id 1765122409

CMakeLists.txt

@@ -97,6 +97,7 @@ set(APP_SOURCES
     "src/core/datatypes/class/CDestructors.cpp"
     "src/core/datatypes/class/SallowDeepCopying.cpp"
     "src/core/datatypes/class/RoleOfThreeFiveZero.cpp"
+    "src/core/string/CString.cpp"
     "src/patterns/structural/Adapter.cpp"
     "src/patterns/structural/Bridge.cpp"
     "src/patterns/structural/Proxy.cpp"

src/core/string/CString.cpp

@@ -0,0 +1,203 @@
+#include <string.h>
+#include <iostream>
+
+namespace {
+
+namespace InitializeString {
+void run() {
+  // Memory layout (addresses are illustrative):
+
+  // Stack (modifiable array)
+  // 0x7fffc000: str2[0] = 'H'
+  // 0x7fffc001: str2[1] = 'e'
+  // 0x7fffc002: str2[2] = 'l'
+  // 0x7fffc003: str2[3] = 'l'
+  // 0x7fffc004: str2[4] = 'o'
+  // 0x7fffc005: str2[5] = '\0'
+  // (str2 starts at 0x7fffc000)
+
+  // Data / Read-only segment (string literal)
+  // 0x00403000: 'H'
+  // 0x00403001: 'e'
+  // 0x00403002: 'l'
+  // 0x00403003: 'l'
+  // 0x00403004: 'o'
+  // 0x00403005: '\0'
+  // (str1 -> points to 0x00403000)
+
+  // Pointer variable
+  // 0x7fffbff0: str1 = 0x00403000   // str1 holds address of string literal
+
+  // 1. As a character array (modifiable)
+  char strArray[] = "this is a strArray literal";
+  std::cout << strArray << " - size " << sizeof(strArray) << " - length "
+            << strlen(strArray) << "\n";
+  strArray[0] ^= ' ';
+  std::cout << strArray << "\n";
+
+  // 2. As a a pointer to a string literal const (read-only)
+  char* strPtr = "this is a strPtr literal";
+  std::cout << strPtr << " - size " << sizeof(strPtr) << " - length "
+            << strlen(strPtr) << "\n";
+  //   strPtr[0] ^= ' '; // ERROR
+
+  // 3. Using sprintf / snprintf (string formatting)
+  char strFormatted[50];
+  int numVar = 21;
+
+  // sprintf (unsafe if buffer too small)
+  sprintf(strFormatted, "sprintf: %d", numVar);
+  std::cout << strFormatted << " - size " << sizeof(strFormatted)
+            << " - length " << strlen(strFormatted) << "\n";
+
+  // snprintf (safer, limits buffer size)
+  snprintf(strFormatted, sizeof(strFormatted), "snprintf %s %d", strArray,
+           numVar);
+  std::cout << strFormatted << " - size " << sizeof(strFormatted)
+            << " - length " << strlen(strFormatted) << "\n";
+}
+}  // namespace InitializeString
+
+namespace CopyString {
+void run() {
+  const char src[] = "CopyStr";
+  char dst[50];
+
+  // 1. Copy full string
+  strcpy(dst, src);
+
+  std::cout << dst << " - size " << sizeof(dst) << " - length " << strlen(dst)
+            << "\n";
+
+  // 2. Copy the number of charactor
+  strncpy(dst, "Hello123", 5);
+  dst[5] = '\0';  // ensure null-termination
+
+  std::cout << dst << " - size " << sizeof(dst) << " - length " << strlen(dst)
+            << "\n";
+}
+}  // namespace CopyString
+
+namespace ConcatString {
+void run() {
+  const char part1[] = "Hello";
+  const char part2[] = "World";
+  char dst[50] = "";
+
+  // 1. Append full str
+  strcat(dst, part1);
+  strcat(dst, part2);
+  strcat(dst, " !!");
+  std::cout << dst << " - size " << sizeof(dst) << " - length " << strlen(dst)
+            << "\n";
+
+  // 2. Append the number of charactors
