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<a class="dropdown-item" tabindex="-1" href="Extended9Blockchain.html#"><b>Chapter 1</b></a>
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<a class="dropdown-item" href="IntroConcSysOverview.html"> 1.1. Introduction to Concurrent Systems</a>
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<a class="dropdown-item" href="SequenceModels.html"> 1.6. Sequence Models in UML</a>
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<a class="dropdown-item" href="StateModelImplementation.html"> 1.7. Extended Example: State Model Implementation</a>
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<a class="dropdown-item disabled"><b>Chapter 2</b></a>
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<a class="dropdown-item" href="ProcessesOverview.html"> 2.1. Processes and OS Basics</a>
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<a class="dropdown-item" href="IPCOverview.html"> 3.1. Concurrency with IPC</a>
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<a class="dropdown-item" href="IPCSems.html"> 3.8. Semaphores</a>
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<a class="dropdown-item" href="SynchOverview.html"> 7.1. Synchronization Primitives</a>
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<a class="dropdown-item" href="SynchProblemsOverview.html"> 8.1. Synchronization Patterns and Problems</a>
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<a class="dropdown-item" href="ProdCons.html"> 8.3. Producer-Consumer Problem</a>
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<a class="dropdown-item" href="ReadWrite.html"> 8.4. Readers-Writers Problem</a>
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<a class="dropdown-item" href="CigSmokers.html"> 8.6. Cigarette Smokers Problem and the Limits of Semaphores and Locks</a>
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<a class="dropdown-item" href="ParallelDistributedOverview.html"> 9.1. Parallel and Distributed Systems</a>
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<a class="dropdown-item" href="ParVConc.html"> 9.2. Parallelism vs. Concurrency</a>
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<a class="dropdown-item" href="Scaling.html"> 9.4. Limits of Parallelism and Scaling</a>
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<a class="dropdown-item" href="DistDataStorage.html"> 9.6. Reliable Data Storage and Location</a>
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<a class="dropdown-item" href="DistConsensus.html"> 9.7. Consensus in Distributed Systems</a>
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<a class="dropdown-item" href="Extended9Blockchain.html"> 9.8. Extended Example: Blockchain Proof-of-Work</a>
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<a class="dropdown-item" href="CLangOverview.html"> A.1. C Language Reintroduction</a>
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<a class="dropdown-item" href="Debugging.html"> A.2. Documentation and Debugging</a>
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<a class="dropdown-item" href="BasicTypes.html"> A.3. Basic Types and Pointers</a>
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<script>ODSA.SETTINGS.DISP_MOD_COMP = true;ODSA.SETTINGS.MODULE_NAME = "Extended9Blockchain";ODSA.SETTINGS.MODULE_LONG_NAME = "Extended Example: Blockchain Proof-of-Work";ODSA.SETTINGS.MODULE_CHAPTER = "Parallel and Distributed Systems"; ODSA.SETTINGS.BUILD_DATE = "2021-06-01 15:31:51"; ODSA.SETTINGS.BUILD_CMAP = false;JSAV_OPTIONS['lang']='en';JSAV_EXERCISE_OPTIONS['code']='java';</script><div class="section" id="extended-example-blockchain-proof-of-work">
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<h1>9.8. Extended Example: Blockchain Proof-of-Work<a class="headerlink" href="Extended9Blockchain.html#extended-example-blockchain-proof-of-work" title="Permalink to this headline">¶</a></h1>
|
||
<p>A blockchain is a sequence of messages that create a verifiable ordering of
|
||
events. Blockchains can be used in a variety of applications, such as
|
||
cryptocurrency (Bitcoin) or other distributed database ledgers. One key idea
|
||
behind a blockchain is that new entries are difficult to generate. A common
|
||
technique is to require a proof-of-work calculation, such as finding a string
|
||
that produces a cryptographic hash value with several leading 0s.</p>
|
||
<p>Consider the example output below. Each line contains a message index (0, 1, 2,
|
||
…) followed by the previous line’s hash value (<code class="docutils literal notranslate"><span class="pre">0000...</span></code>, <code class="docutils literal notranslate"><span class="pre">f74d...</span></code>, and so on), a
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||
timestamp (omitted for brevity), then a log message (“Genesis Block”). The line
|
||
then ends with an integer value (called a <em>nonce</em>), such as <code class="docutils literal notranslate"><span class="pre">0000</span></code>, <code class="docutils literal notranslate"><span class="pre">22d75</span></code>, and
|
||
<code class="docutils literal notranslate"><span class="pre">6ea</span></code> as shown. The entire line ending at the nonce is then used as input to a
|
||
cryptographic hash function. If the output of the hash does not begin with 0s,
|
||
the nonce is increased and the line is re-hashed. For instance, the second line
|
||
required 142,709 (<code class="docutils literal notranslate"><span class="pre">0x22d75</span></code>) attempts before the hash output began with 0s. Once
|
||
this entry is found, it can be added to the blockchain.</p>
|
||
<div class="highlight-none border border-dark rounded-lg bg-light px-0 mb-3 notranslate"><table class="highlighttable"><tr><td class="linenos px-0 mx-0"><div class="linenodiv"><pre class="mb-0">1
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8</pre></div></td><td class="code"><div class="highlight bg-light"><pre class="mb-0"><span></span>$ ./blockchain
|
||
Here is the blockchain:
|
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...0 00000000... [...] Genesis Block ...000000 f74d3a10...
|
||
...1 f74d3a10... [...] Data message 1 ...022d75 0000b38b...
|
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...2 0000b38b... [...] Data message 2 ...0006ea 0000e2c4...
