Partial solution to the realloc lab task. Shows how to read entries using realloc function.<\/p>\n
<\/p>\n
#ifndef REALLOC_EXAMPLE_H\r\n#define REALLOC_EXAMPLE_H\r\n\r\n#define LEN_CUR_CODE 4\r\n#define BUF_LEN 128\r\n#define DEFAULT_INPUT_FILE \"candidates.txt\"\r\n\r\ntypedef struct\r\n{\r\n\tint index;\r\n\tchar *fName;\r\n\tchar *lName;\r\n\tchar curriculum[LEN_CUR_CODE + 1];\r\n\tfloat points;\r\n} Person;\r\n\r\nint ReadList(Person **ppStudentData, char *fileName);\r\nvoid Output(Person *candidates, int n);\r\n\r\n#endif \/\/REALLOC_EXAMPLE_H\r\n<\/pre>\n <\/p>\n
\/**\r\n * File: realloc_example.c\r\n * Author: Risto Heinsar\r\n * Created: 19.03.2014\r\n * Edited: 02.04.2024\r\n *\r\n * Description: The following code will demonstrate how to properly use realloc\r\n * to expand the memory that's already been allocated.\r\n * The file is a part of the IAX0584 lab task and provided as a\r\n * partial lab solution. It implements the less efficient (n + 1)\r\n * expansion strategy which is considered slow in real world.\r\n *\/\r\n\r\n#include <stdio.h>\r\n#include <stdlib.h>\r\n#include <string.h>\r\n#include \"realloc_example.h\"\r\n\r\nint main(void)\r\n{\r\n char fileName[] = DEFAULT_INPUT_FILE;\r\n Person *list = NULL; \/\/ nothing here at present\r\n\r\n \/\/ read the file\r\n int candidateCnt = ReadList(&list, fileName);\r\n\r\n Output(list, candidateCnt);\r\n\r\n \/\/ NB! The sample code does not include freeing the memory.\r\n \/\/ Everything that you allocate for must be freed before exiting the program!\r\n\r\n return EXIT_SUCCESS;\r\n}\r\n\r\n\/**\r\n * Description: Function to read data from a file. During this, a dynamic\r\n * struct array will be created and expanded using realloc()\r\n * Parameters: Double pointer a struct, address of the allocated array will\r\n * be stored there. NB! The memory comes from the heap!\r\n * Pointer to a string with the file name\r\n * Return value: Returns an integer with the number of lines read from the file\r\n * Prerequisites: Datafile fields are separated with either a space\r\n * or a line change, without faulty data, max length of a string\r\n * is up to (LEN_NAME_MAX - 1) and no spaces in strings.\r\n *\/\r\nint ReadList(Person **ppStudentData, char *fileName)\r\n{\r\n \/\/ Opening the file and checking if it opened\r\n FILE *fp = fopen(fileName, \"r\");\r\n if (fp == NULL)\r\n {\r\n perror(\"Error opening input file:\");\r\n exit(EXIT_FAILURE);\r\n }\r\n \r\n \/\/ Main data pointer that's used locally\r\n Person *pData = NULL;\r\n \r\n \/\/ Temporary buffers for data during reading\r\n char bufFName[BUF_LEN], bufLName[BUF_LEN], bufCurrCode[BUF_LEN];\r\n int bufInd;\r\n float bufPoints;\r\n \r\n \/\/ initialize the line count to 0 - nothing read yet\r\n int count = 0;\r\n \r\n \/\/ start by reading one line at a time into the buffers (no memory yet)\r\n while (fscanf(fp, \"%d %s %s %s %f\", &bufInd, bufFName, bufLName, \r\n bufCurrCode, &bufPoints) == 5)\r\n {\r\n \/\/ if a line was successfully read, expanding the memory by 1. Using a \r\n \/\/ temporary pointer to avoid losing memory address when realloc fails\r\n \/\/ during reading (returns NULL, old pointer valid)\r\n Person *pTemp = realloc(pData, sizeof(Person) * (unsigned)(count + 1));\r\n\r\n \/\/ Check if it failed\r\n if (pTemp == NULL)\r\n {\r\n \/\/ TODO: Error behavior!