+  strncat(dst, "1234", 3);
+  std::cout << dst << " - size " << sizeof(dst) << " - length " << strlen(dst)
+            << "\n";
+}
+}  // namespace ConcatString
+
+namespace CompareString {
+void run() {
+  const char str1[] = "abc";
+  const char str2[] = "abcde";
+
+  // 1. Compare full str
+  int result1 = strcmp(str1, "abc");
+  int result2 = strcmp(str1, str2);
+  std::cout << "strcmp(str1, \"abc\") = " << result1 << "\n";
+  std::cout << "strcmp(str1, str2) = " << result2 << "\n";
+
+  // 2. Compare first N characters
+  int result3 = strncmp(str1, str2, 3);
+  std::cout << "strncmp(str1, str2, 3) = " << result3 << "\n";
+}
+}  // namespace CompareString
+
+namespace ParseString {
+void run() {
+  char str[] = "A,B,C,D,";  // OK
+                            //   char* str = "A,B,C,D,"; // ERROR - const
+
+  // 1. Splitting a string by some delimiter
+  // 1.1. strtok - not safe
+  char* delimiter = ",";
+  const char* token = strtok(str, delimiter);
+  while (token != nullptr) {
+    std::cout << "strtok - token :" << token << "\n";
+    token = strtok(NULL, delimiter);
+  }
+  {
+    std::cout << " === problem === \n";
+    char str1[] = "a,b,c";
+    char str2[] = "1,2,3";
+
+    // Parse str1
+    const char* token1 = strtok(str1, delimiter);  // token1 = "a"
+    std::cout << "str1 first token: " << token1 << "\n";
+
+    // Parse str2
+    const char* token2 = strtok(str2, delimiter);  // token2 = "1"
+    std::cout << "str2 first token: " << token2 << "\n";
+
+    // Continue parsing str1
+    token1 = strtok(nullptr, delimiter);  //  Unexpected!
+    std::cout << "str1 second token: " << token1 << "\n";
+  }
+
+  // Have to Reset string for the next handle because strtok
+  char str2[] = "one,two,three";
+  // 1.2. strtok_r - safe
+  char* saveptr;
+  const char* token2 = strtok_r(str2, delimiter, &saveptr);
+  while (token2 != nullptr) {
+    std::cout << "strtok - token :" << token2 << "\n";
+    token2 = strtok_r(NULL, delimiter, &saveptr);
+  }
+
+  // 2. strcspn: find first occurrence of any chars in reject set
+  const char sample[] = "hello123world";
+  size_t pos = strcspn(sample, "0123456789");  // pos = 5
+
+  std::cout << "Sample string: " << sample << "\n";
+  std::cout << "First digit from \"0123456789\" found at index: " << pos
+            << "\n";
+  std::cout << "The digit is: " << sample[pos] << "\n";
+}
+}  // namespace ParseString
+
+namespace NumberConversion {
+void run() {
+  // 1. string to integer
+  const char strNum[] = "100";
+  int num = atoi(strNum);
+  std::cout << num << "\n";
+
+  // 2. string to double
+  const char strNumD[] = "100.1234__123";
+  double numD = atof(strNumD);
+  std::cout << numD << "\n";
+
+  char* end;
+  numD = strtod(strNumD, &end);
+  std::cout << numD << " end part:" << end << "\n";
+}
+}  // namespace NumberConversion
+}  // namespace
+
+struct CStringAutoRunner {
+  CStringAutoRunner() {
+    std::cout << "\n--- C String Example ---\n";
+
+    InitializeString::run();
+    CopyString::run();
+    ConcatString::run();
+    CompareString::run();
+    ParseString::run();
+
+    NumberConversion::run();
+  }
+};
+
+static CStringAutoRunner instance;