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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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<!--Weave of '3/fds' generated by 7-->
<ul class="crumbs"><li><a href="../webs.html">Source</a></li><li><a href="../compiler.html">Compiler Modules</a></li><li><a href="index.html">words</a></li><li><a href="index.html#3">Chapter 3: Words in Sequence</a></li><li><b>Feeds</b></li></ul><p class="purpose">Feeds are conduits for arbitrary text to flow into the lexer, and to be converted into wordings.</p>
<ul class="toc"><li><a href="#SP1">&#167;1. Definitions</a></li><li><a href="#SP3">&#167;3. Feed sessions</a></li><li><a href="#SP4">&#167;4. Feeding a feed</a></li></ul><hr class="tocbar">
<p class="inwebparagraph"><a id="SP1"></a><b>&#167;1. Definitions. </b></p>
<p class="inwebparagraph"><a id="SP2"></a><b>&#167;2. </b>I feel a certain embarrassment about the frequency with which the following
code is needed throughout Inform, to create fresh source text from old. Is
this a shameless hack, sacrificing memory for the sake of a small data
structure to represent wordings? Or is it a deep insight into the
interdependency of lexical analysis and semantic understanding? The reader
must decide.
</p>
<p class="inwebparagraph">Each feed has a unique ID. At present only one is ever open at a time, but
we don't want to assume that.
</p>
<pre class="definitions">
<span class="definitionkeyword">define</span> <span class="constant">feed_t</span><span class="plain"> </span><span class="reserved">int</span><span class="plain"> </span><span class="comment">(not a typedef only because it makes trouble for inweb)</span>
</pre>
<p class="inwebparagraph"><a id="SP3"></a><b>&#167;3. Feed sessions. </b>There are two ways to make a feed. One is simply to call one of the <code class="display"><span class="extract">feed_text</span></code>
routines below and use its output. The other is for a multi-stage process,
that is, for when multiple pieces of text need to go into the same feed:
to start such, call <code class="display"><span class="extract">Feeds::begin</span></code> and get an ID; to end, call <code class="display"><span class="extract">Feeds::end</span></code>
with the corresponding ID back again.
</p>
<pre class="display">
<span class="constant">feed_t</span><span class="plain"> </span><span class="functiontext">Feeds::begin</span><span class="plain">(</span><span class="reserved">void</span><span class="plain">) {</span>
<span class="reserved">return</span><span class="plain"> (</span><span class="constant">feed_t</span><span class="plain">) </span><span class="identifier">lexer_wordcount</span><span class="plain">;</span>
<span class="plain">}</span>
<span class="reserved">wording</span><span class="plain"> </span><span class="functiontext">Feeds::end</span><span class="plain">(</span><span class="constant">feed_t</span><span class="plain"> </span><span class="identifier">id</span><span class="plain">) {</span>
<span class="reserved">return</span><span class="plain"> </span><span class="functiontext">Wordings::new</span><span class="plain">((</span><span class="reserved">int</span><span class="plain">) </span><span class="identifier">id</span><span class="plain">, </span><span class="identifier">lexer_wordcount</span><span class="plain">-1);</span>
<span class="plain">}</span>
</pre>
<p class="inwebparagraph"></p>
<p class="endnote">The function Feeds::begin is used in 2/wa (<a href="2-wa.html#SP7">&#167;7</a>), 4/prf (<a href="4-prf.html#SP53">&#167;53</a>).</p>
<p class="endnote">The function Feeds::end is used in 2/wa (<a href="2-wa.html#SP7">&#167;7</a>), 4/prf (<a href="4-prf.html#SP53">&#167;53</a>).</p>
<p class="inwebparagraph"><a id="SP4"></a><b>&#167;4. Feeding a feed. </b>Within a feed session, we can pass two sorts of text into the lexer: first,
raw strings.
