Program Listing for File baggage.h¶
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// Copyright The OpenTelemetry Authors
// SPDX-License-Identifier: Apache-2.0
#pragma once
#include "opentelemetry/common/kv_properties.h"
#include "opentelemetry/nostd/shared_ptr.h"
#include "opentelemetry/nostd/string_view.h"
#include "opentelemetry/version.h"
OPENTELEMETRY_BEGIN_NAMESPACE
namespace baggage
{
class Baggage
{
public:
static constexpr size_t kMaxKeyValuePairs = 180;
static constexpr size_t kMaxKeyValueSize = 4096;
static constexpr size_t kMaxSize = 8192;
static constexpr char kKeyValueSeparator = '=';
static constexpr char kMembersSeparator = ',';
static constexpr char kMetadataSeparator = ';';
Baggage() : kv_properties_(new opentelemetry::common::KeyValueProperties()) {}
Baggage(size_t size) : kv_properties_(new opentelemetry::common::KeyValueProperties(size)){};
template <class T>
Baggage(const T &keys_and_values)
: kv_properties_(new opentelemetry::common::KeyValueProperties(keys_and_values))
{}
static nostd::shared_ptr<Baggage> GetDefault()
{
static nostd::shared_ptr<Baggage> baggage{new Baggage()};
return baggage;
}
/* Get value for key in the baggage
@returns true if key is found, false otherwise
*/
bool GetValue(nostd::string_view key, std::string &value) const
{
return kv_properties_->GetValue(key, value);
}
/* Returns shared_ptr of new baggage object which contains new key-value pair. If key or value is
invalid, copy of current baggage is returned
*/
nostd::shared_ptr<Baggage> Set(const nostd::string_view &key, const nostd::string_view &value)
{
nostd::shared_ptr<Baggage> baggage(new Baggage(kv_properties_->Size() + 1));
const bool valid_kv = IsValidKey(key) && IsValidValue(value);
if (valid_kv)
{
baggage->kv_properties_->AddEntry(key, value);
}
// add rest of the fields.
kv_properties_->GetAllEntries(
[&baggage, &key, &valid_kv](nostd::string_view e_key, nostd::string_view e_value) {
// if key or value was not valid, add all the entries. Add only remaining entries
// otherwise.
if (!valid_kv || key != e_key)
{
baggage->kv_properties_->AddEntry(e_key, e_value);
}
return true;
});
return baggage;
}
// @return all key-values entries by repeatedly invoking the function reference passed as argument
// for each entry
bool GetAllEntries(
nostd::function_ref<bool(nostd::string_view, nostd::string_view)> callback) const noexcept
{
return kv_properties_->GetAllEntries(callback);
}
// delete key from the baggage if it exists. Returns shared_ptr of new baggage object.
// if key does not exist, copy of current baggage is returned.
// Validity of key is not checked as invalid keys should never be populated in baggage in the
// first place.
nostd::shared_ptr<Baggage> Delete(nostd::string_view key)
{
// keeping size of baggage same as key might not be found in it
nostd::shared_ptr<Baggage> baggage(new Baggage(kv_properties_->Size()));
kv_properties_->GetAllEntries(
[&baggage, &key](nostd::string_view e_key, nostd::string_view e_value) {
if (key != e_key)
baggage->kv_properties_->AddEntry(e_key, e_value);
return true;
});
return baggage;
}
// Returns shared_ptr of baggage after extracting key-value pairs from header
static nostd::shared_ptr<Baggage> FromHeader(nostd::string_view header)
{
if (header.size() > kMaxSize)
{
// header size exceeds maximum threshold, return empty baggage
return GetDefault();
}
common::KeyValueStringTokenizer kv_str_tokenizer(header);
size_t cnt = kv_str_tokenizer.NumTokens(); // upper bound on number of kv pairs
if (cnt > kMaxKeyValuePairs)
{
cnt = kMaxKeyValuePairs;
}
nostd::shared_ptr<Baggage> baggage(new Baggage(cnt));
bool kv_valid;
nostd::string_view key, value;
while (kv_str_tokenizer.next(kv_valid, key, value) && baggage->kv_properties_->Size() < cnt)
{
if (!kv_valid || (key.size() + value.size() > kMaxKeyValueSize))
{
// if kv pair is not valid, skip it
continue;
}
// NOTE : metadata is kept as part of value only as it does not have any semantic meaning.
