| 1 | .\" -*-nroff-*- |
| 2 | .\" |
| 3 | .\" Manual for buffer extension |
| 4 | .\" |
| 5 | .\" (c) 2024 Straylight/Edgeware |
| 6 | .\" |
| 7 | . |
| 8 | .\"----- Licensing notice --------------------------------------------------- |
| 9 | .\" |
| 10 | .\" This file is part of the mLib utilities library. |
| 11 | .\" |
| 12 | .\" mLib is free software: you can redistribute it and/or modify it under |
| 13 | .\" the terms of the GNU Library General Public License as published by |
| 14 | .\" the Free Software Foundation; either version 2 of the License, or (at |
| 15 | .\" your option) any later version. |
| 16 | .\" |
| 17 | .\" mLib is distributed in the hope that it will be useful, but WITHOUT |
| 18 | .\" ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| 19 | .\" FITNESS FOR A PARTICULAR PURPOSE. See the GNU Library General Public |
| 20 | .\" License for more details. |
| 21 | .\" |
| 22 | .\" You should have received a copy of the GNU Library General Public |
| 23 | .\" License along with mLib. If not, write to the Free Software |
| 24 | .\" Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, |
| 25 | .\" USA. |
| 26 | . |
| 27 | .\"-------------------------------------------------------------------------- |
| 28 | .so ../defs.man \" @@@PRE@@@ |
| 29 | . |
| 30 | .\"-------------------------------------------------------------------------- |
| 31 | .TH growbuf 3mLib "9 March 2024" "Straylight/Edgeware" "mLib utilities library" |
| 32 | .\" @GROWBUF_SIZE |
| 33 | .\" @GROWBUF_EXTEND |
| 34 | .\" @GROWBUF_REPLACE |
| 35 | . |
| 36 | .\"-------------------------------------------------------------------------- |
| 37 | .SH NAME |
| 38 | growbuf \- extend buffers efficiently |
| 39 | . |
| 40 | .\"-------------------------------------------------------------------------- |
| 41 | .SH SYNOPSIS |
| 42 | . |
| 43 | .nf |
| 44 | .B "#include <mLib/growbuf.h>" |
| 45 | .PP |
| 46 | .BI "GROWBUF_SIZE(size_t " sz ", size_t " want ", " \c |
| 47 | .BI "size_t " init ", size_t " granule ");" |
| 48 | .PP |
| 49 | .ds mT \fBGROWBUF_EXTEND( |
| 50 | .BI "\*(mTarena *" a ", " type " *" buf ", size_t " sz ", size_t " want "," |
| 51 | .BI "\h'\w'\*(mT'u'size_t " init ", size_t " granule ");" |
| 52 | .ds mT \fBGROWBUF_REPLACE( |
| 53 | .BI "\*(mTarena *" a ", " type " *" buf ", size_t " sz ", size_t " want "," |
| 54 | .BI "\h'\w'\*(mT'u'size_t " init ", size_t " granule ");" |
| 55 | .fi |
| 56 | . |
| 57 | .\"-------------------------------------------------------------------------- |
| 58 | .SH DESCRIPTION |
| 59 | . |
| 60 | The |
| 61 | .B "<mLib/growbuf.h>" |
| 62 | header file defines macros useful for dynamically resizing buffers. |
| 63 | .PP |
| 64 | The situation envisaged is a buffer, at address |
| 65 | .IR buf , |
| 66 | with space to hold |
| 67 | .I sz |
| 68 | objects each of size |
| 69 | .IR granule ; |
| 70 | but it has become necessary to store |
| 71 | .I want |
| 72 | objects in the buffer. |
| 73 | If the current size |
| 74 | .I sz |
| 75 | is zero, then the buffer pointer |
| 76 | .I buf |
| 77 | may be null; |
| 78 | otherwise, it is assumed to have been allocated from the arena |
| 79 | .IR a . |
| 80 | The size |
| 81 | .I init |
| 82 | is a suggested minimal nonzero size, again counting objects of size |
| 83 | .IR granule . |
| 84 | .PP |
| 85 | The |
| 86 | .B GROWBUF_SIZE |
| 87 | macro merely adjusts |
| 88 | .I sz |
| 89 | so that it is at least as large as |
| 90 | .IR want ; |
| 91 | it is |
| 92 | .I assumed |
| 93 | on entry that |
| 94 | .IR sz "\ <\ " want ; |
| 95 | nothing especially terrible will happen if this is not the case, |
| 96 | but unnecessary work will take place, |
| 97 | and |
| 98 | .I sz |
| 99 | will be left nonzero if it was previously zero, |
| 100 | even if |
| 101 | .IR want "\ =\ 0." |
| 102 | .B GROWBUF_SIZE |
| 103 | arranges to increase buffer sizes in a geometric progression |
| 104 | so as to minimize reallocation and copying overheads \(en |
| 105 | the number of reallocations will be |
| 106 | at most logarithmic in the final size |
| 107 | and each byte is copied an (amortized) constant number of times. |
| 108 | .PP |
| 109 | The |
| 110 | .B GROWBUF_EXTEND |
| 111 | macro will additionally resize the buffer, |
| 112 | preserving its contents, |
| 113 | and adjusting |
| 114 | .I buf |
| 115 | to point to its new location; |
| 116 | if |
| 117 | .I want |
| 118 | \(<= |
| 119 | .I sz |
| 120 | then nothing happens. |
| 121 | The |
| 122 | .B GROWBUF_REPLACE |
| 123 | macro is similar, except that it |
| 124 | .I discards |
| 125 | the existing buffer contents if the buffer needs to be adjusted. |
| 126 | . |
| 127 | .\"-------------------------------------------------------------------------- |
| 128 | .SH "SEE ALSO" |
| 129 | . |
| 130 | .BR arena (3), |
| 131 | .BR mLib (3). |
| 132 | . |
| 133 | .\"-------------------------------------------------------------------------- |
| 134 | .SH AUTHOR |
| 135 | . |
| 136 | Mark Wooding, <mdw@distorted.org.uk> |
| 137 | . |
| 138 | .\"----- That's all, folks -------------------------------------------------- |