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...3 0000e2c4... [...] Data message 3 ...00be80 00002c45...
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...4 00002c45... [...] Data message 4 ...019e63 0000a65e...
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...5 0000a65e... [...] Data message 5 ...0188a8 0000cb6f...
|
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</pre></div>
|
||
</td></tr></table></div>
|
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<p>The second field in each line is the previous line’s hash output, which serves
|
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the purpose of declaring that the new line is the only legitimate successor of
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the previous line. That is, each line explicitly ties itself to the previous
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line by including the previous line’s hash in the input. Note that the first
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line, often called a <em>Genesis block</em>, is special, as it does not follow any
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entry. As such, a nonce of 0 is often used for this value and the hash value
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does not need to begin with 0s. In this extended example, we use SHA-1 as a
|
||
cryptographic hash function simply to make the search more efficient. <strong>In
|
||
practice, SHA-1 is considered insecure and should not be use for applications
|
||
like this</strong>.</p>
|
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274</pre></div></td><td class="code"><div class="highlight bg-light"><pre class="mb-0"><span></span><span class="cp">#include</span> <span class="cpf"><assert.h></span><span class="cp"></span>
|
||
<span class="cp">#include</span> <span class="cpf"><inttypes.h></span><span class="cp"></span>
|
||
<span class="cp">#include</span> <span class="cpf"><openssl/sha.h></span><span class="cp"></span>
|
||
<span class="cp">#include</span> <span class="cpf"><pthread.h></span><span class="cp"></span>
|
||
<span class="cp">#include</span> <span class="cpf"><stdbool.h></span><span class="cp"></span>
|
||
<span class="cp">#include</span> <span class="cpf"><stdint.h></span><span class="cp"></span>
|
||
<span class="cp">#include</span> <span class="cpf"><stdio.h></span><span class="cp"></span>
|
||
<span class="cp">#include</span> <span class="cpf"><stdlib.h></span><span class="cp"></span>
|
||
<span class="cp">#include</span> <span class="cpf"><string.h></span><span class="cp"></span>
|
||
<span class="cp">#include</span> <span class="cpf"><time.h></span><span class="cp"></span>
|
||
|
||
<span class="cp">#define ASCTIME_LENGTH 24</span>
|
||
<span class="cp">#define BLOCKCHAIN_ZEROES 3</span>
|
||
|
||
<span class="kt">char</span> <span class="o">*</span> <span class="nf">construct_block</span> <span class="p">(</span><span class="kt">uint64_t</span><span class="p">,</span> <span class="kt">char</span> <span class="o">*</span><span class="p">,</span> <span class="k">struct</span> <span class="n">tm</span> <span class="o">*</span><span class="p">,</span>
|
||
<span class="kt">char</span> <span class="o">*</span><span class="p">,</span> <span class="kt">size_t</span><span class="p">,</span> <span class="kt">uint64_t</span><span class="p">,</span> <span class="kt">size_t</span> <span class="o">*</span><span class="p">);</span>
|
||
<span class="kt">char</span> <span class="o">*</span> <span class="nf">create_genesis_block</span> <span class="p">(</span><span class="kt">void</span><span class="p">);</span>
|
||
<span class="kt">char</span> <span class="o">*</span> <span class="nf">hash_to_string</span> <span class="p">(</span><span class="kt">uint8_t</span> <span class="o">*</span><span class="n">hash</span><span class="p">);</span>
|
||
<span class="kt">char</span> <span class="o">*</span> <span class="nf">append_block</span> <span class="p">(</span><span class="kt">char</span> <span class="o">*</span><span class="p">,</span> <span class="kt">char</span> <span class="o">*</span><span class="p">,</span> <span class="kt">size_t</span><span class="p">);</span>
|
||
|
||
<span class="kt">int</span>
|
||
<span class="nf">main</span> <span class="p">(</span><span class="kt">void</span><span class="p">)</span>
|
||
<span class="p">{</span>
|
||
<span class="kt">size_t</span> <span class="n">number_of_threads</span> <span class="o">=</span> <span class="mi">4</span><span class="p">;</span>
|
||
<span class="kt">size_t</span> <span class="n">number_of_blocks</span> <span class="o">=</span> <span class="mi">10</span><span class="p">;</span>
|
||
|
||
<span class="cm">/* Generate the blockchain pointers and create genesis block */</span>
|
||
<span class="kt">char</span> <span class="o">*</span><span class="n">blockchain</span><span class="p">[</span><span class="n">number_of_blocks</span><span class="p">];</span>
|
||
<span class="n">memset</span> <span class="p">(</span><span class="n">blockchain</span><span class="p">,</span> <span class="mi">0</span><span class="p">,</span> <span class="k">sizeof</span> <span class="p">(</span><span class="n">blockchain</span><span class="p">));</span>
|
||
<span class="n">blockchain</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span> <span class="o">=</span> <span class="n">create_genesis_block</span> <span class="p">();</span>
|
||
|
||
<span class="cm">/* Use a generic message to append each time */</span>
|
||
