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ParallelGrep.c
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ParallelGrep.c
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/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*/
/* Copyright (c) 2016 by Peng (Patric) Zhao
* \file ParallelGrep.cc
* Email: patric.zhao@gmail.com
*/
/****************************************************************************
* INCLUDE
****************************************************************************/
#define _XOPEN_SOURCE 500
#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#include <fcntl.h> /* For open() */
#include <unistd.h> /* For close(), lseek() */
#include <sys/types.h> /* For opendir(), readdir(), closedir() */
#include <dirent.h>
#include <sys/stat.h> /* For stat()/lstat() structure */
#include <pthread.h> /* For pthread_ functions */
#include <string.h> /* For strstr() */
#include <ftw.h> /* For ftw()/nftw() */
#define KB 1024 /* 1K */
#define MB (1024*1024) /* 1M */
#define LINEBUF (4*KB)
#define THREADSNUM 8
#define threshold 2
#define MAXFILES 4096
/****************************************************************************
* CONSTANTS *
****************************************************************************/
/* Save the PATTERN */
const char *targetString_G = NULL;
/****************************************************************************
* STATIC VARIABLES *
****************************************************************************/
static int grepDirRec = 0;
static int useOption = 0;
static int indexFile = 0;
static int finishedGrepSubDir = 0;
/****************************************************************************
* PTHREAD DECLARATION *
****************************************************************************/
pthread_t workThread[THREADSNUM];
pthread_t workThreadPool[THREADSNUM];
static pthread_mutex_t workThreadPoolMux = PTHREAD_MUTEX_INITIALIZER;
//static pthread_cond_t workThreadPoolCond = PTHREAD_COND_INITIALIZER;
/****************************************************************************
* STRUCTURE DECLARATION *
****************************************************************************/
struct task {
char *fname;
int outputPath;
long start;
long end;
};
struct tasklist {
struct task task;
struct tasklist *next;
};
struct tasklist *plHead=NULL, *plTail=NULL;
/****************************************************************************
* GLOBAL FUNCTIONS *
****************************************************************************/
/****************************************************************************
* function : help
* description : print usage
* argument(s) :
* return : NULL
****************************************************************************/
void
help()
{
printf ("Usage : grep [option] PATTERN [FILE|DIRECTORY] \n");
}
/****************************************************************************
* function : parseArg
* description : split the arguments from command line.
* argument(s) :
* return :
****************************************************************************/
void
parseArg(int num, char *string[])
{
//TODO: Does not support the options such as -r, -i. Need to enhance.
if ( num < 3) {
printf("Error: Incorrect arguments!\n");
help();
exit (0);
}
//TODO: Hardcode now, will enhance in the future for usability.
if (!strcmp(string[1],"-r")) {
useOption = 1;
grepDirRec = 1;
indexFile = 3;
targetString_G = string[2];
} else {
useOption = 0;
grepDirRec = 0;
// The search destination is from the argv[2] since the argv[0] and argv[1] are program name and target string.
indexFile = 2;
targetString_G = string[1];
}
}
/****************************************************************************
* function : grepFile
* description : search the PATTERN in the specified file and print out the results.
* argument(s) : a structure with four elements.
* fname , file name
* start , the location to begin search. For sequential algorithm,
* start point is zero.
* end , the location to end search. For sequential algorithm,
* this is the size of the file.
* outputPath , 1 (print the path) or 0 ( don't print the path)
* return : NULL
****************************************************************************/
void*
grepFile(void *arg) {
struct task *file = arg;
FILE *fp_status;
char buf[LINEBUF];
long ret = 0;
long totalSize = file->end - file->start;
long leftSize = totalSize;
if(!(fp_status = fopen(file->fname, "r"))) {
printf("Error: File open failed : %s\n", file->fname);
return NULL;
}
// Starting from the specified point.
if (fseek(fp_status, file->start, SEEK_SET) != 0) {
fclose(fp_status);
return NULL;
}
while (leftSize > 0 && fgets(buf, LINEBUF, fp_status)) {
if (strstr(buf, targetString_G) != NULL) {
if ( file->outputPath == 0 ) {
printf("%s", buf);
} else {
printf("%s:%s", file->fname, buf);
}
}
ret = strlen(buf);
leftSize -= ret;
}
fclose(fp_status);
return NULL;
}
/****************************************************************************
* function : workThreadPoolFun
* description : The work thread from thread pool.
