qpdf/include/qpdf/QUtil.hh

// Copyright (c) 2005-2023 Jay Berkenbilt
//
// This file is part of qpdf.
//
// 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.
//
// Versions of qpdf prior to version 7 were released under the terms
// of version 2.0 of the Artistic License. At your option, you may
// continue to consider qpdf to be licensed under those terms. Please
// see the manual for additional information.

#ifndef QUTIL_HH
#define QUTIL_HH

#include <qpdf/DLL.h>
#include <qpdf/PointerHolder.hh> // unused -- remove in qpdf 12 (see #785)
#include <qpdf/Types.h>
#include <cstdio>
#include <cstring>
#include <ctime>
#include <functional>
#include <list>
#include <memory>
#include <stdexcept>
#include <string>
#include <vector>

class RandomDataProvider;
class Pipeline;

namespace QUtil
{
    // This is a collection of useful utility functions that don't
    // really go anywhere else.
    QPDF_DLL
    std::string int_to_string(long long, int length = 0);
    QPDF_DLL
    std::string uint_to_string(unsigned long long, int length = 0);
    QPDF_DLL
    std::string int_to_string_base(long long, int base, int length = 0);
    QPDF_DLL
    std::string uint_to_string_base(unsigned long long, int base, int length = 0);
    QPDF_DLL
    std::string double_to_string(double, int decimal_places = 0, bool trim_trailing_zeroes = true);

    // These string to number methods throw std::runtime_error on
    // underflow/overflow.
    QPDF_DLL
    long long string_to_ll(char const* str);
    QPDF_DLL
    int string_to_int(char const* str);
    QPDF_DLL
    unsigned long long string_to_ull(char const* str);
    QPDF_DLL
    unsigned int string_to_uint(char const* str);

    // Returns true if this exactly represents a long long. The
    // determination is made by converting the string to a long long,
    // then converting the result back to a string, and then comparing
    // that result with the original string.
    QPDF_DLL
    bool is_long_long(char const* str);

    // Pipeline's write method wants unsigned char*, but we often have
    // some other type of string.  These methods do combinations of
    // const_cast and reinterpret_cast to give us an unsigned char*.
    // They should only be used when it is known that it is safe.
    // None of the pipelines in qpdf modify the data passed to them,
    // so within qpdf, it should always be safe.
    QPDF_DLL
    unsigned char* unsigned_char_pointer(std::string const& str);
    QPDF_DLL
    unsigned char* unsigned_char_pointer(char const* str);

    // Throw QPDFSystemError, which is derived from
    // std::runtime_error, with a string formed by appending to
    // "description: " the standard string corresponding to the
    // current value of errno. You can retrieve the value of errno by
    // calling getErrno() on the QPDFSystemError. Prior to qpdf 8.2.0,
    // this method threw system::runtime_error directly, but since
    // QPDFSystemError is derived from system::runtime_error, old code
    // that specifically catches std::runtime_error will still work.
    QPDF_DLL
    void throw_system_error(std::string const& description);

    // The status argument is assumed to be the return value of a
    // standard library call that sets errno when it fails.  If status
    // is -1, convert the current value of errno to a
    // std::runtime_error that includes the standard error string.
    // Otherwise, return status.
    QPDF_DLL
    int os_wrapper(std::string const& description, int status);

    // If the open fails, throws std::runtime_error. Otherwise, the
    // FILE* is returned. The filename should be UTF-8 encoded, even
    // on Windows. It will be converted as needed on Windows.
    QPDF_DLL
    FILE* safe_fopen(char const* filename, char const* mode);

    // The FILE* argument is assumed to be the return of fopen.  If
    // null, throw std::runtime_error.  Otherwise, return the FILE*
    // argument.
    QPDF_DLL
    FILE* fopen_wrapper(std::string const&, FILE*);

    // This is a little class to help with automatic closing files.
    // You can do something like
    //
    // QUtil::FileCloser fc(QUtil::safe_fopen(filename, "rb"));
    //
    // and then use fc.f to the file. Be sure to actually declare a
    // variable of type FileCloser. Using it as a temporary won't work
    // because it will close the file as soon as it goes out of scope.
    class FileCloser
    {
      public:
        FileCloser(FILE* f) :
            f(f)
        {
        }

