我正在开发一个下载程序，它下载多个部分的文件（每个部分使用异步连接下载），然后将这些部分合并到一个文件中。为此，我使用了libcurl库。
＆＃39; multi_handle2.c＆＃39;的第96行我告诉libcurl只下载一系列字节，但它不遵守给定的范围，因为它下载了整个文件。 这是代码：
multi_handle2.c
#include <stdio.h>
#include <curl/curl.h>
#include "curl_extensions.h"
#define MINIMAL_PROGRESS_FUNCTIONALITY_INTERVAL 1
struct myprogress {
double lastruntime;
CURL *curl;
};
size_t write_data (void *ptr, size_t size, size_t nmemb, FILE *stream)
{
size_t written = fwrite (ptr, size, nmemb, stream);
return written;
}
static int xferinfo (void *p,
curl_off_t dltotal,
curl_off_t dlnow,
curl_off_t ultotal,
curl_off_t ulnow)
{
struct myprogress *myp = (struct myprogress *)p;
CURL *curl = myp->curl;
double curtime = 0;
curl_easy_getinfo (curl, CURLINFO_TOTAL_TIME, &curtime);
if ((curtime - myp->lastruntime) >= MINIMAL_PROGRESS_FUNCTIONALITY_INTERVAL) {
myp->lastruntime = curtime;
fprintf (stderr, "TOTAL TIME: %f \r\n", curtime);
}
fprintf (stderr, "UP: %" CURL_FORMAT_CURL_OFF_T " of %" CURL_FORMAT_CURL_OFF_T
" DOWN %" CURL_FORMAT_CURL_OFF_T " of %" CURL_FORMAT_CURL_OFF_T
"\r\n",
ulnow, ultotal, dlnow, dltotal);
return 0;
}
void get_range(const int index, const int proc_number, const int total, int *begin, int *end)
{
int range = total / proc_number;
*begin = index*range;
*end = *begin+range-1;
if (index+1 == proc_number) {
if (total % proc_number != 0) {
*end += (total % proc_number);
}
}
}
int main()
{
const int PROC_NUMBER = 8;
CURLM *curlm;
CURLMcode res;
int still_running;
CURL *handle[PROC_NUMBER];
FILE *fp[PROC_NUMBER];
struct myprogress prog;
struct finfo_info info;
int index;
char *url = "https://codeload.github.com/GNOME/meld/zip/master";
get_finfo(url, &info);
//printf ("size: %d\n", info.size);
curlm = curl_multi_init();
for (index = 0; index < PROC_NUMBER; index++) {
char filename[15];
sprintf (filename, "part%d", index);
fp[index] = fopen(filename, "wb");
handle[index] = curl_easy_init();
curl_easy_setopt(handle[index], CURLOPT_URL, url);
curl_easy_setopt(handle[index], CURLOPT_WRITEFUNCTION, write_data);
curl_easy_setopt(handle[index], CURLOPT_WRITEDATA, fp[index]);
curl_easy_setopt(handle[index], CURLOPT_XFERINFOFUNCTION, xferinfo);
curl_easy_setopt(handle[index], CURLOPT_XFERINFODATA, &prog);
curl_easy_setopt(handle[index], CURLOPT_NOPROGRESS, 0L);
int begin, end;
char *range = (char *) malloc(sizeof(char*));
get_range(index, PROC_NUMBER, (int)info.size, &begin, &end);
sprintf (range, "%d-%d", begin, end);
printf ("%s\n", range);
curl_easy_setopt(handle[index], CURLOPT_RANGE, range);
curl_multi_add_handle(curlm, handle[index]);
}
res = curl_multi_perform(curlm, &still_running);
/*******************/
do {
struct timeval timeout;
int rc; /* select() return code */
CURLMcode mc; /* curl_multi_fdset() return code */
fd_set fdread;
fd_set fdwrite;
fd_set fdexcep;
int maxfd = -1;
long curl_timeo = -1;
FD_ZERO(&fdread);
FD_ZERO(&fdwrite);
FD_ZERO(&fdexcep);
/* set a suitable timeout to play around with */
timeout.tv_sec = 1;
timeout.tv_usec = 0;
curl_multi_timeout(curlm, &curl_timeo);
if (curl_timeo >= 0) {
timeout.tv_sec = curl_timeo / 1000;
if(timeout.tv_sec > 1)
timeout.tv_sec = 1;
else
timeout.tv_usec = (curl_timeo % 1000) * 1000;
}
mc = curl_multi_fdset(curlm, &fdread, &fdwrite, &fdexcep, &maxfd);
if(mc != CURLM_OK)
{
fprintf(stderr, "curl_multi_fdset() failed, code %d.\n", mc);
break;
}
if(maxfd == -1) {
#ifdef _WIN32
Sleep(100);
rc = 0;
#else
/* Portable sleep for platforms other than Windows. */
struct timeval wait = { 0, 100 * 1000 }; /* 100ms */
rc = select(0, NULL, NULL, NULL, &wait);
#endif
}
else {
/* Note that on some platforms 'timeout' may be modified by select().
