templeos-info/public/Wb/Home/Doc/Hash.DD.HTML

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<pre style="font-family: courier, monospace; font-size: 10pt;">
<a name="l1"></a><span class=cFA>/* Graphics Not Rendered in HTML */</span><span class=cF0>
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<a name="l28"></a>There is a symbol (hash) table for each task. When a sym is not found, the
<a name="l29"></a>parent task's sym table is checked. All tasks chain back to the </span><span class=cF2>Adam</span><span class=cF0> task.
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<a name="l31"></a>TempleOS sym tables are implemented with an array of linked-lists. A num is
<a name="l32"></a>generated from a string by </span><a href="/Wb/Kernel/KHashA.HC#l254"><span class=cF4>HashStr</span></a><span class=cF0>() to index into the array of linked-lists.
<a name="l33"></a>Multiple strings can generate the same num, so linked-lists are built. Newer
<a name="l34"></a>entries overshadow older ones.
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<a name="l36"></a>There are various types of entries. See </span><a href="/Wb/Kernel/KernelA.HH#l686"><span class=cF4>Hash Entry Types</span></a><span class=cF0>.
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<a name="l38"></a></span><span class=cF5>Symbol Look-up</span><span class=cF0> (Used many places including the </span><a href="/Wb/Compiler/Lex.HC#l499"><span class=cF4>JIT Compiler</span></a><span class=cF0> and </span><a href="/Wb/Kernel/KLoad.HC#l19"><span class=cF4>Loader</span></a><span class=cF0>.)
<a name="l39"></a>1) Symbol name is </span><a href="/Wb/Kernel/KHashA.HC#l4"><span class=cF4>hashed</span></a><span class=cF0> by adding and shifting the ASCII of all chars.
<a name="l40"></a>2) </span><a href="/Wb/Kernel/KernelA.HH#l647"><span class=cF4>hash table</span></a><span class=cF0>-&gt;body[] array is indexed.
<a name="l41"></a>3) Linked-lst is traversed until match of text and type of entry.
<a name="l42"></a>4) If not found, </span><a href="/Wb/Kernel/KernelA.HH#l647"><span class=cF4>hash table</span></a><span class=cF0>-&gt;next table is searched.
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<a name="l44"></a>Duplicate entries are allowed -- they overshadow old entries.
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<a name="l46"></a></span><span class=cF5>Address-to-Symbol Look-up</span><span class=cF0> (Slow because not important. We could use trees.)
<a name="l47"></a>1) FunSeg Cache is </span><a href="/Wb/Kernel/FunSeg.HC#l114"><span class=cF4>scanned</span></a><span class=cF0>.
<a name="l48"></a>2) Hash Tables are </span><a href="/Wb/Kernel/FunSeg.HC#l54"><span class=cF4>scanned</span></a><span class=cF0>.
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