        ~FileCloser()
        {
            if (f) {
                fclose(f);
                f = nullptr;
            }
        }

        FILE* f;
    };

    // Attempt to open the file read only and then close again
    QPDF_DLL
    bool file_can_be_opened(char const* filename);

    // Wrap around off_t versions of fseek and ftell if available
    QPDF_DLL
    int seek(FILE* stream, qpdf_offset_t offset, int whence);
    QPDF_DLL
    qpdf_offset_t tell(FILE* stream);

    QPDF_DLL
    bool same_file(char const* name1, char const* name2);

    QPDF_DLL
    void remove_file(char const* path);

    // rename_file will overwrite newname if it exists
    QPDF_DLL
    void rename_file(char const* oldname, char const* newname);

    // Write the contents of filename as a binary file to the
    // pipeline.
    QPDF_DLL
    void pipe_file(char const* filename, Pipeline* p);

    // Return a function that will send the contents of the given file
    // through the given pipeline as binary data.
    QPDF_DLL
    std::function<void(Pipeline*)> file_provider(std::string const& filename);

    // Return the last path element. On Windows, either / or \ are
    // path separators. Otherwise, only / is a path separator. Strip
    // any trailing path separators. Then, if any path separators
    // remain, return everything after the last path separator.
    // Otherwise, return the whole string. As a special case, if a
    // string consists entirely of path separators, the first
    // character is returned.
    QPDF_DLL
    std::string path_basename(std::string const& filename);

    // Returns a dynamically allocated copy of a string that the
    // caller has to delete with delete[].
    QPDF_DLL
    char* copy_string(std::string const&);

    // Returns a shared_ptr<char> with the correct deleter.
    QPDF_DLL
    std::shared_ptr<char> make_shared_cstr(std::string const&);

    // Copy string as a unique_ptr to an array.
    QPDF_DLL
    std::unique_ptr<char[]> make_unique_cstr(std::string const&);

    // Create a shared pointer to an array. From c++20,
    // std::make_shared<T[]>(n) does this.
    template <typename T>
    std::shared_ptr<T>
    make_shared_array(size_t n)
    {
        return std::shared_ptr<T>(new T[n], std::default_delete<T[]>());
    }

    // Returns lower-case hex-encoded version of the string, treating
    // each character in the input string as unsigned.  The output
    // string will be twice as long as the input string.
    QPDF_DLL
    std::string hex_encode(std::string const&);

    // Returns lower-case hex-encoded version of the char including a leading
    // "#".
    QPDF_DLL
    inline std::string hex_encode_char(char);

    // Returns a string that is the result of decoding the input
    // string. The input string may consist of mixed case hexadecimal
    // digits. Any characters that are not hexadecimal digits will be
    // silently ignored. If there are an odd number of hexadecimal
    // digits, a trailing 0 will be assumed.
    QPDF_DLL
    std::string hex_decode(std::string const&);

    // Decode a single hex digit into a char in the range 0 <= char < 16. Return
    // a char >= 16 if digit is not a valid hex digit.
    QPDF_DLL
    inline constexpr char hex_decode_char(char digit) noexcept;

    // Set stdin, stdout to binary mode
    QPDF_DLL
    void binary_stdout();
    QPDF_DLL
    void binary_stdin();
    // Set stdout to line buffered
    QPDF_DLL
    void setLineBuf(FILE*);

    // May modify argv0
    QPDF_DLL
    char* getWhoami(char* argv0);

    // Get the value of an environment variable in a portable fashion.
    // Returns true iff the variable is defined.  If `value' is
    // non-null, initializes it with the value of the variable.
    QPDF_DLL
    bool get_env(std::string const& var, std::string* value = nullptr);

    QPDF_DLL
    time_t get_current_time();

    // Portable structure representing a point in time with second
    // granularity and time zone offset
    struct QPDFTime
    {
        QPDFTime() = default;
        QPDFTime(QPDFTime const&) = default;
        QPDFTime& operator=(QPDFTime const&) = default;
        QPDFTime(int year, int month, int day, int hour, int minute, int second, int tz_delta) :
            year(year),
            month(month),
            day(day),
            hour(hour),
            minute(minute),
            second(second),
            tz_delta(tz_delta)
        {
        }
        int year;  // actual year, no 1900 stuff
        int month; // 1--12
        int day;   // 1--31
        int hour;
        int minute;
        int second;
        int tz_delta; // minutes before UTC
    };

