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libobs-d3d11: Avoid exceptions in shader cache file handling #13538

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libobs-d3d11: Avoid exceptions in shader cache file handling #13538

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94 changes: 55 additions & 39 deletions libobs-d3d11/d3d11-shader.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -27,6 +27,7 @@
#include <filesystem>
#include <fstream>
#include <d3dcompiler.h>
#include <system_error>

void gs_vertex_shader::GetBuffersExpected(const std::vector<D3D11_INPUT_ELEMENT_DESC> &inputs)
{
Expand Down Expand Up @@ -218,6 +219,16 @@ static uint64_t fnv1a_hash(const char *str, size_t len)
return hash;
}

static void remove_cache_file(const std::filesystem::path &cachePath, const char *reason) noexcept
{
blog(LOG_WARNING, "Discarding shader cache file %s: %s",
reinterpret_cast<const char *>(cachePath.u8string().c_str()), reason);

// Intentionally ignored - we don't care about failure here, we just don't want exceptions
std::error_code ec;
std::filesystem::remove(cachePath, ec);
}

void gs_shader::Compile(const char *shaderString, const char *file, const char *target, ID3D10Blob **shader)
{
ComPtr<ID3D10Blob> errorsBlob;
Expand All @@ -239,41 +250,47 @@ void gs_shader::Compile(const char *shaderString, const char *file, const char *
// Increment if on-disk format changes
cachePath += ".v2";

std::fstream cacheFile;
cacheFile.exceptions(std::fstream::badbit | std::fstream::eofbit);
std::ifstream cacheFile(cachePath, std::ios::binary | std::ios::ate);
if (cacheFile.is_open()) {
uint64_t checksum = 0;

if (std::filesystem::exists(cachePath) && !std::filesystem::is_empty(cachePath)) {
cacheFile.open(cachePath, std::ios::in | std::ios::binary | std::ios::ate);
}
std::streamoff len = cacheFile.tellg();

if (cacheFile.is_open()) {
uint64_t checksum;
// Not enough data for checksum + shader
if (len < 0 || len <= static_cast<std::streamoff>(sizeof(checksum))) {
cacheFile.close();
remove_cache_file(cachePath, "truncated or unreadable");
} else {
len -= sizeof(checksum);

try {
std::streampos len = cacheFile.tellg();
// Not enough data for checksum + shader
if (len <= sizeof(checksum)) {
throw std::length_error("File truncated");
}
hr = D3DCreateBlob(len, shader);
if (FAILED(hr)) {
cacheFile.close();
remove_cache_file(cachePath, "cache blob allocation failed");
} else {
cacheFile.seekg(0, std::ios::beg);
cacheFile.read(static_cast<char *>((*shader)->GetBufferPointer()), len);
cacheFile.read(reinterpret_cast<char *>(&checksum), sizeof(checksum));

cacheFile.seekg(0, std::ios::beg);
const bool success = static_cast<bool>(cacheFile);

len -= sizeof(checksum);
D3DCreateBlob(len, shader);
cacheFile.read((char *)(*shader)->GetBufferPointer(), len);
uint64_t calculated_checksum = fnv1a_hash((char *)(*shader)->GetBufferPointer(), len);
if (success) {
uint64_t calculated_checksum =
fnv1a_hash(static_cast<char *>((*shader)->GetBufferPointer()), len);

cacheFile.read((char *)&checksum, sizeof(checksum));
if (calculated_checksum != checksum) {
throw std::exception("Checksum mismatch");
}
if (calculated_checksum == checksum) {
is_cached = true;
}
}

is_cached = true;
} catch (const std::exception &e) {
// Something went wrong reading the cache file, delete it
blog(LOG_WARNING, "Loading shader cache file failed with \"%s\": %s", e.what(), file);
cacheFile.close();
std::filesystem::remove(cachePath);
if (!is_cached) {
(*shader)->Release();
*shader = nullptr;

cacheFile.close();
remove_cache_file(cachePath, !success ? "read error" : "checksum mismatch");
}
}
}
}

Expand All @@ -288,18 +305,17 @@ void gs_shader::Compile(const char *shaderString, const char *file, const char *
}
}

cacheFile.open(cachePath, std::ios::out | std::ios::binary);
if (cacheFile.is_open()) {
try {
uint64_t calculated_checksum =
fnv1a_hash((char *)(*shader)->GetBufferPointer(), (*shader)->GetBufferSize());
std::ofstream outFile(cachePath, std::ios::binary | std::ios::trunc);
if (outFile.is_open()) {
uint64_t calculated_checksum = fnv1a_hash(static_cast<char *>((*shader)->GetBufferPointer()),
(*shader)->GetBufferSize());

cacheFile.write((char *)(*shader)->GetBufferPointer(), (*shader)->GetBufferSize());
cacheFile.write((char *)&calculated_checksum, sizeof(calculated_checksum));
} catch (const std::exception &e) {
blog(LOG_WARNING, "Writing shader cache file failed with \"%s\": %s", e.what(), file);
cacheFile.close();
std::filesystem::remove(cachePath);
outFile.write(static_cast<char *>((*shader)->GetBufferPointer()), (*shader)->GetBufferSize());
outFile.write(reinterpret_cast<char *>(&calculated_checksum), sizeof(calculated_checksum));
outFile.close();

if (outFile.fail()) {
remove_cache_file(cachePath, "write error");
}
}
}
Expand Down
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