557 lines
9.1 KiB
HTML
557 lines
9.1 KiB
HTML
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN""http://www.w3.org/TR/html4/loose.dtd">
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<HTML
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><HEAD
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><TITLE
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>Hash table</TITLE
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><META
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NAME="GENERATOR"
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CONTENT="Modular DocBook HTML Stylesheet Version 1.79"><LINK
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REL="HOME"
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TITLE="libEtPan! API"
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HREF="book1.htm"><LINK
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REL="UP"
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TITLE="Tools and datatypes"
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HREF="c16.htm"><LINK
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REL="PREVIOUS"
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TITLE="List"
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HREF="x88.htm"><LINK
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REL="NEXT"
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TITLE="Buffered I/O"
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HREF="x229.htm"></HEAD
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><BODY
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CLASS="SECT1"
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BGCOLOR="#FFFFFF"
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TEXT="#000000"
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LINK="#0000FF"
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VLINK="#840084"
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ALINK="#0000FF"
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><DIV
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CLASS="NAVHEADER"
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><TABLE
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SUMMARY="Header navigation table"
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WIDTH="100%"
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BORDER="0"
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CELLPADDING="0"
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CELLSPACING="0"
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><TR
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><TH
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COLSPAN="3"
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ALIGN="center"
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>libEtPan! API</TH
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></TR
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><TR
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><TD
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WIDTH="10%"
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ALIGN="left"
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VALIGN="bottom"
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><A
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HREF="x88.htm"
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ACCESSKEY="P"
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>Prev</A
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></TD
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><TD
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WIDTH="80%"
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ALIGN="center"
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VALIGN="bottom"
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>Chapter 2. Tools and datatypes</TD
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><TD
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WIDTH="10%"
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ALIGN="right"
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VALIGN="bottom"
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><A
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HREF="x229.htm"
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ACCESSKEY="N"
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>Next</A
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></TD
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></TR
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></TABLE
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><HR
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ALIGN="LEFT"
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WIDTH="100%"></DIV
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><DIV
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CLASS="SECT1"
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><H1
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CLASS="SECT1"
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><A
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NAME="AEN161"
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>Hash table</A
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></H1
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><PRE
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CLASS="PROGRAMLISTING"
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>#include <libetpan/libetpan.h>
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typedef struct chash chash;
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typedef struct chashcell chashiter;
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typedef struct {
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char * data;
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int len;
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} chashdatum;
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</PRE
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><P
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>
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<B
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CLASS="COMMAND"
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>chash</B
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> is a hash table.
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<B
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CLASS="COMMAND"
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>chashiter</B
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> is a pointer to an element of the
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hash table.
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<B
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CLASS="COMMAND"
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>chashdatum</B
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> is an element to be placed in
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the hash table as a key or a value. It consists in
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data and a corresponding length.
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</P
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><DIV
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CLASS="SECT2"
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><H2
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CLASS="SECT2"
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><A
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NAME="CHASH-NEW"
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>chash_new and chash_free</A
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></H2
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><PRE
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CLASS="PROGRAMLISTING"
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>#define CHASH_COPYNONE 0
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#define CHASH_COPYKEY 1
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#define CHASH_COPYVALUE 2
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#define CHASH_COPYALL (CHASH_COPYKEY | CHASH_COPYVALUE)
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chash * chash_new(int size, int flags);
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void chash_free(chash * hash);
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</PRE
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><P
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> <B
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CLASS="COMMAND"
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>chash_new()</B
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> returns a new empty hash table
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or <B
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CLASS="COMMAND"
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>NULL</B
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> if this
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failed. <B
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CLASS="COMMAND"
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>size</B
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> is the initial size of the
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table used for implementation. <B
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CLASS="COMMAND"
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>flags</B
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> can
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be a combinaison of <B
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CLASS="COMMAND"
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>CHASH_COPYKEY</B
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> and
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<B
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CLASS="COMMAND"
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>CHASH_COPYVALUE</B
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>.
