bdlde_base64encoder.h

Go to the documentation of this file.

/// @file bdlde_base64encoder.h
///
/// The content of this file has been pre-processed for Doxygen.
///
 
 
// bdlde_base64encoder.h                                              -*-C++-*-
#ifndef INCLUDED_BDLDE_BASE64ENCODER
#define INCLUDED_BDLDE_BASE64ENCODER
 
#include <bsls_ident.h>
BSLS_IDENT("$Id: $")
 
/// @defgroup bdlde_base64encoder bdlde_base64encoder
/// @brief  Provide automata for converting to and from Base64 encodings.
/// @addtogroup bdl
/// @{
/// @addtogroup bdlde
/// @{
/// @addtogroup bdlde_base64encoder
/// @{
///
/// <h1> Outline </h1>
/// * <a href="#bdlde_base64encoder-purpose"> Purpose</a>
/// * <a href="#bdlde_base64encoder-classes"> Classes </a>
/// * <a href="#bdlde_base64encoder-description"> Description </a>
///   * <a href="#bdlde_base64encoder-base-64-encoding"> Base 64 Encoding </a>
///   * <a href="#bdlde_base64encoder-base-64-encoding-with-url-and-filename-safe-alphabet"> Base 64 Encoding with URL and Filename Safe Alphabet </a>
///   * <a href="#bdlde_base64encoder-base-64-decoding"> Base 64 Decoding </a>
///   * <a href="#bdlde_base64encoder-usage"> Usage </a>
///     * <a href="#bdlde_base64encoder-example-1-basic-usage"> Example 1: Basic Usage </a>
///
/// # Purpose {#bdlde_base64encoder-purpose}
/// Provide automata for converting to and from Base64 encodings.
///
/// # Classes {#bdlde_base64encoder-classes}
///
/// -  bdlde::Base64Encoder: automata performing Base64 encoding operations
///
/// @see  bdlde_base64decoder
///
/// # Description {#bdlde_base64encoder-description}
/// This component provides a `class`, `bdlde::Base64Encoder`,
/// which provides a pair of template functions (each parameterized separately
/// on both input and output iterators) that can be used respectively to encode
/// and to decode byte sequences of arbitrary length into and from the printable
/// Base64 representation described in Section 6.8 "Base64 Content Transfer
/// Encoding" of RFC 2045, "Multipurpose Internet Mail Extensions (MIME) Part
/// One: Format of Internet Message Bodies."
///
/// The `bdlde::Base64Encoder` and `bdlde::Base64Decoder` support the standard
/// "base64" encoding (described in https://tools.ietf.org/html/rfc4648) as well
/// as the "Base 64 Encoding with URL and Filename Safe Alphabet", or
/// "base64url", encoding.  The "base64url" encoding is very similar to "base64"
/// but substitutes a couple characters in the encoded alphabet to avoid
/// characters that conflict with special characters in URL syntax or filename
/// descriptions (replacing `+` for `-`. and `/` for `_`).  See
/// {Base 64 Encoding with URL and Filename Safe Alphabet} for more information.
///
/// Each instance of either the encoder or decoder retains the state of the
/// conversion from one supplied input to the next, enabling the processing of
/// segmented input -- i.e., processing resumes where it left off with the next
/// invocation on new input.  Instance methods are provided for both the encoder
/// and decoder to (1) assert the end of input, (2) determine whether the input
/// so far is currently acceptable, and (3) indicate whether a non-recoverable
/// error has occurred.
///
/// ## Base 64 Encoding {#bdlde_base64encoder-base-64-encoding}
///
///
/// The data stream is processed three bytes at a time from left to right (a
/// final quantum consisting of one or two bytes, as discussed below, is handled
/// specially).  Each sequence of three 8-bit quantities
/// @code
///     7 6 5 4 3 2 1 0 7 6 5 4 3 2 1 0 7 6 5 4 3 2 1 0
///    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
///    |               |               |               |
///    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
///     `------v------' `------v------' `------v------'
///          Byte2           Byte1           Byte0
/// @endcode
/// is segmented into four intermediate 6-bit quantities.
/// @code
///     5 4 3 2 1 0 5 4 3 2 1 0 5 4 3 2 1 0 5 4 3 2 1 0