</p>
<pre class="display">
<span class="reserved">wording</span><span class="plain"> </span><span class="functiontext">Feeds::feed_text</span><span class="plain">(</span><span class="identifier">wchar_t</span><span class="plain"> *</span><span class="identifier">text</span><span class="plain">) {</span>
<span class="reserved">return</span><span class="plain"> </span><span class="functiontext">Feeds::feed_text_full</span><span class="plain">(</span><span class="identifier">text</span><span class="plain">, </span><span class="identifier">FALSE</span><span class="plain">, </span><span class="identifier">NULL</span><span class="plain">);</span>
<span class="plain">}</span>
<span class="reserved">wording</span><span class="plain"> </span><span class="functiontext">Feeds::feed_stream</span><span class="plain">(</span><span class="identifier">text_stream</span><span class="plain"> *</span><span class="identifier">text</span><span class="plain">) {</span>
<span class="reserved">return</span><span class="plain"> </span><span class="functiontext">Feeds::feed_stream_full</span><span class="plain">(</span><span class="identifier">text</span><span class="plain">, </span><span class="identifier">FALSE</span><span class="plain">, </span><span class="identifier">NULL</span><span class="plain">);</span>
<span class="plain">}</span>
<span class="reserved">wording</span><span class="plain"> </span><span class="functiontext">Feeds::feed_text_expanding_strings</span><span class="plain">(</span><span class="identifier">wchar_t</span><span class="plain"> *</span><span class="identifier">text</span><span class="plain">) {</span>
<span class="reserved">return</span><span class="plain"> </span><span class="functiontext">Feeds::feed_text_full</span><span class="plain">(</span><span class="identifier">text</span><span class="plain">, </span><span class="identifier">TRUE</span><span class="plain">, </span><span class="identifier">NULL</span><span class="plain">);</span>
<span class="plain">}</span>
<span class="reserved">wording</span><span class="plain"> </span><span class="functiontext">Feeds::feed_stream_expanding_strings</span><span class="plain">(</span><span class="identifier">text_stream</span><span class="plain"> *</span><span class="identifier">text</span><span class="plain">) {</span>
<span class="reserved">return</span><span class="plain"> </span><span class="functiontext">Feeds::feed_stream_full</span><span class="plain">(</span><span class="identifier">text</span><span class="plain">, </span><span class="identifier">TRUE</span><span class="plain">, </span><span class="identifier">NULL</span><span class="plain">);</span>
<span class="plain">}</span>
<span class="reserved">wording</span><span class="plain"> </span><span class="functiontext">Feeds::feed_stream_punctuated</span><span class="plain">(</span><span class="identifier">text_stream</span><span class="plain"> *</span><span class="identifier">text</span><span class="plain">, </span><span class="identifier">wchar_t</span><span class="plain"> *</span><span class="identifier">pmarks</span><span class="plain">) {</span>
<span class="reserved">wording</span><span class="plain"> </span><span class="identifier">W</span><span class="plain"> = </span><span class="functiontext">Feeds::feed_stream_full</span><span class="plain">(</span><span class="identifier">text</span><span class="plain">, </span><span class="identifier">FALSE</span><span class="plain">, </span><span class="identifier">pmarks</span><span class="plain">);</span>
<span class="reserved">return</span><span class="plain"> </span><span class="identifier">W</span><span class="plain">;</span>
<span class="plain">}</span>
</pre>
<p class="inwebparagraph"></p>
<p class="endnote">The function Feeds::feed_text appears nowhere else.</p>
<p class="endnote">The function Feeds::feed_stream is used in 2/vcb (<a href="2-vcb.html#SP17">&#167;17</a>), 2/wa (<a href="2-wa.html#SP7">&#167;7</a>, <a href="2-wa.html#SP9">&#167;9</a>).</p>
<p class="endnote">The function Feeds::feed_text_expanding_strings appears nowhere else.</p>
<p class="endnote">The function Feeds::feed_stream_expanding_strings appears nowhere else.</p>
<p class="endnote">The function Feeds::feed_stream_punctuated is used in 4/prf (<a href="4-prf.html#SP26">&#167;26</a>, <a href="4-prf.html#SP54">&#167;54</a>).</p>
<p class="inwebparagraph"><a id="SP5"></a><b>&#167;5. </b>When done, we call <code class="display"><span class="extract">Vocabulary::identify_word_range</span></code>, because we are probably
running long after the initial vocabulary identification phase of Inform.