<span class="kt">char</span> <span class="o">*</span><span class="n">message</span> <span class="o">=</span> <span class="n">calloc</span> <span class="p">(</span><span class="mi">50</span><span class="p">,</span> <span class="k">sizeof</span> <span class="p">(</span><span class="kt">char</span><span class="p">));</span>
|
||
<span class="kt">size_t</span> <span class="n">i</span><span class="p">;</span>
|
||
<span class="k">for</span> <span class="p">(</span><span class="n">i</span> <span class="o">=</span> <span class="mi">1</span><span class="p">;</span> <span class="n">i</span> <span class="o"><</span> <span class="n">number_of_blocks</span><span class="p">;</span> <span class="n">i</span><span class="o">++</span><span class="p">)</span>
|
||
<span class="p">{</span>
|
||
<span class="n">strncpy</span> <span class="p">(</span><span class="n">message</span><span class="p">,</span> <span class="s">"Data message "</span><span class="p">,</span> <span class="mi">50</span><span class="p">);</span>
|
||
<span class="n">snprintf</span> <span class="p">(</span><span class="n">message</span> <span class="o">+</span> <span class="n">strlen</span> <span class="p">(</span><span class="n">message</span><span class="p">),</span> <span class="mi">50</span> <span class="o">-</span> <span class="n">strlen</span> <span class="p">(</span><span class="n">message</span><span class="p">),</span> <span class="s">"%zd"</span><span class="p">,</span> <span class="n">i</span><span class="p">);</span>
|
||
<span class="n">blockchain</span><span class="p">[</span><span class="n">i</span><span class="p">]</span> <span class="o">=</span>
|
||
<span class="n">append_block</span> <span class="p">(</span><span class="n">message</span><span class="p">,</span> <span class="n">blockchain</span><span class="p">[</span><span class="n">i</span><span class="o">-</span><span class="mi">1</span><span class="p">],</span> <span class="n">number_of_threads</span><span class="p">);</span>
|
||
<span class="p">}</span>
|
||
<span class="n">free</span> <span class="p">(</span><span class="n">message</span><span class="p">);</span>
|
||
|
||
<span class="cm">/* Print the results of the computations */</span>
|
||
<span class="n">printf</span> <span class="p">(</span><span class="s">"Here is the blockchain:</span><span class="se">\n</span><span class="s">"</span><span class="p">);</span>
|
||
<span class="k">for</span> <span class="p">(</span><span class="n">i</span> <span class="o">=</span> <span class="mi">0</span><span class="p">;</span> <span class="n">i</span> <span class="o"><</span> <span class="n">number_of_blocks</span><span class="p">;</span> <span class="n">i</span><span class="o">++</span><span class="p">)</span>
|
||
<span class="p">{</span>
|
||
<span class="n">printf</span> <span class="p">(</span><span class="s">" %s</span><span class="se">\n</span><span class="s">"</span><span class="p">,</span> <span class="n">blockchain</span><span class="p">[</span><span class="n">i</span><span class="p">]);</span>
|
||
<span class="n">free</span> <span class="p">(</span><span class="n">blockchain</span><span class="p">[</span><span class="n">i</span><span class="p">]);</span>
|
||
<span class="p">}</span>
|
||
|
||
<span class="k">return</span> <span class="n">EXIT_SUCCESS</span><span class="p">;</span>
|
||
<span class="p">}</span>
|
||
|
||
<span class="cm">/* Parameters for each copy of the mining thread */</span>
|
||
<span class="k">struct</span> <span class="n">mining_params</span> <span class="p">{</span>
|
||
<span class="kt">char</span> <span class="o">*</span><span class="n">block</span><span class="p">;</span>
|
||
<span class="kt">size_t</span> <span class="n">blocklen</span><span class="p">;</span>
|
||
<span class="kt">uint64_t</span> <span class="n">nonce</span><span class="p">;</span>
|
||
<span class="kt">size_t</span> <span class="n">attempts</span><span class="p">;</span>
|
||
<span class="kt">bool</span> <span class="n">success</span><span class="p">;</span>
|
||
<span class="p">};</span>
|
||
|
||
<span class="cm">/* Blockchain mining thread. Each instance of this thread starts</span>
|
||
<span class="cm"> with a block string to work with. The string contains a nonce</span>
|
||
<span class="cm"> that is iteratively incremented until the string hashes to the</span>
|
||
<span class="cm"> correct structure (leading zeroes) or the thread runs out of</span>
|
||
<span class="cm"> attempts. */</span>
|
||
<span class="kt">void</span> <span class="o">*</span>
|
||
<span class="nf">mining_thread</span> <span class="p">(</span><span class="kt">void</span> <span class="o">*</span> <span class="n">_params</span><span class="p">)</span>
|
||
<span class="p">{</span>
|
||
<span class="k">struct</span> <span class="n">mining_params</span> <span class="o">*</span><span class="n">params</span> <span class="o">=</span> <span class="p">(</span><span class="k">struct</span> <span class="n">mining_params</span> <span class="o">*</span><span class="p">)</span> <span class="n">_params</span><span class="p">;</span>
|
||
<span class="kt">char</span> <span class="o">*</span><span class="n">block</span> <span class="o">=</span> <span class="n">params</span><span class="o">-></span><span class="n">block</span><span class="p">;</span>
|
||
<span class="kt">char</span> <span class="o">*</span><span class="n">nonce_loc</span> <span class="o">=</span> <span class="n">block</span> <span class="o">+</span> <span class="n">strlen</span> <span class="p">(</span><span class="n">block</span><span class="p">)</span> <span class="o">-</span> <span class="mi">16</span><span class="p">;</span>
|
||
