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153 lines
4.1 KiB
153 lines
4.1 KiB
#include <stdlib.h>
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#include <stdio.h>
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void displayArray(int arr[], size_t size);
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void displayArrayPtr(int *arr, size_t size);
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int safeCompare(const void *a, const void *b, size_t asize, size_t bsize);
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int valid(void *p);
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void displayArray(int arr[], size_t size) {
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for (size_t i = 0; i < size; i++) {
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// both variants are possible
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printf("%d\n", arr[i]);
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//printf("%d\n", *(arr + i));
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}
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}
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void displayArrayPtr(int *arr, size_t size) {
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for (size_t i = 0; i < size; i++) {
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// both variants are possible
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printf("%d\n", *(arr + i));
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//printf("%d\n", arr[i]);
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}
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}
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int safeCompare(const void *a, const void *b, size_t asize, size_t bsize) {
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if (asize != bsize) {
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return -1;
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}
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int value = 0;
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for (size_t i = 0; i < asize; i++) {
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//value |= a[i] ^ b[i];
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value |= ((char*) a)[i] ^ ((char*) b)[i];
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}
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return value;
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}
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int main(void) {
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int vector[5] = {1,2,3,4,5};
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printf("length of vector: %zu\n", sizeof(vector)/sizeof(int));
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int matrix[2][3] = {{1,2,3},{4,5,6}};
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for (size_t index = 0; index < 2; index++) {
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printf("&matrix[%zu]: %p sizeof(matrix[%zu]): %zu\n",
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index, &matrix[index], index, sizeof(matrix[index]));
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}
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// pointer notation and arrays
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{
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int *pv = vector;
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int value = 3;
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for (size_t index = 0; index < sizeof(vector)/sizeof(int); index++) {
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// all following operations are equivalent
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*pv++ *= value;
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//pv[index] *= value;
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//*(pv + index) *= value;
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//vector[index] *= value;
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}
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for (size_t index = 0; index < sizeof(vector)/sizeof(int); index++) {
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printf("vector[%zu]: %d\n", index, vector[index]);
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}
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}
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// using malloc to create a one-dimensional array
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{
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int *pv = malloc(5 * sizeof(*pv));
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for (size_t i = 0; i < 5; i++) {
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pv[i] = i + 1;
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}
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for (size_t i = 0; i < 5; ++i) {
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*(pv + i) = i + 1;
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}
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for(size_t index = 0; index < 5; index++) {
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printf("pv[%zu]: %d\n", index, pv[index]);
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}
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}
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// passing array to function using array notation
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displayArray(vector, sizeof(vector)/sizeof(int));
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// passing array to function using pointer notation
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displayArrayPtr(vector, sizeof(vector)/sizeof(int));
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// using a one-dimensional array of pointers
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{
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int *arr[5];
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for (size_t i = 0; i < 5; i++) {
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// both variants are equivalent
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arr[i] = malloc(sizeof(arr[i]));
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*arr[i] = i;
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//arr[i][0] = i;
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//*(arr + i) = (int*) malloc(sizeof(int));
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//**(arr + i) = i;
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printf("%d\n", **(arr + i));
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}
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}
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// pointers and multidimensional arrays
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{
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// declare a 2-dimensional array
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int matrix[2][5] = {{1, 2, 3, 4, 5}, {6, 7, 8, 9, 10}};
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for (size_t i = 0; i < 2; i++) {
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for (size_t j = 0; j < 5; j++) {
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printf("matrix[%zu][%zu] Address: %p Value %d\n", i, j, &matrix[i][j], matrix[i][j]);
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}
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}
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// declare a pointer to a 2-dimensional array
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int (*pmatrix)[5] = matrix;
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// 1st row
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printf("%p\n", matrix);
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// 2nd row
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printf("%p\n", matrix + 1);
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// size of 1st row
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printf("sizeof(matrix[0]): %zu\n", sizeof(matrix[0]));
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// access 2nd element
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printf("%p %d\n", matrix[0] + 1, *(matrix[0] + 1));
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}
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// test safeCompare function
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{
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// test with char parameters
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char a[] = "wurst";
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char b[] = "wurst";
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if(safeCompare(a, b, sizeof(a), sizeof(b))) {
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printf("%s ungleich %s\n", a, b);
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} else {
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printf("%s gleich %s\n", a, b);
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}
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// test with int parameters
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int bla[] = {0,1,2,3,4};
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int bli[] = {0,1,2,3,4};
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if(safeCompare(bla, bli, sizeof(bla), sizeof(bli))) {
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printf("%s ungleich %s\n", "bla", "bli");
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} else {
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printf("%s gleich %s\n", "bla", "bli");
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}
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}
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return 0;
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}
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