SyscallIterator: support C++11 range-based for loops

sandbox/linux/seccomp-bpf/syscall_iterator.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "sandbox/linux/seccomp-bpf/syscall_iterator.h"
 
+#include "base/logging.h"
 #include "base/macros.h"
 #include "sandbox/linux/seccomp-bpf/linux_seccomp.h"
 
 namespace sandbox {
 
 namespace {
 
 #if defined(__mips__) && (_MIPS_SIM == _MIPS_SIM_ABI32)
 // This is true for Mips O32 ABI.
 COMPILE_ASSERT(MIN_SYSCALL == __NR_Linux, min_syscall_should_be_4000);
@@ skipping 14 matching lines @@
     {MIN_SYSCALL, MAX_PUBLIC_SYSCALL},
 #if defined(__arm__)
     // ARM EABI includes "ARM private" system calls starting at
     // MIN_PRIVATE_SYSCALL, and a "ghost syscall private to the kernel" at
     // MIN_GHOST_SYSCALL.
     {MIN_PRIVATE_SYSCALL, MAX_PRIVATE_SYSCALL},
     {MIN_GHOST_SYSCALL, MAX_SYSCALL},
 #endif
 };
 
-uint32_t NextSyscall(uint32_t cur, bool invalid_only) {
+// NextSyscall returns the next system call in the specified system
+// call set after |cur|, or 0 if no such system call exists.
+uint32_t NextSyscall(uint32_t cur, SyscallSet set) {
   for (const SyscallRange& range : kValidSyscallRanges) {
     if (range.first > 0 && cur < range.first - 1) {
       return range.first - 1;
     }
     if (cur <= range.last) {
-      if (invalid_only && cur < range.last) {
-        return range.last;
+      if (set == SyscallSet::INVALID_ONLY) {
+        return range.last + 1;
       }
       return cur + 1;
     }
   }
 
   // BPF programs only ever operate on unsigned quantities. So, that's how
   // we iterate; we return values from 0..0xFFFFFFFFu. But there are places,
   // where the kernel might interpret system call numbers as signed
   // quantities, so the boundaries between signed and unsigned values are
   // potential problem cases. We want to explicitly return these values from
   // our iterator.
   if (cur < 0x7FFFFFFFu)
     return 0x7FFFFFFFu;
   if (cur < 0x80000000u)
     return 0x80000000u;
 
-  return 0xFFFFFFFFu;
+  if (cur < 0xFFFFFFFFu)
+    return 0xFFFFFFFFu;
+  return 0;
 }
 
 }  // namespace
 
-uint32_t SyscallIterator::Next() {
-  if (done_) {
-    return num_;
+SyscallIterator begin(SyscallSet set) {
+  return SyscallIterator(set, false);
+}
+
+SyscallIterator end(SyscallSet set) {
+  return SyscallIterator(set, true);
+}
+
+SyscallIterator::SyscallIterator(SyscallSet set, bool done)
+    : set_(set), done_(done), num_(0) {
+  if (set_ == SyscallSet::INVALID_ONLY && !done_ && IsValid(num_)) {
+    ++*this;
+  }
+}
+
+uint32_t SyscallIterator::operator*() const {
+  DCHECK(!done_);
+  return num_;
+}
+
+SyscallIterator& SyscallIterator::operator++() {
+  DCHECK(!done_);
+
+  num_ = NextSyscall(num_, set_);
+  if (num_ == 0) {
+    done_ = true;
   }
 
-  uint32_t val;
-  do {
-    val = num_;
-    num_ = NextSyscall(num_, invalid_only_);
-  } while (invalid_only_ && IsValid(val));
-
-  done_ |= val == 0xFFFFFFFFu;
-  return val;
+  return *this;
 }
 
 bool SyscallIterator::IsValid(uint32_t num) {
   for (const SyscallRange& range : kValidSyscallRanges) {
     if (num >= range.first && num <= range.last) {
       return true;
     }
   }
   return false;
 }
 
+bool operator==(const SyscallIterator& lhs, const SyscallIterator& rhs) {
+  DCHECK(lhs.set_ == rhs.set_);
+  return (lhs.done_ == rhs.done_) && (lhs.num_ == rhs.num_);
+}
+
+bool operator!=(const SyscallIterator& lhs, const SyscallIterator& rhs) {
+  return !(lhs == rhs);
+}
+
 }  // namespace sandbox