Revert "net: remove DnsRRResolver"

This reverts commit r114845.

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@123247 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 116 insertions, 0 deletions

diff --git a/net/base/dns_util.cc b/net/base/dns_util.cc
index 816095b..a49ada8 100644
--- a/net/base/dns_util.cc
+++ b/net/base/dns_util.cc
@@ -101,4 +101,120 @@ std::string TrimEndingDot(const base::StringPiece& host) {
   return host_trimmed.as_string();
 }
 
+bool DnsResponseBuffer::U8(uint8* v) {
+  if (len_ < 1)
+    return false;
+  *v = *p_;
+  p_++;
+  len_--;
+  return true;
+}
+
+bool DnsResponseBuffer::U16(uint16* v) {
+  if (len_ < 2)
+    return false;
+  *v = static_cast<uint16>(p_[0]) << 8 |
+       static_cast<uint16>(p_[1]);
+  p_ += 2;
+  len_ -= 2;
+  return true;
+}
+
+bool DnsResponseBuffer::U32(uint32* v) {
+  if (len_ < 4)
+    return false;
+  *v = static_cast<uint32>(p_[0]) << 24 |
+       static_cast<uint32>(p_[1]) << 16 |
+       static_cast<uint32>(p_[2]) << 8 |
+       static_cast<uint32>(p_[3]);
+  p_ += 4;
+  len_ -= 4;
+  return true;
+}
+
+bool DnsResponseBuffer::Skip(unsigned n) {
+  if (len_ < n)
+    return false;
+  p_ += n;
+  len_ -= n;
+  return true;
+}
+
+bool DnsResponseBuffer::Block(base::StringPiece* out, unsigned len) {
+  if (len_ < len)
+    return false;
+  *out = base::StringPiece(reinterpret_cast<const char*>(p_), len);
+  p_ += len;
+  len_ -= len;
+  return true;
+}
+
+// DNSName parses a (possibly compressed) DNS name from the packet. If |name|
+// is not NULL, then the name is written into it. See RFC 1035 section 4.1.4.
+bool DnsResponseBuffer::DNSName(std::string* name) {
+  unsigned jumps = 0;
+  const uint8* p = p_;
+  unsigned len = len_;
+
+  if (name)
+    name->clear();
+
+  for (;;) {
+    if (len < 1)
+      return false;
+    uint8 d = *p;
+    p++;
+    len--;
+
+    // The two couple of bits of the length give the type of the length. It's
+    // either a direct length or a pointer to the remainder of the name.
+    if ((d & 0xc0) == 0xc0) {
+      // This limit matches the depth limit in djbdns.
+      if (jumps > 100)
+        return false;
+      if (len < 1)
+        return false;
+      uint16 offset = static_cast<uint16>(d) << 8 |
+                      static_cast<uint16>(p[0]);
+      offset &= 0x3ff;
+      p++;
+      len--;
+
+      if (jumps == 0) {
+        p_ = p;
+        len_ = len;
+      }
+      jumps++;
+
+      if (offset >= packet_len_)
+        return false;
+      p = &packet_[offset];
+      len = packet_len_ - offset;
+    } else if ((d & 0xc0) == 0) {
+      uint8 label_len = d;
+      if (len < label_len)
+        return false;
+      if (name && label_len) {
+        if (!name->empty())
+          name->append(".");
+        name->append(reinterpret_cast<const char*>(p), label_len);
+      }
+      p += label_len;
+      len -= label_len;
+
+      if (jumps == 0) {
+        p_ = p;
+        len_ = len;
+      }
+
+      if (label_len == 0)
+        break;
+    } else {
+      return false;
+    }
+  }
+
+  return true;
+}
+
 }  // namespace net