\r\n \/\/ I.e. if you want to free everything and exit, you should free:\r\n \/\/ - all the first names already allocated\r\n \/\/ - all the last names allocated\r\n \/\/ - the struct itself\r\n \r\n \/\/ then close the file and exit\r\n fclose(fp);\r\n exit(EXIT_FAILURE);\r\n }\r\n\r\n \/\/ Make both pointers point at the memory location\r\n pData = pTemp;\r\n\r\n \/\/ Copy data from buffers to the struct array\r\n\r\n \/\/ Now allocate + copy data for the string buffers\r\n \/\/ Note 1: Both pData[i].member or (pData + i)->member can be used\r\n \/\/ Note 2: strdup() combines strlen, malloc and strcpy\r\n (pData + count)->fName = strdup(bufFName);\r\n if ((pData + count)->fName == NULL)\r\n {\r\n \/\/ TODO: error behavior here\r\n }\r\n\r\n \/\/ numbers can be copied directly, there already is memory in the struct\r\n (pData + count)->points = bufPoints;\r\n\r\n \/\/ another line successfully read\r\n count++;\r\n }\r\n \/\/ using the dbl pointer to make sure main() knows where my struct array is\r\n *ppStudentData = pData;\r\n\r\n \/\/ close the file\r\n fclose(fp);\r\n\r\n \/\/ and return the number of lines read\r\n return count;\r\n}\r\n\r\n\r\n\/**\r\n * Description: Prints out the list of candidates who applied, one per line.\r\n * Parameters: candidateList - pointer to the list of candidates\r\n * n - number of candidates in the list\r\n * Return value: none\r\n *\/\r\nvoid Output(Person *candidates, int n)\r\n{\r\n printf(\"The candidates are:\\n\");\r\n for (int i = 0; i < n; i++)\r\n {\r\n \/\/ the fields which were incomplete are not printed at this point. \r\n printf(\"%d %s <last name> <curriculum> %.2f\\n\", (candidates + i)->index,\r\n (candidates + i)->fName,\r\n (candidates + i)->points);\r\n }\r\n}\r\n<\/pre>\n <\/p>\n<\/div>\n
\n <\/p>\n
#ifndef REALLOC_EXAMPLE_H\r\n#define REALLOC_EXAMPLE_H\r\n\r\n#define LEN_CUR_CODE 4\r\n#define BUF_LEN 128\r\n#define DEFAULT_INPUT_FILE \"candidates.txt\"\r\n\r\ntypedef struct\r\n{\r\n\tint index;\r\n\tchar *fName;\r\n\tchar *lName;\r\n\tchar curriculum[LEN_CUR_CODE + 1];\r\n\tfloat points;\r\n} Person;\r\n\r\nPerson * ReadList(int *cnt, char *fileName);\r\nvoid Output(Person *candidates, int n);\r\n\r\n#endif\r\n<\/pre>\n <\/p>\n
\/**\r\n * File: realloc_example.c\r\n * Author: Risto Heinsar\r\n * Created: 19.03.2014\r\n * Edited: 02.04.2024\r\n *\r\n * Description: The following code will demonstrate how to properly use realloc\r\n * to expand the memory that's already been allocated.\r\n * The file is a part of the IAX0584 lab task and provided as a\r\n * partial lab solution. It implements the less efficient (n + 1)\r\n * expansion strategy which is considered slow in real world.\r\n *\/\r\n\r\n#include <stdio.h>\r\n#include <stdlib.h>\r\n#include <string.h>\r\n#include \"realloc_example.h\"\r\n\r\nint main(void)\r\n{\r\n char fileName[] = DEFAULT_INPUT_FILE;\r\n int total;\r\n\r\n \/\/ read the file\r\n Person *candidates = ReadList(&total, fileName);\r\n\r\n Output(candidates, total);\r\n\r\n \/\/ NB! The sample code does not include freeing the memory.\r\n \/\/ Everything that you allocate for must be freed before exiting the program!\r\n\r\n return EXIT_SUCCESS;\r\n}\r\n\r\n\/**\r\n * Description: Function to read data from a file. During this, a dynamic\r\n * struct array will be created and expanded using realloc()\r\n * Pointer to a string with the file name\r\n * Parameters: Pointer to an integer where to store the candidate count\r\n * Pointer to a string with the file name\r\n * Return value: Returns the structure pointer where the memory was allocated\r\n * and data stored at.\r\n * Prerequisites: Datafile fields are separated with either a space\r\n * or a line change, without faulty data, max length of a string\r\n * is up to (LEN_NAME_MAX - 1) and no spaces in strings.