    QPDF_DLL
    QPDFTime get_current_qpdf_time();

    // Convert a QPDFTime structure to a PDF timestamp string, which
    // is "D:yyyymmddhhmmss<z>" where <z> is either "Z" for UTC or
    // "-hh'mm'" or "+hh'mm'" for timezone offset. <z> may also be
    // omitted. Examples: "D:20210207161528-05'00'",
    // "D:20210207211528Z", "D:20210207211528". See
    // get_current_qpdf_time and the QPDFTime structure above.
    QPDF_DLL
    std::string qpdf_time_to_pdf_time(QPDFTime const&);

    // Convert QPDFTime to a second-granularity ISO-8601 timestamp.
    QPDF_DLL
    std::string qpdf_time_to_iso8601(QPDFTime const&);

    // Convert a PDF timestamp string to a QPDFTime. If syntactically
    // valid, return true and fill in qtm. If not valid, return false,
    // and do not modify qtm. If qtm is null, just check the validity
    // of the string.
    QPDF_DLL
    bool pdf_time_to_qpdf_time(std::string const&, QPDFTime* qtm = nullptr);

    // Convert PDF timestamp to a second-granularity ISO-8601
    // timestamp. If syntactically valid, return true and initialize
    // iso8601. Otherwise, return false.
    bool pdf_time_to_iso8601(std::string const& pdf_time, std::string& iso8601);

    // Return a string containing the byte representation of the UTF-8
    // encoding for the unicode value passed in.
    QPDF_DLL
    std::string toUTF8(unsigned long uval);

    // Return a string containing the byte representation of the
    // UTF-16 big-endian encoding for the unicode value passed in.
    // Unrepresentable code points are converted to U+FFFD.
    QPDF_DLL
    std::string toUTF16(unsigned long uval);

    // If utf8_val.at(pos) points to the beginning of a valid
    // UTF-8-encoded character, return the codepoint of the character
    // and set error to false. Otherwise, return 0xfffd and set error
    // to true. In all cases, pos is advanced to the next position
    // that may begin a valid character. When the string has been
    // consumed, pos will be set to the string length. It is an error
    // to pass a value of pos that is greater than or equal to the
    // length of the string.
    QPDF_DLL
    unsigned long get_next_utf8_codepoint(std::string const& utf8_val, size_t& pos, bool& error);

    // Test whether this is a UTF-16 string. This is indicated by
    // first two bytes being 0xFE 0xFF (big-endian) or 0xFF 0xFE
    // (little-endian), each of which is the encoding of U+FEFF, the
    // Unicode marker. Starting in qpdf 10.6.2, this detects
    // little-endian as well as big-endian. Even though the PDF spec
    // doesn't allow little-endian, most readers seem to accept it.
    QPDF_DLL
    bool is_utf16(std::string const&);

    // Test whether this is an explicit UTF-8 string as allowed by the
    // PDF 2.0 spec. This is indicated by first three bytes being 0xEF
    // 0xBB 0xBF, which is the UTF-8 encoding of U+FEFF.
    QPDF_DLL
    bool is_explicit_utf8(std::string const&);

    // Convert a UTF-8 encoded string to UTF-16 big-endian.
    // Unrepresentable code points are converted to U+FFFD.
    QPDF_DLL
    std::string utf8_to_utf16(std::string const& utf8);

    // Convert a UTF-8 encoded string to the specified single-byte
    // encoding system by replacing all unsupported characters with
    // the given unknown_char.
    QPDF_DLL
    std::string utf8_to_ascii(std::string const& utf8, char unknown_char = '?');
    QPDF_DLL
    std::string utf8_to_win_ansi(std::string const& utf8, char unknown_char = '?');
    QPDF_DLL
    std::string utf8_to_mac_roman(std::string const& utf8, char unknown_char = '?');
    QPDF_DLL
    std::string utf8_to_pdf_doc(std::string const& utf8, char unknown_char = '?');