<span class="kt">size_t</span> <span class="n">count</span> <span class="o">=</span> <span class="mi">0</span><span class="p">;</span>
|
||
<span class="kt">uint8_t</span> <span class="n">hash</span><span class="p">[</span><span class="n">SHA_DIGEST_LENGTH</span><span class="p">];</span>
|
||
|
||
<span class="k">while</span> <span class="p">(</span><span class="n">count</span> <span class="o"><</span> <span class="n">params</span><span class="o">-></span><span class="n">attempts</span><span class="p">)</span>
|
||
<span class="p">{</span>
|
||
<span class="cm">/* Update nonce in the string and re-calculate the hash */</span>
|
||
<span class="n">snprintf</span> <span class="p">(</span><span class="n">nonce_loc</span><span class="p">,</span> <span class="mi">17</span><span class="p">,</span> <span class="s">"%016"</span> <span class="n">PRIx64</span><span class="p">,</span> <span class="n">params</span><span class="o">-></span><span class="n">nonce</span><span class="o">++</span><span class="p">);</span>
|
||
<span class="n">memset</span> <span class="p">(</span><span class="n">hash</span><span class="p">,</span> <span class="mi">0</span><span class="p">,</span> <span class="n">SHA_DIGEST_LENGTH</span><span class="p">);</span>
|
||
<span class="kt">unsigned</span> <span class="kt">char</span> <span class="o">*</span><span class="n">md</span> <span class="o">=</span>
|
||
<span class="n">SHA1</span> <span class="p">((</span><span class="kt">unsigned</span> <span class="kt">char</span> <span class="o">*</span><span class="p">)</span><span class="n">block</span><span class="p">,</span> <span class="p">(</span><span class="kt">unsigned</span> <span class="kt">long</span><span class="p">)</span> <span class="n">params</span><span class="o">-></span><span class="n">blocklen</span><span class="p">,</span> <span class="n">hash</span><span class="p">);</span>
|
||
|
||
<span class="cm">/* Check to see if the hash begins with the desired number of</span>
|
||
<span class="cm"> leading zeroes */</span>
|
||
<span class="kt">bool</span> <span class="n">zeroes</span> <span class="o">=</span> <span class="nb">true</span><span class="p">;</span>
|
||
<span class="kt">int</span> <span class="n">i</span> <span class="o">=</span> <span class="mi">0</span><span class="p">;</span>
|
||
<span class="k">for</span> <span class="p">(</span><span class="n">i</span> <span class="o">=</span> <span class="mi">0</span><span class="p">;</span> <span class="n">i</span> <span class="o"><</span> <span class="n">BLOCKCHAIN_ZEROES</span><span class="p">;</span> <span class="n">i</span><span class="o">++</span><span class="p">)</span>
|
||
<span class="k">if</span> <span class="p">(</span><span class="n">md</span><span class="p">[</span><span class="n">i</span><span class="p">]</span> <span class="o">!=</span> <span class="mi">0</span><span class="p">)</span> <span class="n">zeroes</span> <span class="o">=</span> <span class="nb">false</span><span class="p">;</span>
|
||
|
||
<span class="cm">/* If the leading zeroes match, update the block and exit */</span>
|
||
<span class="k">if</span> <span class="p">(</span><span class="n">zeroes</span><span class="p">)</span>
|
||
<span class="p">{</span>
|
||
<span class="kt">char</span> <span class="o">*</span><span class="n">hash_str</span> <span class="o">=</span> <span class="n">hash_to_string</span> <span class="p">(</span><span class="n">md</span><span class="p">);</span>
|
||
<span class="n">block</span><span class="p">[</span><span class="n">strlen</span> <span class="p">(</span><span class="n">block</span><span class="p">)]</span> <span class="o">=</span> <span class="sc">' '</span><span class="p">;</span>
|
||
<span class="n">strncat</span> <span class="p">(</span><span class="n">block</span><span class="p">,</span> <span class="n">hash_str</span><span class="p">,</span> <span class="n">SHA_DIGEST_LENGTH</span> <span class="o">*</span> <span class="mi">2</span><span class="p">);</span>
|
||
<span class="n">free</span> <span class="p">(</span><span class="n">hash_str</span><span class="p">);</span>
|
||
<span class="n">params</span><span class="o">-></span><span class="n">success</span> <span class="o">=</span> <span class="nb">true</span><span class="p">;</span>
|
||
<span class="n">pthread_exit</span> <span class="p">(</span><span class="nb">NULL</span><span class="p">);</span>
|
||
<span class="p">}</span>
|
||
<span class="n">count</span><span class="o">++</span><span class="p">;</span>
|
||
<span class="p">}</span>
|
||
<span class="n">pthread_exit</span> <span class="p">(</span><span class="nb">NULL</span><span class="p">);</span>
|
||
<span class="p">}</span>
|
||
|
||
<span class="cm">/* Create a block to append to the end of the chain. Can be</span>
|
||
<span class="cm"> parallelized for improved performance, but blockchain</span>
|
||
<span class="cm"> calculations are designed to be slow. */</span>
|
||
<span class="kt">char</span> <span class="o">*</span>
|
||
<span class="nf">append_block</span> <span class="p">(</span><span class="kt">char</span> <span class="o">*</span><span class="n">data</span><span class="p">,</span> <span class="kt">char</span> <span class="o">*</span><span class="n">previous</span><span class="p">,</span> <span class="kt">size_t</span> <span class="n">num_threads</span><span class="p">)</span>
|
||
<span class="p">{</span>
|
||
<span class="kt">uint64_t</span> <span class="n">index</span> <span class="o">=</span> <span class="p">(</span><span class="kt">uint64_t</span><span class="p">)</span> <span class="n">strtoul</span> <span class="p">((</span><span class="kt">char</span> <span class="o">*</span><span class="p">)</span><span class="n">previous</span><span class="p">,</span> <span class="nb">NULL</span><span class="p">,</span> <span class="mi">16</span><span class="p">);</span>