* Retrieve the file from free list and grep.Exit when no any available task in the list.
* argument(s) : Needn't
* return : NULL
****************************************************************************/
void*
workThreadPoolFun(void *arg)
{
struct tasklist *plTmp = NULL;
while (1) {
pthread_mutex_lock(&workThreadPoolMux);
// TODO: Awake by a signal from main thread to avoid "while" loop
// in order to save the CPU resources.
//pthread_cond_wait(&workThreadPoolCond, &workThreadPoolMux);
if (plHead != NULL && plHead->next != NULL) {
// Get task from the tail of the list.
if (plHead->next == plTail) {
plTmp = plTail;
plTail = plHead;
plTail->next = NULL;
} else {
plTmp = plHead->next;
plHead->next = plTmp->next;
plTmp->next = NULL;
}
pthread_mutex_unlock(&workThreadPoolMux);
grepFile((void *)&plTmp->task);
// free memory from malloc/strdup by addFilesIntoFreeList
if (plTmp->task.fname != NULL) {
free(plTmp->task.fname);
plTmp->task.fname = NULL;
}
if (plTmp != NULL) {
free(plTmp);
plTmp = NULL;
}
} else {
// All tasks are finished so exit, otherwise continue wait the new task
// added into list.
if (finishedGrepSubDir == 1) {
pthread_mutex_unlock(&workThreadPoolMux);
pthread_exit(NULL);
}
pthread_mutex_unlock(&workThreadPoolMux);
}
}
}
/****************************************************************************
* function : initThreadPool
* description : create THREADSNUM threads to work later.
* argument(s) :
* return : return number of available threads.
****************************************************************************/
int
initThreadPool()
{
// create threads pool
int i = 0;
int error = 0;
int num = 0;
for (i = 0; i < THREADSNUM; i++) {
error = pthread_create(&workThreadPool[i], NULL, workThreadPoolFun, NULL);
if (error != 0) {
break;
}
++num;
}
return num;
}
/****************************************************************************
* function : joinThreadPool
* description : wait all threads finish.
* argument(s) :
* return :
****************************************************************************/
void
joinThreadPool()
{
int i = 0;
// wait working thread to join
for (i = 0; i < THREADSNUM; i++) {
pthread_join(workThreadPool[i],NULL);
}
return;
}
/****************************************************************************
* function : addFilesIntoFreeList
* description : add the file into the tail of free list.
* argument(s) :
* return : 0 (continue) or other (break from nftw)
****************************************************************************/
static int
addFilesIntoFreeList(const char *fpath, const struct stat *sb,
int tflag, struct FTW *ftwbuf)
{
struct tasklist *plTmp = NULL;
if (tflag == FTW_F) {
// Add a file in tail of the task list.
plTmp = (struct tasklist *) malloc (sizeof(struct tasklist));
if (plTmp == NULL) {
// No enough memory to save file info so that the program will exit
// by returning a non-zero number.
return 1;
}
// Save file info. strdup will allocate additional memory so don't forget free it.
plTmp->task.fname = strdup(fpath);
plTmp->task.start = 0;
plTmp->task.end = sb->st_size;
plTmp->task.outputPath = 1;
plTmp->next = NULL;
// When tail and head point to the same node, will have conflict thus using lock protect.
pthread_mutex_lock(&workThreadPoolMux);
plTail->next = plTmp;
plTail = plTail->next;
// TODO: Awake sleeped thread but the signal will lose if all thread is working now.
// Need a new approach.
//pthread_cond_signal(&workThreadPoolCond);
pthread_mutex_unlock(&workThreadPoolMux);
}
// return 0 to continue.
return 0;
}
/****************************************************************************
* function : testList
* description : just for testing.
* argument(s) :
* return :
****************************************************************************/
void
testList(struct tasklist * head) {
struct tasklist *plTmp = NULL;
while (head != plTail && head->next != NULL) {
plTmp = head->next;
head->next = plTmp->next;
plTmp->next= NULL;
// printf("Patric name = %s, size = %d\n", plTmp->task.fname, plTmp->task.end - plTmp->task.start);
if (plTmp->task.fname != NULL) {
free(plTmp->task.fname);
plTmp->task.fname = NULL;
}
if (plTmp != NULL) {
free(plTmp);
plTmp = NULL;
}
}
}
/****************************************************************************
* function : grepDirParallel
* description : search the directory recursively
* create and join the thread pool
* argument(s) :
* return :
****************************************************************************/
void
grepDirParallel(const char *path) {
int flag = 0;
pthread_mutex_lock(&workThreadPoolMux);
// The head node used to point to files that need to be searched.