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<B
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CLASS="COMMAND"
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>CHASH_COPYKEY</B
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> enables copy of key, so
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that the initial value used for <B
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CLASS="COMMAND"
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>chash_set()</B
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>
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</P
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><P
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> <B
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CLASS="COMMAND"
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>chash_free()</B
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> releases memory used by the
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hash table.
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</P
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></DIV
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><DIV
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CLASS="SECT2"
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><H2
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CLASS="SECT2"
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><A
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NAME="CHASH-GET"
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>chash_set and chash_get</A
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></H2
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><PRE
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CLASS="PROGRAMLISTING"
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>int chash_set(chash * hash,
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chashdatum * key, chashdatum * value, chashdatum * oldvalue);
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int chash_get(chash * hash,
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chashdatum * key, chashdatum * result);
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</PRE
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><P
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> <B
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CLASS="COMMAND"
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>chash_set()</B
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> adds a new element into the
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hash table. If a previous element had the same key, it is
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returns into oldvalue if <B
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CLASS="COMMAND"
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>oldvalue</B
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> is
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different of NULL.
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Medium complexity is O(1).
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</P
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><P
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> returns -1 if it fails, 0 on success.
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</P
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><P
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> <B
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CLASS="COMMAND"
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>chash_get()</B
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>returns the corresponding value
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of the given key. If there is no corresponding value, -1 is
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returned. 0 on success.
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Medium complexity is O(1).
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</P
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><DIV
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CLASS="EXAMPLE"
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><A
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NAME="AEN191"
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></A
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><P
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><B
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>Example 2-9. chash insert and lookup</B
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></P
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><PRE
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CLASS="PROGRAMLISTING"
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>int main(void)
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{
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chash * hash;
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int r;
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chashdatum key;
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chashdatum value;
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char * str1 = "my-data";
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char * str2 = "my-data";
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hash = chash_new(CHASH_DEFAULTSIZE, CHASH_COPYNONE);
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key.data = "foo";
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key.len = strlen("foo");
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value.data = str1;
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value.data = strlen(str1) + 1;
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/* + 1 is needed to get the terminal zero in the returned string */
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r = chash_set(hash, &key, &value, NULL);
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if (r < 0)
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goto free_hash;
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key.data = "bar";
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key.len = strlen("bar");
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value.data = str2;
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value.data = strlen(str2) + 1;
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if (r < 0)
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goto free_hash;
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key.data = "foo";
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key.len = strlen("foo");
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r = chash_get(hash, &key, &value);
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if (r < 0) {
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printf("element not found\n");
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}
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else {
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char * str;
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str = value.data;
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printf("found : %s", str);
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}
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chash_free(hash);
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exit(EXIT_SUCCESS);
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free_hash:
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chash_free(hash);
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err:
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exit(EXIT_FAILURE);
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}
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</PRE
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></DIV
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></DIV
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><DIV
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CLASS="SECT2"
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><H2
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CLASS="SECT2"
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><A
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NAME="CHASH-DELETE"
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>chash_delete</A
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></H2
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><PRE
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CLASS="PROGRAMLISTING"
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>int chash_delete(chash * hash,
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chashdatum * key, chashdatum * oldvalue);
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</PRE
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><P
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> deletes the key/value pair given the corresponding key.
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The value is returned in old_value.
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If there is no corresponding value, -1 is returned. 0 on success.
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Medium complexity is O(1).
