blob: 57e549831e0461b996f63b0be122322e95789ccf [file] [log] [blame]
// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include <algorithm>
#include <iterator>
#include <map>
#include <string>
#include <unordered_set>
#include "base/base64.h"
#include "base/containers/hash_tables.h"
#include "base/containers/span.h"
#include "base/files/file_path.h"
#include "base/lazy_instance.h"
#include "base/logging.h"
#include "base/rand_util.h"
#include "base/stl_util.h"
#include "base/strings/string_number_conversions.h"
#include "base/strings/string_split.h"
#include "base/strings/string_util.h"
#include "base/strings/utf_string_conversions.h"
#include "build/build_config.h"
#include "net/base/mime_util.h"
#include "net/base/platform_mime_util.h"
#include "net/http/http_util.h"
#include "starboard/common/string.h"
using std::string;
namespace net {
// Singleton utility class for mime types.
class MimeUtil : public PlatformMimeUtil {
public:
bool GetMimeTypeFromExtension(const base::FilePath::StringType& ext,
std::string* mime_type) const;
bool GetMimeTypeFromFile(const base::FilePath& file_path,
std::string* mime_type) const;
bool GetWellKnownMimeTypeFromExtension(const base::FilePath::StringType& ext,
std::string* mime_type) const;
bool GetPreferredExtensionForMimeType(
const std::string& mime_type,
base::FilePath::StringType* extension) const;
#if defined(STARBOARD)
bool IsSupportedImageMimeType(const std::string& mime_type) const;
#endif
bool MatchesMimeType(const std::string &mime_type_pattern,
const std::string &mime_type) const;
bool ParseMimeTypeWithoutParameter(const std::string& type_string,
std::string* top_level_type,
std::string* subtype) const;
bool IsValidTopLevelMimeType(const std::string& type_string) const;
private:
friend struct base::LazyInstanceTraitsBase<MimeUtil>;
#if defined(STARBOARD)
MimeUtil() { InitializeMimeTypesMaps(); }
void InitializeMimeTypesMaps();
typedef std::unordered_set<std::string> MimeMappings;
MimeMappings image_map_;
#else
MimeUtil() = default;
#endif
bool GetMimeTypeFromExtensionHelper(const base::FilePath::StringType& ext,
bool include_platform_types,
std::string* mime_type) const;
}; // class MimeUtil
// This variable is Leaky because we need to access it from WorkerPool threads.
static base::LazyInstance<MimeUtil>::Leaky g_mime_util =
LAZY_INSTANCE_INITIALIZER;
struct MimeInfo {
const char* const mime_type;
// Comma-separated list of possible extensions for the type. The first
// extension is considered preferred.
const char* const extensions;
};
// Order of entries in the following mapping lists matters only when the same
// extension is shared between multiple MIME types.
static const MimeInfo kPrimaryMappings[] = {
// Must precede audio/webm .
{"video/webm", "webm"},
{"application/wasm", "wasm"},
{"application/x-chrome-extension", "crx"},
{"application/xhtml+xml", "xhtml,xht,xhtm"},
{"audio/flac", "flac"},
{"audio/mp3", "mp3"},
{"audio/ogg", "ogg,oga,opus"},
{"audio/wav", "wav"},
{"audio/webm", "webm"},
{"audio/x-m4a", "m4a"},
{"image/gif", "gif"},
{"image/jpeg", "jpeg,jpg"},
{"image/png", "png"},
{"image/apng", "png"},
{"image/webp", "webp"},
{"multipart/related", "mht,mhtml"},
{"text/css", "css"},
{"text/html", "html,htm,shtml,shtm"},
{"text/javascript", "js,mjs"},
{"text/xml", "xml"},
{"video/mp4", "mp4,m4v"},
{"video/ogg", "ogv,ogm"},
};
static const MimeInfo kSecondaryMappings[] = {
// Must precede image/vnd.microsoft.icon .
{"image/x-icon", "ico"},
{"application/epub+zip", "epub"},
{"application/font-woff", "woff"},
{"application/gzip", "gz,tgz"},
{"application/javascript", "js"},
{"application/json", "json"}, // Per http://www.ietf.org/rfc/rfc4627.txt.
