Endianness management

Endianness management and minor changes to the test app

Author: calderonil

end.h

@@ -0,0 +1,39 @@
+/*
+Spatial Bloom Filter C++ Library (libSBF-cpp)
+Copyright (C) 2017  Luca Calderoni, Dario Maio,
+University of Bologna
+Copyright (C) 2017  Paolo Palmieri,
+Cranfield University
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU Lesser General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU Lesser General Public License for more details.
+
+You should have received a copy of the GNU Lesser General Public License
+along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#pragma once
+
+#ifndef END_H
+#define END_H
+
+#include <stdint.h>
+
+int is_big_endian(void)
+{
+	union {
+		uint32_t i;
+		char c[4];
+	} bi = { 0x01020304 };
+
+	return bi.c[0] == 1;
+}
+
+#endif /* END_H */

sbf.cpp

@@ -264,8 +264,8 @@ void SBF::PrintFilter(int mode)
     printf("Filter details:\n");
     printf("Number of cells: %d\n",this->cells);
     printf("Size in Bytes: %d\n",this->size);
-    printf("Filter sparsity: %f\n",this->GetFilterSparsity());
-    printf("Filter fpp: %f\n",this->GetFilterFpp());
+    printf("Filter sparsity: %.5f\n",this->GetFilterSparsity());
+    printf("Filter fpp: %.5f\n",this->GetFilterFpp());
     printf("Number of mapped elements: %d\n",this->members);
     printf("Number of hash collisions: %d\n",this->collisions);
 
@@ -301,8 +301,8 @@ void SBF::PrintFilter(int mode)
 
     printf("\nEmersion and Fpp:\n");
     for(int j = 1; j < this->AREA_number+1; j++){
-        if(this->GetAreaFlotation(j)) printf("Area %d: emersion %f, flotation safe, fpp %f",j,this->GetAreaEmersion(j),this->AREA_fpp[j]);
-        else printf("Area %d: emersion %f, flotation unsafe, fpp %f",j,this->GetAreaEmersion(j),this->AREA_fpp[j]);
+        if(this->GetAreaFlotation(j)) printf("Area %d: emersion %.5f, flotation safe, fpp %.5f",j,this->GetAreaEmersion(j),this->AREA_fpp[j]);
+        else printf("Area %d: emersion %.5f, flotation unsafe, fpp %.5f",j,this->GetAreaEmersion(j),this->AREA_fpp[j]);
         printf("\n");
     }
     printf("\n");
@@ -318,6 +318,9 @@ void SBF::SaveToDisk(std::string path, int mode)
 
     myfile.open (path.c_str());
 
+	myfile.setf(std::ios_base::fixed, std::ios_base::floatfield);
+	myfile.precision(5);
+
     if(mode){
 
         myfile << "hash_family" << ";" << this->HASH_family << std::endl;
@@ -395,7 +398,15 @@ void SBF::Insert(char *string, int size, int area)
 
         // Copies the truncated digest (one byte at a time) in an integer
         // variable (endian independent)
-        unsigned int digest_index = (digest32[0] << 24) | (digest32[1] << 16) | (digest32[2] << 8) | digest32[3];
+		unsigned int digest_index;
+		if (this->BIG_end) {
+			digest_index = (digest32[0] << 24) | (digest32[1] << 16) | (digest32[2] << 8) | digest32[3];
+		}
+		else
+		{
+			digest_index = (digest32[3] << 24) | (digest32[2] << 16) | (digest32[1] << 8) | digest32[0];
+		}
+        
 
         // Shifts bits in order to preserve only the first 'bit_mapping'
         // least significant bits
@@ -444,9 +455,16 @@ int SBF::Check(char *string, int size)
              digest32[i] = digest[i];
         }
 