|
||
|
||
<span class="kt">char</span> <span class="o">*</span><span class="n">prev_hash</span> <span class="o">=</span> <span class="n">calloc</span> <span class="p">(</span><span class="n">SHA_DIGEST_LENGTH</span> <span class="o">*</span> <span class="mi">2</span> <span class="o">+</span> <span class="mi">1</span><span class="p">,</span> <span class="k">sizeof</span> <span class="p">(</span><span class="kt">char</span><span class="p">));</span>
|
||
<span class="n">strncpy</span> <span class="p">(</span><span class="n">prev_hash</span><span class="p">,</span>
|
||
<span class="p">(</span><span class="kt">char</span> <span class="o">*</span><span class="p">)</span><span class="o">&</span><span class="n">previous</span><span class="p">[</span><span class="n">strlen</span> <span class="p">((</span><span class="kt">char</span> <span class="o">*</span><span class="p">)</span><span class="n">previous</span><span class="p">)</span> <span class="o">-</span> <span class="n">SHA_DIGEST_LENGTH</span> <span class="o">*</span> <span class="mi">2</span><span class="p">],</span>
|
||
<span class="n">SHA_DIGEST_LENGTH</span> <span class="o">*</span> <span class="mi">2</span><span class="p">);</span>
|
||
|
||
<span class="cm">/* Last block was validated, now construct a new block */</span>
|
||
<span class="kt">time_t</span> <span class="n">now</span> <span class="o">=</span> <span class="n">time</span> <span class="p">(</span><span class="nb">NULL</span><span class="p">);</span>
|
||
<span class="kt">size_t</span> <span class="n">blocklen</span> <span class="o">=</span> <span class="mi">0</span><span class="p">;</span>
|
||
<span class="kt">char</span> <span class="o">*</span><span class="n">block</span> <span class="o">=</span>
|
||
<span class="n">construct_block</span> <span class="p">(</span><span class="n">index</span> <span class="o">+</span> <span class="mi">1</span><span class="p">,</span> <span class="n">prev_hash</span><span class="p">,</span> <span class="n">localtime</span> <span class="p">(</span><span class="o">&</span><span class="n">now</span><span class="p">),</span>
|
||
<span class="n">data</span><span class="p">,</span> <span class="n">strlen</span> <span class="p">(</span><span class="n">data</span><span class="p">),</span> <span class="mi">0</span><span class="p">,</span> <span class="o">&</span><span class="n">blocklen</span><span class="p">);</span>
|
||
<span class="n">free</span> <span class="p">(</span><span class="n">prev_hash</span><span class="p">);</span>
|
||
|
||
<span class="cm">/* Repeatedly implement a fork/join pattern until the search is</span>
|
||
<span class="cm"> successful. Each time through the while-loop, create a fixed</span>
|
||
<span class="cm"> number of threads that will perform a maximum number of</span>
|
||
<span class="cm"> calculations with different nonces. For instance, using</span>
|
||
<span class="cm"> 1,000,000 attempts per thread, the first thread will use nonces</span>
|
||
<span class="cm"> 0 through 999,999, the second 1,000,000 through 1,999,999, and</span>
|
||
<span class="cm"> so forth. Once all threads have run, check to see if any were</span>
|
||
<span class="cm"> successful. If not, create a new set of threads that continue</span>
|
||
<span class="cm"> with the next group of possible nonces. */</span>
|
||
|
||
<span class="kt">size_t</span> <span class="n">attempts_per_thread</span> <span class="o">=</span> <span class="mi">1000000</span><span class="p">;</span>
|
||
<span class="kt">uint64_t</span> <span class="n">nonce</span> <span class="o">=</span> <span class="mi">0</span><span class="p">;</span>
|
||
<span class="kt">bool</span> <span class="n">success</span> <span class="o">=</span> <span class="nb">false</span><span class="p">;</span>
|
||
|
||
<span class="k">while</span> <span class="p">(</span><span class="o">!</span> <span class="n">success</span><span class="p">)</span>
|
||
<span class="p">{</span>
|
||
<span class="k">struct</span> <span class="n">mining_params</span> <span class="n">params</span><span class="p">[</span><span class="n">num_threads</span><span class="p">];</span>
|
||
<span class="n">pthread_t</span> <span class="kr">thread</span><span class="p">[</span><span class="n">num_threads</span><span class="p">];</span>
|
||
<span class="kt">int</span> <span class="n">i</span><span class="p">;</span>
|
||
<span class="k">for</span> <span class="p">(</span><span class="n">i</span> <span class="o">=</span> <span class="mi">0</span><span class="p">;</span> <span class="n">i</span> <span class="o"><</span> <span class="n">num_threads</span><span class="p">;</span> <span class="n">i</span><span class="o">++</span><span class="p">)</span>
|
||
<span class="p">{</span>
|
||
<span class="cm">/* Each thread needs its own copy of the block, so that</span>
|
||
<span class="cm"> it can change the nonce portion of the string. Note</span>
|
||
<span class="cm"> that we cannot just use strdup() here, because that</span>
|
||
<span class="cm"> would not allocate the additional bytes needed to</span>
|
||
<span class="cm"> append the hash for the successul search. */</span>
|
||
<span class="n">params</span><span class="p">[</span><span class="n">i</span><span class="p">].</span><span class="n">block</span> <span class="o">=</span>
|
||