{"application/octet-stream", "bin,exe,com"},
{"application/pdf", "pdf"},
{"application/pkcs7-mime", "p7m,p7c,p7z"},
{"application/pkcs7-signature", "p7s"},
{"application/postscript", "ps,eps,ai"},
{"application/rdf+xml", "rdf"},
{"application/rss+xml", "rss"},
{"application/vnd.android.package-archive", "apk"},
{"application/vnd.mozilla.xul+xml", "xul"},
{"application/x-gzip", "gz,tgz"},
{"application/x-mpegurl", "m3u8"},
{"application/x-shockwave-flash", "swf,swl"},
{"application/x-tar", "tar"},
{"application/zip", "zip"},
{"audio/mpeg", "mp3"},
{"image/bmp", "bmp"},
{"image/jpeg", "jfif,pjpeg,pjp"},
{"image/svg+xml", "svg,svgz"},
{"image/tiff", "tiff,tif"},
{"image/vnd.microsoft.icon", "ico"},
{"image/x-png", "png"},
{"image/x-xbitmap", "xbm"},
{"message/rfc822", "eml"},
{"text/calendar", "ics"},
{"text/html", "ehtml"},
{"text/plain", "txt,text"},
{"text/x-sh", "sh"},
{"text/xml", "xsl,xbl,xslt"},
{"video/mpeg", "mpeg,mpg"},
};
#if defined(STARBOARD)
// The following functions are copied from old Chromium libs.
// From WebKit's WebCore/platform/MIMETypeRegistry.cpp:
static const char* const supported_image_types[] = {
"image/jpeg", "image/pjpeg", "image/jpg", "image/webp",
"image/png", "image/gif", "image/bmp",
"image/x-icon", // ico
"image/x-xbitmap", // xbm
"application/json" // Lottie animations
};
void MimeUtil::InitializeMimeTypesMaps() {
for (size_t i = 0; i < arraysize(supported_image_types); ++i)
image_map_.insert(supported_image_types[i]);
}
bool MimeUtil::IsSupportedImageMimeType(const std::string& mime_type) const {
return image_map_.find(mime_type) != image_map_.end();
}
#endif
// Finds mime type of |ext| from |mappings|.
template <size_t num_mappings>
static const char* FindMimeType(const MimeInfo (&mappings)[num_mappings],
const std::string& ext) {
for (const auto& mapping : mappings) {
const char* extensions = mapping.extensions;
for (;;) {
size_t end_pos = strcspn(extensions, ",");
// The length check is required to prevent the StringPiece below from
// including uninitialized memory if ext is longer than extensions.
if (end_pos == ext.size() &&
base::EqualsCaseInsensitiveASCII(
base::StringPiece(extensions, ext.size()), ext)) {
return mapping.mime_type;
}
extensions += end_pos;
if (!*extensions)
break;
extensions += 1; // skip over comma
}
}
return NULL;
}
static base::FilePath::StringType StringToFilePathStringType(
const base::StringPiece& string_piece) {
#if defined(OS_WIN)
return base::UTF8ToUTF16(string_piece);
#else
return string_piece.as_string();
#endif
}
// Helper used in MimeUtil::GetPreferredExtensionForMimeType() to search
// preferred extension in MimeInfo arrays.
template <size_t num_mappings>
static bool FindPreferredExtension(const MimeInfo (&mappings)[num_mappings],
const std::string& mime_type,
base::FilePath::StringType* result) {
// There is no preferred extension for "application/octet-stream".
if (mime_type == "application/octet-stream")
return false;
for (const auto& mapping : mappings) {
if (mapping.mime_type == mime_type) {
const char* extensions = mapping.extensions;
const char* extension_end = strchr(extensions, ',');
int len = extension_end ? extension_end - extensions
: strlen(extensions);
*result = StringToFilePathStringType(base::StringPiece(extensions, len));
return true;
}
}
return false;
}
bool MimeUtil::GetMimeTypeFromExtension(const base::FilePath::StringType& ext,
string* result) const {
return GetMimeTypeFromExtensionHelper(ext, true, result);
}
bool MimeUtil::GetWellKnownMimeTypeFromExtension(
const base::FilePath::StringType& ext,
string* result) const {
return GetMimeTypeFromExtensionHelper(ext, false, result);
}
bool MimeUtil::GetPreferredExtensionForMimeType(
const std::string& mime_type,
base::FilePath::StringType* extension) const {
// Search the MIME type in the platform DB first, then in kPrimaryMappings and
// kSecondaryMappings.
