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/* Copyright (c) 2016-2019 The Khronos Group Inc.
* Copyright (c) 2016-2019 Valve Corporation
* Copyright (c) 2016-2019 LunarG, Inc.
* Copyright (c) 2016-2019 Google Inc.
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* See the License for the specific language governing permissions and
* limitations under the License.
#include <cassert>
#include <sstream>
#include <string>
#include <vector>
* Parameter name string supporting deferred formatting for array subscripts.
* Custom parameter name class with support for deferred formatting of names containing array subscripts. The class stores
* a format string and a pointer to an array of index values, and performs string formatting when an accessor function is called to
* retrieve the name string. This class was primarily designed to be used with validation functions that receive a parameter name
* string and value as arguments, and print an error message that includes the parameter name when the value fails a validation
* test. Using standard strings with these validation functions requires that parameter names containing array subscripts be
* formatted before each validation function is called, performing the string formatting even when the value passes validation
* and the string is not used:
* sprintf(name, "pCreateInfo[%d].sType", i);
* validate_stype(name, pCreateInfo[i].sType);
* With the ParameterName class, a format string and a pointer to an array of format values are stored by the ParameterName object
* that is provided to the validation function. String formatting is then performed only when the validation function retrieves the
* name string from the ParameterName object:
* validate_stype(ParameterName("pCreateInfo[%i].sType", IndexVector{ i }), pCreateInfo[i].sType);
* Since the IndexVector is not copied into the object, the lifetime of the ParameterName should not outlast the lifetime of
* the IndexVector, but that's fine given how it is used in parameter validation.
class ParameterName {
/// Container for index values to be used with parameter name string formatting.
typedef std::initializer_list<size_t> IndexVector;
/// Format specifier for the parameter name string, to be replaced by an index value. The parameter name string must contain
/// one format specifier for each index value specified.
const char *const IndexFormatSpecifier = "%i";
* Construct a ParameterName object from a string literal, without formatting.
* @param source Paramater name string without format specifiers.
* @pre The source string must not contain the %i format specifier.
ParameterName(const char *source) : source_(source), args_(nullptr), num_indices_(0) { assert(IsValid()); }
* Construct a ParameterName object from a string literal, with formatting.
* @param source Paramater name string with format specifiers.
* @param args Array index values to be used for formatting.
* @pre The number of %i format specifiers contained by the source string must match the number of elements contained
* by the index vector.
ParameterName(const char *source, const IndexVector &args)
: source_(source), args_(args.size() ? args.begin() : (const size_t *)nullptr), num_indices_(args.size()) {
/// Retrive the formatted name string.
std::string get_name() const { return (num_indices_ == 0) ? std::string(source_) : Format(); }
/// Replace the %i format specifiers in the source string with the values from the index vector.
std::string Format() const {
std::string::size_type current = 0;
std::string::size_type last = 0;
std::stringstream format;
std::string source(source_);
for (size_t i = 0; i < num_indices_; ++i) {
auto index = args_[i];
current = source.find(IndexFormatSpecifier, last);
if (current == std::string::npos) {
format << source.substr(last, (current - last)) << index;
last = current + strlen(IndexFormatSpecifier);
format << source.substr(last, std::string::npos);
return format.str();
/// Check that the number of %i format specifiers in the source string matches the number of elements in the index vector.
bool IsValid() {
// Count the number of occurances of the format specifier
uint32_t count = 0;
std::string source(source_);
std::string::size_type pos = source.find(IndexFormatSpecifier);
while (pos != std::string::npos) {
pos = source.find(IndexFormatSpecifier, pos + 1);
return (count == num_indices_);
const char *source_; ///< Format string.
const size_t *args_; ///< Array index values for formatting.
size_t num_indices_; ///< Number of array index values.