從pthread運行pthreads

Question

我有一個文件，其中包含一個文件名列表，其中我想要搜索一個詞並替換它 我修改了一些代碼，僅僅顯示相關部分 問題是如果我有隻有一個文件在該列表中，它不會用多線程處理它，因爲線程只在我有多個文件時才工作 所以我想保留當前的線程配置，但我想在處理部分添加一些線程 我有驗證碼：

struct words_list { 
    char word[20]; 
    struct words_list * next; 
}; 
FILE * INFILE; 
int num_thread = 10; 
// Mutex variables 
pthread_mutex_t input_queue; 
pthread_mutex_t word_list; 


int main(int argc,char **argv) 
{ 
    //some code is missing 

    if((INFILE = fopen(myfile,"r")) == NULL) { 
     fprintf(stderr,"Can't open input file\n"); 
     exit(0); 
    } 

    for(i = 0 ; i < number_thread; i++) 
    { 
     if(pthread_create(&thread_id[i],NULL,&search,NULL) != 0) 
     { 
      i--; 
      fprintf(stderr,RED "\nError in creating thread\n" NONE); 
     } 
    } 
    for(i = 0 ; i < number_thread; i++) 
     if(pthread_join(thread_id[i],NULL) != 0) 
     { 
      fprintf(stderr,RED "\nError in joining thread\n" NONE); 
     } 

    fflush(INFILE); 
    fclose(INFILE); 
} 

void * search(void * data) 
{ 
    char file[20]; 
    while (!feof(INFILE)) 
    { 
     if (fgets(file,sizeof(file),INFILE) != NULL) 
     { 
      if (strlen(file) < 8) 
       break; 
      if (file[strlen (file) - 1] == '\n') 
       file[strlen (file) - 1] = '\0'; 
     } 
     process(file); 
    } 
    return NULL; 
} 


void process(char *filename) 
{ 
    char buff[512]; 
    char word[20]; 
    struct words_list * curr_word = first_word; 

    if(verbose != 0) 
     fprintf(stderr,"Processing: %s\n",filename); 
    while(curr_word != NULL) 
    { 
     //some code missing 
     pthread_mutex_lock(&word_list); 
     strncpy(word,curr_word->word,sizeof(word) - 1); 
     pthread_mutex_unlock(&word_list); 


      **//replace_word must run with multiple threads** 

     ret = replace_word(word,buff,sizeof(buff)); 

      //end of threads part 



     //code missing 
    } 
} 

我怎樣才能在加粗部分添加其他並行線程所以它可以用多個線程處理每個文件？

Answer 1

而不是爲每個文件分配一個線程。爲什麼你不應該分配一個線程來處理每個文件的部分。如下所示，我爲文件中的每50個字節的數據分配一個線程。在這種技術中，即使列表中只有一個文件，仍然可以使用多個線程來解析它。希望能幫助到你。

#include "stdio.h" 
#include "pthread.h" 
#include "sys/stat.h" 
#include "string.h" 
#include "fcntl.h" 

#define TOTAL_NUMBER_THREADS 100 

struct words_list { 
    char word[20]; 
    struct words_list * next; 
}; 

struct file_segment { 
    char filename[50]; 
    size_t foffset; 
    size_t size; 
}fs[TOTAL_NUMBER_THREADS]; 

FILE * INFILE; 
int num_thread=0; 

// Mutex variables 
pthread_mutex_t input_queue; 
pthread_mutex_t word_list; 
pthread_t thread_id[TOTAL_NUMBER_THREADS]; 

void *process(void *arg); 

void segment_file(char *filename) 
{ 
    int fd; 
    int offset=0; 
    struct stat statbuf; 
    size_t size; 

    fd = open(filename, O_RDONLY); 
    if(fd < 0) 
    { 
     perror("fopen"); 
     return; 
    } 

    fstat(fd, &statbuf); 
    size=statbuf.st_size; 

    while((offset < size) && (num_thread <= 100)) 
    { 
     strncpy(fs[num_thread].filename, filename, sizeof(fs[num_thread].filename)); 
     fs[num_thread].foffset=offset; 
     fs[num_thread].size=(size>50)?50:size; 
     offset+=fs[num_thread].size; 

     if(pthread_create(&thread_id[num_thread],NULL,&process,&fs[num_thread]) != 0) 
     { 
     fprintf(stderr,"\nError in creating thread\n"); 
     } 
     num_thread++; 
    } 

    return; 
} 

void *process(void *arg) 
{ 
    char buf[50]; 
    struct file_segment *fs; 
    char word[20]; 
    //struct words_list * curr_word = first_word; 
    fs = (struct file_segment *) arg; 
    FILE *fp; 

    fp=fopen(fs->filename, "r"); 
    fseek(fp, fs->foffset, SEEK_SET); 
    fread(buf,1,fs->size,fp); 

    while(curr_word != NULL) 
    { 
     //some code missing 
     pthread_mutex_lock(&word_list); 
     strncpy(word,curr_word->word,sizeof(word) - 1); 
     pthread_mutex_unlock(&word_list); 


      **//replace_word must run with multiple threads** 

     ret = replace_word(word,buff,sizeof(buff)); 

      //end of threads part 
     //code missing 
    } 

    //printf("Filename: %s\n Info: %s\n", fs->filename, buf); 
    printf("%s", buf); 

    return; 
} 

int main(int argc,char **argv) 
{ 
    //some code is missing 
    char file[50]; 
    int i; 

    if((INFILE = fopen("list.txt","r")) == NULL) { 
     fprintf(stderr,"Can't open input file\n"); 
     return 0; } 

    while (!feof(INFILE)) 
    { 
     if (fgets(file,sizeof(file),INFILE) != NULL) 
     { 
      if (strlen(file) < 8) 
       break; 
      if (file[strlen (file) - 1] == '\n') 
       file[strlen (file) - 1] = '\0'; 
     } 
     segment_file(file); 
    } 

    for(i = 0 ; i < num_thread; i++) 
     if(pthread_join(thread_id[i],NULL) != 0) 
     { 
      fprintf(stderr,"\nError in joining thread\n"); 
     } 

    fflush(INFILE); 
    fclose(INFILE); 
}