return GetPlatformPreferredExtensionForMimeType(mime_type, extension) ||
FindPreferredExtension(kPrimaryMappings, mime_type, extension) ||
FindPreferredExtension(kSecondaryMappings, mime_type, extension);
}
bool MimeUtil::GetMimeTypeFromFile(const base::FilePath& file_path,
string* result) const {
base::FilePath::StringType file_name_str = file_path.Extension();
if (file_name_str.empty())
return false;
return GetMimeTypeFromExtension(file_name_str.substr(1), result);
}
bool MimeUtil::GetMimeTypeFromExtensionHelper(
const base::FilePath::StringType& ext,
bool include_platform_types,
string* result) const {
// Avoids crash when unable to handle a long file path. See crbug.com/48733.
const unsigned kMaxFilePathSize = 65536;
if (ext.length() > kMaxFilePathSize)
return false;
// Reject a string which contains null character.
base::FilePath::StringType::size_type nul_pos =
ext.find(FILE_PATH_LITERAL('\0'));
if (nul_pos != base::FilePath::StringType::npos)
return false;
// We implement the same algorithm as Mozilla for mapping a file extension to
// a mime type. That is, we first check a hard-coded list (that cannot be
// overridden), and then if not found there, we defer to the system registry.
// Finally, we scan a secondary hard-coded list to catch types that we can
// deduce but that we also want to allow the OS to override.
base::FilePath path_ext(ext);
const string ext_narrow_str = path_ext.AsUTF8Unsafe();
const char* mime_type = FindMimeType(kPrimaryMappings, ext_narrow_str);
if (mime_type) {
*result = mime_type;
return true;
}
if (include_platform_types && GetPlatformMimeTypeFromExtension(ext, result))
return true;
mime_type = FindMimeType(kSecondaryMappings, ext_narrow_str);
if (mime_type) {
*result = mime_type;
return true;
}
return false;
}
// Tests for MIME parameter equality. Each parameter in the |mime_type_pattern|
// must be matched by a parameter in the |mime_type|. If there are no
// parameters in the pattern, the match is a success.
//
// According rfc2045 keys of parameters are case-insensitive, while values may
// or may not be case-sensitive, but they are usually case-sensitive. So, this
// function matches values in *case-sensitive* manner, however note that this
// may produce some false negatives.
bool MatchesMimeTypeParameters(const std::string& mime_type_pattern,
const std::string& mime_type) {
typedef std::map<std::string, std::string> StringPairMap;
const std::string::size_type semicolon = mime_type_pattern.find(';');
const std::string::size_type test_semicolon = mime_type.find(';');
if (semicolon != std::string::npos) {
if (test_semicolon == std::string::npos)
return false;
base::StringPairs pattern_parameters;
base::SplitStringIntoKeyValuePairs(mime_type_pattern.substr(semicolon + 1),
'=', ';', &pattern_parameters);
base::StringPairs test_parameters;
base::SplitStringIntoKeyValuePairs(mime_type.substr(test_semicolon + 1),
'=', ';', &test_parameters);
// Put the parameters to maps with the keys converted to lower case.
StringPairMap pattern_parameter_map;
for (const auto& pair : pattern_parameters) {
pattern_parameter_map[base::ToLowerASCII(pair.first)] = pair.second;
}
StringPairMap test_parameter_map;
for (const auto& pair : test_parameters) {
test_parameter_map[base::ToLowerASCII(pair.first)] = pair.second;
}
if (pattern_parameter_map.size() > test_parameter_map.size())
return false;
for (const auto& parameter_pair : pattern_parameter_map) {
const auto& test_parameter_pair_it =
test_parameter_map.find(parameter_pair.first);
if (test_parameter_pair_it == test_parameter_map.end())
return false;
if (parameter_pair.second != test_parameter_pair_it->second)
return false;
}
}
return true;
}
// This comparison handles absolute maching and also basic
// wildcards. The plugin mime types could be:
// application/x-foo
// application/*
// application/*+xml
// *
// Also tests mime parameters -- all parameters in the pattern must be present
// in the tested type for a match to succeed.
