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<a href="#pub-methods">Public Member Functions</a> </div>
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<h1>gri_lfsr Class Reference<div class="ingroups"><a class="el" href="group__misc.html">Miscellaneous</a></div></h1> </div>
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<p>Fibonacci Linear Feedback Shift Register using specified polynomial maskGenerates a maximal length pseudo-random sequence of length 2^degree-1.
<a href="#_details">More...</a></p>
<p><code>#include <<a class="el" href="gri__lfsr_8h_source.html">gri_lfsr.h</a>></code></p>
<p><a href="classgri__lfsr-members.html">List of all members.</a></p>
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Public Member Functions</h2></td></tr>
<tr><td class="memItemLeft" align="right" valign="top"> </td><td class="memItemRight" valign="bottom"><a class="el" href="classgri__lfsr.html#a9d75c0d9937724f0784ccbae11114950">gri_lfsr</a> (uint32_t mask, uint32_t seed, uint32_t reg_len)</td></tr>
<tr><td class="memItemLeft" align="right" valign="top">unsigned char </td><td class="memItemRight" valign="bottom"><a class="el" href="classgri__lfsr.html#ab48a354944fe18d9d261be11aa558b0f">next_bit</a> ()</td></tr>
<tr><td class="memItemLeft" align="right" valign="top">unsigned char </td><td class="memItemRight" valign="bottom"><a class="el" href="classgri__lfsr.html#afd1989999dcc0306a1b73f5822d38357">next_bit_scramble</a> (unsigned char input)</td></tr>
<tr><td class="memItemLeft" align="right" valign="top">unsigned char </td><td class="memItemRight" valign="bottom"><a class="el" href="classgri__lfsr.html#af23672b2652cbfa71cd34d99b5b3edd2">next_bit_descramble</a> (unsigned char input)</td></tr>
<tr><td class="memItemLeft" align="right" valign="top">void </td><td class="memItemRight" valign="bottom"><a class="el" href="classgri__lfsr.html#af04de11f558b49d79265df6f32f343c1">pre_shift</a> (int num)</td></tr>
<tr><td class="memItemLeft" align="right" valign="top">int </td><td class="memItemRight" valign="bottom"><a class="el" href="classgri__lfsr.html#ab11f525cf4205ac9e77ed3b23d353812">mask</a> () const </td></tr>
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<hr/><a name="_details"></a><h2>Detailed Description</h2>
<div class="textblock"><p>Fibonacci Linear Feedback Shift Register using specified polynomial mask</p>
<p>Generates a maximal length pseudo-random sequence of length 2^degree-1. </p>
<p>Constructor: gri_lfsr(int mask, int seed, int reg_len);</p>
<p>mask - polynomial coefficients representing the locations of feedback taps from a shift register which are xor'ed together to form the new high order bit.</p>
<p>Some common masks might be: x^4 + x^3 + x^0 = 0x19 x^5 + x^3 + x^0 = 0x29 x^6 + x^5 + x^0 = 0x61</p>
<p>seed - the initialization vector placed into the register durring initialization. Low order bit corresponds to x^0 coefficient -- the first to be shifted as output.</p>
<p>reg_len - specifies the length of the feedback shift register to be used. Durring each iteration, the register is rightshifted one and the new bit is placed in bit reg_len. reg_len should generally be at least order(mask) + 1</p>
<p>see <a href="http://en.wikipedia.org/wiki/Linear_feedback_shift_register">http://en.wikipedia.org/wiki/Linear_feedback_shift_register</a> for more explanation.</p>
<p><a class="el" href="classgri__lfsr.html#ab48a354944fe18d9d261be11aa558b0f">next_bit()</a> - Standard LFSR operation</p>
<p>Perform one cycle of the LFSR. The output bit is taken from the shift register LSB. The shift register MSB is assigned from the modulo 2 sum of the masked shift register.</p>
<p><a class="el" href="classgri__lfsr.html#afd1989999dcc0306a1b73f5822d38357">next_bit_scramble(unsigned char input)</a> - Scramble an input stream</p>
<p>Perform one cycle of the LFSR. The output bit is taken from the shift register LSB. The shift register MSB is assigned from the modulo 2 sum of the masked shift register and the input LSB.</p>
<p><a class="el" href="classgri__lfsr.html#af23672b2652cbfa71cd34d99b5b3edd2">next_bit_descramble(unsigned char input)</a> - Descramble an input stream</p>
