ZIP 207: improvements to the pseudocode.

Signed-off-by: Daira Hopwood <[email protected]>
zcash · Mar 27, 2020 · c4c4037 · c4c4037
1 parent 93a7b08
commit c4c4037
Show file tree

Hide file tree

Showing 2 changed files with 54 additions and 36 deletions.
diff --git a/zip-0207.html b/zip-0207.html
@@ -234,16 +234,17 @@
     <span class="n">Consensus</span><span class="o">::</span><span class="n">FundingStream</span> <span class="n">idx</span><span class="p">,</span>
     <span class="n">std</span><span class="o">::</span><span class="n">vector</span><span class="o">&lt;</span><span class="n">std</span><span class="o">::</span><span class="n">string</span><span class="o">&gt;</span> <span class="n">addresses</span><span class="p">,</span>
     <span class="kt">uint64_t</span> <span class="n">valueNumerator</span><span class="p">,</span>
-    <span class="kt">uint64_t</span> <span class="n">valueDenominator</span><span class="p">)</span>
+    <span class="kt">uint64_t</span> <span class="n">valueDenominator</span><span class="p">,</span>
+    <span class="kt">int</span> <span class="n">startHeight</span><span class="p">,</span>
+    <span class="kt">int</span> <span class="n">endHeight</span><span class="p">)</span>
 <span class="p">{</span>
     <span class="n">assert</span><span class="p">(</span><span class="n">valueNumerator</span> <span class="o">&lt;</span> <span class="n">valueDenominator</span><span class="p">);</span>
     <span class="n">assert</span><span class="p">(</span><span class="n">valueNumerator</span> <span class="o">&lt;</span> <span class="n">INT64_MAX</span> <span class="o">/</span> <span class="n">MAX_MONEY</span><span class="p">);</span>
     <span class="n">params</span><span class="p">.</span><span class="n">vFundingPeriods</span><span class="p">[</span><span class="n">idx</span><span class="p">].</span><span class="n">addresses</span> <span class="o">=</span> <span class="n">addresses</span><span class="p">;</span>
     <span class="n">params</span><span class="p">.</span><span class="n">vFundingPeriods</span><span class="p">[</span><span class="n">idx</span><span class="p">].</span><span class="n">valueNumerator</span> <span class="o">=</span> <span class="n">valueNumerator</span><span class="p">;</span>
     <span class="n">params</span><span class="p">.</span><span class="n">vFundingPeriods</span><span class="p">[</span><span class="n">idx</span><span class="p">].</span><span class="n">valueDenominator</span> <span class="o">=</span> <span class="n">valueDenominator</span><span class="p">;</span>
-    <span class="n">params</span><span class="p">.</span><span class="n">vFundingPeriods</span><span class="p">[</span><span class="n">idx</span><span class="p">].</span><span class="n">startHeight</span> <span class="o">=</span>
-        <span class="n">params</span><span class="p">.</span><span class="n">vUpgrades</span><span class="p">[</span><span class="n">Consensus</span><span class="o">::</span><span class="n">UPGRADE_BLOSSOM</span><span class="p">].</span><span class="n">nActivationHeight</span><span class="p">;</span>
-    <span class="n">params</span><span class="p">.</span><span class="n">vFundingPeriods</span><span class="p">[</span><span class="n">idx</span><span class="p">].</span><span class="n">endHeight</span> <span class="o">=</span> <span class="n">HeightForHalving</span><span class="p">(</span><span class="n">params</span><span class="p">,</span> <span class="mi">1</span><span class="p">);</span>
+    <span class="n">params</span><span class="p">.</span><span class="n">vFundingPeriods</span><span class="p">[</span><span class="n">idx</span><span class="p">].</span><span class="n">startHeight</span> <span class="o">=</span> <span class="n">startHeight</span><span class="p">;</span>
+    <span class="n">params</span><span class="p">.</span><span class="n">vFundingPeriods</span><span class="p">[</span><span class="n">idx</span><span class="p">].</span><span class="n">endHeight</span> <span class="o">=</span> <span class="n">endHeight</span><span class="p">;</span>
     <span class="n">assert</span><span class="p">(</span><span class="n">params</span><span class="p">.</span><span class="n">vFundingPeriods</span><span class="p">[</span><span class="n">idx</span><span class="p">].</span><span class="n">startHeight</span> <span class="o">&lt;</span> <span class="n">params</span><span class="p">.</span><span class="n">vFundingPeriods</span><span class="p">[</span><span class="n">idx</span><span class="p">].</span><span class="n">endHeight</span><span class="p">);</span>
 <span class="p">};</span>
 
