C語言服務器開發(fā)與PDF文件處理

在C語言中進行服務器開發(fā)并處理PDF文件是一個復雜但非常有價值的任務，尤其在需要提供文檔服務或報告生成功能的應用程序中，以下內容將詳細介紹如何使用C語言進行服務器開發(fā)以及如何操作PDF文件。

服務器開發(fā)基礎

網絡編程基礎

使用C語言進行服務器開發(fā)首先需要了解網絡編程的基本概念，包括套接字（Socket）的使用、TCP/IP協(xié)議等，以下是一個簡單的TCP服務器示例：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
void error(const char msg) {
    perror(msg);
    exit(1);
}
int main(int argc, char argv[]) {
    int sockfd, newsockfd;
    socklen_t clilen;
    char buffer[256];
    struct sockaddr_in serv_addr, cli_addr;
    int n;
    if (argc < 2) {
        fprintf(stderr,"ERROR, no port provided
");
        exit(1);
    }
    sockfd = socket(AF_INET, SOCK_STREAM, 0);
    if (sockfd < 0) 
       error("ERROR opening socket");
    
    memset((char ) &serv_addr, 0, sizeof(serv_addr));
    serv_addr.sin_family = AF_INET;
    serv_addr.sin_addr.s_addr = INADDR_ANY;
    serv_addr.sin_port = htons(atoi(argv[1]));
    
    if (bind(sockfd, (struct sockaddr ) &serv_addr, sizeof(serv_addr)) < 0) 
              error("ERROR on binding");
    
    listen(sockfd,5);
    clilen = sizeof(cli_addr);
    
    while (1) {
        newsockfd = accept(sockfd, (struct sockaddr ) &cli_addr, &clilen);
        if (newsockfd < 0) 
            error("ERROR on accept");
        
        memset(buffer,0,256);
        n = read(newsockfd,buffer,255);
        if (n < 0) error("ERROR reading from socket");
        
        printf("Here is the message: %s
",buffer);
        n = write(newsockfd,"I got your message",18);
        if (n < 0) error("ERROR writing to socket");
        close(newsockfd);
    }
    close(sockfd);
    return 0; 
}

多線程和并發(fā)處理

為了處理多個客戶端的請求，可以使用多線程，POSIX線程庫（pthread）是常用的選擇，以下是一個簡單的多線程服務器示例：

#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
void client_handler(void socket_desc) {
    int sock = (int)socket_desc;
    char client_message[2000];
    
    while( (recv(sock, client_message, 2000, 0)) > 0) {
        printf("Message received: %s
", client_message);
        write(sock, "Message received
", strlen("Message received
"));
        memset(client_message, 0, 2000);
    }
    
    if(read_size == 0) {
        puts("Client disconnected");
    } else if(read_size == -1) {
        perror("recv failed");
    }
    
    free(socket_desc);
    return 0;
}
int main(int argc, char argv[]) {
    int socket_desc, client_sock, c;
    struct sockaddr_in server, client;
    pthread_t thread_id;
    
    socket_desc = socket(AF_INET, SOCK_STREAM, 0);
    if (socket_desc == -1) {
        printf("Could not create socket");
    }
    
    server.sin_family = AF_INET;
    server.sin_addr.s_addr = INADDR_ANY;
    server.sin_port = htons(8888);
    
    if(bind(socket_desc, (struct sockaddr )&server, sizeof(server)) < 0) {
        perror("bind failed. Error");
        return 1;
    }
    
    listen(socket_desc, 3);
    
    puts("Waiting for incoming connections...");
    c = sizeof(struct sockaddr_in);
    
    while((client_sock = accept(socket_desc, (struct sockaddr )&client, (socklen_t)&c))) {
        puts("Connection accepted");
        
        pthread_t sniffer_thread;
        int new_sock = malloc(1);
        new_sock = client_sock;
        
        if(pthread_create(&sniffer_thread, NULL, client_handler, (void) new_sock) < 0) {
            perror("could not create thread");
            return 1;
        }
        
