Merge pull request #3125 from mozilla/utf8-regressions

Fix some regressions from Alphabet refactoring (Fixes #3123)

native_client/alphabet.cc

@@ -57,6 +57,9 @@ Alphabet::init(const char *config_file)
     if (line == " ") {
       space_label_ = label;
     }
+    if (line.length() == 0) {
+      continue;
+    }
     label_to_str_[label] = line;
     str_to_label_[line] = label;
     ++label;
@@ -187,3 +190,14 @@ Alphabet::Encode(const std::string& input) const
   }
   return result;
 }
+
+std::vector<unsigned int>
+UTF8Alphabet::Encode(const std::string& input) const
+{
+  std::vector<unsigned int> result;
+  for (auto byte_char : input) {
+    std::string byte_str(1, byte_char);
+    result.push_back(EncodeSingle(byte_str));
+  }
+  return result;
+}

native_client/alphabet.h

@@ -52,7 +52,7 @@ class Alphabet {
 
   // Encode a sequence of character/output classes into a sequence of labels.
   // Characters are assumed to always take a single Unicode codepoint.
-  std::vector<unsigned int> Encode(const std::string& input) const;
+  virtual std::vector<unsigned int> Encode(const std::string& input) const;
 
 protected:
   size_t size_;
@@ -77,7 +77,8 @@ class UTF8Alphabet : public Alphabet
   int init(const char*) override {
     return 0;
   }
-};
 
+  std::vector<unsigned int> Encode(const std::string& input) const override;
+};
 
 #endif //ALPHABET_H

native_client/ctcdecode/__init__.py

@@ -3,7 +3,9 @@
 from . import swigwrapper # pylint: disable=import-self
 from .swigwrapper import UTF8Alphabet
 
-__version__ = swigwrapper.__version__
+# This module is built with SWIG_PYTHON_STRICT_BYTE_CHAR so we must handle
+# string encoding explicitly, here and throughout this file.
+__version__ = swigwrapper.__version__.decode('utf-8')
 
 # Hack: import error codes by matching on their names, as SWIG unfortunately
 # does not support binding enums to Python in a scoped manner yet.
@@ -30,7 +32,7 @@ def __init__(self, alpha=None, beta=None, scorer_path=None, alphabet=None):
             assert beta is not None, 'beta parameter is required'
             assert scorer_path, 'scorer_path parameter is required'
 
-            err = self.init(scorer_path, alphabet)
+            err = self.init(scorer_path.encode('utf-8'), alphabet)
             if err != 0:
                 raise ValueError('Scorer initialization failed with error code 0x{:X}'.format(err))
 
@@ -41,15 +43,27 @@ class Alphabet(swigwrapper.Alphabet):
     """Convenience wrapper for Alphabet which calls init in the constructor"""
     def __init__(self, config_path):
         super(Alphabet, self).__init__()
-        err = self.init(config_path)
+        err = self.init(config_path.encode('utf-8'))
         if err != 0:
             raise ValueError('Alphabet initialization failed with error code 0x{:X}'.format(err))
 
+    def EncodeSingle(self, input):
+        return super(Alphabet, self).EncodeSingle(input.encode('utf-8'))
+
     def Encode(self, input):
-        """Convert SWIG's UnsignedIntVec to a Python list"""
-        res = super(Alphabet, self).Encode(input)
+        # Convert SWIG's UnsignedIntVec to a Python list
+        res = super(Alphabet, self).Encode(input.encode('utf-8'))
         return [el for el in res]
 
+    def DecodeSingle(self, input):
+        res = super(Alphabet, self).DecodeSingle(input)
+        return res.decode('utf-8')
+
+    def Decode(self, input):
+        res = super(Alphabet, self).Decode(input)
+        return res.decode('utf-8')
+
+
 
 def ctc_beam_search_decoder(probs_seq,
                             alphabet,

native_client/ctcdecode/ctc_beam_search_decoder.cpp

@@ -182,8 +182,9 @@ DecoderState::decode(size_t num_results) const
   // score the last word of each prefix that doesn't end with space
   if (ext_scorer_) {
     for (size_t i = 0; i < beam_size_ && i < prefixes_copy.size(); ++i) {
-      auto prefix = prefixes_copy[i];
-      if (!ext_scorer_->is_scoring_boundary(prefix->parent, prefix->character)) {
+      PathTrie* prefix = prefixes_copy[i];
+      PathTrie* prefix_boundary = ext_scorer_->is_utf8_mode() ? prefix : prefix->parent;
+      if (prefix_boundary && !ext_scorer_->is_scoring_boundary(prefix_boundary, prefix->character)) {
         float score = 0.0;
         std::vector<std::string> ngram = ext_scorer_->make_ngram(prefix);
         bool bos = ngram.size() < ext_scorer_->get_max_order();

native_client/ctcdecode/swigwrapper.i

@@ -3,6 +3,7 @@
 %{
 #include "ctc_beam_search_decoder.h"
 #define SWIG_FILE_WITH_INIT
+#define SWIG_PYTHON_STRICT_BYTE_CHAR
 #include "workspace_status.h"
 %}