154 lines
5.7 KiB
Groff
154 lines
5.7 KiB
Groff
'\"
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'\" Copyright (c) 1993 The Regents of the University of California.
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'\" Copyright (c) 1994-1996 Sun Microsystems, Inc.
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'\"
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'\" See the file "license.terms" for information on usage and redistribution
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'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
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'\"
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'\" SCCS: @(#) DString.3 1.19 96/03/25 20:01:32
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'\"
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.so man.macros
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.TH Tcl_DString 3 7.4 Tcl "Tcl Library Procedures"
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.BS
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.SH NAME
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Tcl_DStringInit, Tcl_DStringAppend, Tcl_DStringAppendElement, Tcl_DStringStartSublist, Tcl_DStringEndSublist, Tcl_DStringLength, Tcl_DStringValue, Tcl_DStringSetLength, Tcl_DStringFree, Tcl_DStringResult, Tcl_DStringGetResult \- manipulate dynamic strings
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.SH SYNOPSIS
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.nf
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\fB#include <tcl.h>\fR
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.sp
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\fBTcl_DStringInit\fR(\fIdsPtr\fR)
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.sp
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char *
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\fBTcl_DStringAppend\fR(\fIdsPtr, string, length\fR)
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.sp
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char *
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\fBTcl_DStringAppendElement\fR(\fIdsPtr, string\fR)
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.sp
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\fBTcl_DStringStartSublist\fR(\fIdsPtr\fR)
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.sp
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\fBTcl_DStringEndSublist\fR(\fIdsPtr\fR)
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.sp
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int
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\fBTcl_DStringLength\fR(\fIdsPtr\fR)
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.sp
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char *
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\fBTcl_DStringValue\fR(\fIdsPtr\fR)
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.sp
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.VS
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\fBTcl_DStringSetLength\fR(\fIdsPtr, newLength\fR)
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.VE
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.sp
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\fBTcl_DStringFree\fR(\fIdsPtr\fR)
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.sp
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\fBTcl_DStringResult\fR(\fIinterp, dsPtr\fR)
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.sp
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.VS
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\fBTcl_DStringGetResult\fR(\fIinterp, dsPtr\fR)
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.VE
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.SH ARGUMENTS
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.AS Tcl_DString newLength
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.AP Tcl_DString *dsPtr in/out
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Pointer to structure that is used to manage a dynamic string.
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.AP char *string in
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Pointer to characters to add to dynamic string.
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.AP int length in
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Number of characters from string to add to dynamic string. If -1,
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add all characters up to null terminating character.
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.AP int newLength in
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New length for dynamic string, not including null terminating
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character.
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.AP Tcl_Interp *interp in/out
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Interpreter whose result is to be set from or moved to the
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dynamic string.
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.BE
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.SH DESCRIPTION
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.PP
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Dynamic strings provide a mechanism for building up arbitrarily long
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strings by gradually appending information. If the dynamic string is
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short then there will be no memory allocation overhead; as the string
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gets larger, additional space will be allocated as needed.
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.PP
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\fBTcl_DStringInit\fR initializes a dynamic string to zero length.
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The Tcl_DString structure must have been allocated by the caller.
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No assumptions are made about the current state of the structure;
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anything already in it is discarded.
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If the structure has been used previously, \fBTcl_DStringFree\fR should
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be called first to free up any memory allocated for the old
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string.
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.PP
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\fBTcl_DStringAppend\fR adds new information to a dynamic string,
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allocating more memory for the string if needed.
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If \fIlength\fR is less than zero then everything in \fIstring\fR
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is appended to the dynamic string; otherwise \fIlength\fR
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specifies the number of bytes to append.
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\fBTcl_DStringAppend\fR returns a pointer to the characters of
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the new string. The string can also be retrieved from the
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\fIstring\fR field of the Tcl_DString structure.
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.PP
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\fBTcl_DStringAppendElement\fR is similar to \fBTcl_DStringAppend\fR
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except that it doesn't take a \fIlength\fR argument (it appends
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all of \fIstring\fR) and it converts the string to a proper list element
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before appending.
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\fBTcl_DStringAppendElement\fR adds a separator space before the
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new list element unless the new list element is the first in a
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list or sub-list (i.e. either the current string is empty, or it
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contains the single character ``{'', or the last two characters of
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the current string are `` {'').
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\fBTcl_DStringAppendElement\fR returns a pointer to the
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characters of the new string.
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.PP
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\fBTcl_DStringStartSublist\fR and \fBTcl_DStringEndSublist\fR can be
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used to create nested lists.
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To append a list element that is itself a sublist, first
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call \fBTcl_DStringStartSublist\fR, then call \fBTcl_DStringAppendElement\fR
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for each of the elements in the sublist, then call
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\fBTcl_DStringEndSublist\fR to end the sublist.
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\fBTcl_DStringStartSublist\fR appends a space character if needed,
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followed by an open brace; \fBTcl_DStringEndSublist\fR appends
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a close brace.
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Lists can be nested to any depth.
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.PP
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\fBTcl_DStringLength\fR is a macro that returns the current length
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of a dynamic string (not including the terminating null character).
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\fBTcl_DStringValue\fR is a macro that returns a pointer to the
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current contents of a dynamic string.
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.PP
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.VS
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.PP
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\fBTcl_DStringSetLength\fR changes the length of a dynamic string.
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If \fInewLength\fR is less than the string's current length, then
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the string is truncated.
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If \fInewLength\fR is greater than the string's current length,
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then the string will become longer and new space will be allocated
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for the string if needed.
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However, \fBTcl_DStringSetLength\fR will not initialize the new
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space except to provide a terminating null character; it is up to the
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caller to fill in the new space.
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\fBTcl_DStringSetLength\fR does not free up the string's storage space
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even if the string is truncated to zero length, so \fBTcl_DStringFree\fR
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will still need to be called.
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.VE
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.PP
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\fBTcl_DStringFree\fR should be called when you're finished using
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the string. It frees up any memory that was allocated for the string
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and reinitializes the string's value to an empty string.
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.PP
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\fBTcl_DStringResult\fR sets the result of \fIinterp\fR to the value of
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the dynamic string given by \fIdsPtr\fR. It does this by moving
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a pointer from \fIdsPtr\fR to \fIinterp->result\fR.
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This saves the cost of allocating new memory and copying the string.
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\fBTcl_DStringResult\fR also reinitializes the dynamic string to
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an empty string.
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.PP
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.VS
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\fBTcl_DStringGetResult\fR does the opposite of \fBTcl_DStringResult\fR.
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It sets the value of \fIdsPtr\fR to the result of \fIinterp\fR and
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it clears \fIinterp\fR's result.
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If possible it does this by moving a pointer rather than by copying
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the string.
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.VE
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.SH KEYWORDS
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append, dynamic string, free, result
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