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normalizer.cc
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normalizer.cc
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// Copyright 2016 Google Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.!
#include "normalizer.h"
#include <utility>
#include <vector>
#include "common.h"
#include "third_party/absl/strings/match.h"
#include "third_party/absl/strings/string_view.h"
#include "third_party/absl/strings/strip.h"
#include "third_party/darts_clone/darts.h"
#include "util.h"
namespace sentencepiece {
namespace normalizer {
constexpr int Normalizer::kMaxTrieResultsSize;
Normalizer::Normalizer(const NormalizerSpec &spec,
const TrainerSpec &trainer_spec)
: spec_(&spec),
treat_whitespace_as_suffix_(trainer_spec.treat_whitespace_as_suffix()),
status_(util::OkStatus()) {
Init();
}
Normalizer::Normalizer(const NormalizerSpec &spec)
: spec_(&spec), status_(util::OkStatus()) {
Init();
}
Normalizer::~Normalizer() {}
void Normalizer::Init() {
absl::string_view index = spec_->precompiled_charsmap();
if (!index.empty()) {
absl::string_view trie_blob, normalized;
#ifdef IS_BIG_ENDIAN
status_ = DecodePrecompiledCharsMap(index, &trie_blob, &normalized,
&precompiled_charsmap_buffer_);
#else
status_ = DecodePrecompiledCharsMap(index, &trie_blob, &normalized);
#endif
if (!status_.ok()) return;
// Reads the body of double array.
trie_ = std::make_unique<Darts::DoubleArray>();
// The second arg of set_array is not the size of blob,
// but the number of double array units.
trie_->set_array(const_cast<char *>(trie_blob.data()),
trie_blob.size() / trie_->unit_size());
normalized_ = normalized.data();
}
}
util::Status Normalizer::Normalize(absl::string_view input,
std::string *normalized,
std::vector<size_t> *norm_to_orig) const {
norm_to_orig->clear();
normalized->clear();
if (input.empty()) {
return util::OkStatus();
}
RETURN_IF_ERROR(status());
int consumed = 0;
// Ignores heading space.
if (spec_->remove_extra_whitespaces()) {
while (!input.empty()) {
const auto p = NormalizePrefix(input);
if (p.first != " ") {
break;
}
input.remove_prefix(p.second);
consumed += p.second;
}
}
// all chars are whitespace.
if (input.empty()) {
return util::OkStatus();
}
// Reserves the output buffer to avoid re-allocations.
const size_t kReservedSize = input.size() * 3;
normalized->reserve(kReservedSize);
norm_to_orig->reserve(kReservedSize);
// Replaces white space with U+2581 (LOWER ONE EIGHT BLOCK)
// if escape_whitespaces() is set (default = true).
const absl::string_view kSpaceSymbol = "\xe2\x96\x81";
// adds kSpaceSymbol to the current context.
auto add_ws = [this, &consumed, &normalized, &norm_to_orig, &kSpaceSymbol]() {
if (spec_->escape_whitespaces()) {
normalized->append(kSpaceSymbol.data(), kSpaceSymbol.size());
for (size_t n = 0; n < kSpaceSymbol.size(); ++n) {
norm_to_orig->push_back(consumed);
}
} else {
normalized->append(" ");
norm_to_orig->push_back(consumed);
}
};
// Adds a space symbol as a prefix (default is true)
// With this prefix, "world" and "hello world" are converted into
// "_world" and "_hello_world", which help the trainer to extract
// "_world" as one symbol.
if (!treat_whitespace_as_suffix_ && spec_->add_dummy_prefix()) add_ws();
bool is_prev_space = spec_->remove_extra_whitespaces();
while (!input.empty()) {
auto p = NormalizePrefix(input);
absl::string_view sp = p.first;
// Removes heading spaces in sentence piece,
// if the previous sentence piece ends with whitespace.
while (is_prev_space && absl::ConsumePrefix(&sp, " ")) {
}
if (!sp.empty()) {
const char *data = sp.data();
for (size_t n = 0; n < sp.size(); ++n) {
if (spec_->escape_whitespaces() && data[n] == ' ') {
// replace ' ' with kSpaceSymbol.
normalized->append(kSpaceSymbol.data(), kSpaceSymbol.size());
for (size_t m = 0; m < kSpaceSymbol.size(); ++m) {
norm_to_orig->push_back(consumed);
}
} else {
*normalized += data[n];
norm_to_orig->push_back(consumed);
}
}
// Checks whether the last character of sp is whitespace.
is_prev_space = absl::EndsWith(sp, " ");
}
consumed += p.second;
input.remove_prefix(p.second);
if (!spec_->remove_extra_whitespaces()) {
is_prev_space = false;
}
}
// Ignores trailing space.
if (spec_->remove_extra_whitespaces()) {
const absl::string_view space =
spec_->escape_whitespaces() ? kSpaceSymbol : " ";
while (absl::EndsWith(*normalized, space)) {
const int length = normalized->size() - space.size();
CHECK_GE_OR_RETURN(length, 0);
consumed = (*norm_to_orig)[length];
normalized->resize(length);
norm_to_orig->resize(length);
}
}
// Adds a space symbol as a suffix (default is false)
if (treat_whitespace_as_suffix_ && spec_->add_dummy_prefix()) add_ws();
norm_to_orig->push_back(consumed);
CHECK_EQ_OR_RETURN(norm_to_orig->size(), normalized->size() + 1);
return util::OkStatus();
}
std::string Normalizer::Normalize(absl::string_view input) const {
std::vector<size_t> norm_to_orig;
std::string normalized;
Normalize(input, &normalized, &norm_to_orig).IgnoreError();
return normalized;
}
std::pair<absl::string_view, int> Normalizer::NormalizePrefix(
absl::string_view input) const {
std::pair<absl::string_view, int> result;
if (input.empty()) return result;
if (matcher_ != nullptr) {
bool found = false;
const int mblen = matcher_->PrefixMatch(input, &found);
if (found) return std::make_pair(input.substr(0, mblen), mblen);
}
size_t longest_length = 0;
int longest_value = 0;
if (trie_ != nullptr) {
// Allocates trie_results in stack, which makes the encoding speed 36%
// faster. (38k sentences/sec => 60k sentences/sec). Builder checks that the
// result size never exceeds kMaxTrieResultsSize. This array consumes
// 0.5kByte in stack, which is less than default stack frames (16kByte).