<span class="n">calloc</span> <span class="p">(</span><span class="n">blocklen</span> <span class="o">+</span> <span class="mi">2</span> <span class="o">+</span> <span class="mi">2</span> <span class="o">*</span> <span class="n">SHA_DIGEST_LENGTH</span><span class="p">,</span> <span class="k">sizeof</span> <span class="p">(</span><span class="kt">char</span><span class="p">));</span>
|
||
<span class="n">strncpy</span> <span class="p">(</span><span class="n">params</span><span class="p">[</span><span class="n">i</span><span class="p">].</span><span class="n">block</span><span class="p">,</span> <span class="n">block</span><span class="p">,</span> <span class="n">blocklen</span><span class="p">);</span>
|
||
<span class="n">params</span><span class="p">[</span><span class="n">i</span><span class="p">].</span><span class="n">blocklen</span> <span class="o">=</span> <span class="n">blocklen</span><span class="p">;</span>
|
||
<span class="n">params</span><span class="p">[</span><span class="n">i</span><span class="p">].</span><span class="n">nonce</span> <span class="o">=</span> <span class="n">nonce</span><span class="p">;</span>
|
||
<span class="n">params</span><span class="p">[</span><span class="n">i</span><span class="p">].</span><span class="n">attempts</span> <span class="o">=</span> <span class="n">attempts_per_thread</span><span class="p">;</span>
|
||
<span class="n">params</span><span class="p">[</span><span class="n">i</span><span class="p">].</span><span class="n">success</span> <span class="o">=</span> <span class="nb">false</span><span class="p">;</span>
|
||
<span class="n">pthread_create</span> <span class="p">(</span><span class="o">&</span><span class="kr">thread</span><span class="p">[</span><span class="n">i</span><span class="p">],</span> <span class="nb">NULL</span><span class="p">,</span> <span class="n">mining_thread</span><span class="p">,</span> <span class="o">&</span><span class="n">params</span><span class="p">[</span><span class="n">i</span><span class="p">]);</span>
|
||
|
||
<span class="cm">/* The starting nonce for each thread is repeatedly</span>
|
||
<span class="cm"> incremented to ensure no two threads search the same</span>
|
||
<span class="cm"> set of values */</span>
|
||
<span class="n">nonce</span> <span class="o">+=</span> <span class="n">attempts_per_thread</span><span class="p">;</span>
|
||
<span class="p">}</span>
|
||
|
||
<span class="cm">/* For this group of threads, check to see if any were</span>
|
||
<span class="cm"> successful. If so, replace the generated block string with</span>
|
||
<span class="cm"> that thread's copy. */</span>
|
||
<span class="k">for</span> <span class="p">(</span><span class="n">i</span> <span class="o">=</span> <span class="mi">0</span><span class="p">;</span> <span class="n">i</span> <span class="o"><</span> <span class="n">num_threads</span><span class="p">;</span> <span class="n">i</span><span class="o">++</span><span class="p">)</span>
|
||
<span class="p">{</span>
|
||
<span class="n">pthread_join</span> <span class="p">(</span><span class="kr">thread</span><span class="p">[</span><span class="n">i</span><span class="p">],</span> <span class="nb">NULL</span><span class="p">);</span>
|
||
<span class="k">if</span> <span class="p">(</span><span class="n">params</span><span class="p">[</span><span class="n">i</span><span class="p">].</span><span class="n">success</span> <span class="o">&&</span> <span class="o">!</span><span class="n">success</span><span class="p">)</span>
|
||
<span class="p">{</span>
|
||
<span class="n">free</span> <span class="p">(</span><span class="n">block</span><span class="p">);</span>
|
||
<span class="n">block</span> <span class="o">=</span> <span class="n">params</span><span class="p">[</span><span class="n">i</span><span class="p">].</span><span class="n">block</span><span class="p">;</span>
|
||
<span class="n">success</span> <span class="o">=</span> <span class="nb">true</span><span class="p">;</span>
|
||
<span class="p">}</span>
|
||
<span class="k">else</span>
|
||
<span class="n">free</span> <span class="p">(</span><span class="n">params</span><span class="p">[</span><span class="n">i</span><span class="p">].</span><span class="n">block</span><span class="p">);</span>
|
||
<span class="p">}</span>
|
||
<span class="p">}</span>
|
||
|
||
<span class="k">return</span> <span class="n">block</span><span class="p">;</span>
|
||
<span class="p">}</span>
|
||
|
||
<span class="cm">/* Create a genesis block to serve as the foundation */</span>
|
||
<span class="kt">char</span> <span class="o">*</span>
|
||
<span class="nf">create_genesis_block</span> <span class="p">(</span><span class="kt">void</span><span class="p">)</span>
|
||
<span class="p">{</span>
|
||
<span class="cm">/* Start off with a bogus 0 hash */</span>
|
||
<span class="kt">uint8_t</span> <span class="n">hash</span><span class="p">[</span><span class="n">SHA_DIGEST_LENGTH</span><span class="p">];</span>
|
||
<span class="n">memset</span> <span class="p">(</span><span class="n">hash</span><span class="p">,</span> <span class="mi">0</span><span class="p">,</span> <span class="n">SHA_DIGEST_LENGTH</span><span class="p">);</span>
|
||
<span class="kt">char</span> <span class="o">*</span><span class="n">hash_str</span> <span class="o">=</span> <span class="n">hash_to_string</span> <span class="p">(</span><span class="n">hash</span><span class="p">);</span>
|
||
|
||
<span class="cm">/* Create a genesis block with the current time */</span>
|
||
<span class="kt">time_t</span> <span class="n">now</span> <span class="o">=</span> <span class="n">time</span> <span class="p">(</span><span class="nb">NULL</span><span class="p">);</span>
|
||