// Don't save actual file info into head node and just use for a pointer.
plHead = (struct tasklist *) malloc (sizeof(struct tasklist));
if (plHead == NULL) {
return;
}
plHead->next = NULL;
plTail = plHead;
// Don't go into the linked dir.
flag |= FTW_PHYS;
// Tell work threads that new tasks will be added into list, keep working.
finishedGrepSubDir = 0;
pthread_mutex_unlock(&workThreadPoolMux);
initThreadPool();
// Using nftw() recursive search all files.
nftw(path, addFilesIntoFreeList, MAXFILES, flag);
// Tell work threads that they could exit when finished current task.
pthread_mutex_lock(&workThreadPoolMux);
finishedGrepSubDir = 1;
pthread_mutex_unlock(&workThreadPoolMux);
// Intenal testing. Exclusive with thread pool.
//testList(plHead);
joinThreadPool();
if (plHead != NULL) {
free (plHead);
plHead = NULL;
}
return;
}
/****************************************************************************
* function : grepFileParallel
* description : divide a big file into several small parts.
* argument(s) :
* return :
****************************************************************************/
void
grepFileParallel(const char *file, long size, int threadNum) {
FILE* fp = NULL;
int i = 0;
int posAdd = 0;
long blockSize = size / threadNum;
struct task arg[threadNum];
if ((fp = fopen(file,"r")) == NULL) {
printf("Error: Could not open the file! \n");
return;
}
for (i = 0; i < threadNum - 1; i++) {
// Basic size of each block for threads.
arg[i].fname = (char *)file;
arg[i].start = i * blockSize + posAdd;
arg[i].end = (i + 1) * blockSize - 1 ;
arg[i].outputPath = 0;
// Adjust the size to the next '\n', thus the file could be divided by line.
fseek(fp, arg[i].end, SEEK_SET);
for (posAdd = 0; fgetc(fp) != '\n'; posAdd++ );
arg[i].end += posAdd ;
// Start thread to grep sub-domain.
pthread_create(&workThread[i], NULL, grepFile, (void *)&arg[i]);
}
// The last domain is an irregular block compared with former blocks.
arg[threadNum - 1].fname = (char *) file;
arg[threadNum - 1].start = (threadNum - 1) * blockSize + posAdd;
arg[threadNum - 1].end = size - 1;
arg[threadNum - 1].outputPath = 0;
pthread_create(&workThread[i], NULL, grepFile, (void *)&arg[i]);
// The file descriptor is only used in main thread.
// Thus, close it without influence for other threads.
fclose(fp);
for (i = 0; i < threadNum; i++) {
pthread_join(workThread[i],NULL);
}
}
/****************************************************************************
* function : main
* description :
* grep PATTERN FILE
* grep PATTERN DIR
* argument(s) :
* return :
****************************************************************************/
int
main(int argc, char *argv[]) {
struct stat info;
parseArg(argc,argv);
while (indexFile < argc) {
if (lstat(argv[indexFile], &info) == -1) {
printf("Error: Could not open the specified file or directory.\n");
}
// The marco S_ISDIR is defined in stat.h
if (S_ISDIR(info.st_mode)) {
// Recursive search if "-r" option is used.
if (grepDirRec == 1) {
grepDirParallel(argv[indexFile]);
}
} else {
// For small files don't bother PARALLEL algrithm.
if ( info.st_size > threshold * MB ) {
grepFileParallel(argv[indexFile], info.st_size, THREADSNUM);
} else {
struct task fileInfo;
fileInfo.fname = argv[indexFile];
fileInfo.start = 0;
fileInfo.end = info.st_size;
// Print out the file path when search more than one file.
if (indexFile > 3) {
fileInfo.outputPath = 1;
} else {
fileInfo.outputPath = 0;
}
grepFile((void *)&fileInfo);
}
}
// Deal with the next one.
++indexFile;
}
return 0;
}