92 lines
4.0 KiB
Groff
92 lines
4.0 KiB
Groff
'\"
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'\" Copyright (c) 1997 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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.TH Tcl_ByteArrayObj 3 8.1 Tcl "Tcl Library Procedures"
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.so man.macros
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.BS
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.SH NAME
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Tcl_NewByteArrayObj, Tcl_SetByteArrayObj, Tcl_GetByteArrayFromObj, Tcl_SetByteArrayLength \- manipulate Tcl values as a arrays of bytes
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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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Tcl_Obj *
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\fBTcl_NewByteArrayObj\fR(\fIbytes, length\fR)
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.sp
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void
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\fBTcl_SetByteArrayObj\fR(\fIobjPtr, bytes, length\fR)
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.sp
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unsigned char *
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\fBTcl_GetByteArrayFromObj\fR(\fIobjPtr, lengthPtr\fR)
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.sp
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unsigned char *
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\fBTcl_SetByteArrayLength\fR(\fIobjPtr, length\fR)
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.SH ARGUMENTS
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.AS "const unsigned char" *lengthPtr in/out
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.AP "const unsigned char" *bytes in
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The array of bytes used to initialize or set a byte-array value. May be NULL
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even if \fIlength\fR is non-zero.
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.AP int length in
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The length of the array of bytes. It must be >= 0.
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.AP Tcl_Obj *objPtr in/out
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For \fBTcl_SetByteArrayObj\fR, this points to the value to be converted to
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byte-array type. For \fBTcl_GetByteArrayFromObj\fR and
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\fBTcl_SetByteArrayLength\fR, this points to the value from which to get
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the byte-array value; if \fIobjPtr\fR does not already point to a byte-array
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value, it will be converted to one.
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.AP int *lengthPtr out
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If non-NULL, filled with the length of the array of bytes in the value.
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.BE
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.SH DESCRIPTION
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.PP
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These procedures are used to create, modify, and read Tcl byte-array values
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from C code. Byte-array values are typically used to hold the
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results of binary IO operations or data structures created with the
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\fBbinary\fR command. In Tcl, an array of bytes is not equivalent to a
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string. Conceptually, a string is an array of Unicode characters, while a
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byte-array is an array of 8-bit quantities with no implicit meaning.
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Accessor functions are provided to get the string representation of a
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byte-array or to convert an arbitrary value to a byte-array. Obtaining the
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string representation of a byte-array value (by calling
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\fBTcl_GetStringFromObj\fR) produces a properly formed UTF-8 sequence with a
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one-to-one mapping between the bytes in the internal representation and the
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UTF-8 characters in the string representation.
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.PP
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\fBTcl_NewByteArrayObj\fR and \fBTcl_SetByteArrayObj\fR will
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create a new value of byte-array type or modify an existing value to have a
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byte-array type. Both of these procedures set the value's type to be
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byte-array and set the value's internal representation to a copy of the
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array of bytes given by \fIbytes\fR. \fBTcl_NewByteArrayObj\fR returns a
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pointer to a newly allocated value with a reference count of zero.
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\fBTcl_SetByteArrayObj\fR invalidates any old string representation and, if
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the value is not already a byte-array value, frees any old internal
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representation. If \fIbytes\fR is NULL then the new byte array contains
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arbitrary values.
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.PP
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\fBTcl_GetByteArrayFromObj\fR converts a Tcl value to byte-array type and
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returns a pointer to the value's new internal representation as an array of
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bytes. The length of this array is stored in \fIlengthPtr\fR if
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\fIlengthPtr\fR is non-NULL. The storage for the array of bytes is owned by
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the value and should not be freed. The contents of the array may be
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modified by the caller only if the value is not shared and the caller
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invalidates the string representation.
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.PP
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\fBTcl_SetByteArrayLength\fR converts the Tcl value to byte-array type
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and changes the length of the value's internal representation as an
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array of bytes. If \fIlength\fR is greater than the space currently
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allocated for the array, the array is reallocated to the new length; the
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newly allocated bytes at the end of the array have arbitrary values. If
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\fIlength\fR is less than the space currently allocated for the array,
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the length of array is reduced to the new length. The return value is a
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pointer to the value's new array of bytes.
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.SH "SEE ALSO"
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Tcl_GetStringFromObj, Tcl_NewObj, Tcl_IncrRefCount, Tcl_DecrRefCount
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.SH KEYWORDS
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value, binary data, byte array, utf, unicode, internationalization
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