</p>
<pre class="display">
<span class="reserved">wording</span><span class="plain"> </span><span class="functiontext">Feeds::feed_text_full</span><span class="plain">(</span><span class="identifier">wchar_t</span><span class="plain"> *</span><span class="identifier">text</span><span class="plain">, </span><span class="reserved">int</span><span class="plain"> </span><span class="identifier">expand_strings</span><span class="plain">, </span><span class="identifier">wchar_t</span><span class="plain"> *</span><span class="identifier">nonstandard</span><span class="plain">) {</span>
<span class="reserved">source_location</span><span class="plain"> </span><span class="identifier">as_if_from_nowhere</span><span class="plain">;</span>
<span class="identifier">as_if_from_nowhere</span><span class="plain">.</span><span class="element">file_of_origin</span><span class="plain"> = </span><span class="identifier">NULL</span><span class="plain">;</span>
<span class="identifier">as_if_from_nowhere</span><span class="plain">.</span><span class="element">line_number</span><span class="plain"> = </span><span class="constant">1</span><span class="plain">;</span>
<span class="functiontext">Lexer::feed_begins</span><span class="plain">(</span><span class="identifier">as_if_from_nowhere</span><span class="plain">);</span>
<span class="identifier">lexer_divide_strings_at_text_substitutions</span><span class="plain"> = </span><span class="identifier">expand_strings</span><span class="plain">;</span>
<span class="identifier">lexer_allow_I6_escapes</span><span class="plain"> = </span><span class="identifier">TRUE</span><span class="plain">;</span>
<span class="reserved">if</span><span class="plain"> (</span><span class="identifier">nonstandard</span><span class="plain">) {</span>
<span class="identifier">lexer_punctuation_marks</span><span class="plain"> = </span><span class="identifier">nonstandard</span><span class="plain">;</span>
<span class="identifier">lexer_allow_I6_escapes</span><span class="plain"> = </span><span class="identifier">FALSE</span><span class="plain">;</span>
<span class="plain">} </span><span class="reserved">else</span>
<span class="identifier">lexer_punctuation_marks</span><span class="plain"> = </span><span class="constant">STANDARD_PUNCTUATION_MARKS</span><span class="plain">;</span>
<span class="reserved">for</span><span class="plain"> (</span><span class="reserved">int</span><span class="plain"> </span><span class="identifier">i</span><span class="plain">=0; </span><span class="identifier">text</span><span class="plain">[</span><span class="identifier">i</span><span class="plain">] != </span><span class="constant">0</span><span class="plain">; </span><span class="identifier">i</span><span class="plain">++) {</span>
<span class="reserved">int</span><span class="plain"> </span><span class="identifier">last_cr</span><span class="plain">, </span><span class="identifier">cr</span><span class="plain">, </span><span class="identifier">next_cr</span><span class="plain">;</span>
<span class="reserved">if</span><span class="plain"> (</span><span class="identifier">i</span><span class="plain"> &gt; </span><span class="constant">0</span><span class="plain">) </span><span class="identifier">last_cr</span><span class="plain"> = </span><span class="identifier">text</span><span class="plain">[</span><span class="identifier">i</span><span class="plain">-1]; </span><span class="reserved">else</span><span class="plain"> </span><span class="identifier">last_cr</span><span class="plain"> = </span><span class="identifier">EOF</span><span class="plain">;</span>
<span class="identifier">cr</span><span class="plain"> = </span><span class="identifier">text</span><span class="plain">[</span><span class="identifier">i</span><span class="plain">];</span>