@@ -252,9 +253,11 @@
 
     <span class="n">consensus</span><span class="p">.</span><span class="n">nFundingPeriodLength</span> <span class="o">=</span> <span class="n">consensus</span><span class="p">.</span><span class="n">nSubsidyPostBlossomHalvingInterval</span> <span class="o">/</span> <span class="mi">48</span><span class="p">;</span>
 
-    <span class="n">AddZIP207FundingStream</span><span class="p">(</span><span class="n">consensus</span><span class="p">,</span> <span class="n">Consensus</span><span class="o">::</span><span class="n">FS_ECC</span><span class="p">,</span> <span class="n">FS_ECC_ADDRESSES</span><span class="p">,</span> <span class="mi">7</span><span class="p">,</span> <span class="mi">100</span><span class="p">);</span>
-    <span class="n">AddZIP207FundingStream</span><span class="p">(</span><span class="n">consensus</span><span class="p">,</span> <span class="n">Consensus</span><span class="o">::</span><span class="n">FS_ZF</span><span class="p">,</span>  <span class="n">FS_ZF_ADDRESSES</span><span class="p">,</span>  <span class="mi">5</span><span class="p">,</span> <span class="mi">100</span><span class="p">);</span>
-    <span class="n">AddZIP207FundingStream</span><span class="p">(</span><span class="n">consensus</span><span class="p">,</span> <span class="n">Consensus</span><span class="o">::</span><span class="n">FS_MG</span><span class="p">,</span>  <span class="n">FS_MG_ADDRESSES</span><span class="p">,</span>  <span class="mi">8</span><span class="p">,</span> <span class="mi">100</span><span class="p">);</span>
+    <span class="kt">int</span> <span class="n">devFundStartHeight</span> <span class="o">=</span> <span class="n">HeightForHalving</span><span class="p">(</span><span class="n">params</span><span class="p">,</span> <span class="mi">1</span><span class="p">);</span>
+    <span class="kt">int</span> <span class="n">devFundEndHeight</span>   <span class="o">=</span> <span class="n">HeightForHalving</span><span class="p">(</span><span class="n">params</span><span class="p">,</span> <span class="mi">2</span><span class="p">);</span>
+    <span class="n">AddZIP207FundingStream</span><span class="p">(</span><span class="n">consensus</span><span class="p">,</span> <span class="n">Consensus</span><span class="o">::</span><span class="n">FS_ECC</span><span class="p">,</span> <span class="n">FS_ECC_ADDRESSES</span><span class="p">,</span> <span class="mi">7</span><span class="p">,</span> <span class="mi">100</span><span class="p">,</span> <span class="n">devFundStartHeight</span><span class="p">,</span> <span class="n">devFundEndHeight</span><span class="p">);</span>
+    <span class="n">AddZIP207FundingStream</span><span class="p">(</span><span class="n">consensus</span><span class="p">,</span> <span class="n">Consensus</span><span class="o">::</span><span class="n">FS_ZF</span><span class="p">,</span>  <span class="n">FS_ZF_ADDRESSES</span><span class="p">,</span>  <span class="mi">5</span><span class="p">,</span> <span class="mi">100</span><span class="p">,</span> <span class="n">devFundStartHeight</span><span class="p">,</span> <span class="n">devFundEndHeight</span><span class="p">);</span>
+    <span class="n">AddZIP207FundingStream</span><span class="p">(</span><span class="n">consensus</span><span class="p">,</span> <span class="n">Consensus</span><span class="o">::</span><span class="n">FS_MG</span><span class="p">,</span>  <span class="n">FS_MG_ADDRESSES</span><span class="p">,</span>  <span class="mi">8</span><span class="p">,</span> <span class="mi">100</span><span class="p">,</span> <span class="n">devFundStartHeight</span><span class="p">,</span> <span class="n">devFundEndHeight</span><span class="p">);</span>
 