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</P
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><DIV
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CLASS="EXAMPLE"
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><A
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NAME="AEN198"
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></A
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><P
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><B
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>Example 2-10. key deletion in a chash</B
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></P
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><PRE
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CLASS="PROGRAMLISTING"
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>int main(void)
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{
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chash * hash;
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int r;
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chashdatum key;
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chashdatum value;
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char * str1 = "my-data";
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char * str2 = "my-data";
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hash = build_hash();
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key.data = "foo";
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key.len = strlen("foo");
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chash_delete(hash, &key, &value);
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/* it will never be possible to lookup "foo" */
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key.data = "foo";
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key.len = strlen("foo");
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r = chash_get(hash, &key, &value);
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if (r < 0) {
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printf("element not found\n");
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}
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else {
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char * str;
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str = value.data;
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printf("found : %s", str);
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}
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chash_free(hash);
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exit(EXIT_SUCCESS);
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free_hash:
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chash_free(hash);
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err:
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exit(EXIT_FAILURE);
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}
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</PRE
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></DIV
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></DIV
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><DIV
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CLASS="SECT2"
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><H2
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CLASS="SECT2"
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><A
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NAME="CHASH-RESIZE"
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>chash_resize</A
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></H2
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><PRE
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CLASS="PROGRAMLISTING"
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>int chash_resize(chash * hash, int size);
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</PRE
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><P
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> <B
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CLASS="COMMAND"
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>chash_resize()</B
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> changes the size of the
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table used for implementation of the hash table.
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returns 0 on success, -1 on failure.
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</P
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></DIV
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><DIV
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CLASS="SECT2"
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><H2
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CLASS="SECT2"
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><A
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NAME="CHASH-BEGIN"
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>running through the chash</A
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></H2
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><PRE
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CLASS="PROGRAMLISTING"
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>chashiter * chash_begin(chash * hash);
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chashiter * chash_next(chash * hash, chashiter * iter);
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void chash_key(chashiter * iter, chashdatum * result);
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void chash_value(chashiter iter, chashdatum * result);
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</PRE
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><P
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> <B
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CLASS="COMMAND"
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>chash_begin()</B
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> returns a pointer to the
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first element of the hash table. Returns
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<B
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CLASS="COMMAND"
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>NULL</B
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> if there is no elements in the hash
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table.
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Complexity is O(n).
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</P
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><P
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> <B
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CLASS="COMMAND"
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>chash_next()</B
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> returns a pointer to the next
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element of the hash table. Returns <B
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CLASS="COMMAND"
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>NULL</B
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>
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if there is no next element.
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Complexity is O(n) but n calls to chash_next() also has
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a complexity of O(n).
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</P
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><P
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> <B
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CLASS="COMMAND"
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>chash_key()</B
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> returns the key of the given
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element of the hash table.
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</P
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><P
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> <B
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CLASS="COMMAND"
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>chash_value</B
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> returns the value of the
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given element of the hash table.
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</P
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||
|
|
><DIV
|
||
|
|
CLASS="EXAMPLE"
|
||
|
|
><A
|
||
|
|
NAME="AEN219"
|
||
|
|
></A
|
||
|
|
><P
|
||
|
|
><B
|
||
|
|
>Example 2-11. running through a chash</B
|
||
|
|
></P
|
||
|
|
><PRE
|
||
|
|
CLASS="PROGRAMLISTING"
|
||
|
|
>int main(void)
|
||
|
|
{
|
||
|
|
chash * hash;
|
||
|
|
int r;
|
||
|
|
chashiter * iter;
|
||
|
|
|
||
|
|
hash = build_hash();
|
||
|
|
|
||
|
|
/* this will display all the values stored in the hash */
|
||
|
|
for(iter = chash_begin(hash) ; iter != NULL ; iter =
|
||
|
|
chash_next(hash, iter)) {
|
||
|
|
chashdatum key;
|
||
|
|
chashdatum value;
|
||
|
|
char * str;
|
||
|
|
|
||
|
|
chash_value(iter, &value);
|
||
|
|
str = value.data;
|
||
|
|
printf("%s\n", str);
|
||
|
|
}
|
||
|
|
|
||
|
|
chash_free(hash);
|
||
|
|
}
|
||
|
|
</PRE
|
||
|
|
></DIV
|
||
|
|
></DIV
|
||
|
|
><DIV
|
||
|
|
CLASS="SECT2"
|
||
|
|
><H2
|
||
|
|
CLASS="SECT2"
|
||
|
|
><A
|
||
|
|
NAME="CHASH-COUNT"
|
||
|
|
>chash_size and chash_count</A
|
||
|
|
></H2
|
||
|
|
><PRE
|
||
|
|
CLASS="PROGRAMLISTING"
|
||
|
|
>int chash_size(chash * hash);
|
||
|
|
|
||
|
|
int chash_count(chash * hash);
|
||
|
|
</PRE
|
||
|
|
><P
|
||
|
|
> <B
|
||
|
|
CLASS="COMMAND"
|
||
|
|
>chash_size()</B
|
||
|
|
> returns the size of the table
|
||
|
|
used for implementation of the hash table.