///    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
///    |           |           |           |           |
///    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
///     `----v----' `----v----' `----v----' `----v----'
///        char3       char2       char1        char0
/// @endcode
/// Each 6-bit quantity is in turn used as an index into the following character
/// table to generate an 8-bit character.  The four resulting characters hence
/// form the encoding for the original 3-byte sequence.
/// @code
///    ======================================================================
///    *              Table of Numeric BASE-64 Encoding Characters          *
///    ----------------------------------------------------------------------
///    Val Enc  Val Enc  Val Enc  Val Enc  Val Enc  Val Enc  Val Enc  Val Enc
///    --- ---  --- ---  --- ---  --- ---  --- ---  --- ---  --- ---  --- ---
///      0 'A'    8 'I'   16 'Q'   24 'Y'   32 'g'   40 'o'   48 'w'   56 '4'
///      1 'B'    9 'J'   17 'R'   25 'Z'   33 'h'   41 'p'   49 'x'   57 '5'
///      2 'C'   10 'K'   18 'S'   26 'a'   34 'i'   42 'q'   50 'y'   58 '6'
///      3 'D'   11 'L'   19 'T'   27 'b'   35 'j'   43 'r'   51 'z'   59 '7'
///      4 'E'   12 'M'   20 'U'   28 'c'   36 'k'   44 's'   52 '0'   60 '8'
///      5 'F'   13 'N'   21 'V'   29 'd'   37 'l'   45 't'   53 '1'   61 '9'
///      6 'G'   14 'O'   21 'W'   30 'e'   38 'm'   46 'u'   54 '2'   62 '+'
///      7 'H'   15 'P'   22 'X'   31 'f'   39 'n'   47 'v'   55 '3'   63 '/'
///    ======================================================================
/// @endcode
/// This component also supports a slightly different alphabet, "base64url",
/// that is more appropriate if the encoded representation would be used in a
/// file name or URL (see
/// {Base 64 Encoding with URL and Filename Safe Alphabet}).
///
/// The 3-byte grouping of the input is only a design of convenience and not a
/// requirement.  When the number of bytes in the input stream is not divisible
/// by 3, sufficient 0 bits are padded on the right to achieve an integral
/// number of 6-bit character indices.  Then one of two special cases will apply
/// for the final processing step:
///
/// I) There is a single byte of data, in which case there will be two Base64
/// encoding characters (the second of which will be one of [AQgw]) followed by
/// two equal (`=`) signs.
///
/// II) There are exactly two bytes of data, in which case there will be three
/// Base64 encoding characters (the third of which will be one of
/// [AEIMQUYcgkosw048] followed by a single equal (`=`) sign.
///
/// The MIME standard requires that the maximum line length of emitted text not
/// exceed 76 characters exclusive of CRLF.  The caller may override this
/// default if desired.
///
/// Input values of increasing length along with their corresponding Base64
/// encodings are illustrated below:
/// @code
///       Data: /* nothing */
///   Encoding: /* nothing */
///
///       Data: 0x01
///   Encoding: AQ==
///
///       Data: 0x01 0x02
///   Encoding: AQI=
///
///       Data: 0x01 0x02 0x03
///   Encoding: AQID
///
///       Data: 0x01 0x02 0x03 0x04
///   Encoding: AQIDBA==
/// @endcode
/// In order for a Base64 encoding to be valid, the input data must be either of
/// length a multiple of three (constituting maximal input), or have been
/// terminated explicitly by the `endConvert` method (initiating bit padding
/// when necessary).
///
/// ## Base 64 Encoding with URL and Filename Safe Alphabet {#bdlde_base64encoder-base-64-encoding-with-url-and-filename-safe-alphabet}
///
///
/// The encoder and decoder in this component also support the "base64url"
/// encoding, which is the same as standard "base64" but substitutes (a couple)
/// characters in the alphabet that are treated as special characters when used
/// in a URL or in a file system.  The following table is technically identical