bool MimeUtil::MatchesMimeType(const std::string& mime_type_pattern,
const std::string& mime_type) const {
if (mime_type_pattern.empty())
return false;
std::string::size_type semicolon = mime_type_pattern.find(';');
const std::string base_pattern(mime_type_pattern.substr(0, semicolon));
semicolon = mime_type.find(';');
const std::string base_type(mime_type.substr(0, semicolon));
if (base_pattern == "*" || base_pattern == "*/*")
return MatchesMimeTypeParameters(mime_type_pattern, mime_type);
const std::string::size_type star = base_pattern.find('*');
if (star == std::string::npos) {
if (base::EqualsCaseInsensitiveASCII(base_pattern, base_type))
return MatchesMimeTypeParameters(mime_type_pattern, mime_type);
else
return false;
}
// Test length to prevent overlap between |left| and |right|.
if (base_type.length() < base_pattern.length() - 1)
return false;
base::StringPiece base_pattern_piece(base_pattern);
base::StringPiece left(base_pattern_piece.substr(0, star));
base::StringPiece right(base_pattern_piece.substr(star + 1));
if (!base::StartsWith(base_type, left, base::CompareCase::INSENSITIVE_ASCII))
return false;
if (!right.empty() &&
!base::EndsWith(base_type, right, base::CompareCase::INSENSITIVE_ASCII))
return false;
return MatchesMimeTypeParameters(mime_type_pattern, mime_type);
}
// See http://www.iana.org/assignments/media-types/media-types.xhtml
static const char* const kLegalTopLevelTypes[] = {
"application", "audio", "example", "image", "message",
"model", "multipart", "text", "video",
};
bool MimeUtil::ParseMimeTypeWithoutParameter(
const std::string& type_string,
std::string* top_level_type,
std::string* subtype) const {
std::vector<std::string> components = base::SplitString(
type_string, "/", base::TRIM_WHITESPACE, base::SPLIT_WANT_ALL);
if (components.size() != 2 ||
!HttpUtil::IsToken(components[0]) ||
!HttpUtil::IsToken(components[1]))
return false;
if (top_level_type)
*top_level_type = components[0];
if (subtype)
*subtype = components[1];
return true;
}
bool MimeUtil::IsValidTopLevelMimeType(const std::string& type_string) const {
std::string lower_type = base::ToLowerASCII(type_string);
for (const char* const legal_type : kLegalTopLevelTypes) {
if (lower_type.compare(legal_type) == 0)
return true;
}
return type_string.size() > 2 &&
base::StartsWith(type_string, "x-",
base::CompareCase::INSENSITIVE_ASCII);
}
//----------------------------------------------------------------------------
// Wrappers for the singleton
//----------------------------------------------------------------------------
#if defined(STARBOARD)
bool IsSupportedImageMimeType(const std::string& mime_type) {
return g_mime_util.Get().IsSupportedImageMimeType(mime_type);
}
#endif
bool GetMimeTypeFromExtension(const base::FilePath::StringType& ext,
std::string* mime_type) {
return g_mime_util.Get().GetMimeTypeFromExtension(ext, mime_type);
}
bool GetMimeTypeFromFile(const base::FilePath& file_path,
std::string* mime_type) {
return g_mime_util.Get().GetMimeTypeFromFile(file_path, mime_type);
}
bool GetWellKnownMimeTypeFromExtension(const base::FilePath::StringType& ext,
std::string* mime_type) {
return g_mime_util.Get().GetWellKnownMimeTypeFromExtension(ext, mime_type);
}
bool GetPreferredExtensionForMimeType(const std::string& mime_type,
base::FilePath::StringType* extension) {
return g_mime_util.Get().GetPreferredExtensionForMimeType(mime_type,
extension);
}
bool MatchesMimeType(const std::string& mime_type_pattern,
const std::string& mime_type) {
return g_mime_util.Get().MatchesMimeType(mime_type_pattern, mime_type);
}
bool ParseMimeTypeWithoutParameter(const std::string& type_string,
std::string* top_level_type,
std::string* subtype) {
return g_mime_util.Get().ParseMimeTypeWithoutParameter(
type_string, top_level_type, subtype);
}
bool IsValidTopLevelMimeType(const std::string& type_string) {