     <span class="p">...</span>
 <span class="p">}</span>
@@ -264,25 +267,31 @@
     <span class="k">const</span> <span class="n">Consensus</span><span class="o">::</span><span class="n">Params</span><span class="o">&amp;</span> <span class="n">params</span><span class="p">,</span>
     <span class="n">Consensus</span><span class="o">::</span><span class="n">FundingStream</span> <span class="n">idx</span><span class="p">)</span>
 <span class="p">{</span>
-    <span class="c1">// Integer division is floor division in C++</span>
-    <span class="k">auto</span> <span class="n">curPeriod</span> <span class="o">=</span> <span class="p">(</span>
-        <span class="n">nHeight</span> <span class="o">+</span> <span class="n">params</span><span class="p">.</span><span class="n">nSubsidyPostBlossomHalvingInterval</span> <span class="o">-</span> <span class="n">HeightForHalving</span><span class="p">(</span><span class="n">params</span><span class="p">,</span> <span class="mi">1</span><span class="p">)</span>
-    <span class="p">)</span> <span class="o">/</span> <span class="n">params</span><span class="p">.</span><span class="n">nFundingPeriodLength</span><span class="p">;</span>
-    <span class="k">auto</span> <span class="n">startPeriod</span> <span class="o">=</span> <span class="p">(</span>
-        <span class="n">params</span><span class="p">.</span><span class="n">vFundingPeriods</span><span class="p">[</span><span class="n">idx</span><span class="p">].</span><span class="n">startHeight</span>
-            <span class="o">+</span> <span class="n">params</span><span class="p">.</span><span class="n">nSubsidyPostBlossomHalvingInterval</span>
-            <span class="o">-</span> <span class="n">HeightForHalving</span><span class="p">(</span><span class="n">params</span><span class="p">,</span> <span class="mi">1</span><span class="p">)</span>
-    <span class="p">)</span> <span class="o">/</span> <span class="n">params</span><span class="p">.</span><span class="n">nFundingPeriodLength</span><span class="p">;</span>
+    <span class="n">assert</span><span class="p">(</span><span class="n">nHeight</span> <span class="o">&lt;=</span> <span class="n">INT_MAX</span> <span class="o">-</span> <span class="n">params</span><span class="p">.</span><span class="n">nSubsidyPostBlossomHalvingInterval</span><span class="p">);</span>
+    <span class="n">assert</span><span class="p">(</span><span class="n">params</span><span class="p">.</span><span class="n">vFundingPeriods</span><span class="p">[</span><span class="n">idx</span><span class="p">].</span><span class="n">startHeight</span> <span class="o">&lt;=</span> <span class="n">INT_MAX</span> <span class="o">-</span> <span class="n">params</span><span class="p">.</span><span class="n">nSubsidyPostBlossomHalvingInterval</span><span class="p">);</span>
+
+    <span class="kt">int</span> <span class="n">curPeriodNumerator</span> <span class="o">=</span> <span class="n">nHeight</span> <span class="o">+</span> <span class="n">params</span><span class="p">.</span><span class="n">nSubsidyPostBlossomHalvingInterval</span> <span class="o">-</span> <span class="n">HeightForHalving</span><span class="p">(</span><span class="n">params</span><span class="p">,</span> <span class="mi">1</span><span class="p">);</span>
+    <span class="kt">int</span> <span class="n">startPeriodNumerator</span> <span class="o">=</span> <span class="n">params</span><span class="p">.</span><span class="n">vFundingPeriods</span><span class="p">[</span><span class="n">idx</span><span class="p">].</span><span class="n">startHeight</span> <span class="o">+</span> <span class="n">params</span><span class="p">.</span><span class="n">nSubsidyPostBlossomHalvingInterval</span>
+        <span class="o">-</span> <span class="n">HeightForHalving</span><span class="p">(</span><span class="n">params</span><span class="p">,</span> <span class="mi">1</span><span class="p">);</span>
+
+    <span class="c1">// Integer division is floor division for nonnegative integers in C++</span>
+    <span class="n">assert</span><span class="p">(</span><span class="n">curPeriodNumerator</span> <span class="o">&gt;=</span> <span class="mi">0</span><span class="p">);</span>
+    <span class="n">assert</span><span class="p">(</span><span class="n">startPeriodNumerator</span> <span class="o">&gt;=</span> <span class="mi">0</span><span class="p">);</span>
+    <span class="k">auto</span> <span class="n">curPeriod</span> <span class="o">=</span> <span class="n">curPeriodNumerator</span> <span class="o">/</span> <span class="n">params</span><span class="p">.</span><span class="n">nFundingPeriodLength</span><span class="p">;</span>
+    <span class="k">auto</span> <span class="n">startPeriod</span> <span class="o">=</span> <span class="n">startPeriodNumerator</span> <span class="o">/</span> <span class="n">params</span><span class="p">.</span><span class="n">nFundingPeriodLength</span><span class="p">;</span>
     <span class="k">auto</span> <span class="n">addressIndex</span> <span class="o">=</span> <span class="n">curPeriod</span> <span class="o">-</span> <span class="n">startPeriod</span><span class="p">;</span>
-    <span class="k">return</span> <span class="n">params</span><span class="p">.</span><span class="n">vFundingPeriods</span><span class="p">[</span><span class="n">idx</span><span class="p">].</span><span class="n">addresses</span><span class="p">[</span><span class="n">addressIndex</span><span class="p">];</span>
+
+    <span class="k">auto</span> <span class="n">addresses</span> <span class="o">=</span> <span class="n">params</span><span class="p">.</span><span class="n">vFundingPeriods</span><span class="p">[</span><span class="n">idx</span><span class="p">].</span><span class="n">addresses</span><span class="p">;</span>
+    <span class="n">assert</span><span class="p">(</span><span class="n">addressIndex</span> <span class="o">&gt;=</span> <span class="mi">0</span> <span class="o">&amp;&amp;</span> <span class="n">addressIndex</span> <span class="o">&lt;</span> <span class="n">addresses</span><span class="p">.</span><span class="n">size</span><span class="p">());</span>
+    <span class="k">return</span> <span class="n">addresses</span><span class="p">[</span><span class="n">addressIndex</span><span class="p">];</span>
 <span class="p">};</span>
 