|
||
|
|
Complexity is O(1).
|
||
|
|
</P
|
||
|
|
><P
|
||
|
|
> <B
|
||
|
|
CLASS="COMMAND"
|
||
|
|
>chash_count()</B
|
||
|
|
> returns the number of
|
||
|
|
elements in the hash table.
|
||
|
|
Complexity is O(1).
|
||
|
|
</P
|
||
|
|
></DIV
|
||
|
|
></DIV
|
||
|
|
><DIV
|
||
|
|
CLASS="NAVFOOTER"
|
||
|
|
><HR
|
||
|
|
ALIGN="LEFT"
|
||
|
|
WIDTH="100%"><TABLE
|
||
|
|
SUMMARY="Footer navigation table"
|
||
|
|
WIDTH="100%"
|
||
|
|
BORDER="0"
|
||
|
|
CELLPADDING="0"
|
||
|
|
CELLSPACING="0"
|
||
|
|
><TR
|
||
|
|
><TD
|
||
|
|
WIDTH="33%"
|
||
|
|
ALIGN="left"
|
||
|
|
VALIGN="top"
|
||
|
|
><A
|
||
|
|
HREF="x88.htm"
|
||
|
|
ACCESSKEY="P"
|
||
|
|
>Prev</A
|
||
|
|
></TD
|
||
|
|
><TD
|
||
|
|
WIDTH="34%"
|
||
|
|
ALIGN="center"
|
||
|
|
VALIGN="top"
|
||
|
|
><A
|
||
|
|
HREF="book1.htm"
|
||
|
|
ACCESSKEY="H"
|
||
|
|
>Home</A
|
||
|
|
></TD
|
||
|
|
><TD
|
||
|
|
WIDTH="33%"
|
||
|
|
ALIGN="right"
|
||
|
|
VALIGN="top"
|
||
|
|
><A
|
||
|
|
HREF="x229.htm"
|
||
|
|
ACCESSKEY="N"
|
||
|
|
>Next</A
|
||
|
|
></TD
|
||
|
|
></TR
|
||
|
|
><TR
|
||
|
|
><TD
|
||
|
|
WIDTH="33%"
|
||
|
|
ALIGN="left"
|
||
|
|
VALIGN="top"
|
||
|
|
>List</TD
|
||
|
|
><TD
|
||
|
|
WIDTH="34%"
|
||
|
|
ALIGN="center"
|
||
|
|
VALIGN="top"
|
||
|
|
><A
|
||
|
|
HREF="c16.htm"
|
||
|
|
ACCESSKEY="U"
|
||
|
|
>Up</A
|
||
|
|
></TD
|
||
|
|
><TD
|
||
|
|
WIDTH="33%"
|
||
|
|
ALIGN="right"
|
||
|
|
VALIGN="top"
|
||
|
|
>Buffered I/O</TD
|
||
|
|
></TR
|
||
|
|
></TABLE
|
||
|
|
></DIV
|
||
|
|
></BODY
|
||
|
|
></HTML
|
||
|
|
>
|