1 files changed, 62 insertions, 0 deletions
diff --git a/core/vm/analysis.go b/core/vm/analysis.go
new file mode 100644
index 0000000..0ccf47b
--- /dev/null
+++ b/core/vm/analysis.go
@@ -0,0 +1,62 @@
+// Copyright 2014 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package vm
+
+// bitvec is a bit vector which maps bytes in a program.
+// An unset bit means the byte is an opcode, a set bit means
+// it's data (i.e. argument of PUSHxx).
+type bitvec []byte
+
+func (bits *bitvec) set(pos uint64) {
+	(*bits)[pos/8] |= 0x80 >> (pos % 8)
+}
+func (bits *bitvec) set8(pos uint64) {
+	(*bits)[pos/8] |= 0xFF >> (pos % 8)
+	(*bits)[pos/8+1] |= ^(0xFF >> (pos % 8))
+}
+
+// codeSegment checks if the position is in a code segment.
+func (bits *bitvec) codeSegment(pos uint64) bool {
+	return ((*bits)[pos/8] & (0x80 >> (pos % 8))) == 0
+}
+
+// codeBitmap collects data locations in code.
+func codeBitmap(code []byte) bitvec {
+	// The bitmap is 4 bytes longer than necessary, in case the code
+	// ends with a PUSH32, the algorithm will push zeroes onto the
+	// bitvector outside the bounds of the actual code.
+	bits := make(bitvec, len(code)/8+1+4)
+	for pc := uint64(0); pc < uint64(len(code)); {
+		op := OpCode(code[pc])
+
+		if op >= PUSH1 && op <= PUSH32 {
+			numbits := op - PUSH1 + 1
+			pc++
+			for ; numbits >= 8; numbits -= 8 {
+				bits.set8(pc) // 8
+				pc += 8
+			}
+			for ; numbits > 0; numbits-- {
+				bits.set(pc)
+				pc++
+			}
+		} else {
+			pc++
+		}
+	}
+	return bits
+}