/* 
 These functions are belonged to a libray which can be used to transfer file
 simplely.
 
 Copyright (C) 1994-1995, Li Suke, School of Software,Peking University
 This  is free software; you can redistribute it and/or
 modify it freely.

 This software  is distributed in the hope that it will be useful,
 but WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. 
*/

#include <sys/types.h>
#include <stdio.h>
#include <unistd.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <string.h>
#include "rw.h"

/***
 *  len: store the total receving data byte number
 *
 */
ssize_t readall(int fd, void* buf,size_t *len){
   size_t nleft;
   ssize_t nread;
   ssize_t total;
   char *ptr;
   ptr = buf;
   nleft = *len;
   total = 0;
   while( nleft > 0){
      if((nread = read(fd,ptr,*len)) == -1){
         perror("readall");
         break;
      }
      if(nread ==0)
         break;
      nleft -= nread;
      ptr += nread;
      total += nread;
      *len = nleft;
   } 
   *len = total;
   return (nread==-1)?-1:0;
}

/***
 *  len: store the total sending data byte number
 *
 */
ssize_t writeall(int fd, void* buf,size_t *len){
   size_t nleft;
   ssize_t nwrite;
   ssize_t total;
   const char *ptr;
   ptr = buf;
   nleft = *len;
   total = 0;
   while( nleft > 0){
      if((nwrite = write(fd,ptr,*len))== -1){
         perror("write all");
         break;
      }
      nleft -= nwrite;
      ptr += nwrite;
      total += nwrite;
      *len = nleft;
   } 
   *len = total;
   return (nwrite==-1)?-1:0;
}

/* read the commond from client, the command format is 
   content+\r\n
   return value:
       0: succesful
       -1: failure
*/   
int read_cmd(int sockfd,char* cmd_buf,int len){
   char line[MAX_LEN];
   int my_len = 0;
   int total_len =0;
   char *ptr;
   int can_read;
   if(len > MAX_LEN)
      len = MAX_LEN;
   can_read = 1;
   strcpy(cmd_buf,"\0");
   while(can_read){
      if((my_len = read(sockfd, line,len))<0 ){
           perror("read");
           return -1;
      }
      total_len = total_len + my_len;
      if(total_len > len){
           printf("Recieve command error!\n");
           return -1;
      }
      if((ptr=strstr(line,"\r\n"))==NULL){
        if(total_len <= len)
           strcat(cmd_buf, line); 
      }else{
        strncat(cmd_buf,line,ptr-line);
        can_read = 0;
      }
      printf("Client requests file: %s\n",cmd_buf);   
   }
   return 0;
}

/* Send a file to client
   return value:
   0: successful
   -1: failure
*/

int send_file(int sockfd,char *file_name)
{
  int file_fd;
  int file_size;
  int read_left;
  int len;
  int error_flag;
  int readlen;
  struct stat file_state;
  char buffer[MAX_LEN];
  int dot_number = 0;
  if((file_fd = open(file_name,O_RDONLY)) == -1){
     perror("open");
     return -1;
  }
  if(fstat(file_fd, &file_state)==-1){
     perror("fstat");
     return -1;
  }
  file_size = file_state.st_size;
  read_left = file_size;
  len = MAX_LEN;
  while(read_left > 0){
     /* now read the file */
     readlen = MAX_LEN;
     error_flag = readall(file_fd,buffer,&readlen);
     if(error_flag<0 ){
        return -1;
     }
     read_left -= readlen;
     len = readlen;
     error_flag = writeall(sockfd,buffer,&len);
     if(error_flag == -1)
         return -1;
     if(readlen ==0 && read_left!=0){
         printf("the file is not read fully!\n");   
         return -1;         
     }
     if(read_left ==0){
         printf("\nServer sent file over!\n");                  
     }
  }    
  close(file_fd);
  return 0;
}