return g_mime_util.Get().IsValidTopLevelMimeType(type_string);
}
namespace {
// From http://www.w3schools.com/media/media_mimeref.asp and
// http://plugindoc.mozdev.org/winmime.php
static const char* const kStandardImageTypes[] = {
"image/bmp",
"image/cis-cod",
"image/gif",
"image/ief",
"image/jpeg",
"image/webp",
"image/pict",
"image/pipeg",
"image/png",
"image/svg+xml",
"image/tiff",
"image/vnd.microsoft.icon",
"image/x-cmu-raster",
"image/x-cmx",
"image/x-icon",
"image/x-portable-anymap",
"image/x-portable-bitmap",
"image/x-portable-graymap",
"image/x-portable-pixmap",
"image/x-rgb",
"image/x-xbitmap",
"image/x-xpixmap",
"image/x-xwindowdump"
};
static const char* const kStandardAudioTypes[] = {
"audio/aac",
"audio/aiff",
"audio/amr",
"audio/basic",
"audio/flac",
"audio/midi",
"audio/mp3",
"audio/mp4",
"audio/mpeg",
"audio/mpeg3",
"audio/ogg",
"audio/vorbis",
"audio/wav",
"audio/webm",
"audio/x-m4a",
"audio/x-ms-wma",
"audio/vnd.rn-realaudio",
"audio/vnd.wave"
};
static const char* const kStandardVideoTypes[] = {
"video/avi",
"video/divx",
"video/flc",
"video/mp4",
"video/mpeg",
"video/ogg",
"video/quicktime",
"video/sd-video",
"video/webm",
"video/x-dv",
"video/x-m4v",
"video/x-mpeg",
"video/x-ms-asf",
"video/x-ms-wmv"
};
struct StandardType {
const char* const leading_mime_type;
const char* const* standard_types;
size_t standard_types_len;
};
static const StandardType kStandardTypes[] = {
{ "image/", kStandardImageTypes, arraysize(kStandardImageTypes) },
{ "audio/", kStandardAudioTypes, arraysize(kStandardAudioTypes) },
{ "video/", kStandardVideoTypes, arraysize(kStandardVideoTypes) },
{ NULL, NULL, 0 }
};
// GetExtensionsFromHardCodedMappings() adds file extensions (without a leading
// dot) to the set |extensions|, for all MIME types matching |mime_type|.
//
// The meaning of |mime_type| depends on the value of |prefix_match|:
//
// * If |prefix_match = false| then |mime_type| is an exact (case-insensitive)
// string such as "text/plain".
//
// * If |prefix_match = true| then |mime_type| is treated as the prefix for a
// (case-insensitive) string. For instance "Text/" would match "text/plain".
void GetExtensionsFromHardCodedMappings(
base::span<const MimeInfo> mappings,
const std::string& mime_type,
bool prefix_match,
std::unordered_set<base::FilePath::StringType>* extensions) {
for (const auto& mapping : mappings) {
base::StringPiece cur_mime_type(mapping.mime_type);
if (base::StartsWith(cur_mime_type, mime_type,
base::CompareCase::INSENSITIVE_ASCII) &&
(prefix_match || (cur_mime_type.length() == mime_type.length()))) {
for (const base::StringPiece& this_extension : base::SplitStringPiece(
mapping.extensions, ",", base::TRIM_WHITESPACE,
base::SPLIT_WANT_ALL)) {
extensions->insert(StringToFilePathStringType(this_extension));
}
}
}
}
void GetExtensionsHelper(const char* const* standard_types,
size_t standard_types_len,
const std::string& leading_mime_type,
std::unordered_set<base::FilePath::StringType>* extensions) {
for (size_t i = 0; i < standard_types_len; ++i) {
g_mime_util.Get().GetPlatformExtensionsForMimeType(standard_types[i],
extensions);
}
// Also look up the extensions from hard-coded mappings in case that some
// supported extensions are not registered in the system registry, like ogg.
GetExtensionsFromHardCodedMappings(kPrimaryMappings, leading_mime_type, true,
extensions);
GetExtensionsFromHardCodedMappings(kSecondaryMappings, leading_mime_type,
true, extensions);
}
// Note that the elements in the source set will be appended to the target
// vector.
template <class T>
void UnorderedSetToVector(std::unordered_set<T>* source,
std::vector<T>* target) {
size_t old_target_size = target->size();
target->resize(old_target_size + source->size());
size_t i = 0;
for (auto iter = source->begin(); iter != source->end(); ++iter, ++i)
(*target)[old_target_size + i] = *iter;
}
// Characters to be used for mime multipart boundary.
