this cleaned up functions and global constants and hid them away in to their header and source files

tarfunc.cpp

@@ -0,0 +1,60 @@
+/* this file contains function definitions for parsing a tar file.
+ *
+ * by Marcel Nowicki (github@epenis.de | github.com/blindi0815)
+ */
+
+#include "tarfunc.h"
+#include "tarconst.h"
+#include <string>
+#include <cmath>
+
+// checks if a valid modern tar file - ustar
+bool tar::validTar(std::istream &file) {
+    file.seekg(tarconstant::mgcfieldByte.first);
+    char* buffer = new char [tarconstant::mgcfieldByte.second];
+    file.read(buffer, tarconstant::mgcfieldByte.second);
+    std::string magicfield(&buffer[0], 5);
+    delete[] buffer;
+    file.seekg(0);
+    return magicfield == tarconstant::mgcfield ? true: false;
+}
+
+// checks if a 512byte block consist only of 0 or \0
+bool tar::eof (const char* buf) {
+    std::string test(&buf[0]);
+    std::erase(test, '\0');
+    std::erase(test, '0');
+    if (test.empty())
+        return true;
+    return false;
+}
+
+// gets size of an item in bytes. assumes octal encoding.
+uint64_t tar::getitemsize(const char* buf){
+    std::string asciisize(&buf[tarconstant::itemoctlnByte.first], tarconstant::itemoctlnByte.second);
+    uint64_t itemsize{};
+    uint8_t power = tarconstant::itemoctlnByte.second - 1;
+    for (auto i : asciisize) {
+        uint8_t value = i - '0';
+        itemsize += static_cast<uint64_t >(value * std::pow(8, power));
+        power--;
+    }
+    return itemsize;
+}
+
+// gets type of an item
+std::string tar::getitemtype(char &n) {
+    // read itemtype
+    switch (n){
+        case '0': case '\0':
+            return tarconstant::typeFile;
+        case '1':
+            return tarconstant::typeHard;
+        case '2':
+            return tarconstant::typeSym;
+        case '5':
+            return tarconstant::typeDir;
+        default:
+            return tarconstant::typeOther;
+    }
+}