<p>Perform one cycle of the LFSR. The output bit is taken from the modulo 2 sum of the masked shift register and the input LSB. The shift register MSB is assigned from the LSB of the input.</p>
<p>See <a href="http://en.wikipedia.org/wiki/Scrambler">http://en.wikipedia.org/wiki/Scrambler</a> for operation of these last two functions (see multiplicative scrambler.) </p>
</div><hr/><h2>Constructor & Destructor Documentation</h2>
<a class="anchor" id="a9d75c0d9937724f0784ccbae11114950"></a><!-- doxytag: member="gri_lfsr::gri_lfsr" ref="a9d75c0d9937724f0784ccbae11114950" args="(uint32_t mask, uint32_t seed, uint32_t reg_len)" -->
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<td class="memname">gri_lfsr::gri_lfsr </td>
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<td class="paramtype">uint32_t </td>
<td class="paramname"><em>mask</em>, </td>
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<td class="paramtype">uint32_t </td>
<td class="paramname"><em>seed</em>, </td>
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<td class="paramtype">uint32_t </td>
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<td>)</td>
<td></td><td><code> [inline]</code></td>
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<hr/><h2>Member Function Documentation</h2>
<a class="anchor" id="ab11f525cf4205ac9e77ed3b23d353812"></a><!-- doxytag: member="gri_lfsr::mask" ref="ab11f525cf4205ac9e77ed3b23d353812" args="() const " -->
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<td class="memname">int gri_lfsr::mask </td>
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<td> const<code> [inline]</code></td>
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<a class="anchor" id="ab48a354944fe18d9d261be11aa558b0f"></a><!-- doxytag: member="gri_lfsr::next_bit" ref="ab48a354944fe18d9d261be11aa558b0f" args="()" -->
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<td class="memname">unsigned char gri_lfsr::next_bit </td>
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<p>Referenced by <a class="el" href="classgri__lfsr.html#af04de11f558b49d79265df6f32f343c1">pre_shift()</a>.</p>
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<a class="anchor" id="af23672b2652cbfa71cd34d99b5b3edd2"></a><!-- doxytag: member="gri_lfsr::next_bit_descramble" ref="af23672b2652cbfa71cd34d99b5b3edd2" args="(unsigned char input)" -->
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<td class="memname">unsigned char gri_lfsr::next_bit_descramble </td>
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<td class="paramtype">unsigned char </td>
<td class="paramname"><em>input</em></td><td>)</td>
<td><code> [inline]</code></td>
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<a class="anchor" id="afd1989999dcc0306a1b73f5822d38357"></a><!-- doxytag: member="gri_lfsr::next_bit_scramble" ref="afd1989999dcc0306a1b73f5822d38357" args="(unsigned char input)" -->
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<td class="memname">unsigned char gri_lfsr::next_bit_scramble </td>
<td>(</td>
<td class="paramtype">unsigned char </td>
<td class="paramname"><em>input</em></td><td>)</td>
<td><code> [inline]</code></td>
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<a class="anchor" id="af04de11f558b49d79265df6f32f343c1"></a><!-- doxytag: member="gri_lfsr::pre_shift" ref="af04de11f558b49d79265df6f32f343c1" args="(int num)" -->
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<td class="memname">void gri_lfsr::pre_shift </td>
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<td class="paramname"><em>num</em></td><td>)</td>
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<p>Rotate the register through x number of bits where we are just throwing away the results to get queued up correctly </p>
<p>References <a class="el" href="classgri__lfsr.html#ab48a354944fe18d9d261be11aa558b0f">next_bit()</a>.</p>
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<hr/>The documentation for this class was generated from the following file:<ul>
<li><a class="el" href="gri__lfsr_8h_source.html">gri_lfsr.h</a></li>
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