    // These versions return true if the conversion was successful and
    // false if any unrepresentable characters were found and had to
    // be substituted with the unknown character.
    QPDF_DLL
    bool utf8_to_ascii(std::string const& utf8, std::string& ascii, char unknown_char = '?');
    QPDF_DLL
    bool utf8_to_win_ansi(std::string const& utf8, std::string& win, char unknown_char = '?');
    QPDF_DLL
    bool utf8_to_mac_roman(std::string const& utf8, std::string& mac, char unknown_char = '?');
    QPDF_DLL
    bool utf8_to_pdf_doc(std::string const& utf8, std::string& pdfdoc, char unknown_char = '?');

    // Convert a UTF-16 encoded string to UTF-8. Unrepresentable code
    // points are converted to U+FFFD.
    QPDF_DLL
    std::string utf16_to_utf8(std::string const& utf16);

    // Convert from the specified single-byte encoding system to
    // UTF-8. There is no ascii_to_utf8 because all ASCII strings are
    // already valid UTF-8.
    QPDF_DLL
    std::string win_ansi_to_utf8(std::string const& win);
    QPDF_DLL
    std::string mac_roman_to_utf8(std::string const& mac);
    QPDF_DLL
    std::string pdf_doc_to_utf8(std::string const& pdfdoc);

    // Analyze a string for encoding. We can't tell the difference
    // between any single-byte encodings, and we can't tell for sure
    // whether a string that happens to be valid UTF-8 isn't a
    // different encoding, but we can at least tell a few things to
    // help us guess. If there are no characters with the high bit
    // set, has_8bit_chars is false, and the other values are also
    // false, even though ASCII strings are valid UTF-8. is_valid_utf8
    // means that the string is non-trivially valid UTF-8. Although
    // the PDF spec requires UTF-16 to be UTF-16BE, qpdf (and just
    // about everything else) accepts UTF-16LE (as of 10.6.2).
    QPDF_DLL
    void analyze_encoding(
        std::string const& str, bool& has_8bit_chars, bool& is_valid_utf8, bool& is_utf16);

    // Try to compensate for previously incorrectly encoded strings.
    // We want to compensate for the following errors:
    //
    // * The string was supposed to be UTF-8 but was one of the
    //   single-byte encodings
    // * The string was supposed to be PDF Doc but was either UTF-8 or
    //   one of the other single-byte encodings
    //
    // The returned vector always contains the original string first,
    // and then it contains what the correct string would be in the
    // event that the original string was the result of any of the
    // above errors.
    //
    // This method is useful for attempting to recover a password that
    // may have been previously incorrectly encoded. For example, the
    // password was supposed to be UTF-8 but the previous application
    // used a password encoded in WinAnsi, or if the previous password
    // was supposed to be PDFDoc but was actually given as UTF-8 or
    // WinAnsi, this method would find the correct password.
    QPDF_DLL
    std::vector<std::string> possible_repaired_encodings(std::string);

    // Return a cryptographically secure random number.
    QPDF_DLL
    long random();

    // Initialize a buffer with cryptographically secure random bytes.
    QPDF_DLL
    void initializeWithRandomBytes(unsigned char* data, size_t len);

    // Supply a random data provider. Starting in qpdf 10.0.0, qpdf
    // uses the crypto provider as its source of random numbers. If
    // you are using the native crypto provider, then qpdf will either
    // use the operating system's secure random number source or, only
    // if enabled at build time, an insecure random source from
    // stdlib. The caller is responsible for managing the memory for
    // the RandomDataProvider. This method modifies a static variable.
    // If you are providing your own random data provider, you should
    // call this at the beginning of your program before creating any
    // QPDF objects. Passing a null to this method will reset the
    // library back to its default random data provider.
    QPDF_DLL
    void setRandomDataProvider(RandomDataProvider*);

    // This returns the random data provider that would be used the
    // next time qpdf needs random data.  It will never return null.
    // If no random data provider has been provided and the library
    // was not compiled with any random data provider available, an
    // exception will be thrown.
    QPDF_DLL
    RandomDataProvider* getRandomDataProvider();