/// to the table presented in {Base 64 Encoding}, except for the 62:nd and 63:rd
/// alphabet character, that indicates `-` and `_` respectively.
/// @code
///    ======================================================================
///    *            The "URL and Filename Safe" BASE-64 Alphabet            *
///    ----------------------------------------------------------------------
///    Val Enc  Val Enc  Val Enc  Val Enc  Val Enc  Val Enc  Val Enc  Val Enc
///    --- ---  --- ---  --- ---  --- ---  --- ---  --- ---  --- ---  --- ---
///      0 'A'    8 'I'   16 'Q'   24 'Y'   32 'g'   40 'o'   48 'w'   56 '4'
///      1 'B'    9 'J'   17 'R'   25 'Z'   33 'h'   41 'p'   49 'x'   57 '5'
///      2 'C'   10 'K'   18 'S'   26 'a'   34 'i'   42 'q'   50 'y'   58 '6'
///      3 'D'   11 'L'   19 'T'   27 'b'   35 'j'   43 'r'   51 'z'   59 '7'
///      4 'E'   12 'M'   20 'U'   28 'c'   36 'k'   44 's'   52 '0'   60 '8'
///      5 'F'   13 'N'   21 'V'   29 'd'   37 'l'   45 't'   53 '1'   61 '9'
///      6 'G'   14 'O'   22 'W'   30 'e'   38 'm'   46 'u'   54 '2'   62 '-'
///      7 'H'   15 'P'   23 'X'   31 'f'   39 'n'   47 'v'   55 '3'   63 '_'
///    ======================================================================
/// @endcode
/// ## Base 64 Decoding {#bdlde_base64encoder-base-64-decoding}
///
///
/// The degree to which decoding detects errors can significantly affect
/// performance.  The standard permits all non-Base64 characters to be treated
/// as whitespace.  One variant mode of this decoder does just that; the other
/// reports an error if a bad (i.e., non-whitespace) character is detected.  The
/// mode of the instance is configurable.  The standard imposes a maximum of 76
/// characters exclusive of CRLF; however, the decoder implemented in this
/// component will handle lines of arbitrary length.
///
/// The following kinds of errors can occur during decoding and are reported
/// with the following priority:
/// @code
/// BAD DATA: A character (other than whitespace) that is not a member of the
///           Base64 character set (including '=').  Note that this error
///           is detected only if the 'decoder' is explicitly configured (at
///           construction) to do so.
///
/// BAD FORMAT: An '=' character precedes a valid numeric Base64 character,
///             more than two '=' characters appear (possibly separated by
///             non-Base64 characters), a numeric Base64 character other than
///             [AEIMQUYcgkosw048] precedes a single terminal '=' character,
///             or a character other than [AQgw] precedes a terminal pair of
///             consecutive '=' characters.
/// @endcode
/// The `isError` method is used to detect such anomalies, and the `numIn`
/// output parameter (indicating the number of input characters consumed) or
/// possibly the iterator itself (for iterators with reference-semantics)
/// identifies the offending character.
///
/// Note that the existence of an `=` can be used to reliably indicate the end
/// of the valid data, but no such assurance is possible when the length (in
/// bytes) of the initial input data sequence before encoding was evenly
/// divisible by 3.
///
/// ## Usage {#bdlde_base64encoder-usage}
///
///
/// This section illustrates intended use of this component.
///
/// ### Example 1: Basic Usage {#bdlde_base64encoder-example-1-basic-usage}
///
///
/// The following example shows how to use a `bdlde::Base64Encoder` object to
/// implement a function, `streamEncoder`, that reads text from a
/// `bsl::istream`, encodes that text in base 64 representation, and writes the
/// encoded text to a `bsl::ostream`.  `streamEncoder` returns 0 on success
/// and a negative value if the input data could not be successfully encoded or
/// if there is an I/O error.
/// @code
/// streamencoder.h                    -*-C++-*-
///
/// /// Read the entire contents of the specified input stream 'is', convert
/// /// the input plain text to base 64 encoding, and write the encoded text
