Mitigate spoofing attempt using Latin letters.

net/base/lookup_string_in_fixed_set.cc

Index: net/base/lookup_string_in_fixed_set.cc
diff --git a/net/base/lookup_string_in_fixed_set.cc b/net/base/lookup_string_in_fixed_set.cc
deleted file mode 100644
index 5c145f8cd63ebbb04d68bf2cd12275498cf9aa41..0000000000000000000000000000000000000000
--- a/net/base/lookup_string_in_fixed_set.cc
+++ /dev/null
@@ -1,198 +0,0 @@
-// Copyright 2015 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 "net/base/lookup_string_in_fixed_set.h"
-
-#include "base/logging.h"
-
-namespace net {
-
-namespace {
-
-// Read next offset from |pos|, increment |offset| by that amount, and increment
-// |pos| either to point to the start of the next encoded offset in its node, or
-// nullptr, if there are no remaining offsets.
-//
-// Returns true if an offset could be read; false otherwise.
-inline bool GetNextOffset(const unsigned char** pos,
-                          const unsigned char** offset) {
-  if (*pos == nullptr)
-    return false;
-
-  size_t bytes_consumed;
-  switch (**pos & 0x60) {
-    case 0x60:  // Read three byte offset
-      *offset += (((*pos)[0] & 0x1F) << 16) | ((*pos)[1] << 8) | (*pos)[2];
-      bytes_consumed = 3;
-      break;
-    case 0x40:  // Read two byte offset
-      *offset += (((*pos)[0] & 0x1F) << 8) | (*pos)[1];
-      bytes_consumed = 2;
-      break;
-    default:
-      *offset += (*pos)[0] & 0x3F;
-      bytes_consumed = 1;
-  }
-  if ((**pos & 0x80) != 0) {
-    *pos = nullptr;
-  } else {
-    *pos += bytes_consumed;
-  }
-  return true;
-}
-
-// Check if byte at |offset| is last in label.
-bool IsEOL(const unsigned char* offset) {
-  return (*offset & 0x80) != 0;
-}
-
-// Check if byte at |offset| matches key. This version matches both end-of-label
-// chars and not-end-of-label chars.
-bool IsMatch(const unsigned char* offset, char key) {
-  return (*offset & 0x7F) == key;
-}
-
-// Read return value at |offset|, if it is a return value. Returns true if a
-// return value could be read, false otherwise.
-bool GetReturnValue(const unsigned char* offset, int* return_value) {
-  // Return values are always encoded as end-of-label chars (so the high bit is
-  // set). So byte values in the inclusive range [0x80, 0x9F] encode the return
-  // values 0 through 31 (though make_dafsa.py doesn't currently encode values
-  // higher than 7). The following code does that translation.
-  if ((*offset & 0xE0) == 0x80) {
-    *return_value = *offset & 0x1F;
-    return true;
-  }
-  return false;
-}
-
-}  // namespace
-
-FixedSetIncrementalLookup::FixedSetIncrementalLookup(const unsigned char* graph,
-                                                     size_t length)
-    : pos_(graph), end_(graph + length), pos_is_label_character_(false) {}
-
-FixedSetIncrementalLookup::FixedSetIncrementalLookup(
-    const FixedSetIncrementalLookup& other) = default;
-
-FixedSetIncrementalLookup& FixedSetIncrementalLookup::operator=(
-    const FixedSetIncrementalLookup& other) = default;
-
-FixedSetIncrementalLookup::~FixedSetIncrementalLookup() {}
-
-bool FixedSetIncrementalLookup::Advance(char input) {
-  if (!pos_) {
-    // A previous input exhausted the graph, so there are no possible matches.
-    return false;
-  }
-
-  // Only ASCII printable chars are supported by the current DAFSA format -- the
-  // high bit (values 0x80-0xFF) is reserved as a label-end signifier, and the
-  // low values (values 0x00-0x1F) are reserved to encode the return values. So
-  // values outside this range will never be in the dictionary.
