HTTP协议（超文本传输协议）

以后有空系统整理：

1. 维基百科：点这里，其中说到请求的方法有一种是

　　POST向指定资源提交数据进行处理请求（例如提交表单或者上传文件）。数据被包含在请求体中。POST请求可能会导致新的资源的建立和/或已有资源的修改。

2. 可以结合breakpad的代码深入理解一下：

http_upload.h

View Code

// Copyright (c) 2006, Google Inc.
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
//     * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
//     * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
//     * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

#include "common/linux/http_upload.h"

#include <assert.h>
#include <dlfcn.h>
#include "third_party/curl/curl.h"

namespace {

// Callback to get the response data from server.
static size_t WriteCallback(void *ptr, size_t size,
size_t nmemb, void *userp) {
if (!userp)
return 0;

std::string *response = reinterpret_cast<std::string *>(userp);
size_t real_size = size * nmemb;
response->append(reinterpret_cast<char *>(ptr), real_size);
return real_size;
}

}  // namespace

namespace google_breakpad {

static const char kUserAgent[] = "Breakpad/1.0 (Linux)";

// static
bool HTTPUpload::SendRequest(const string &url,
const map<string, string> ¶meters,
const string &upload_file,
const string &file_part_name,
const string &proxy,
const string &proxy_user_pwd,
const string &ca_certificate_file,
string *response_body,
string *error_description) {
if (!CheckParameters(parameters))
return false;

void *curl_lib = dlopen("libcurl.so", RTLD_NOW);
if (!curl_lib) {
if (error_description != NULL)
*error_description = dlerror();
curl_lib = dlopen("libcurl.so.4", RTLD_NOW);
}
if (!curl_lib) {
// Debian gives libcurl a different name when it is built against GnuTLS
// instead of OpenSSL.
curl_lib = dlopen("libcurl-gnutls.so.4", RTLD_NOW);
}
if (!curl_lib) {
curl_lib = dlopen("libcurl.so.3", RTLD_NOW);
}
if (!curl_lib) {
return false;
}

CURL* (*curl_easy_init)(void);
*(void**) (&curl_easy_init) = dlsym(curl_lib, "curl_easy_init");
CURL *curl = (*curl_easy_init)();
if (error_description != NULL)
*error_description = "No Error";

if (!curl) {
dlclose(curl_lib);
return false;
}

CURLcode err_code = CURLE_OK;
CURLcode (*curl_easy_setopt)(CURL *, CURLoption, ...);
*(void**) (&curl_easy_setopt) = dlsym(curl_lib, "curl_easy_setopt");
(*curl_easy_setopt)(curl, CURLOPT_URL, url.c_str());
(*curl_easy_setopt)(curl, CURLOPT_USERAGENT, kUserAgent);
// Set proxy information if necessary.
if (!proxy.empty())
(*curl_easy_setopt)(curl, CURLOPT_PROXY, proxy.c_str());
if (!proxy_user_pwd.empty())
(*curl_easy_setopt)(curl, CURLOPT_PROXYUSERPWD, proxy_user_pwd.c_str());

if (!ca_certificate_file.empty())
(*curl_easy_setopt)(curl, CURLOPT_CAINFO, ca_certificate_file.c_str());

struct curl_httppost *formpost = NULL;
struct curl_httppost *lastptr = NULL;
// Add form data.
CURLFORMcode (*curl_formadd)(struct curl_httppost **, struct curl_httppost **, ...);
*(void**) (&curl_formadd) = dlsym(curl_lib, "curl_formadd");
map<string, string>::const_iterator iter = parameters.begin();
for (; iter != parameters.end(); ++iter)
(*curl_formadd)(&formpost, &lastptr,
CURLFORM_COPYNAME, iter->first.c_str(),
CURLFORM_COPYCONTENTS, iter->second.c_str(),
CURLFORM_END);

// Add form file.
(*curl_formadd)(&formpost, &lastptr,
CURLFORM_COPYNAME, file_part_name.c_str(),
CURLFORM_FILE, upload_file.c_str(),
CURLFORM_END);

(*curl_easy_setopt)(curl, CURLOPT_HTTPPOST, formpost);

// Disable 100-continue header.
struct curl_slist *headerlist = NULL;
char buf[] = "Expect:";
struct curl_slist* (*curl_slist_append)(struct curl_slist *, const char *);
*(void**) (&curl_slist_append) = dlsym(curl_lib, "curl_slist_append");
headerlist = (*curl_slist_append)(headerlist, buf);
(*curl_easy_setopt)(curl, CURLOPT_HTTPHEADER, headerlist);

if (response_body != NULL) {
(*curl_easy_setopt)(curl, CURLOPT_WRITEFUNCTION, WriteCallback);
(*curl_easy_setopt)(curl, CURLOPT_WRITEDATA,
reinterpret_cast<void *>(response_body));
}

// Fail if 400+ is returned from the web server.
(*curl_easy_setopt)(curl, CURLOPT_FAILONERROR, 1);

CURLcode (*curl_easy_perform)(CURL *);
*(void**) (&curl_easy_perform) = dlsym(curl_lib, "curl_easy_perform");
err_code = (*curl_easy_perform)(curl);
const char* (*curl_easy_strerror)(CURLcode);
*(void**) (&curl_easy_strerror) = dlsym(curl_lib, "curl_easy_strerror");
#ifndef NDEBUG
if (err_code != CURLE_OK)
fprintf(stderr, "Failed to send http request to %s, error: %s\n",
url.c_str(),
(*curl_easy_strerror)(err_code));
#endif
if (error_description != NULL)
*error_description = (*curl_easy_strerror)(err_code);

void (*curl_easy_cleanup)(CURL *);
*(void**) (&curl_easy_cleanup) = dlsym(curl_lib, "curl_easy_cleanup");
(*curl_easy_cleanup)(curl);
if (formpost != NULL) {
void (*curl_formfree)(struct curl_httppost *);
*(void**) (&curl_formfree) = dlsym(curl_lib, "curl_formfree");
(*curl_formfree)(formpost);
}
if (headerlist != NULL) {
void (*curl_slist_free_all)(struct curl_slist *);
*(void**) (&curl_slist_free_all) = dlsym(curl_lib, "curl_slist_free_all");
(*curl_slist_free_all)(headerlist);
}
dlclose(curl_lib);
return err_code == CURLE_OK;
}

// static
bool HTTPUpload::CheckParameters(const map<string, string> ¶meters) {
for (map<string, string>::const_iterator pos = parameters.begin();
pos != parameters.end(); ++pos) {
const string &str = pos->first;
if (str.size() == 0)
return false;  // disallow empty parameter names
for (unsigned int i = 0; i < str.size(); ++i) {
int c = str[i];
if (c < 32 || c == '"' || c > 127) {
return false;
}
}
}
return true;
}

}  // namespace google_breakpad