), fconfigure(n) +eof(n), fblocked(n), fconfigure(n), file(n) .SH KEYWORDS blocking, channel, end of line, end of file, nonblocking, read, translation |