Bitwise operators with pointers
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#include <stdio.h>#include <assert.h>#include <signal.h>void myHandler(int iSig) {printf("In myHandler with argument %d\n", iSig);}int main() {void( * pfRet)(int) = signal(SIGINT, myHandler);assert(pfRet != SIG_ERR);printf("Entering an infinite loop\n");while (1) {printf(".");}return 0; // use CTRL+\ to exit}
#include <stdio.h>#include <sys/types.h>#include <unistd.h>int glbvar = 6;int main() {int locvar = 88;pid_t pid;printf("Before fork()\n");if ((pid = fork()) == 0) {/* child */glbvar++;locvar++;} else if (pid > 0) {/* parent */sleep(2);} elseperror("fork error");printf("pid=%d, glbvar=%d, locvar=%d\n", getpid(), glbvar, locvar);return 0;} /* end main */
// compile: gcc socketTCPServer.c -o socketTCPServer.out// usage : ./socketTCPServer.out port// Server#include <sys/socket.h>#include <netinet/in.h>#include <arpa/inet.h>#include <stdio.h>#include <stdlib.h>#include <unistd.h>#include <errno.h>#include <string.h>#include <sys/types.h>int main(int argc, char *argv[]){int listenfd = 0, connfd = 0, cli_size, portno;struct sockaddr_in serv_addr, cli_addr;char sendBuff[1025];if((listenfd = socket(AF_INET, SOCK_STREAM, 0)) == -1){printf("socket error\n");exit(EXIT_FAILURE);}memset(&serv_addr, '0', sizeof(serv_addr));memset(sendBuff, '0', sizeof(sendBuff));serv_addr.sin_family = AF_INET;serv_addr.sin_addr.s_addr = htonl(INADDR_ANY);portno = atoi(argv[1]);serv_addr.sin_port = htons(portno);const int on = 1;setsockopt(listenfd, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on));if(bind(listenfd, (struct sockaddr*)&serv_addr, sizeof(serv_addr)) == -1){printf("bind error\n");exit(EXIT_FAILURE);}if(listen(listenfd, 5) == -1){printf("listen error\n");exit(EXIT_FAILURE);}while(1){cli_size = sizeof(cli_addr);if((connfd = accept(listenfd, (struct sockaddr*)&cli_addr, &cli_size)) == -1){printf("accept error\n");exit(EXIT_FAILURE);}strcpy(sendBuff, "Server Message: SUCCESS\n");write(connfd, sendBuff, strlen(sendBuff));close(connfd);sleep(1);}return 0;}
#include <stdio.h>#include <stdlib.h>// give an array of identical coins (ints), represented by 1's and one 2// we can find the heavy coin (2) by summing the contents of the thirdsint sum_subarr(int arr[], int l, int r){int sum = 0;for(int i = l; i <= r; i++){sum += arr[i];}return sum;}int heavy_coin(int arr[], int l, int r){if(r == l){return r;}int midl = l + (r - l)/3;int midr = r - (r - l)/3;int lw = sum_subarr(arr, l, midl);int mw = sum_subarr(arr, midl + 1, midr);if ( lw > mw ){return heavy_coin(arr, l, midl);}else if ( lw < mw ){return heavy_coin(arr, midl + 1, midr);}else{return heavy_coin(arr, midr + 1, r);}}int main(int argc, char *argv[]){int arr[] = {1,1,1,1,2,1,1,1,1};int l = 0;int r = 8;int res = -1;res = heavy_coin(arr, l, r);printf("Hevy coin is at index: %d\n", res);return EXIT_SUCCESS;}
//===============replaceString.c===============#include "replaceString.h"//Normally I'd make a replaceStringMalloc to return a malloced string or a replaceStringMut to change the original string, but I'm not satisfied with those function names so it's best just to do to = (char*)malloc(replaceStringLength(from, replace, replacement)); replaceString(to, from, replace, replacement);//If this was c++, I'd have no problem just overloading replaceString//Returns the length of the resulting string (minus the null char)size_t replaceStringLength(const char* from, const char* replace, const char* replacement){size_t fromLength = strlen(from);size_t replaceLength = strlen(replace);size_t replacementLength = strlen(replacement);size_t fromEndIt = 0;size_t toLength = 0;while(fromEndIt < fromLength){int replaceIt = 0;while(replaceIt < replaceLength && (fromEndIt+replaceIt) < fromLength && from[fromEndIt + replaceIt] == replace[replaceIt]){++replaceIt;}if(replaceIt == replaceLength){//Update from buffer iterator