clientLibrary.c

/**
 * @file clientLibrary.c
 * @brief Object Store Client Library Implementation
 *
 * Implements the client-side API for communicating with the object store server.
 * Handles socket connection, protocol message formatting, and response parsing.
 *
 * @author Gennaro Baratta
 * @date 2018/19
 */

#define _POSIX_C_SOURCE 200809L
#include <assert.h>
#include <clientLibrary.h>
#include <string.h>
#include <sys/time.h>

/* Global connection state */
int sockfd;        /**< Socket file descriptor for server connection */
int notused, n;    /**< Temporary variables for syscall returns */

/**
 * Implementation of os_connect
 * Creates Unix socket, connects to server, sends REGISTER command
 */
int os_connect(char* name) {
  struct sockaddr_un serv_addr;

  /* Create Unix domain socket */
  SYSCALL(sockfd, socket(AF_UNIX, SOCK_STREAM, 0), "socket");
  memset(&serv_addr, '0', sizeof(serv_addr));

  /* Set up server address */
  serv_addr.sun_family = AF_UNIX;
  strncpy(serv_addr.sun_path, SOCKNAME, strlen(SOCKNAME) + 1);

  /* Connect to server */
  SYSCALL(notused,
          connect(sockfd, (struct sockaddr*)&serv_addr, sizeof(serv_addr)),
          "connect");

  /* Send REGISTER command */
  char buf[BUFSIZE] = "";
  sprintf(buf, "REGISTER %s \n", name);

  SYSCALL(notused, writen(sockfd, buf, strlen(buf)), "writen client");

  /* Read response */
  memset(buf, 0, BUFSIZE);
  SYSCALL(n, read(sockfd, buf, BUFSIZE), "read client");

  /* Return 0 if "OK", -1 otherwise */
  return strncmp(buf, "OK", 2);
}

/**
 * Implementation of os_disconnect
 * Sends LEAVE command and closes socket
 */
int os_disconnect() {
  char buf[BUFSIZE];
  memset(buf, 0, BUFSIZE);

  /* Send LEAVE command */
  SYSCALL(notused, writen(sockfd, "LEAVE \n", 8), "writen");

  /* Read response */
  SYSCALL(n, read(sockfd, buf, BUFSIZE), "read client");

  /* Close socket */
  close(sockfd);

  /* Return 0 if "OK", -1 otherwise */
  return strncmp(buf, "OK", 2);
}

/**
 * Implementation of os_store
 * Sends STORE command with object name, length, and binary data
 */
int os_store(char* name, void* block, size_t len) {
  assert(block);
  char buf[BUFSIZE] = "";

  /* Send STORE command header: "STORE <name> <len>\n" */
  sprintf(buf, "STORE %s %zu \n", name, len);
  SYSCALL(notused, writen(sockfd, buf, strlen(buf)), "writen client");

  /* Send binary data */
  SYSCALL(notused, writen(sockfd, block, len), "writen client");

  /* Read response */
  memset(buf, 0, BUFSIZE);
  SYSCALL(n, read(sockfd, buf, BUFSIZE), "read client");

  /* Return 0 if "OK", -1 otherwise */
  return strncmp(buf, "OK", 2);
}

/**
 * Implementation of os_retrieve
 * Sends RETRIEVE command and parses "DATA <len>\n<data>" response
 * Handles data larger than buffer size by reading in chunks
 */
void* os_retrieve(char* name) {
  assert(name);
  char buf[BUFSIZE];
  char* data;
  char *token1, *token2, *token3, *tokptr;
  int ret;

  /* Send RETRIEVE command */
  sprintf(buf, "RETRIVE %s \n", name);
  SYSCALL(notused, writen(sockfd, buf, strlen(buf)), "writen client");

  /* Read response header */
  memset(buf, 0, BUFSIZE);
  SYSCALL(n, read(sockfd, buf, BUFSIZE - 1), "read client");

  /* Parse response: should be "DATA <len>\n<data>" or "KO <message>\n" */
  CHECKNULL(token1, strtok_r(buf, " ", &tokptr), "strtok_r retrive");

  /* Check for error response */
  if (strncmp(token1, "KO", 2) == 0) {
    return NULL;
  }

  /* Parse data length */
  token2 = strtok_r(NULL, "\n", &tokptr);
  if (!token2) {
    return NULL;
  }
  size_t lenNum = strlen(token2) - 1;
  size_t len = strtol(token2, NULL, 10);

  /* Get pointer to data in buffer */
  CHECKNULL(token3, strtok_r(NULL, " ", &tokptr), "strtok_r3 retrive");

  /* Calculate how much data is already in buffer */
  size_t maxLenBlock = BUFSIZE - strlen("DATA  \n ") - lenNum - 1;

  /* Allocate buffer for full data */
  CHECKNULL(data, calloc((len + 1), sizeof(char)), "malloc");

  /* Copy data from initial read */
  memcpy(data, token3, len < maxLenBlock ? len : maxLenBlock);

  /* If data is larger than buffer, read remaining bytes */
  if (len > maxLenBlock) {
    void* bufferino = calloc(len - maxLenBlock + 1, sizeof(char));
    SYSCALL(ret, readn(sockfd, bufferino, len - maxLenBlock), "read file");
    if (ret > 0) {
      memcpy(data + maxLenBlock, bufferino, ret);
    }
    free(bufferino);
  }

  return data;
}

/**
 * Implementation of os_delete
 * Sends DELETE command with object name
 */
int os_delete(char* name) {
  assert(name);
  char buf[BUFSIZE] = "";

  /* Send DELETE command */
  sprintf(buf, "DELETE %s \n", name);
  SYSCALL(notused, writen(sockfd, buf, strlen(buf)), "writen client");

  /* Read response */
  memset(buf, 0, BUFSIZE);
  SYSCALL(n, read(sockfd, buf, BUFSIZE), "read client");

  /* Return 0 if "OK", -1 otherwise */
  return strncmp(buf, "OK", 2);
}