base/FileUtils.cpp

// Copyright 2020 The Android Open Source Project
//
// 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
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#include "base/FileUtils.h"
#include "base/EintrWrapper.h"

#include <assert.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <sys/types.h>
#include "msvc.h"
#ifdef _MSC_VER
//#include "msvc-posix.h"
#else
#include <unistd.h>
#endif

#ifdef _WIN32
#include <io.h>
#endif

#include <fstream>
#include <sstream>
#include <string>
#include <utility>

namespace android {

bool readFileIntoString(int fd, std::string* file_contents) {
#ifdef _MSC_VER
    if (fd < 0) return false; // msvc does not handle fd -1 very well.
#endif

    off_t size = lseek(fd, 0, SEEK_END);
    if (size == (off_t)-1) {
        return false;
    }
    off_t err = lseek(fd, 0, SEEK_SET);
    if (err == (off_t)-1) {
        return false;
    }

    std::string buf((size_t)size, '\0');
    ssize_t result = HANDLE_EINTR(read(fd, &buf[0], size));
    if (result != size) {
        return false;
    }
    *file_contents = std::move(buf);
    return true;
}

bool writeStringToFile(int fd, const std::string& file_contents) {
#ifdef _MSC_VER
    // msvc does not handle fd -1 very well.
    if (fd < 0)  return false;

    ssize_t result = HANDLE_EINTR(
            _write(fd, file_contents.c_str(), file_contents.size()));
#else
    ssize_t result = HANDLE_EINTR(
            write(fd, file_contents.c_str(), file_contents.size()));
#endif
    if (result != (ssize_t)file_contents.size()) {
        return false;
    }
    return true;
}

base::Optional<std::string> readFileIntoString(const std::string& name) {
    std::ifstream is(name, std::ios_base::binary);
    if (!is) {
        return {};
    }

    std::ostringstream ss;
    ss << is.rdbuf();
    return ss.str();
}

bool setFileSize(int fd, int64_t size) {
#ifdef _WIN32
#ifdef _MSC_VER
    if (fd < 0) return false; // msvc does not handle fd -1 very well.
#endif
    return _chsize_s(fd, size) == 0;
#else
    return ftruncate(fd, size) == 0;
#endif
}

}  // namespace android