-        // Copies the truncated digest (one byte at a time) in an integer
-        // variable (endian independent)
-        unsigned int digest_index = (digest32[0] << 24) | (digest32[1] << 16) | (digest32[2] << 8) | digest32[3];
+		// Copies the truncated digest (one byte at a time) in an integer
+		// variable (endian independent)
+		unsigned int digest_index;
+		if (this->BIG_end) {
+			digest_index = (digest32[0] << 24) | (digest32[1] << 16) | (digest32[2] << 8) | digest32[3];
+		}
+		else
+		{
+			digest_index = (digest32[3] << 24) | (digest32[2] << 16) | (digest32[1] << 8) | digest32[0];
+		}
 
         // Shifts bits in order to preserve only the first 'bit_mapping' least
         // significant bits

sbf.h

@@ -37,6 +37,8 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #include "linux/libexport.h"
 #endif
 
+#include "end.h"
+
 #include <fstream>
 #include <iostream>
 #include <math.h>
@@ -69,6 +71,7 @@ namespace sbf {
 		int *AREA_cells;
 		int *AREA_self_collisions;
 		float *AREA_fpp;
+		int BIG_end;
 
 		// Private methods (commented in the sbf.cpp)
 		void SetCell(unsigned int index, int area);
@@ -124,6 +127,9 @@ namespace sbf {
 			if (HASH_number <= 0 || HASH_number > MAX_HASH_NUMBER) throw std::invalid_argument("Invalid number of hash runs.");
 			if (salt_path.length() == 0) throw std::invalid_argument("Invalid hash salt path.");
 
+			// Checks whether the execution is being performed on a big endian or little endian machine
+			this->BIG_end = is_big_endian();
+
 			// Defines the number of bytes required for each cell depending on AREA_number
 			// In order to reduce the memory footprint of the filter, we use 1 byte 
 			// for a number of areas <= 255, 2 bytes for a up to MAX_AREA_NUMBER

test-app/test-app.cpp

@@ -143,15 +143,16 @@ int main() {
 		std::cout << "Enter the print mode to use:" << std::endl;
 		std::cout << "1 (prints filter information to the standard output)" << std::endl;
 		std::cout << "2 (prints filter information and cells values to the standard output)" << std::endl;
-		std::cout << "3 (save both filter and related meta data to disk)" << std::endl;
+		std::cout << "3 (save filter statistics and meta data to disk)" << std::endl;
+		std::cout << "4 (save both filter and related meta data to disk)" << std::endl;
 		std::cout << "(press ENTER to ignore)..." << std::endl;
 		getline(std::cin, input);
 
 		if (input.empty()) break;
 		else {
 			std::istringstream istr(input);
 			istr >> print_mode;
-			if (print_mode != 1 && print_mode != 2 && print_mode != 3) print_mode = 0;
+			if (print_mode != 1 && print_mode != 2 && print_mode != 3 && print_mode != 4) print_mode = 0;
 			break;
 		}
 
@@ -225,7 +226,8 @@ int main() {
 	//prints filter to the standard output or saves it to disk
 	if (print_mode == 1) myFilter->PrintFilter(0);
 	if (print_mode == 2) myFilter->PrintFilter(1);
-	if (print_mode == 3) {
+	if (print_mode == 3) myFilter->SaveToDisk("stats" + buf + ".csv", 1);
+	if (print_mode == 4) {
 		myFilter->SaveToDisk("filter" + buf + ".csv", 0);
 		myFilter->SaveToDisk("stats" + buf + ".csv", 1);
 	}
@@ -258,7 +260,7 @@ int main() {
 		}
 		printf("Well recognised: %d\n", well_recognised);
 		printf("Elements assigned to a wrong set: %d\n", exchanged_elements);
-		printf("Exchange rate: %f\n", (float)exchanged_elements / (float)n);
+		printf("Exchange rate: %.5f\n", (float)exchanged_elements / (float)n);
 		myfile.close();
 	}
 	else {
@@ -304,7 +306,7 @@ int main() {
 			}
 			printf("Well recognised: %d\n", well_recognised);
 			printf("False positives: %d\n", false_positives);
-			printf("False positives rate: %f\n", (float)false_positives / (float)nver);
+			printf("False positives rate: %.5f\n", (float)false_positives / (float)nver);
 			myfile.close();
 		}
 		else {