diff options
Diffstat (limited to 'doc/SetChanErr.3')
| -rw-r--r-- | doc/SetChanErr.3 | 153 |
1 files changed, 83 insertions, 70 deletions
diff --git a/doc/SetChanErr.3 b/doc/SetChanErr.3 index 3d37f59..13bd94a 100644 --- a/doc/SetChanErr.3 +++ b/doc/SetChanErr.3 @@ -33,60 +33,65 @@ Refers to the Tcl channel whose bypass area is accessed. .AP Tcl_Interp* interp in Refers to the Tcl interpreter whose bypass area is accessed. .AP Tcl_Obj* msg in -Error message put into a bypass area. A list of return options and values, -followed by a string message. Both message and the option/value information -are optional. +Error message put into a bypass area. A list of return options and +values, followed by a string message. Both message and the +option/value information are optional. .AP Tcl_Obj** msgPtr out -Reference to a place where the message stored in the accessed bypass area can -be stored in. +Reference to a place where the message stored in the accessed bypass +area can be stored in. .BE .SH DESCRIPTION .PP -The current definition of a Tcl channel driver does not permit the direct -return of arbitrary error messages, except for the setting and retrieval of -channel options. All other functions are restricted to POSIX error codes. +The current definition of a Tcl channel driver does not permit the +direct return of arbitrary error messages, except for the setting and +retrieval of channel options. All other functions are restricted to +POSIX error codes. .PP -The functions described here overcome this limitation. Channel drivers are -allowed to use \fBTcl_SetChannelError\fR and \fBTcl_SetChannelErrorInterp\fR -to place arbitrary error messages in \fBbypass areas\fR defined for channels -and interpreters. And the generic I/O layer uses \fBTcl_GetChannelError\fR and -\fBTcl_GetChannelErrorInterp\fR to look for messages in the bypass areas and -arrange for their return as errors. The POSIX error codes set by a driver are -used now if and only if no messages are present. +The functions described here overcome this limitation. Channel drivers +are allowed to use \fBTcl_SetChannelError\fR and +\fBTcl_SetChannelErrorInterp\fR to place arbitrary error messages in +\fBbypass areas\fI defined for channels and interpreters. And the +generic I/O layer uses \fBTcl_GetChannelError\fR and +\fBTcl_GetChannelErrorInterp\fR to look for messages in the bypass +areas and arrange for their return as errors. The posix error codes +set by a driver are used now if and only if no messages are present. .PP -\fBTcl_SetChannelError\fR stores error information in the bypass area of the -specified channel. The number of references to the \fBmsg\fR value goes up by -one. Previously stored information will be discarded, by releasing the -reference held by the channel. The channel reference must not be NULL. +\fBTcl_SetChannelError\fR stores error information in the bypass area +of the specified channel. The number of references to the \fBmsg\fR +object goes up by one. Previously stored information will be +discarded, by releasing the reference held by the channel. The channel +reference must not be NULL. .PP -\fBTcl_SetChannelErrorInterp\fR stores error information in the bypass area of -the specified interpreter. The number of references to the \fBmsg\fR value -goes up by one. Previously stored information will be discarded, by releasing -the reference held by the interpreter. The interpreter reference must not be -NULL. +\fBTcl_SetChannelErrorInterp\fR stores error information in the bypass +area of the specified interpreter. The number of references to the +\fBmsg\fR object goes up by one. Previously stored information will be +discarded, by releasing the reference held by the interpreter. The +interpreter reference must not be NULL. .PP -\fBTcl_GetChannelError\fR places either the error message held in the bypass -area of the specified channel into \fImsgPtr\fR, or NULL; and resets the -bypass, that is, after an invocation all following invocations will return -NULL, until an intervening invocation of \fBTcl_SetChannelError\fR with a -non-NULL message. The \fImsgPtr\fR must not be NULL. The reference count of -the message is not touched. The reference previously held by the channel is -now held by the caller of the function and it is its responsibility to release -that reference when it is done with the value. +\fBTcl_GetChannelError\fR places either the error message held in the +bypass area of the specified channel into \fImsgPtr\fR, or NULL; and +resets the bypass. I.e. after an invocation all following invocations +will return NULL, until an intervening invocation of +\fBTcl_SetChannelError\fR with a non-NULL message. The \fImsgPtr\fR +must not be NULL. The reference count of the message is not touched. +The reference previously held by the channel is now held by the caller +of the function and it is its