/// /// to the specified output stream 'os'.  Return 0 on success, and a
/// /// negative value otherwise.
/// int streamEncoder(bsl::ostream& os, bsl::istream& is);
/// @endcode
/// We will use fixed-sized input and output buffers in the implementation, but,
/// because of the flexibility of `bsl::istream` and the output-buffer
/// monitoring functionality of `bdlde::Base64Encoder`, the fixed buffer sizes
/// do *not* limit the quantity of data that can be read, encoded, or written to
/// the output stream.  The implementation file is as follows.
/// @code
/// streamencoder.cpp                  -*-C++-*-
///
/// #include <streamencoder.h>
///
/// #include <bdlde_base64encoder.h>
///
/// namespace BloombergLP {
///
/// int streamEncoder(bsl::ostream& os, bsl::istream& is)
/// {
///     enum {
///         SUCCESS      =  0,
///         ENCODE_ERROR = -1,
///         IO_ERROR     = -2
///     };
/// @endcode
/// We declare a `bdlde::Base64Encoder` object `converter`, which will encode
/// the input data.  Note that various internal buffers and cursors are used as
/// needed without further comment.  We read as much data as is available from
/// the user-supplied input stream `is` *or* as much as will fit in
/// `inputBuffer` before beginning conversion.
/// @code
///    bdlde::Base64Encoder converter;
///
///    const int INBUFFER_SIZE  = 1 << 10;
///    const int OUTBUFFER_SIZE = 1 << 10;
///
///    char inputBuffer[INBUFFER_SIZE];
///    char outputBuffer[OUTBUFFER_SIZE];
///
///    char *output    = outputBuffer;
///    char *outputEnd = outputBuffer + sizeof outputBuffer;
///
///    while (is.good()) {  // input stream not exhausted
///
///        is.read(inputBuffer, sizeof inputBuffer);
/// @endcode
/// With `inputBuffer` now populated, we'll use `converter` in an inner `while`
/// loop to encode the input and write the encoded data to `outputBuffer` (via
/// the `output` cursor').  Note that if the call to `converter.convert` fails,
/// our function terminates with a negative status.
/// @code
///        const char *input    = inputBuffer;
///        const char *inputEnd = input + is.gcount();
///
///        while (input < inputEnd) { // input encoding not complete
///
///            int numOut;
///            int numIn;
///
///            int status = converter.convert(output, &numOut, &numIn,
///                                           input,   inputEnd,
///                                           outputEnd - output);
///            if (status < 0) {
///                return ENCODE_ERROR;                               // RETURN
///            }
/// @endcode
/// If the call to `converter.convert` returns successfully, we'll see if the
/// output buffer is full, and if so, write its contents to the user-supplied
/// output stream `os`.  Note how we use the values of `numOut` and `numIn`
/// generated by `convert` to update the relevant cursors.
/// @code
///            output += numOut;
///            input  += numIn;
///
///            if (output == outputEnd) {  // output buffer full; write data
///                os.write (outputBuffer, sizeof outputBuffer);
///                if (os.fail()) {
///                    return IO_ERROR;                               // RETURN
///                }
///                output = outputBuffer;
///            }
///        }
///    }
/// @endcode
/// We have now exited both the input and the "encode" loops.  `converter` may
/// still hold encoded output characters, and so we call `converter.endConvert`
/// to emit any retained output.  To guarantee correct behavior, we call this
/// method in an infinite loop, because it is possible that the retained output
/// can fill the output buffer.  In that case, we solve the problem by writing
/// the contents of the output buffer to `os` within the loop.  The most likely
/// case, however, is that `endConvert` will return 0, in which case we exit the
/// loop and write any data remaining in `outputBuffer` to `os`.  As above, if
