src/ui/lib/escher/shaders/util/spirv_file_util.h

// Copyright 2019 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef SRC_UI_LIB_ESCHER_SHADERS_UTIL_SPIRV_FILE_UTIL_H_
#define SRC_UI_LIB_ESCHER_SHADERS_UTIL_SPIRV_FILE_UTIL_H_

#include <vector>

#include "src/ui/lib/escher/vk/shader_variant_args.h"

namespace escher {
namespace shader_util {

// Writes the given spirv to a file on disk, whose name is generated based on the original shader
// name plus a hash value based on the provided ShaderVariantArgs.
bool WriteSpirvToDisk(const std::vector<uint32_t>& spirv, const ShaderVariantArgs& args,
                      const std::string& base_path, const std::string& shader_name);

// Reads the spirv for a shader given the original file name and a list of args. Generates the
// spirv file name based on the hash it calculates and sees if there is anything on disk to read.
// If so, the function returns true and the code is stored in the out_spirv parameter.
bool ReadSpirvFromDisk(const ShaderVariantArgs& args, const std::string& base_path,
                       const std::string& shader_name, std::vector<uint32_t>* out_spirv);

// Checks to see if there already exists a spirv file on disk and if the newly compiled spirv
// is different from it. If a file already exists and the contents are the same, then the shader
// source code has not been updated and there is no need to update the spirv file on disk.
//
// It would also be possible to simply check the time stamp of the spirv file on disk against
// the file for the source code to see if the latter is newer than the former and rebuild off
// of that. However, doing it this way would cause the spirv to be regenerated even if the
// changes to the source code did not result in spirv changes (for example - someone could have
// simply modified a comment or fixed some spacing/styling issues, which would not result in
// a spirv change). So to avoid superfluous changes, we compare the old and new spirv directly.
bool SpirvExistsOnDisk(const ShaderVariantArgs& args, const std::string& abs_root,
                       const std::string& shader_name, const std::vector<uint32_t>& spirv);

}  // namespace shader_util
}  // namespace escher

#endif  // SRC_UI_LIB_ESCHER_SHADERS_UTIL_SPIRV_FILE_UTIL_H_