<span class="reserved">if</span><span class="plain"> (</span><span class="identifier">cr</span><span class="plain"> != </span><span class="constant">0</span><span class="plain">) </span><span class="identifier">next_cr</span><span class="plain"> = </span><span class="identifier">text</span><span class="plain">[</span><span class="identifier">i</span><span class="plain">+1]; </span><span class="reserved">else</span><span class="plain"> </span><span class="identifier">next_cr</span><span class="plain"> = </span><span class="identifier">EOF</span><span class="plain">;</span>
<span class="functiontext">Lexer::feed_triplet</span><span class="plain">(</span><span class="identifier">last_cr</span><span class="plain">, </span><span class="identifier">cr</span><span class="plain">, </span><span class="identifier">next_cr</span><span class="plain">);</span>
<span class="plain">}</span>
<span class="reserved">wording</span><span class="plain"> </span><span class="identifier">LEXW</span><span class="plain"> = </span><span class="functiontext">Lexer::feed_ends</span><span class="plain">(</span><span class="identifier">FALSE</span><span class="plain">, </span><span class="identifier">NULL</span><span class="plain">);</span>
<span class="functiontext">Vocabulary::identify_word_range</span><span class="plain">(</span><span class="identifier">LEXW</span><span class="plain">);</span>
<span class="reserved">return</span><span class="plain"> </span><span class="identifier">LEXW</span><span class="plain">;</span>
<span class="plain">}</span>
<span class="reserved">wording</span><span class="plain"> </span><span class="functiontext">Feeds::feed_stream_full</span><span class="plain">(</span><span class="identifier">text_stream</span><span class="plain"> *</span><span class="identifier">text</span><span class="plain">, </span><span class="reserved">int</span><span class="plain"> </span><span class="identifier">expand_strings</span><span class="plain">, </span><span class="identifier">wchar_t</span><span class="plain"> *</span><span class="identifier">nonstandard</span><span class="plain">) {</span>
<span class="reserved">source_location</span><span class="plain"> </span><span class="identifier">as_if_from_nowhere</span><span class="plain">;</span>
<span class="identifier">as_if_from_nowhere</span><span class="plain">.</span><span class="element">file_of_origin</span><span class="plain"> = </span><span class="identifier">NULL</span><span class="plain">;</span>
<span class="identifier">as_if_from_nowhere</span><span class="plain">.</span><span class="element">line_number</span><span class="plain"> = </span><span class="constant">1</span><span class="plain">;</span>
<span class="functiontext">Lexer::feed_begins</span><span class="plain">(</span><span class="identifier">as_if_from_nowhere</span><span class="plain">);</span>
<span class="identifier">lexer_divide_strings_at_text_substitutions</span><span class="plain"> = </span><span class="identifier">expand_strings</span><span class="plain">;</span>
<span class="identifier">lexer_allow_I6_escapes</span><span class="plain"> = </span><span class="identifier">TRUE</span><span class="plain">;</span>
<span class="reserved">if</span><span class="plain"> (</span><span class="identifier">nonstandard</span><span class="plain">) {</span>
<span class="identifier">lexer_punctuation_marks</span><span class="plain"> = </span><span class="identifier">nonstandard</span><span class="plain">;</span>
<span class="identifier">lexer_allow_I6_escapes</span><span class="plain"> = </span><span class="identifier">FALSE</span><span class="plain">;</span>
<span class="plain">} </span><span class="reserved">else</span>
<span class="identifier">lexer_punctuation_marks</span><span class="plain"> = </span><span class="constant">STANDARD_PUNCTUATION_MARKS</span><span class="plain">;</span>
<span class="reserved">for</span><span class="plain"> (</span><span class="reserved">int</span><span class="plain"> </span><span class="identifier">i</span><span class="plain">=0, </span><span class="identifier">L</span><span class="plain">=</span><span class="identifier">Str::len</span><span class="plain">(</span><span class="identifier">text</span><span class="plain">); </span><span class="identifier">i</span><span class="plain">&lt;</span><span class="identifier">L</span><span class="plain">; </span><span class="identifier">i</span><span class="plain">++) {</span>