/// `endConvert` fails, we exit the function with a negative return status.
/// @code
///    while (1) {
///
///        int numOut;
///
///        int more = converter.endConvert(output, &numOut, outputEnd-output);
///        if (more < 0) {
///            return ENCODE_ERROR;                                   // RETURN
///        }
///
///        output += numOut;
///
///        if (!more) { // no more output
///            break;
///        }
///
///        assert (output == outputEnd);  // output buffer is full
///
///        os.write (outputBuffer, sizeof outputBuffer);  // write buffer
///        if (os.fail()) {
///            return IO_ERROR;                                       // RETURN
///        }
///        output = outputBuffer;
///    }
///
///    if (output > outputBuffer) { // still data in output buffer; write it
///                                 // all
///        os.write(outputBuffer, output - outputBuffer);
///    }
///
///    return (is.eof() && os.good()) ? SUCCESS : IO_ERROR;
/// }
///
/// } // Close namespace BloombergLP
/// @endcode
/// For ease of reading, we repeat the full content of the `streamencoder.cpp`
/// file without interruption.
/// @code
/// streamencoder.cpp                  -*-C++-*-
///
/// #include <streamencoder.h>
///
/// #include <bdlde_base64encoder.h>
///
/// namespace BloombergLP {
///
/// int streamEncoder(bsl::ostream& os, bsl::istream& is)
/// {
///     enum {
///         SUCCESS      =  0,
///         ENCODE_ERROR = -1,
///         IO_ERROR     = -2
///     };
///
///     bdlde::Base64Encoder converter;
///
///     const int INBUFFER_SIZE  = 1 << 10;
///     const int OUTBUFFER_SIZE = 1 << 10;
///
///     char inputBuffer[INBUFFER_SIZE];
///     char outputBuffer[OUTBUFFER_SIZE];
///
///     char *output    = outputBuffer;
///     char *outputEnd = outputBuffer + sizeof outputBuffer;
///
///     while (is.good()) {  // input stream not exhausted
///
///         is.read(inputBuffer, sizeof inputBuffer);
///
///         const char *input    = inputBuffer;
///         const char *inputEnd = input + is.gcount();
///
///         while (input < inputEnd) { // input encoding not complete
///
///             int numOut;
///             int numIn;
///
///             int status = converter.convert(output, &numOut, &numIn,
///                                            input,   inputEnd,
///                                            outputEnd - output);
///             if (status < 0) {
///                 return ENCODE_ERROR;                               // RETURN
///             }
///
///             output += numOut;
///             input  += numIn;
///
///             if (output == outputEnd) {  // output buffer full; write data
///                 os.write(outputBuffer, sizeof outputBuffer);
///                 if (os.fail()) {
///                     return IO_ERROR;                               // RETURN
///                 }
///                 output = outputBuffer;
///             }
///         }
///     }
///
///     while (1) {
///
///         int numOut;
///
///         int more = converter.endConvert(output, &numOut, outputEnd-output);
///         if (more < 0) {
///             return ENCODE_ERROR;                                   // RETURN
///         }
///
///         output += numOut;
///
///         if (!more) { // no more output
///             break;
///         }
///
///         assert (output == outputEnd);  // output buffer is full
///
///         os.write (outputBuffer, sizeof outputBuffer);  // write buffer
///         if (os.fail()) {
///             return IO_ERROR;                                       // RETURN
///         }
///         output = outputBuffer;
///     }
///
///     if (output > outputBuffer) {
///         os.write (outputBuffer, output - outputBuffer);
///     }
///
///     return (is.eof() && os.good()) ? SUCCESS : IO_ERROR;
/// }
///
/// }  // close namespace BloombergLP
/// @endcode
/// @}
/** @} */
/** @} */
 