 <span class="n">CAmount</span> <span class="nf">FundingStreamValue</span><span class="p">(</span>
     <span class="kt">int</span> <span class="n">nHeight</span><span class="p">,</span>
     <span class="k">const</span> <span class="n">Consensus</span><span class="o">::</span><span class="n">Params</span><span class="o">&amp;</span> <span class="n">params</span><span class="p">,</span>
     <span class="n">Consensus</span><span class="o">::</span><span class="n">FundingStream</span> <span class="n">idx</span><span class="p">)</span>
 <span class="p">{</span>
-    <span class="c1">// Integer division is floor division in C++</span>
+    <span class="c1">// Integer division is floor division for nonnegative integers in C++</span>
     <span class="k">return</span> <span class="n">CAmount</span><span class="p">((</span>
         <span class="n">GetBlockSubsidy</span><span class="p">(</span><span class="n">nHeight</span><span class="p">,</span> <span class="n">params</span><span class="p">)</span> <span class="o">*</span> <span class="n">params</span><span class="p">.</span><span class="n">vFundingPeriods</span><span class="p">[</span><span class="n">idx</span><span class="p">].</span><span class="n">valueNumerator</span>
     <span class="p">)</span> <span class="o">/</span> <span class="n">params</span><span class="p">.</span><span class="n">vFundingPeriods</span><span class="p">[</span><span class="n">idx</span><span class="p">].</span><span class="n">valueDenominator</span><span class="p">);</span>