<span class="reserved">int</span><span class="plain"> </span><span class="identifier">last_cr</span><span class="plain">, </span><span class="identifier">cr</span><span class="plain">, </span><span class="identifier">next_cr</span><span class="plain">;</span>
<span class="reserved">if</span><span class="plain"> (</span><span class="identifier">i</span><span class="plain"> &gt; </span><span class="constant">0</span><span class="plain">) </span><span class="identifier">last_cr</span><span class="plain"> = </span><span class="identifier">Str::get_at</span><span class="plain">(</span><span class="identifier">text</span><span class="plain">, </span><span class="identifier">i</span><span class="plain">-1); </span><span class="reserved">else</span><span class="plain"> </span><span class="identifier">last_cr</span><span class="plain"> = </span><span class="identifier">EOF</span><span class="plain">;</span>
<span class="identifier">cr</span><span class="plain"> = </span><span class="identifier">Str::get_at</span><span class="plain">(</span><span class="identifier">text</span><span class="plain">, </span><span class="identifier">i</span><span class="plain">);</span>
<span class="reserved">if</span><span class="plain"> (</span><span class="identifier">cr</span><span class="plain"> != </span><span class="constant">0</span><span class="plain">) </span><span class="identifier">next_cr</span><span class="plain"> = </span><span class="identifier">Str::get_at</span><span class="plain">(</span><span class="identifier">text</span><span class="plain">, </span><span class="identifier">i</span><span class="plain">+1); </span><span class="reserved">else</span><span class="plain"> </span><span class="identifier">next_cr</span><span class="plain"> = </span><span class="identifier">EOF</span><span class="plain">;</span>
<span class="functiontext">Lexer::feed_triplet</span><span class="plain">(</span><span class="identifier">last_cr</span><span class="plain">, </span><span class="identifier">cr</span><span class="plain">, </span><span class="identifier">next_cr</span><span class="plain">);</span>
<span class="plain">}</span>
<span class="reserved">wording</span><span class="plain"> </span><span class="identifier">LEXW</span><span class="plain"> = </span><span class="functiontext">Lexer::feed_ends</span><span class="plain">(</span><span class="identifier">FALSE</span><span class="plain">, </span><span class="identifier">NULL</span><span class="plain">);</span>
<span class="functiontext">Vocabulary::identify_word_range</span><span class="plain">(</span><span class="identifier">LEXW</span><span class="plain">);</span>
<span class="reserved">return</span><span class="plain"> </span><span class="identifier">LEXW</span><span class="plain">;</span>
<span class="plain">}</span>
</pre>
<p class="inwebparagraph"></p>
<p class="endnote">The function Feeds::feed_text_full is used in <a href="#SP4">&#167;4</a>, 4/prf (<a href="4-prf.html#SP29_1">&#167;29.1</a>).</p>
<p class="endnote">The function Feeds::feed_stream_full is used in <a href="#SP4">&#167;4</a>.</p>
<p class="inwebparagraph"><a id="SP6"></a><b>&#167;6. </b>The only other possible action is to splice:
</p>
<pre class="display">
<span class="reserved">wording</span><span class="plain"> </span><span class="functiontext">Feeds::feed_wording</span><span class="plain">(</span><span class="reserved">wording</span><span class="plain"> </span><span class="identifier">W</span><span class="plain">) {</span>
<span class="reserved">return</span><span class="plain"> </span><span class="functiontext">Lexer::splice_words</span><span class="plain">(</span><span class="identifier">W</span><span class="plain">);</span>
<span class="plain">}</span>
</pre>
<p class="inwebparagraph"></p>
<p class="endnote">The function Feeds::feed_wording appears nowhere else.</p>
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