/** @addtogroup bdl
 * @{
 */
/** @addtogroup bdlde
 * @{
 */
/** @addtogroup bdlde_base64encoder
 * @{
 */
 
#include <bdlscm_version.h>
 
#include <bdlde_base64alphabet.h>
#include <bdlde_base64encoderoptions.h>
 
#include <bsls_assert.h>
#include <bsls_deprecatefeature.h>
#include <bsls_review.h>
 
#include <bsl_cstddef.h>
#include <bsl_limits.h>
 
 
namespace bdlde {
 
                            // ===================
                            // class Base64Encoder
                            // ===================
 
/// This class implements a mechanism capable of converting data of
/// arbitrary length to its corresponding Base64 representation.
///
/// See @ref bdlde_base64encoder 
class Base64Encoder {
 
    // TYPES
    typedef Base64EncoderOptions EncoderOptions;
 
  public:
    // PUBLIC TYPES
    typedef Base64Alphabet::Enum Alphabet;
 
    // PUBLIC CLASS DATA
    static const Alphabet    e_BASIC = Base64Alphabet::e_BASIC;
    static const Alphabet    e_URL   = Base64Alphabet::e_URL;
 
  private:
    // PRIVATE TYPES
    enum State {
        // Symbolic state values.
 
        e_ERROR_STATE     = -1, // Input is irreparably invalid.
        e_INITIAL_STATE   =  0, // Ready to accept input.
        e_DONE_STATE      =  1  // Any additional input is an error.
    };
 
    // INSTANCE DATA
    const int           d_maxLineLength;  // maximum length of output line
    int                 d_lineLength;     // current length of output line
    int                 d_outputLength;   // total number of output characters
    unsigned            d_stack;          // storage of non-emitted input
    int                 d_bitsInStack;    // number of bits in 'd_stack'
    const char * const  d_alphabet_p;     // alphabet
    State               d_state;          // state as per above enum 'State'
    const Alphabet      d_alphabet;       // alphabet
    const bool          d_isPadded;       // is output tail-padded with '='
 
  private:
    // NOT IMPLEMENTED
    Base64Encoder(const Base64Encoder&);
    Base64Encoder& operator=(const Base64Encoder&);
 
    // PRIVATE CLASS METHODS
 
    /// Return the expected length of output, not including CRLF's, given
    /// the specified `options` and `inputLength`.  The behavior is
    /// undefined if `inputLength` is large enough to overflow the result.
    static
    bsl::size_t lengthWithoutCrlfs(const EncoderOptions& options,
                                   bsl::size_t           inputLength);
 
    // PRIVATE MANIPULATORS
 
    /// Append a soft new line to the specified `out` if necessary and then
    /// append the specified `character` without the total number of emitted
    /// characters equaling the specified `maxLength`.  The behavior is
    /// undefined unless the total number of emitted characters does not
    /// equal `maxLength` at entry to this method.
    template <class OUTPUT_ITERATOR>
    void append(OUTPUT_ITERATOR *out, char character, int maxLength);
 
    /// Append a soft new line to the specified `out` if necessary and then
    /// emit an internally buffered character without the total number of
    /// emitted characters equaling the specified `maxLength`.  The
    /// behavior is undefined unless the total number of emitted characters
    /// does not equal `maxLength` at entry to this method and the internal
    /// buffer contains at least one character of output.
    template <class OUTPUT_ITERATOR>
    void encode(OUTPUT_ITERATOR *out, int maxLength);
 
    /// Set the state to the specified `newState`.
    void setState(State newState);
 