//
// TODO(rsleevi): crbug.com/575779: Follow the spec or fix the spec.
// The RFC 2046 spec says the alphanumeric characters plus the
// following characters are legal for boundaries: '()+_,-./:=?
// However the following characters, though legal, cause some sites
// to fail: (),./:=+
constexpr base::StringPiece kMimeBoundaryCharacters(
"0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ");
// Size of mime multipart boundary.
const size_t kMimeBoundarySize = 69;
} // namespace
void GetExtensionsForMimeType(
const std::string& unsafe_mime_type,
std::vector<base::FilePath::StringType>* extensions) {
if (unsafe_mime_type == "*/*" || unsafe_mime_type == "*")
return;
const std::string mime_type = base::ToLowerASCII(unsafe_mime_type);
std::unordered_set<base::FilePath::StringType> unique_extensions;
if (base::EndsWith(mime_type, "/*", base::CompareCase::INSENSITIVE_ASCII)) {
std::string leading_mime_type = mime_type.substr(0, mime_type.length() - 1);
// Find the matching StandardType from within kStandardTypes, or fall
// through to the last (default) StandardType.
const StandardType* type = nullptr;
for (const StandardType& standard_type : kStandardTypes) {
type = &standard_type;
if (type->leading_mime_type &&
leading_mime_type == type->leading_mime_type) {
break;
}
}
DCHECK(type);
GetExtensionsHelper(type->standard_types,
type->standard_types_len,
leading_mime_type,
&unique_extensions);
} else {
g_mime_util.Get().GetPlatformExtensionsForMimeType(mime_type,
&unique_extensions);
// Also look up the extensions from hard-coded mappings in case that some
// supported extensions are not registered in the system registry, like ogg.
GetExtensionsFromHardCodedMappings(kPrimaryMappings, mime_type, false,
&unique_extensions);
GetExtensionsFromHardCodedMappings(kSecondaryMappings, mime_type, false,
&unique_extensions);
}
UnorderedSetToVector(&unique_extensions, extensions);
}
NET_EXPORT std::string GenerateMimeMultipartBoundary() {
// Based on RFC 1341, section "7.2.1 Multipart: The common syntax":
// Because encapsulation boundaries must not appear in the body parts being
// encapsulated, a user agent must exercise care to choose a unique
// boundary. The boundary in the example above could have been the result of
// an algorithm designed to produce boundaries with a very low probability
// of already existing in the data to be encapsulated without having to
// prescan the data.
// [...]
// the boundary parameter [...] consists of 1 to 70 characters from a set of
// characters known to be very robust through email gateways, and NOT ending
// with white space.
// [...]
// boundary := 0*69<bchars> bcharsnospace
// bchars := bcharsnospace / " "
// bcharsnospace := DIGIT / ALPHA / "'" / "(" / ")" / "+" /
// "_" / "," / "-" / "." / "/" / ":" / "=" / "?"
std::string result;
result.reserve(kMimeBoundarySize);
result.append("----MultipartBoundary--");
while (result.size() < (kMimeBoundarySize - 4)) {
char c = kMimeBoundaryCharacters[base::RandInt(
0, kMimeBoundaryCharacters.size() - 1)];
result.push_back(c);
}
result.append("----");
// Not a strict requirement - documentation only.
DCHECK_EQ(kMimeBoundarySize, result.size());
return result;
}
void AddMultipartValueForUpload(const std::string& value_name,
const std::string& value,
const std::string& mime_boundary,
const std::string& content_type,
std::string* post_data) {
DCHECK(post_data);
// First line is the boundary.
post_data->append("--" + mime_boundary + "\r\n");
// Next line is the Content-disposition.
post_data->append("Content-Disposition: form-data; name=\"" +
value_name + "\"\r\n");
if (!content_type.empty()) {
// If Content-type is specified, the next line is that.
post_data->append("Content-Type: " + content_type + "\r\n");
}
// Leave an empty line and append the value.
post_data->append("\r\n" + value + "\r\n");
}
void AddMultipartFinalDelimiterForUpload(const std::string& mime_boundary,
std::string* post_data) {
DCHECK(post_data);
post_data->append("--" + mime_boundary + "--\r\n");
}
} // namespace net