// but, we need to extract it (else Decode on value will return error)
nostd::string_view metadata;
auto metadata_separator = value.find(kMetadataSeparator);
if (metadata_separator != std::string::npos)
{
metadata = value.substr(metadata_separator);
value = value.substr(0, metadata_separator);
}
bool err = 0;
auto key_str = UrlDecode(common::StringUtil::Trim(key), err);
auto value_str = UrlDecode(common::StringUtil::Trim(value), err);
if (err == false && IsValidKey(key_str) && IsValidValue(value_str))
{
if (!metadata.empty())
{
value_str.append(metadata.data(), metadata.size());
}
baggage->kv_properties_->AddEntry(key_str, value_str);
}
}
return baggage;
}
// Creates string from baggage object.
std::string ToHeader() const
{
std::string header_s;
bool first = true;
kv_properties_->GetAllEntries([&](nostd::string_view key, nostd::string_view value) {
if (!first)
{
header_s.push_back(kMembersSeparator);
}
else
{
first = false;
}
header_s.append(UrlEncode(key));
header_s.push_back(kKeyValueSeparator);
// extracting metadata from value. We do not encode metadata
auto metadata_separator = value.find(kMetadataSeparator);
if (metadata_separator != std::string::npos)
{
header_s.append(UrlEncode(value.substr(0, metadata_separator)));
auto metadata = value.substr(metadata_separator);
header_s.append(std::string(metadata.data(), metadata.size()));
}
else
{
header_s.append(UrlEncode(value));
}
return true;
});
return header_s;
}
private:
static bool IsPrintableString(nostd::string_view str)
{
for (const auto ch : str)
{
if (ch < ' ' || ch > '~')
{
return false;
}
}
return true;
}
static bool IsValidKey(nostd::string_view key) { return key.size() && IsPrintableString(key); }
static bool IsValidValue(nostd::string_view value) { return IsPrintableString(value); }
// Uri encode key value pairs before injecting into header
// Implementation inspired from : https://golang.org/src/net/url/url.go?s=7851:7884#L264
static std::string UrlEncode(nostd::string_view str)
{
auto to_hex = [](char c) -> char {
static const char *hex = "0123456789ABCDEF";
return hex[c & 15];
};
std::string ret;
for (auto c : str)
{
if (std::isalnum(c) || c == '-' || c == '_' || c == '.' || c == '~')
{
ret.push_back(c);
}
else if (c == ' ')
{
ret.push_back('+');
}
else
{
ret.push_back('%');
ret.push_back(to_hex(c >> 4));
ret.push_back(to_hex(c & 15));
}
}
return ret;
}
// Uri decode key value pairs after extracting from header
static std::string UrlDecode(nostd::string_view str, bool &err)
{
auto IsHex = [](char c) {
return std::isdigit(c) || (c >= 'A' && c <= 'F') || (c >= 'a' && c <= 'f');
};
auto from_hex = [](char c) -> char {
return std::isdigit(c) ? c - '0' : std::toupper(c) - 'A' + 10;
};
std::string ret;
for (size_t i = 0; i < str.size(); i++)
{
if (str[i] == '%')
{
if (i + 2 >= str.size() || !IsHex(str[i + 1]) || !IsHex(str[i + 2]))
{
err = 1;
return "";
}
ret.push_back(from_hex(str[i + 1]) << 4 | from_hex(str[i + 2]));
i += 2;
}
else if (str[i] == '+')
{
ret.push_back(' ');
}
else if (std::isalnum(str[i]) || str[i] == '-' || str[i] == '_' || str[i] == '.' ||
str[i] == '~')
{
ret.push_back(str[i]);
}
else
{
err = 1;
return "";
}
}
return ret;
}
private:
// Store entries in a C-style array to avoid using std::array or std::vector.
nostd::unique_ptr<opentelemetry::common::KeyValueProperties> kv_properties_;
};
} // namespace baggage
OPENTELEMETRY_END_NAMESPACE