diff --git a/zip-0207.rst b/zip-0207.rst
@@ -236,16 +236,17 @@ Example implementation
         Consensus::FundingStream idx,
         std::vector<std::string> addresses,
         uint64_t valueNumerator,
-        uint64_t valueDenominator)
+        uint64_t valueDenominator,
+        int startHeight,
+        int endHeight)
     {
         assert(valueNumerator < valueDenominator);
         assert(valueNumerator < INT64_MAX / MAX_MONEY);
         params.vFundingPeriods[idx].addresses = addresses;
         params.vFundingPeriods[idx].valueNumerator = valueNumerator;
         params.vFundingPeriods[idx].valueDenominator = valueDenominator;
-        params.vFundingPeriods[idx].startHeight =
-            params.vUpgrades[Consensus::UPGRADE_BLOSSOM].nActivationHeight;
-        params.vFundingPeriods[idx].endHeight = HeightForHalving(params, 1);
+        params.vFundingPeriods[idx].startHeight = startHeight;
+        params.vFundingPeriods[idx].endHeight = endHeight;
         assert(params.vFundingPeriods[idx].startHeight < params.vFundingPeriods[idx].endHeight);
     };
 
@@ -254,9 +255,11 @@ Example implementation
 
         consensus.nFundingPeriodLength = consensus.nSubsidyPostBlossomHalvingInterval / 48;
 
-        AddZIP207FundingStream(consensus, Consensus::FS_ECC, FS_ECC_ADDRESSES, 7, 100);
-        AddZIP207FundingStream(consensus, Consensus::FS_ZF,  FS_ZF_ADDRESSES,  5, 100);
-        AddZIP207FundingStream(consensus, Consensus::FS_MG,  FS_MG_ADDRESSES,  8, 100);
+        int devFundStartHeight = HeightForHalving(params, 1);
+        int devFundEndHeight   = HeightForHalving(params, 2);
+        AddZIP207FundingStream(consensus, Consensus::FS_ECC, FS_ECC_ADDRESSES, 7, 100, devFundStartHeight, devFundEndHeight);
+        AddZIP207FundingStream(consensus, Consensus::FS_ZF,  FS_ZF_ADDRESSES,  5, 100, devFundStartHeight, devFundEndHeight);
+        AddZIP207FundingStream(consensus, Consensus::FS_MG,  FS_MG_ADDRESSES,  8, 100, devFundStartHeight, devFundEndHeight);
 
         ...
     }
@@ -266,25 +269,31 @@ Example implementation
         const Consensus::Params& params,
         Consensus::FundingStream idx)
     {
-        // Integer division is floor division in C++
-        auto curPeriod = (
-            nHeight + params.nSubsidyPostBlossomHalvingInterval - HeightForHalving(params, 1)
-        ) / params.nFundingPeriodLength;
-        auto startPeriod = (
-            params.vFundingPeriods[idx].startHeight
-                + params.nSubsidyPostBlossomHalvingInterval
-                - HeightForHalving(params, 1)
-        ) / params.nFundingPeriodLength;
+        assert(nHeight <= INT_MAX - params.nSubsidyPostBlossomHalvingInterval);
+        assert(params.vFundingPeriods[idx].startHeight <= INT_MAX - params.nSubsidyPostBlossomHalvingInterval);
+
+        int curPeriodNumerator = nHeight + params.nSubsidyPostBlossomHalvingInterval - HeightForHalving(params, 1);
+        int startPeriodNumerator = params.vFundingPeriods[idx].startHeight + params.nSubsidyPostBlossomHalvingInterval
+            - HeightForHalving(params, 1);
+
+        // Integer division is floor division for nonnegative integers in C++
+        assert(curPeriodNumerator >= 0);
+        assert(startPeriodNumerator >= 0);
+        auto curPeriod = curPeriodNumerator / params.nFundingPeriodLength;
+        auto startPeriod = startPeriodNumerator / params.nFundingPeriodLength;
         auto addressIndex = curPeriod - startPeriod;
-        return params.vFundingPeriods[idx].addresses[addressIndex];
+
+        auto addresses = params.vFundingPeriods[idx].addresses;
+        assert(addressIndex >= 0 && addressIndex < addresses.size());
+        return addresses[addressIndex];
     };
 
     CAmount FundingStreamValue(
         int nHeight,
         const Consensus::Params& params,
         Consensus::FundingStream idx)
     {
-        // Integer division is floor division in C++
+        // Integer division is floor division for nonnegative integers in C++
         return CAmount((
             GetBlockSubsidy(nHeight, params) * params.vFundingPeriods[idx].valueNumerator
         ) / params.vFundingPeriods[idx].valueDenominator);