src/tint/utils/file/tmpfile_windows.cc

// Copyright 2021 The Dawn & Tint Authors
//
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// GEN_BUILD:CONDITION(tint_build_is_win)

#include <fcntl.h>
#include <io.h>
#include <stdio.h>

#include <cstdio>

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

namespace tint {

namespace {

std::string TmpFilePath(const std::string& ext) {
    char name[L_tmpnam];
    // As we're adding an extension, to ensure the file is really unique, try
    // creating it, failing if it already exists.
    while (tmpnam_s(name, L_tmpnam - 1) == 0) {
        std::string name_with_ext = std::string(name) + ext;

        // Use MS-specific _sopen_s as it allows us to create the file in exclusive mode (_O_EXCL)
        // so that it returns an error if the file already exists.
        int fh = 0;
        errno_t e = _sopen_s(&fh, name_with_ext.c_str(),                    //
                             /* _OpenFlag */ _O_RDWR | _O_CREAT | _O_EXCL,  //
                             /* _ShareFlag */ _SH_DENYNO,
                             /* _PermissionMode */ _S_IREAD | _S_IWRITE);
        if (e == 0) {
            _close(fh);
            return name_with_ext;
        }
    }
    return {};
}

}  // namespace

TmpFile::TmpFile(std::string ext) : path_(TmpFilePath(ext)) {}

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

bool TmpFile::Append(std::span<const std::byte> data) const {
    FILE* file = nullptr;
    if (fopen_s(&file, path_.c_str(), "ab") != 0) {
        return false;
    }
    // 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;
}

}  // namespace tint