\r\n *\/\r\nPerson * ReadList(int *cnt, char *fileName)\r\n{\r\n \/\/ Opening the file and checking if it opened\r\n FILE *fp = fopen(fileName, \"r\");\r\n if (fp == NULL)\r\n {\r\n perror(\"Error opening input file:\");\r\n exit(EXIT_FAILURE);\r\n }\r\n \/\/ Main data pointer that's used locally\r\n Person *pData = NULL;\r\n \r\n \/\/ Temporary buffers for data during reading\r\n char bufFName[BUF_LEN], bufLName[BUF_LEN], bufCurrCode[BUF_LEN];\r\n int bufInd;\r\n float bufPoints;\r\n \r\n \/\/ Initialize the line count to 0 - nothing read yet\r\n int count = 0;\r\n \r\n \/\/ start by reading one line at a time into the buffers (no memory yet)\r\n while (fscanf(fp, \"%d %s %s %s %f\", &bufInd, bufFName, bufLName, \r\n bufCurrCode, &bufPoints) == 5)\r\n {\r\n \/\/ if a line was successfully read, expanding the memory by 1. Using a \r\n \/\/ temporary pointer to avoid losing memory address when realloc fails\r\n \/\/ during reading (returns NULL, old pointer valid)\r\n Person *pTemp = realloc(pData, sizeof(Person) * (unsigned)(count + 1));\r\n\r\n \/\/ Check if it failed\r\n if (pTemp == NULL)\r\n {\r\n \/\/ TODO: Error behavior!\r\n \/\/ I.e. if you want to free everything and exit, you should free:\r\n \/\/ - all the first names already allocated\r\n \/\/ - all the last names allocated\r\n \/\/ - the struct itself\r\n \r\n \/\/ then close the file and exit\r\n fclose(fp);\r\n exit(EXIT_FAILURE);\r\n }\r\n\r\n \/\/ Make both pointers point at the memory location\r\n pData = pTemp;\r\n\r\n \/\/ Copy data from buffers to the struct array\r\n\r\n \/\/ Now allocate + copy data for the string buffers\r\n \/\/ Note 1: Both pData[i].member or (pData + i)->member can be used\r\n \/\/ Note 2: strdup() combines strlen, malloc and strcpy\r\n (pData + count)->fName = strdup(bufFName);\r\n if ((pData + count)->fName == NULL)\r\n {\r\n \/\/ TODO: error behavior here\r\n }\r\n\r\n \/\/ numbers can be copied directly, there already is memory in the struct\r\n (pData + count)->points = bufPoints;\r\n\r\n \/\/ another line successfully read\r\n count++;\r\n }\r\n \r\n \/\/ using a pointer to store the number of lines that were read\r\n *cnt = count;\r\n \r\n \/\/ now just close the file\r\n fclose(fp);\r\n \r\n \/\/ and return the pointer to the struct array we just allocated\r\n return pData;\r\n}\r\n\r\n\r\n\/**\r\n * Description: Prints out the list of candidates who applied, one per line.\r\n * Parameters: candidateList - pointer to the list of candidates\r\n * n - number of candidates in the list\r\n * Return value: none\r\n *\/\r\nvoid Output(Person *candidates, int n)\r\n{\r\n printf(\"The candidates are:\\n\");\r\n for (int i = 0; i < n; i++)\r\n {\r\n \/\/ the fields which were incomplete are not printed at this point. \r\n printf(\"%d %s <last name> <curriculum> %.2f\\n\", (candidates + i)->index,\r\n (candidates + i)->fName,\r\n (candidates + i)->points);\r\n }\r\n}\r\n<\/pre>\n <\/p>\n<\/div><\/div><\/div>\n","protected":false},"excerpt":{"rendered":"
Partial solution to the realloc lab task. Shows how to read entries using realloc function.<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":2361,"menu_order":15,"comment_status":"closed","ping_status":"closed","template":"page-templates\/code-width-wide.php","meta":{"footnotes":""},"class_list":["post-4645","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/blue.pri.ee\/ttu\/wp-json\/wp\/v2\/pages\/4645","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/blue.pri.ee\/ttu\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/blue.pri.ee\/ttu\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/blue.pri.ee\/ttu\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/blue.pri.ee\/ttu\/wp-json\/wp\/v2\/comments?post=4645"}],"version-history":[{"count":3,"href":"https:\/\/blue.pri.ee\/ttu\/wp-json\/wp\/v2\/pages\/4645\/revisions"}],"predecessor-version":[{"id":9979,"href":"https:\/\/blue.pri.ee\/ttu\/wp-json\/wp\/v2\/pages\/4645\/revisions\/9979"}],"up":[{"embeddable":true,"href":"https:\/\/blue.pri.ee\/ttu\/wp-json\/wp\/v2\/pages\/2361"}],"wp:attachment":[{"href":"https:\/\/blue.pri.ee\/ttu\/wp-json\/wp\/v2\/media?parent=4645"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}