responsibility to release that reference +when it is done with the object. .PP -\fBTcl_GetChannelErrorInterp\fR places either the error message held in the -bypass area of the specified interpreter into \fImsgPtr\fR, or NULL; and -resets the bypass, that is, after an invocation all following invocations will -return NULL, until an intervening invocation of -\fBTcl_SetChannelErrorInterp\fR with a non-NULL message. The \fImsgPtr\fR must -not be NULL. The reference count of the message is not touched. The reference -previously held by the interpreter is now held by the caller of the function -and it is its responsibility to release that reference when it is done with -the value. +\fBTcl_GetChannelErrorInterp\fR places either the error message held +in the bypass area of the specified interpreter into \fImsgPtr\fR, or +NULL; and resets the bypass. I.e. after an invocation all following +invocations will return NULL, until an intervening invocation of +\fBTcl_SetChannelErrorInterp\fR with a non-NULL message. The +\fImsgPtr\fR must not be NULL. The reference count of the message is +not touched. The reference previously held by the interpreter is now +held by the caller of the function and it is its responsibility to +release that reference when it is done with the object. +.PP +Which functions of a channel driver are allowed to use which bypass +function is listed below, as is which functions of the public channel +API may leave a messages in the bypass areas. .PP -Which functions of a channel driver are allowed to use which bypass function -is listed below, as is which functions of the public channel API may leave a -messages in the bypass areas. .IP \fBTcl_DriverCloseProc\fR May use \fBTcl_SetChannelErrorInterp\fR, and only this function. .IP \fBTcl_DriverInputProc\fR @@ -98,43 +103,51 @@ May use \fBTcl_SetChannelError\fR, and only this function. .IP \fBTcl_DriverWideSeekProc\fR May use \fBTcl_SetChannelError\fR, and only this function. .IP \fBTcl_DriverSetOptionProc\fR -Has already the ability to pass arbitrary error messages. Must \fInot\fR use -any of the new functions. +Has already the ability to pass arbitrary error messages. Must +\fBnot\fR use any of the new functions. .IP \fBTcl_DriverGetOptionProc\fR Has already the ability to pass arbitrary error messages. Must -\fInot\fR use any of the new functions. +\fBnot\fR use any of the new functions. .IP \fBTcl_DriverWatchProc\fR -Must \fInot\fR use any of the new functions. Is internally called and has no -ability to return any type of error whatsoever. +Must \fBnot\fR use any of the new functions. Is internally called and +has no ability to return any type of error whatsoever. .IP \fBTcl_DriverBlockModeProc\fR May use \fBTcl_SetChannelError\fR, and only this function. .IP \fBTcl_DriverGetHandleProc\fR -Must \fInot\fR use any of the new functions. It is only a low-level function, -and not used by Tcl commands. +Must \fBnot\fR use any of the new functions. It is only a low-level +function, and not used by Tcl commands. .IP \fBTcl_DriverHandlerProc\fR -Must \fInot\fR use any of the new functions. Is internally called and has no -ability to return any type of error whatsoever. +Must \fBnot\fR use any of the new functions. Is internally called and +has no ability to return any type of error whatsoever. .PP -Given the information above the following public functions of the Tcl C API -are affected by these changes; when these functions are called, the channel -may now contain a stored arbitrary error message requiring processing by the -caller. -.DS -.ta 1.9i 4i -\fBTcl_Flush\fR \fBTcl_GetsObj\fR \fBTcl_Gets\fR -\fBTcl_ReadChars\fR \fBTcl_ReadRaw\fR \fBTcl_Read\fR -\fBTcl_Seek\fR \fBTcl_StackChannel\fR \fBTcl_Tell\fR -\fBTcl_WriteChars\fR \fBTcl_WriteObj\fR \fBTcl_WriteRaw\fR -\fBTcl_Write\fR -.DE +Given the information above the following public functions of the Tcl +C API are affected by these changes. I.e. when these functions are +called the channel may now contain a stored arbitrary error message +requiring processing by the caller. .PP -All other API functions are unchanged. In particular, the functions below +.IP \fBTcl_StackChannel\fR +.IP \fBTcl_Seek\fR +.IP \fBTcl_Tell\fR +.IP \fBTcl_ReadRaw\fR +.IP \fBTcl_Read\fR +.IP \fBTcl_ReadChars\fR +.IP \fBTcl_Gets\fR +.IP \fBTcl_GetsObj\fR +.IP \fBTcl_Flush\fR +.IP \fBTcl_WriteRaw\fR +.IP \fBTcl_WriteObj\fR +.IP \fBTcl_Write\fR +.IP \fBTcl_WriteChars\fR +.PP +All other API functions are unchanged. Especially the functions below leave all their error information in the interpreter result. -.DS -.ta 1.9i 4i -\fBTcl_Close\fR \fBTcl_UnstackChannel\fR \fBTcl_UnregisterChannel\fR -.DE +.PP +.IP \fBTcl_Close\fR +.IP \fBTcl_UnregisterChannel\fR +.IP \fBTcl_UnstackChannel\fR + .SH "SEE ALSO" Tcl_Close(3), Tcl_OpenFileChannel(3), Tcl_SetErrno(3) + .SH KEYWORDS channel driver, error messages, channel type |