diff options
Diffstat (limited to 'doc')
| -rw-r--r-- | doc/SetChanErr.3 | 155 |
1 files changed, 71 insertions, 84 deletions
diff --git a/doc/SetChanErr.3 b/doc/SetChanErr.3 index b063121..a118155 100644 --- a/doc/SetChanErr.3 +++ b/doc/SetChanErr.3 @@ -4,7 +4,7 @@ '\" See the file "license.terms" for information on usage and redistribution '\" of this file, and for a DISCLAIMER OF ALL WARRANTIES. '\" -'\" RCS: @(#) $Id: SetChanErr.3,v 1.4 2007/12/13 15:22:31 dgp Exp $ +'\" RCS: @(#) $Id: SetChanErr.3,v 1.5 2008/12/17 21:05:05 dkf Exp $ .so man.macros .TH Tcl_SetChannelError 3 8.5 Tcl "Tcl Library Procedures" .BS @@ -34,65 +34,60 @@ 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\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. +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. .PP -\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. +\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 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. +\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. I.e. after an invokation all following invokations -will return NULL, until an intervening invokation 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. +\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 invokation all following invokations will return +NULL, until an intervening invokation 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. I.e. after an invokation all following -invokations will return NULL, until an intervening invokation 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. +\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 invokation all following invokations will +return NULL, until an intervening invokation 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. .IP \fBTcl_DriverCloseProc\fR May use \fBTcl_SetChannelErrorInterp\fR, and only this function. .IP \fBTcl_DriverInputProc\fR @@ -104,51 +99,43 @@ 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 -\fBnot\fR use any of the new functions. +Has already the ability to pass arbitrary error messages. Must \fInot\fR use +any of the new functions. .IP \fBTcl_DriverGetOptionProc\fR Has already the ability to pass arbitrary error messages. Must -\fBnot\fR use any of the new functions. +\fInot\fR use any of the new functions. .IP \fBTcl_DriverWatchProc\fR -Must \fBnot\fR use any of the new functions. Is internally called and -has no ability to return any type of error whatsoever. +Must \fInot\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 \fBnot\fR use any of the new functions. It is only a low-level -function, and not used by Tcl commands. +Must \fInot\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 \fBnot\fR use any of the new functions. Is internally called and -has no ability to return any type of error whatsoever. +Must \fInot\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. I.e. when these functions are -called the channel may now contain a stored arbitrary error message -requiring processing by the caller. +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 .PP -.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 +All other API functions are unchanged. In particular, the functions below leave all their error information in the interpreter result. -.PP -.IP \fBTcl_Close\fR -.IP \fBTcl_UnregisterChannel\fR -.IP \fBTcl_UnstackChannel\fR - +.DS +.ta 1.9i 4i +\fBTcl_Close\fR \fBTcl_UnstackChannel\fR \fBTcl_UnregisterChannel\fR +.DE .SH "SEE ALSO" Tcl_Close(3), Tcl_OpenFileChannel(3), Tcl_SetErrno(3) - .SH KEYWORDS channel driver, error messages, channel type |