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<?php |
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namespace BitWasp\Bitcoin\Script\Path; |
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use BitWasp\Bitcoin\Script\Interpreter\Stack; |
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use BitWasp\Bitcoin\Script\Opcodes; |
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use BitWasp\Bitcoin\Script\ScriptInterface; |
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class BranchInterpreter |
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{ |
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/** |
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* @var array |
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*/ |
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private $disabledOps = [ |
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Opcodes::OP_CAT, Opcodes::OP_SUBSTR, Opcodes::OP_LEFT, Opcodes::OP_RIGHT, |
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Opcodes::OP_INVERT, Opcodes::OP_AND, Opcodes::OP_OR, Opcodes::OP_XOR, |
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Opcodes::OP_2MUL, Opcodes::OP_2DIV, Opcodes::OP_MUL, Opcodes::OP_DIV, |
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Opcodes::OP_MOD, Opcodes::OP_LSHIFT, Opcodes::OP_RSHIFT |
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]; |
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/** |
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* @param ScriptInterface $script |
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* @return ScriptBranch[] |
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*/ |
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public function getScriptBranches(ScriptInterface $script) |
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{ |
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$ast = $this->getAstForLogicalOps($script); |
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$paths = $ast->flags(); |
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$results = []; |
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if (count($paths) > 1) { |
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foreach ($paths as $path) { |
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$results[] = $this->getBranchForPath($script, $path); |
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} |
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} else { |
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$results[] = $this->getBranchForPath($script, []); |
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} |
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return $results; |
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} |
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/** |
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* Build tree of dependent logical ops |
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* @param ScriptInterface $script |
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* @return LogicOpNode |
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*/ |
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public function getAstForLogicalOps(ScriptInterface $script) |
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{ |
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$root = new LogicOpNode(null); |
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$nextId = 1; |
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$current = $root; |
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$segments = [$root]; |
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foreach ($script->getScriptParser()->decode() as $op) { |
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switch ($op->getOp()) { |
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case Opcodes::OP_IF: |
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list ($node0, $node1) = $current->split(); |
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$segments[$nextId++] = $node0; |
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$segments[$nextId++] = $node1; |
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$current = $node1; |
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break; |
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case Opcodes::OP_NOTIF: |
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list ($node0, $node1) = $current->split(); |
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$segments[$nextId++] = $node0; |
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$segments[$nextId++] = $node1; |
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$current = $node0; |
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break; |
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case Opcodes::OP_ENDIF: |
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$current = $current->getParent(); |
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break; |
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case Opcodes::OP_ELSE: |
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if ($current->getValue() === false) { |
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throw new \RuntimeException("Unbalanced conditional"); |
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} |
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$current = $current->getParent()->getChild(0); |
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break; |
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} |
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} |
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return $root; |
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} |
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/** |
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* Given a script and path, attempt to produce a ScriptBranch instance |
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* |
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* @param ScriptInterface $script |
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* @param bool[] $path |
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* @return ScriptBranch |
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*/ |
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public function getBranchForPath(ScriptInterface $script, array $path) |
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{ |
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$stack = new Stack(); |
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foreach (array_reverse($path) as $setting) { |
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$stack->push($setting); |
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} |
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$segments = $this->evaluateUsingStack($script, $stack); |
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return new ScriptBranch($script, $path, $segments); |
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} |
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/** |
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* @param Stack $vfStack |
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* @param bool $value |
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* @return bool |
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*/ |
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private function checkExec(Stack $vfStack, $value) |
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{ |
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$ret = 0; |
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foreach ($vfStack as $item) { |
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if ($item === $value) { |
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$ret++; |
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} |
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} |
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return $ret; |
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} |
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/** |
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* @param ScriptInterface $script |
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* @param Stack $mainStack |
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* @return PathTrace |
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*/ |
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public function evaluateUsingStack(ScriptInterface $script, Stack $mainStack) |
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{ |
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$vfStack = new Stack(); |
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$parser = $script->getScriptParser(); |
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$tracer = new PathTracer(); |
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foreach ($parser as $i => $operation) { |
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$opCode = $operation->getOp(); |
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$fExec = !$this->checkExec($vfStack, false); |
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if (in_array($opCode, $this->disabledOps, true)) { |
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throw new \RuntimeException('Disabled Opcode'); |
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} |
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if (Opcodes::OP_IF <= $opCode && $opCode <= Opcodes::OP_ENDIF) { |
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switch ($opCode) { |
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case Opcodes::OP_IF: |
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case Opcodes::OP_NOTIF: |
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// <expression> if [statements] [else [statements]] endif |
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$value = false; |
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if ($fExec) { |
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if ($mainStack->isEmpty()) { |
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throw new \RuntimeException('Unbalanced conditional'); |
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} |
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$value = $mainStack->pop(); |
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if ($opCode === Opcodes::OP_NOTIF) { |
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$value = !$value; |
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} |
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} |
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$vfStack->push($value); |
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break; |
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case Opcodes::OP_ELSE: |
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if ($vfStack->isEmpty()) { |
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throw new \RuntimeException('Unbalanced conditional'); |
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} |
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$vfStack->push(!$vfStack->pop()); |
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break; |
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case Opcodes::OP_ENDIF: |
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if ($vfStack->isEmpty()) { |
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throw new \RuntimeException('Unbalanced conditional'); |
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} |
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$vfStack->pop(); |
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break; |
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} |
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$tracer->operation($operation); |
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} else if ($fExec) { |
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// Fill up trace with executed opcodes |
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$tracer->operation($operation); |
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} |
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} |
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if (count($vfStack) !== 0) { |
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throw new \RuntimeException('Unbalanced conditional at script end'); |
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} |
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if (count($mainStack) !== 0) { |
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throw new \RuntimeException('Values remaining after script execution - invalid branch data'); |
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} |
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return $tracer->done(); |
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} |
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} |
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Bit-Wasp /
bitcoin-php