positionstoLength += (fromEndIt + replacementLength);from += (fromEndIt + replaceLength);fromEndIt = 0;continue;}++fromEndIt;}toLength += fromEndIt;return toLength;}//Baller replaceString by Leif Messinger//Needs null terminated from, replace, and replacement strings as well as a large block of memory to store the result.void replaceString(char* to, const char* from, const char* replace, const char* replacement){size_t fromLength = strlen(from);size_t replaceLength = strlen(replace);size_t replacementLength = strlen(replacement);size_t fromEndIt = 0;while(fromEndIt < fromLength){int replaceIt = 0;while(replaceIt < replaceLength && (fromEndIt+replaceIt) < fromLength && from[fromEndIt + replaceIt] == replace[replaceIt]){++replaceIt;}if(replaceIt == replaceLength){//Copy the string before the matched bitmemcpyToAndShiftPointers(to, from, fromEndIt);//Copy the replacement toomemcpyToAndShiftPointer(to, replacement, replacementLength);//Update from buffer iterator positionsfrom += replaceLength;fromEndIt = 0;continue; //I don't want this thing to get incremented again}++fromEndIt;}//Copy the rest of the unmatched stringmemcpyToAndShiftPointer(to, from, fromEndIt);to[0] = '\0'; //Should work}//===============replaceString.h===============#ifndef REPLACE_STRING_H#define REPLACE_STRING_H#include <string.h>#define memcpyToAndShiftPointer(to,from,n); memcpy((to),(from),(n)); (to) += (n);#define memcpyToAndShiftPointers(to,from,n); memcpy((to),(from),(n)); (to) += (n); (from) += n;//Normally I'd make a replaceStringMalloc to return a malloced string or a replaceStringMut to change the original string, but I'm not satisfied with those function names so it's best just to do to = (char*)malloc(replaceStringLength(from, replace, replacement)); replaceString(to, from, replace, replacement);//If this was c++, I'd have no problem just overloading replaceString//Returns the length of the resulting string (minus the null char)size_t replaceStringLength(const char* from, const char* replace, const char* replacement);//Baller replaceString by Leif Messinger//Needs null terminated from, replace, and replacement strings as well as a large block of memory to store the result.void replaceString(char* to, const char* from, const char* replace, const char* replacement);#endif//===============replaceStringMain.c===============#include <stdio.h>#include <stdlib.h>#include "replaceString.h"#define BUFFER_SIZE (1<<21) //About a mebibyte//There could be matches between buffers, so make sure the buffer size you set it to is good enough for your application. Basically as big as your input.//Replaces strings from sdtin, then outputs it to stdout//./a.out [[replace], [replacement]]...int main(int argc, char** argv){char* buffer1 = (char*) malloc(BUFFER_SIZE);char* buffer2 = (char*) malloc(BUFFER_SIZE);if(buffer1 == NULL || buffer2 == NULL){perror("You need a couple MBs of ram my boy");return 1;}while(!feof(stdin)){fread(buffer1, BUFFER_SIZE, 1, stdin);char* activeBuffer = buffer1;char* inactiveBuffer = buffer2;char* tmp;for(size_t i = 1; (i + 1) < argc; i += 2){//puts(activeBuffer);replaceString(inactiveBuffer, activeBuffer, argv[i], argv[i+1]);//Swap bufferstmp = activeBuffer;activeBuffer = inactiveBuffer;inactiveBuffer = tmp;}fputs(activeBuffer, stdout);}free(buffer1);free(buffer2);return 0;}
// The following code is the fast inverse square root implementation from Quake III Arena// this code has been stripped of C preprocessor directives, but includes the exact original comment textfloat Q_rsqrt( float number ){long i;float x2, y;const float threehalfs = 1.5F;x2 = number * 0.5F;y = number;i = * ( long * ) &y; // evil floating point bit level hackingi = 0x5f3759df - ( i >> 1 ); // what the fuck?y = * ( float * ) &i;y = y * ( threehalfs - ( x2 * y * y ) ); // 1st iteration// y = y * ( threehalfs - ( x2 * y * y ) ); // 2nd iteration, this can be removedreturn y;}