<span class="kt">size_t</span> <span class="n">blocklen</span> <span class="o">=</span> <span class="mi">0</span><span class="p">;</span>
|
||
<span class="kt">char</span> <span class="o">*</span><span class="n">genesis</span> <span class="o">=</span>
|
||
<span class="n">construct_block</span> <span class="p">(</span><span class="mi">0</span><span class="p">,</span> <span class="p">(</span><span class="kt">char</span><span class="o">*</span><span class="p">)</span> <span class="n">hash_str</span><span class="p">,</span> <span class="n">localtime</span> <span class="p">(</span><span class="o">&</span><span class="n">now</span><span class="p">),</span>
|
||
<span class="s">"Genesis Block"</span><span class="p">,</span> <span class="mi">13</span><span class="p">,</span> <span class="mi">0</span><span class="p">,</span> <span class="o">&</span><span class="n">blocklen</span><span class="p">);</span>
|
||
<span class="n">free</span> <span class="p">(</span><span class="n">hash_str</span><span class="p">);</span>
|
||
|
||
<span class="cm">/* Compute the hash of the genesis block and append it */</span>
|
||
<span class="kt">unsigned</span> <span class="kt">char</span> <span class="o">*</span><span class="n">md</span> <span class="o">=</span>
|
||
<span class="n">SHA1</span> <span class="p">((</span><span class="kt">unsigned</span> <span class="kt">char</span> <span class="o">*</span><span class="p">)</span><span class="n">genesis</span><span class="p">,</span> <span class="p">(</span><span class="kt">unsigned</span> <span class="kt">long</span><span class="p">)</span> <span class="n">blocklen</span><span class="p">,</span> <span class="n">hash</span><span class="p">);</span>
|
||
<span class="n">hash_str</span> <span class="o">=</span> <span class="n">hash_to_string</span> <span class="p">(</span><span class="n">md</span><span class="p">);</span>
|
||
<span class="n">genesis</span><span class="p">[</span><span class="n">strlen</span> <span class="p">((</span><span class="kt">char</span> <span class="o">*</span><span class="p">)</span><span class="n">genesis</span><span class="p">)]</span> <span class="o">=</span> <span class="sc">' '</span><span class="p">;</span>
|
||
<span class="n">strncat</span> <span class="p">((</span><span class="kt">char</span> <span class="o">*</span><span class="p">)</span><span class="n">genesis</span><span class="p">,</span> <span class="n">hash_str</span><span class="p">,</span> <span class="n">SHA_DIGEST_LENGTH</span> <span class="o">*</span> <span class="mi">2</span><span class="p">);</span>
|
||
<span class="n">free</span> <span class="p">(</span><span class="n">hash_str</span><span class="p">);</span>
|
||
|
||
<span class="k">return</span> <span class="n">genesis</span><span class="p">;</span>
|
||
<span class="p">}</span>
|
||
|
||
<span class="cm">/* Constrct a block of the following form:</span>
|
||
|
||
<span class="cm"> index.previous hash.[timestamp].data.nonce</span>
|
||
|
||
<span class="cm"> (Dots denote spaces for readability of the line.)</span>
|
||
<span class="cm"> Note that the dynamic allocation also includes space for this</span>
|
||
<span class="cm"> block's hash at the end, but those bytes are initialized to</span>
|
||
<span class="cm"> all 0. */</span>
|
||
<span class="kt">char</span> <span class="o">*</span>
|
||
<span class="nf">construct_block</span> <span class="p">(</span><span class="kt">uint64_t</span> <span class="n">index</span><span class="p">,</span> <span class="kt">char</span> <span class="o">*</span><span class="n">previous</span><span class="p">,</span>
|
||
<span class="k">struct</span> <span class="n">tm</span> <span class="o">*</span><span class="n">timestamp</span><span class="p">,</span> <span class="kt">char</span> <span class="o">*</span><span class="n">data</span><span class="p">,</span> <span class="kt">size_t</span> <span class="n">length</span><span class="p">,</span>
|
||
<span class="kt">uint64_t</span> <span class="n">nonce</span><span class="p">,</span> <span class="kt">size_t</span> <span class="o">*</span><span class="n">block_length</span><span class="p">)</span>
|
||
<span class="p">{</span>
|
||
<span class="o">*</span><span class="n">block_length</span> <span class="o">=</span>
|
||
<span class="mi">16</span> <span class="o">+</span> <span class="mi">16</span> <span class="o">+</span> <span class="n">length</span> <span class="o">+</span> <span class="mi">4</span> <span class="o">+</span> <span class="c1">// index, nonce, length, spaces</span>
|
||
<span class="n">SHA_DIGEST_LENGTH</span> <span class="o">*</span> <span class="mi">2</span> <span class="o">+</span> <span class="c1">// previous hash</span>
|
||
<span class="n">ASCTIME_LENGTH</span> <span class="o">+</span> <span class="mi">2</span><span class="p">;</span> <span class="c1">// [ASCII timestamp]</span>
|
||
|
||
<span class="cm">/* Allocate extra space for the block's hash, as well */</span>
|
||
<span class="kt">char</span> <span class="o">*</span><span class="n">block</span> <span class="o">=</span>
|
||
<span class="n">calloc</span> <span class="p">(</span><span class="o">*</span><span class="n">block_length</span> <span class="o">+</span> <span class="mi">2</span> <span class="o">+</span> <span class="n">SHA_DIGEST_LENGTH</span> <span class="o">*</span> <span class="mi">2</span><span class="p">,</span> <span class="k">sizeof</span> <span class="p">(</span><span class="kt">char</span><span class="p">));</span>
|
||
|
||
<span class="cm">/* Both the index and the nonce are padded with leading 0s to be</span>
|
||
<span class="cm"> fixed width */</span>
|
||