    // Filename is UTF-8 encoded, even on Windows, as described in the
    // comments for safe_fopen.
    QPDF_DLL
    std::list<std::string> read_lines_from_file(char const* filename, bool preserve_eol = false);
    QPDF_DLL
    std::list<std::string> read_lines_from_file(std::istream&, bool preserve_eol = false);
    QPDF_DLL
    std::list<std::string> read_lines_from_file(FILE*, bool preserve_eol = false);
    QPDF_DLL
    void read_lines_from_file(
        std::function<bool(char&)> next_char,
        std::list<std::string>& lines,
        bool preserve_eol = false);

    QPDF_DLL
    void read_file_into_memory(char const* filename, std::shared_ptr<char>& file_buf, size_t& size);

    QPDF_DLL
    std::string read_file_into_string(char const* filename);
    QPDF_DLL
    std::string read_file_into_string(FILE* f, std::string_view filename = "");

    // This used to be called strcasecmp, but that is a macro on some
    // platforms, so we have to give it a name that is not likely to
    // be a macro anywhere.
    QPDF_DLL
    int str_compare_nocase(char const*, char const*);

    // These routines help the tokenizer recognize certain character
    // classes without using ctype, which we avoid because of locale
    // considerations.
    QPDF_DLL
    inline bool is_hex_digit(char);

    QPDF_DLL
    inline bool is_space(char);

    QPDF_DLL
    inline bool is_digit(char);

    QPDF_DLL
    inline bool is_number(char const*);

    // This method parses the numeric range syntax used by the qpdf
    // command-line tool. May throw std::runtime_error.
    QPDF_DLL
    std::vector<int> parse_numrange(char const* range, int max);

#ifndef QPDF_NO_WCHAR_T
    // If you are building qpdf on a stripped down system that doesn't
    // have wchar_t, such as may be the case in some embedded
    // environments, you may define QPDF_NO_WCHAR_T in your build.
    // This symbol is never defined automatically. Search for wchar_t
    // in qpdf's top-level README.md file for details.

    // Take an argv array consisting of wchar_t, as when wmain is
    // invoked, convert all UTF-16 encoded strings to UTF-8, and call
    // another main.
    QPDF_DLL
    int call_main_from_wmain(int argc, wchar_t* argv[], std::function<int(int, char*[])> realmain);
    QPDF_DLL
    int call_main_from_wmain(
        int argc,
        wchar_t const* const argv[],
        std::function<int(int, char const* const[])> realmain);
#endif // QPDF_NO_WCHAR_T

    // Try to return the maximum amount of memory allocated by the
    // current process and its threads. Return 0 if unable to
    // determine. This is Linux-specific and not implemented to be
    // completely reliable. It is used during development for
    // performance testing to detect changes that may significantly
    // change memory usage. It is not recommended for use for other
    // purposes.
    QPDF_DLL
    size_t get_max_memory_usage();
}; // namespace QUtil

inline bool
QUtil::is_hex_digit(char ch)
{
    return hex_decode_char(ch) < '\20';
}

inline bool
QUtil::is_space(char ch)
{
    return ch == ' ' || ch == '\n' || ch == '\r' || ch == '\t' || ch == '\f' || ch == '\v';
}

inline bool
QUtil::is_digit(char ch)
{
    return ((ch >= '0') && (ch <= '9'));
}

inline bool
QUtil::is_number(char const* p)
{
    // ^[\+\-]?(\.\d*|\d+(\.\d*)?)$
    if (!*p) {
        return false;
    }
    if ((*p == '-') || (*p == '+')) {
        ++p;
    }
    bool found_dot = false;
    bool found_digit = false;
    for (; *p; ++p) {
        if (*p == '.') {
            if (found_dot) {
                // only one dot
                return false;
            }
            found_dot = true;
        } else if (QUtil::is_digit(*p)) {
            found_digit = true;
        } else {
            return false;
        }
    }
    return found_digit;
}

inline std::string
QUtil::hex_encode_char(char c)
{
    static auto constexpr hexchars = "0123456789abcdef";
    return {'#', hexchars[static_cast<unsigned char>(c) >> 4], hexchars[c & 0x0f]};
}

inline constexpr char
QUtil::hex_decode_char(char digit) noexcept
{
    return digit <= '9' && digit >= '0'
        ? char(digit - '0')
        : (digit >= 'a' ? char(digit - 'a' + 10) : (digit >= 'A' ? char(digit - 'A' + 10) : '\20'));
}

#endif // QUTIL_HH