        pthread_detach(sniffer_thread);
    }
    
    if (client_sock < 0) {
        perror("accept failed");
        return 1;
    }
    
    return 0;
}

PDF文件處理

PDF庫選擇

在C語言中處理PDF文件，可以選擇一些開源的PDF庫，如LibPDF、Poppler等，這里以Poppler為例，它是一個功能強大的PDF處理庫。

安裝Poppler庫

首先需要在系統(tǒng)中安裝Poppler庫，例如在Ubuntu系統(tǒng)上可以使用以下命令：

sudo apt-get install libpoppler-cpp-dev

基本操作示例

以下是一個簡單的示例，展示如何使用Poppler庫加載和獲取PDF文檔的基本信息：

#include <iostream>
#include <poppler-document.h>
#include <poppler-page.h>
#include <poppler-global.h>
#include <poppler-splash.h>
#include <poppler-toc.h>
#include <poppler-goo-pdf.h>
#include <poppler-embedded-file.h>
#include <poppler-annots.h>
#include <poppler-form.h>
#include <poppler-outputdev.h>
#include <poppler-private.h> // For GooString and GooList classes
#include <poppler-config.h> // For KPathSeason etc.
#include <poppler-version.h> // For popplerVersionCStr() function etc.
using namespace poppler;
int main(int argc, char argv[]) {
    if (argc != 2) {
        std::cerr << "Usage: " << argv[0] << " <PDF-file>" << std::endl;
        return 1;
    }
    const char filename = argv[1];
    Document doc = document_open(filename);
    if (!doc) {
        std::cerr << "Error: Unable to open document." << std::endl;
        return 1;
    }
    std::cout << "Title: " << doc->title() << std::endl;
    std::cout << "Num Pages: " << doc->numPages() << std::endl;
    std::cout << "Author: " << doc->author() << std::endl;
    std::cout << "Subject: " << doc->subject() << std::endl;
    std::cout << "Keywords: " << doc->keywords() << std::endl;
    std::cout << "Creator: " << doc->creator() << std::endl;
    std::cout << "Producer: " << doc->producer() << std::endl;
    std::cout << "Creation Date: " << doc->creationDate() << std::endl;
    std::cout << "Modification Date: " << doc->modificationDate() << std::endl;
    std::cout << "Is Encrypted: " << (doc->isEncrypted() ? "Yes" : "No") << std::endl;
    std::cout << "Is Locked: " << (doc->isLocked() ? "Yes" : "No") << std::endl;
    std::cout << "Is Linearized: " << (doc->isLinearized() ? "Yes" : "No") << std::endl;
    std::cout << "Is Form: " << (doc->isForm() ? "Yes" : "No") << std::endl;
    std::cout << "Is PDF/A: " << (doc->isPDFA() ? "Yes" : "No") << std::endl;
    std::cout << "Is PDF/UA: " << (doc->isPDFUA() ? "Yes" : "No") << std::endl;
    std::cout << "Is PDF/X: " << (doc->isPDFX() ? "Yes" : "No") << std::endl;
    std::cout << "Is PDF/E: " << (doc->isPDFE() ? "Yes" : "No") << std::endl;
    std::cout << "Is PDF/VT: " << (doc->isPDFVT() ? "Yes" : "No") << std::endl;
    delete doc;
    return 0;
}

FAQs（常見問題解答）

Q1: 如何在C語言中實現(xiàn)一個簡單的多線程服務器？

A1: 在C語言中實現(xiàn)一個簡單的多線程服務器，可以使用POSIX線程庫（pthread），首先需要創(chuàng)建一個監(jiān)聽套接字，然后在一個循環(huán)中接受客戶端連接，對于每個新的連接，創(chuàng)建一個新的線程來處理該連接，可以使用pthread_create函數來創(chuàng)建新線程，并將客戶端套接字傳遞給線程函數，在線程函數中，可以讀取客戶端發(fā)送的數據并進行相應處理，確保在主線程中關閉監(jiān)聽套接字，以下是一個簡單的多線程服務器示例代碼：

#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
void client_handler(void socket_desc) {
    int sock = (int)socket_desc;
    char client_message[2000];
    int read_size;
    // 接收來自客戶端的消息并回顯
    while((read_size = recv(sock, client_message, 2000, 0)) > 0) {
        write(sock, client_message, strlen(client_message));
    }
    if(read_size == 0) {
        puts("Client disconnected");
    } else if(read_size == -1) {
        perror("recv failed");
    }
    free(socket_desc);
    return 0;
}