<span class="n">snprintf</span> <span class="p">(</span><span class="n">block</span><span class="p">,</span> <span class="mi">17</span><span class="p">,</span> <span class="s">"%016"</span> <span class="n">PRIx64</span><span class="p">,</span> <span class="n">index</span><span class="p">);</span>
|
||
<span class="n">block</span><span class="p">[</span><span class="mi">16</span><span class="p">]</span> <span class="o">=</span> <span class="sc">' '</span><span class="p">;</span>
|
||
<span class="n">strncat</span> <span class="p">(</span><span class="n">block</span><span class="p">,</span> <span class="n">previous</span><span class="p">,</span> <span class="n">SHA_DIGEST_LENGTH</span> <span class="o">*</span> <span class="mi">2</span><span class="p">);</span>
|
||
|
||
<span class="cm">/* For the [timestamp] the asctime returns a trailing</span>
|
||
<span class="cm"> '\n' that must be overwritten with the ']' */</span>
|
||
<span class="n">block</span><span class="p">[</span><span class="n">SHA_DIGEST_LENGTH</span> <span class="o">*</span> <span class="mi">2</span> <span class="o">+</span> <span class="mi">17</span><span class="p">]</span> <span class="o">=</span> <span class="sc">' '</span><span class="p">;</span>
|
||
<span class="n">block</span><span class="p">[</span><span class="n">SHA_DIGEST_LENGTH</span> <span class="o">*</span> <span class="mi">2</span> <span class="o">+</span> <span class="mi">18</span><span class="p">]</span> <span class="o">=</span> <span class="sc">'['</span><span class="p">;</span>
|
||
<span class="n">strncat</span> <span class="p">(</span><span class="n">block</span><span class="p">,</span> <span class="n">asctime</span> <span class="p">(</span><span class="n">timestamp</span><span class="p">),</span> <span class="o">*</span><span class="n">block_length</span> <span class="o">-</span> <span class="n">strlen</span> <span class="p">(</span><span class="n">block</span><span class="p">));</span>
|
||
<span class="n">block</span><span class="p">[</span><span class="n">strlen</span> <span class="p">(</span><span class="n">block</span><span class="p">)</span> <span class="o">-</span> <span class="mi">1</span><span class="p">]</span> <span class="o">=</span> <span class="sc">']'</span><span class="p">;</span>
|
||
|
||
<span class="cm">/* For readability of data, add a space before and after */</span>
|
||
<span class="n">block</span><span class="p">[</span><span class="n">strlen</span> <span class="p">(</span><span class="n">block</span><span class="p">)]</span> <span class="o">=</span> <span class="sc">' '</span><span class="p">;</span>
|
||
<span class="n">strncat</span> <span class="p">(</span><span class="n">block</span><span class="p">,</span> <span class="n">data</span><span class="p">,</span> <span class="n">length</span><span class="p">);</span>
|
||
<span class="n">block</span><span class="p">[</span><span class="o">*</span><span class="n">block_length</span> <span class="o">-</span> <span class="mi">17</span><span class="p">]</span> <span class="o">=</span> <span class="sc">' '</span><span class="p">;</span>
|
||
|
||
<span class="n">snprintf</span> <span class="p">(</span><span class="n">block</span> <span class="o">+</span> <span class="o">*</span><span class="n">block_length</span> <span class="o">-</span> <span class="mi">16</span><span class="p">,</span> <span class="mi">17</span><span class="p">,</span> <span class="s">"%016"</span> <span class="n">PRIx64</span><span class="p">,</span> <span class="n">nonce</span><span class="p">);</span>
|
||
|
||
<span class="k">return</span> <span class="n">block</span><span class="p">;</span>
|
||
<span class="p">}</span>
|
||
|
||
<span class="cm">/* Convert a SHA hash to a readable hex string */</span>
|
||
<span class="kt">char</span> <span class="o">*</span>
|
||
<span class="nf">hash_to_string</span> <span class="p">(</span><span class="kt">uint8_t</span> <span class="o">*</span><span class="n">hash</span><span class="p">)</span>
|
||
<span class="p">{</span>
|
||
<span class="kt">size_t</span> <span class="n">j</span><span class="p">;</span>
|
||
<span class="kt">char</span> <span class="o">*</span><span class="n">str</span> <span class="o">=</span> <span class="n">calloc</span> <span class="p">(</span><span class="n">SHA_DIGEST_LENGTH</span> <span class="o">*</span> <span class="mi">2</span> <span class="o">+</span> <span class="mi">1</span><span class="p">,</span> <span class="k">sizeof</span> <span class="p">(</span><span class="kt">char</span><span class="p">));</span>
|
||
|
||
<span class="cm">/* Each byte gets split into two hex digits */</span>
|
||
<span class="k">for</span> <span class="p">(</span><span class="n">j</span> <span class="o">=</span> <span class="mi">0</span><span class="p">;</span> <span class="n">j</span> <span class="o"><</span> <span class="n">SHA_DIGEST_LENGTH</span><span class="p">;</span> <span class="n">j</span><span class="o">++</span><span class="p">)</span>
|
||
<span class="n">sprintf</span> <span class="p">(</span><span class="o">&</span><span class="n">str</span><span class="p">[</span><span class="n">j</span><span class="o">*</span><span class="mi">2</span><span class="p">],</span> <span class="s">"%02x"</span><span class="p">,</span> <span class="n">hash</span><span class="p">[</span><span class="n">j</span><span class="p">]);</span>
|
||
<span class="k">return</span> <span class="n">str</span><span class="p">;</span>
|
||
<span class="p">}</span>
|
||
</pre></div>
|
||
</td></tr></table></div>
|
||
</div>
|
||
|
||
|
||
</div>
|
||
|
||
|
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