-  if (input >= 0x20) {
-    if (pos_is_label_character_) {
-      // Currently processing a label, so it is only necessary to check the byte
-      // at |pos_| to see if it encodes a character matching |input|.
-      bool is_last_char_in_label = IsEOL(pos_);
-      bool is_match = IsMatch(pos_, input);
-      if (is_match) {
-        // If this is not the last character in the label, the next byte should
-        // be interpreted as a character or return value. Otherwise, the next
-        // byte should be interpreted as a list of child node offsets.
-        ++pos_;
-        DCHECK(pos_ < end_);
-        pos_is_label_character_ = !is_last_char_in_label;
-        return true;
-      }
-    } else {
-      const unsigned char* offset = pos_;
-      // Read offsets from |pos_| until the label of the child node at |offset|
-      // matches |input|, or until there are no more offsets.
-      while (GetNextOffset(&pos_, &offset)) {
-        DCHECK(offset < end_);
-        DCHECK((pos_ == nullptr) || (pos_ < end_));
-
-        // |offset| points to a DAFSA node that is a child of the original node.
-        //
-        // The low 7 bits of a node encodes a character value; the high bit
-        // indicates whether it's the last character in the label.
-        //
-        // Note that |*offset| could also be a result code value, but these are
-        // really just out-of-range ASCII values, encoded the same way as
-        // characters. Since |input| was already validated as a printable ASCII
-        // value ASCII value, IsMatch will never return true if |offset| is a
-        // result code.
-        bool is_last_char_in_label = IsEOL(offset);
-        bool is_match = IsMatch(offset, input);
-
-        if (is_match) {
-          // If this is not the last character in the label, the next byte
-          // should be interpreted as a character or return value. Otherwise,
-          // the next byte should be interpreted as a list of child node
-          // offsets.
-          pos_ = offset + 1;
-          DCHECK(pos_ < end_);
-          pos_is_label_character_ = !is_last_char_in_label;
-          return true;
-        }
-      }
-    }
-  }
-
-  // If no match was found, then end of the DAFSA has been reached.
-  pos_ = nullptr;
-  pos_is_label_character_ = false;
-  return false;
-}
-
-int FixedSetIncrementalLookup::GetResultForCurrentSequence() const {
-  int value = kDafsaNotFound;
-  // Look to see if there is a next character that's a return value.
-  if (pos_is_label_character_) {
-    // Currently processing a label, so it is only necessary to check the byte
-    // at |pos_| to see if encodes a return value.
-    GetReturnValue(pos_, &value);
-  } else {
-    // Otherwise, |pos_| is an offset list (or nullptr). Explore the list of
-    // child nodes (given by their offsets) to find one whose label is a result
-    // code.
-    //
-    // This search uses a temporary copy of |pos_|, since mutating |pos_| could
-    // skip over a node that would be important to a subsequent Advance() call.
-    const unsigned char* temp_pos = pos_;
-
-    // Read offsets from |temp_pos| until either |temp_pos| is nullptr or until
-    // the byte at |offset| contains a result code (encoded as an ASCII
-    // character below 0x20).
-    const unsigned char* offset = pos_;
-    while (GetNextOffset(&temp_pos, &offset)) {
-      DCHECK(offset < end_);
-      DCHECK((temp_pos == nullptr) || temp_pos < end_);
-      if (GetReturnValue(offset, &value))
-        break;
-    }
-  }
-  return value;
-}
-
-int LookupStringInFixedSet(const unsigned char* graph,
-                           size_t length,
-                           const char* key,
-                           size_t key_length) {
-  // Do an incremental lookup until either the end of the graph is reached, or
-  // until every character in |key| is consumed.
-  FixedSetIncrementalLookup lookup(graph, length);
-  const char* key_end = key + key_length;
-  while (key != key_end) {
-    if (!lookup.Advance(*key))
-      return kDafsaNotFound;
-    key++;
-  }
-  // The entire input was consumed without reaching the end of the graph. Return
-  // the result code (if present) for the current position, or kDafsaNotFound.
-  return lookup.GetResultForCurrentSequence();
-}
-
-}  // namespace net