Better string handling

The text and pattern are now streamed directly (skipping saving them to
strings).
Knowing exactly what string was matched has now been delegated to
the Rabin_fingerprint_process.

README.md

@@ -2,9 +2,20 @@
 
 Code used for my Bachelor's Thesis
 
+# Issues
+When reading the pattern from a file, according to UNIX standards ([read details here](https://unix.stackexchange.com/questions/18743/whats-the-point-in-adding-a-new-line-to-the-end-of-a-file)) a "text file" has to end on a newline.  
+This adds an unintended newline to the end of the pattern, so to avoid adding said newline, write the file using:  
+`echo -n word > pattern.txt`  
+or if you use Vim, remove the newline using  
+```
+:set binary
+:set noeol
+:wq
+```
+
 # Versions
 ## Current Version
-Compared to V1, this current state `generate_initial_irreducible_polynomials.sage`, `generate_random_irreducible_polynomial.sage`, and `multiply_polynomials_modulo_polynomial.sage` have been removed from the main folder, as they have already been used for implementing their corresponding features in `general_library.cpp`. They will be preserved in the V1 folder.  
+Compared to V1, in this current state `generate_initial_irreducible_polynomials.sage`, `generate_random_irreducible_polynomial.sage`, and `multiply_polynomials_modulo_polynomial.sage` have been removed from the main folder, as they have already been used for implementing their corresponding features in `general_library.cpp`. They will be preserved in the V1 folder.  
 
 This version also contains code relating to Porat-Porat and other random code stumps. This code is going to be completely reimplemented, but is preserved for now to avoid redoing work.  
 

books/pattern.txt

@@ -0,0 +1 @@
+word

processes.cpp

@@ -27,3 +27,33 @@ void Rabin_fingerprint_process::stream_bit (bool b) {
 uint32_t Rabin_fingerprint_process::get_fingerprint() {
     return phi.get_fingerprint();
 }
+
+std::string Rabin_fingerprint_process::get_string_in_window() {
+    // check if window contains a whole number of chars
+    if ((window_size_in_bits & 0b111) != 0)
+        throw std::logic_error("The fingerprinting window doesn't contain a whole number of chars (counting the bits), so it doesn't make sense to return it as a string.");
+
+    #ifndef NDEBUG
+    if (window.size() != window_size_in_bits)
+        throw std::logic_error("False match! The sliding window isn't even filled yet, which means you matched the pattern of a substring shorter than the pattern. This case should be handled/avoided elsewhere, so we throw an error.");
+    #endif
+
+    std::ostringstream os;
+    for (size_t i = 0; i < window.size()>>3; i++) {
+        // cycle the char
+        char c = 0;
+        for (size_t j = 0; j < 8; j++) {
+            bool b = window.front();
+            window.pop();
+            window.push(b);
+            c <<= 1;
+            c |= b;
+        }
+
+        os << c;
+    }
+
+    std::string s = os.str();
+
+    return s;
+}

processes.hpp

@@ -6,6 +6,8 @@
 
 #include <stdint.h>
 #include <queue>
+#include <string>
+#include <sstream>
 
 class Rabin_fingerprint_process {
     public:
@@ -13,6 +15,7 @@ class Rabin_fingerprint_process {
         void stream_char(char c);
         void stream_bit(bool b);
         uint32_t get_fingerprint();
+        std::string get_string_in_window();
 
     private:
         std::queue<bool> window;

simple_string_matching.cpp

@@ -1,6 +1,6 @@
 /* #define NDEBUG */
 /* #include "Rabin_fingerprint.hpp" */
-/* #include "general_library.hpp" */
+#include "general_library.hpp"
 #include "processes.hpp"
 
 #include <iostream>
@@ -9,46 +9,42 @@
 #include <string>
 #include <fstream>
 
-void print_match (size_t index, size_t length, std::string &T) {
-    std::cout << "Match found at index " << index << " with the text \"";
-    for (size_t i = 0; i < length; i++)
-        std::cout << T[index + i];
-    std::cout << "\"" << std::endl;
-}
-
 int main() {
-    /* std::ifstream ifs("books/the_complete_works_of_william_shakespeare.txt"); */
+    /* std::ifstream T("books/the_complete_works_of_william_shakespeare.txt"); */
-    std::ifstream ifs("books/genji_monogatari_english.txt");
+    std::ifstream T("books/genji_monogatari_english.txt");
-    std::string T( (std::istreambuf_iterator<char>(ifs) ),
+    std::ifstream P("books/pattern.txt");
-                    (std::istreambuf_iterator<char>() ) );
-
-    std::string P = "word";
 
+    char c;
+    size_t P_length = 0;
     std::cout << "Searching for pattern:" << std::endl;
-    std::cout << "    " << P << std::endl;
+    std::cout << "    ";
-    /* std::cout << "in text:" << std::endl; */
+    while(P.get(c)) {
-    /* std::cout << "    " << T << std::endl; */
+        std::cout << c;
-    std::cout << std::endl;
+        P_length++;
+
+    }
+    std::cout << std::endl << std::endl;
+
+    P.clear();                 // clear fail and eof bits
+    P.seekg(0, std::ios::beg); // back to the start!
 
     uint32_t irreducible_polynomial = get_random_irreducible_polynomial_in_Z2(31);
-    size_t window_size_in_bits = P.length()*8;
+    size_t window_size_in_bits = P_length*8;
 
     // Hash the pattern
     Rabin_fingerprint_process phiP(irreducible_polynomial, (size_t)window_size_in_bits);
-    for (char c : P)
+    while(P.get(c)) {
         phiP.stream_char(c);
+    }
 
     // Hash the text
     Rabin_fingerprint_process phiT(irreducible_polynomial, window_size_in_bits);
-    for (size_t i = 0; i < P.length(); i++)
+    size_t index = 0;
-        phiT.stream_char(T[i]);
+    while(T.get(c)) {
+        phiT.stream_char(c);
+        index++;
         if (phiT.get_fingerprint() == phiP.get_fingerprint())
-        print_match(0, P.length(), T);
+            std::cout << "Match found at index " << index-P_length << " with the text \"" << phiT.get_string_in_window() << "\"" << std::endl;
-
-    for (size_t i = P.length(); i < T.length(); i++) {
-        phiT.stream_char(T[i]);
-        if (phiT.get_fingerprint() == phiP.get_fingerprint())
-            print_match(i-P.length()+1, P.length(), T);
     }
 
     std::cout << std::endl;