Darts::DoubleArray::result_pair_type
trie_results[Normalizer::kMaxTrieResultsSize];
const size_t num_nodes = trie_->commonPrefixSearch(
input.data(), trie_results, Normalizer::kMaxTrieResultsSize,
input.size());
// Finds the longest rule.
for (size_t k = 0; k < num_nodes; ++k) {
if (longest_length == 0 || trie_results[k].length > longest_length) {
longest_length = trie_results[k].length; // length of prefix
longest_value = trie_results[k].value; // pointer to |normalized_|.
}
}
}
if (longest_length == 0) {
size_t length = 0;
if (!string_util::IsValidDecodeUTF8(input, &length)) {
// Found a malformed utf8.
// The rune is set to be 0xFFFD (REPLACEMENT CHARACTER),
// which is a valid Unicode of three bytes in utf8,
// but here we only consume one byte.
result.second = 1;
static const char kReplacementChar[] = "\xEF\xBF\xBD";
result.first = absl::string_view(kReplacementChar);
} else {
result.second = length;
result.first = absl::string_view(input.data(), result.second);
}
} else {
result.second = longest_length;
// No need to pass the size of normalized sentence,
// since |normalized| is delimitered by "\0".
result.first = absl::string_view(&normalized_[longest_value]);
}
return result;
}
// static
std::string Normalizer::EncodePrecompiledCharsMap(
absl::string_view trie_blob, absl::string_view normalized) {
// <trie size(4byte)><double array trie><normalized string>
std::string blob;
blob.append(string_util::EncodePOD<uint32_t>(trie_blob.size()));
blob.append(trie_blob.data(), trie_blob.size());
#ifdef IS_BIG_ENDIAN
uint32_t *data = reinterpret_cast<uint32_t *>(blob.data());
for (int i = 0; i < blob.size() / 4; ++i) data[i] = util::Swap32(data[i]);
#endif
blob.append(normalized.data(), normalized.size());
return blob;
}
// static
util::Status Normalizer::DecodePrecompiledCharsMap(
absl::string_view blob, absl::string_view *trie_blob,
absl::string_view *normalized, std::string *buffer) {
uint32_t trie_blob_size = 0;
if (blob.size() <= sizeof(trie_blob_size) ||
!string_util::DecodePOD<uint32_t>(
absl::string_view(blob.data(), sizeof(trie_blob_size)),
&trie_blob_size)) {
return util::InternalError("Blob for normalization rule is broken.");
}
#ifdef IS_BIG_ENDIAN
trie_blob_size = util::Swap32(trie_blob_size);
#endif
if (trie_blob_size >= blob.size()) {
return util::InternalError("Trie data size exceeds the input blob size.");
}
blob.remove_prefix(sizeof(trie_blob_size));
#ifdef IS_BIG_ENDIAN
CHECK_OR_RETURN(buffer);
buffer->assign(blob.data(), trie_blob_size);
uint32_t *data = reinterpret_cast<uint32_t *>(const_cast<char *>(buffer->data()));
for (int i = 0; i < buffer->size() / 4; ++i) data[i] = util::Swap32(data[i]);
*trie_blob = absl::string_view(buffer->data(), trie_blob_size);
#else
*trie_blob = absl::string_view(blob.data(), trie_blob_size);
#endif
blob.remove_prefix(trie_blob_size);
*normalized = absl::string_view(blob.data(), blob.size());
return util::OkStatus();
}
PrefixMatcher::PrefixMatcher(const std::set<absl::string_view> &dic) {
if (dic.empty()) return;
std::vector<const char *> key;
key.reserve(dic.size());
for (const auto &it : dic) key.push_back(it.data());
trie_ = std::make_unique<Darts::DoubleArray>();
if (trie_->build(key.size(), const_cast<char **>(&key[0]), nullptr,
nullptr) != 0) {
LOG(ERROR) << "Failed to build the TRIE for PrefixMatcher";
trie_.reset();
}
}
int PrefixMatcher::PrefixMatch(absl::string_view w, bool *found) const {
if (trie_ == nullptr) {
if (found) *found = false;
return std::min<int>(w.size(), string_util::OneCharLen(w.data()));
}
constexpr int kResultSize = 64;
Darts::DoubleArray::result_pair_type trie_results[kResultSize];
const int num_nodes =
trie_->commonPrefixSearch(w.data(), trie_results, kResultSize, w.size());
if (found) *found = (num_nodes > 0);
if (num_nodes == 0) {
return std::min<int>(w.size(), string_util::OneCharLen(w.data()));
}
int mblen = 0;
for (int i = 0; i < num_nodes; ++i) {
mblen = std::max<int>(trie_results[i].length, mblen);
}
return mblen;
}
std::string PrefixMatcher::GlobalReplace(absl::string_view w,
absl::string_view out) const {
std::string result;
while (!w.empty()) {
bool found = false;
const int mblen = PrefixMatch(w, &found);
if (found) {
result.append(out.data(), out.size());
} else {
result.append(w.data(), mblen);
}
w.remove_prefix(mblen);
}
return result;
}
} // namespace normalizer
} // namespace sentencepiece