[Engine] add TN/ITN functions (#3047)

* add AddBlk, ReverseFrac function
* rename text processing functions

runtime/engine/common/utils/text_process.cc

+#include "utils/text_process.h"
+
+namespace ppspeech {
+
+std::string DelBlank(const std::string& str) {
+    std::string out = "";
+    int ptr_in = 0;    //  the pointer of input string (for traversal)
+    int end = str.size();
+    int ptr_out = -1;  //  the pointer of output string (last char)
+    while (ptr_in != end) {
+        while (ptr_in != end && str[ptr_in] == ' ') {
+            ptr_in += 1;
+        }
+        if (ptr_in == end) 
+            return out;
+        if (ptr_out != -1 && isalpha(str[ptr_in]) && isalpha(str[ptr_out]) && str[ptr_in-1] == ' ')
+            // add a space when the last and current chars are in English and there have space(s) between them
+            out += ' ';
+        out += str[ptr_in];
+        ptr_out = ptr_in;
+        ptr_in += 1;
+    }
+    return out;
+}
+
+std::string AddBlank(const std::string& str) {
+    std::string out = "";
+    int ptr = 0;  // the pointer of the input string
+    int end = str.size();
+    while (ptr != end) {
+        if (isalpha(str[ptr])) {
+            if (ptr == 0 or str[ptr-1] != ' ')
+                out += " ";  // add pre-space for an English word
+            while (isalpha(str[ptr])) {
+                out += str[ptr];
+                ptr += 1;
+            }
+            out += " ";  // add post-space for an English word
+        } else {
+            out += str[ptr];
+            ptr += 1;
+        }
+    }
+    return out;
+}
+
+std::string ReverseFraction(const std::string& str) {
+    std::string out = "";
+    int ptr = 0;   // the pointer of the input string
+    int end = str.size();
+    int left, right, frac;  // the start index of the left tag, right tag and '/'.
+    left = right = frac = 0;
+    int len_tag = 5;  // length of "<tag>"
+
+    while (ptr != end) {
+        // find the position of left tag, right tag and '/'. (xxx<tag>num1/num2</tag>)
+        left = str.find("<tag>", ptr);
+        if (left == -1)
+            break;
+        out += str.substr(ptr, left - ptr);  // content before left tag (xxx)
+        frac = str.find("/", left);
+        right = str.find("<tag>", frac);
+        
+        out += str.substr(frac + 1, right - frac - 1) + '/' + 
+               str.substr(left + len_tag, frac - left - len_tag);  // num2/num1
+        ptr = right + len_tag;
+    }
+    if (ptr != end) {
+        out += str.substr(ptr, end - ptr);
+    }
+    return out;
+}
+
+}  // namespace ppspeech
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runtime/engine/common/utils/text_process.h

+#include <string>
+#include <vector>
+#include <cctype>
+
+namespace ppspeech {
+
+std::string DelBlank(const std::string& str);
+
+std::string AddBlank(const std::string& str);
+
+std::string ReverseFraction(const std::string& str);
+
+}  // namespace ppspeech
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runtime/engine/common/utils/text_process_test.cc

+#include "utils/text_process.h"
+
+#include <gtest/gtest.h>
+#include <gmock/gmock.h>
+
+TEST(TextProcess, DelBlankTest) {
+    std::string test_str = "我 今天     去 了 超市     花了   120 元。";
+    std::string out_str = ppspeech::DelBlank(test_str);
+    int ret = out_str.compare("我今天去了超市花了120元。");
+    EXPECT_EQ(ret, 0);
+
+    test_str = "how are you today";
+    out_str = ppspeech::DelBlank(test_str);
+    ret = out_str.compare("how are you today");
+    EXPECT_EQ(ret, 0);
+
+    test_str = "我 的 paper 在 哪里？";
+    out_str = ppspeech::DelBlank(test_str);
+    ret = out_str.compare("我的paper在哪里？");
+    EXPECT_EQ(ret, 0);
+}
+
+TEST(TextProcess, AddBlankTest) {
+    std::string test_str = "how are you";
+    std::string out_str = ppspeech::AddBlank(test_str);
+    int ret = out_str.compare(" how  are  you ");
+    EXPECT_EQ(ret, 0);
+
+    test_str = "欢迎来到China。";
+    out_str = ppspeech::AddBlank(test_str);
+    ret = out_str.compare("欢迎来到 China 。");
+    EXPECT_EQ(ret, 0);
+}
+
+TEST(TextProcess, ReverseFractionTest) {
+    std::string test_str = "<tag>3/1<tag>";
+    std::string out_str = ppspeech::ReverseFraction(test_str);
+    int ret = out_str.compare("1/3");
+    std::cout<<out_str<<std::endl;
+    EXPECT_EQ(ret, 0);
+
+    test_str = "<tag>3/1<tag> <tag>100/10000<tag>";
+    out_str = ppspeech::ReverseFraction(test_str);
+    ret = out_str.compare("1/3 10000/100");
+    std::cout<<out_str<<std::endl;
+    EXPECT_EQ(ret, 0);
+}
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