If you need access to the original value save a copy beforehand. */
rc = select(maxfd+1, &fdread, &fdwrite, &fdexcep, &timeout);
}
switch(rc) {
case -1:
/* select error */
break;
case 0:
default:
/* timeout or readable/writable sockets */
curl_multi_perform(curlm, &still_running);
break;
}
} while(still_running);
/*******************/
if (res != CURLM_OK)
printf ("failed\n");
/* finals */
for (index = 0; index < PROC_NUMBER; index++) {
curl_multi_remove_handle(curlm, handle[index]);
curl_easy_cleanup(handle[index]);
fclose(fp[index]);
}
return 0;
}
curl_extensions.c
#include "curl_extensions.h"
#include <stdio.h>
#include <curl/curl.h>
static size_t finfo_memory_callback (void *contents,
size_t size,
size_t nmemb,
void *userp)
{
size_t realsize = size * nmemb;
struct finfo_memory *mem = (struct finfo_memory *)userp;
mem->memory = realloc(mem->memory, mem->size + realsize + 1);
if(mem->memory == NULL) {
/* out of memory! */
printf("not enough memory (realloc returned NULL)\n");
return 0;
}
memcpy(&(mem->memory[mem->size]), contents, realsize);
mem->size += realsize;
mem->memory[mem->size] = 0;
if (DEBUG) {
printf ("size: %d\n", realsize);
}
return realsize;
}
static int finfo_xferinfo (void *p,
curl_off_t dltotal,
curl_off_t dlnow,
curl_off_t ultotal,
curl_off_t ulnow)
{
struct finfo_progress *myp = (struct finfo_progress *)p;
myp->dltotal = dltotal;
if (DEBUG) {
printf ("getting size: %d\n", dltotal);
}
return (int)dltotal;
}
void get_finfo(char *url,
struct finfo_info *pointer)
{
CURL *curl;
CURLcode res;
struct finfo_progress prog;
struct finfo_memory chunk;
chunk.memory = malloc(1);
chunk.size = 0;
curl = curl_easy_init();
if (curl) {
curl_easy_setopt(curl, CURLOPT_URL, url);
curl_easy_setopt(curl, CURLOPT_XFERINFOFUNCTION, finfo_xferinfo);
curl_easy_setopt(curl, CURLOPT_XFERINFODATA, &prog);
curl_easy_setopt(curl, CURLOPT_NOPROGRESS, 0L);
curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, finfo_memory_callback);
curl_easy_setopt(curl, CURLOPT_WRITEDATA, (void *)&chunk);
res = curl_easy_perform(curl);
if (res != CURLE_OK)
fprintf (stderr, "%s\n", curl_easy_strerror(res));
curl_easy_cleanup(curl);
}
pointer->size = (size_t) prog.dltotal;
//return !(res != CURLE_OK);
}
//int main()
//{
// struct finfo_info info;
// get_finfo ("https://raw.githubusercontent.com/bagder/curl/master/docs/examples/10-at-a-time.c", &info);
// printf ("size: %d\n", info.size);
//
// get_finfo ("http://download.cdn.mozilla.net/pub/firefox/releases/39.0/linux-i686/pt-BR/firefox-39.0.tar.bz2", &info);
// printf ("size: %d\n", info.size);
//}
curl_extensions.h
#ifndef _CURL_EXTENSIONS_H
#define _CURL_EXTENSIONS_H
#include <curl/curl.h>
#define DEBUG 0
struct finfo_progress {
curl_off_t dltotal;
};
struct finfo_memory {
char *memory;
size_t size;
};
struct finfo_info {
size_t size;
};
static size_t finfo_memory_callback (void *contents, size_t size, size_t nmemb, void *userp);
static int finfo_xferinfo (void *p,
curl_off_t dltotal,
curl_off_t dlnow,
curl_off_t ultotal,
curl_off_t ulnow);
int finfo(char *url);
#endif /* _CURL_EXTENSIONS_H */
编译：
gcc multi_handle2.c -I curl_extensions.h curl_extensions.c -o multi_handle2 -lcurl
答案 0 :(得分：0)
HTTP服务器不会被强制遵守Range标头，它只是来自客户端的请求，有时/经常被服务器忽略。因此，您可能只是要求服务器不想播放Range，或者您只是要求服务器可以提供的特定URL。如果输出是动态生成的，通常就是后者。
A server MAY ignore the Range header field.
（CURLOPT_RANGE手册页现已更新，以提及此事实。）