src/tint/utils/file/tmpfile_posix.cc

// Copyright 2021 The Dawn & Tint Authors
//
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// modification, are permitted provided that the following conditions are met:
//
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//    this list of conditions and the following disclaimer in the documentation
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// GEN_BUILD:CONDITION(tint_build_is_linux || tint_build_is_mac)

#include <unistd.h>

#include <limits>

#include "src/tint/utils/file/tmpfile.h"
#include "src/tint/utils/ice/ice.h"
#include "src/utils/compiler.h"

namespace tint {

namespace {

std::string TmpFilePath(std::string ext) {
    char const* dir = getenv("TMPDIR");
    if (dir == nullptr) {
        dir = "/tmp";
    }

    // mkstemps requires an `int` for the file extension name but STL represents
    // size_t. Pre-C++20 there the behavior for unsigned-to-signed conversion
    // (when the source value exceeds the representable range) is implementation
    // defined. While such a large file extension is unlikely in practice, we
    // enforce this here at runtime.
    TINT_ASSERT(ext.length() <= static_cast<size_t>(std::numeric_limits<int>::max()));
    std::string name = std::string(dir) + "/tint_XXXXXX" + ext;
    int file = mkstemps(&name[0], static_cast<int>(ext.length()));
    if (file != -1) {
        close(file);
        return name;
    }
    return "";
}

}  // namespace

TmpFile::TmpFile(std::string extension) : path_(TmpFilePath(std::move(extension))) {}

TmpFile::~TmpFile() {
    if (!path_.empty()) {
        remove(path_.c_str());
    }
}

bool TmpFile::Append(std::span<const std::byte> data) const {
    if (auto* file = fopen(path_.c_str(), "ab")) {
        // SAFETY: The source buffer is data.data() and its size is data.size() bytes, which is
        // bounds-safe for this write.
        DAWN_UNSAFE_BUFFERS(fwrite(data.data(), 1, data.size(), file));
        fclose(file);
        return true;
    }
    return false;
}

}  // namespace tint