    // PRIVATE ACCESSORS
 
    /// Return `true` if an output sequence of the specified `numBytes` from
    /// this encoder would be an acceptable input to a `Base64Decoder`
    /// expecting padded input, and `false` otherwise.  The behavior is
    /// undefined unless padding is enabled.
    bool isResidualOutput(int numBytes) const;
 
    /// Return the state of this encoder.
    State state() const;
 
  public:
    // CLASS METHODS
 
    /// Return the exact number of encoded bytes that would result from an
    /// input byte sequence of the specified `inputLength` provided to the
    /// `convert` method of an encoder configured with the specified
    /// `options`.  The behavior is undefined if `inputLength` is large
    /// enough for the result to overflow a `size_t`.
    static bsl::size_t encodedLength(const EncoderOptions& options,
                                     bsl::size_t           inputLength);
 
    BSLS_DEPRECATE_FEATURE("bdl",
                           "encodedLength",
                           "use overload with 'options'")
    /// Return the exact number of encoded bytes that would result from an
    /// input byte sequence of the specified `inputLength` provided to the
    /// `convert` method of an encoder with the maximum allowable
    /// line-length of the output being 76 characters (as recommended by the
    /// MIME standard).  The behavior is undefined unless
    /// `0 <= inputLength`.
    ///
    static
    int encodedLength(int inputLength);
    /// @deprecated  use the overload with `options` instead.
 
    BSLS_DEPRECATE_FEATURE("bdl",
                           "encodedLength",
                           "use overload with 'options'")
    /// Return the exact number of encoded bytes that would result from an
    /// input byte sequence of the specified `inputLength` provided to the
    /// `convert` method of an encoder configured with the specified
    /// `maxLineLength`.  The behavior is undefined unless
    /// `0 <= inputLength` and `0 <= maxLineLength`.  Note that if
    /// `maxLineLength` is 0, no CRLF characters will appear in the output.
    /// Note also that the number of encoded bytes need not be the number of
    /// *output* bytes.
    ///
    /// @deprecated  use the overload with `options` instead.
    static
    int encodedLength(int inputLength, int maxLineLength);
 
    /// Return the exact number of encoded lines that would result from an
    /// input byte sequence of the specified `inputLength` provided to the
    /// `convert` method of an encoder configured with the specified
    /// `options`.  The behavior is undefined if `inputLength` is large
    /// enough to overflow the result.
    static bsl::size_t encodedLines(const EncoderOptions& options,
                                    bsl::size_t           inputLength);
 
    BSLS_DEPRECATE_FEATURE("bdl",
                           "encodedLines",
                           "use overload with 'options'")
    /// Return the exact number of encoded lines that would result from an
    /// input byte sequence of the specified `inputLength` provided to the
    /// `convert` method of an encoder with the maximum allowable
    /// line-length of the output being 76 characters (as recommended by the
    /// MIME standard).  The behavior is undefined unless
    /// `0 <= inputLength`.  Note also that the number of encoded bytes need
    /// not be the number of *output* bytes.
    ///
    static
    int encodedLines(int inputLength);
    /// @deprecated  use the overload with `options` instead.
 
    BSLS_DEPRECATE_FEATURE("bdl",
                           "encodedLines",
                           "use overload with 'options'")
    /// Return the exact number of encoded lines that would result from an
    /// input byte sequence of the specified `inputLength` provided to the
    /// `convert` method of an encoder configured with the specified
    /// `maxLineLength`.  The behavior is undefined unless
    /// `0 <= inputLength` and `0 <= maxLineLength`.  Note that if
    /// `maxLineLength` is 0, no CRLF characters will appear in the output.
    /// Note also that the number of encoded bytes need not be the number of
    /// *output* bytes.
    ///
    /// @deprecated  use the overload with `options` instead.
    static
    int encodedLines(int inputLength, int maxLineLength);
 
    // CREATORS
 
    explicit
    Base64Encoder(const EncoderOptions& options = EncoderOptions::mime());
 
    BSLS_DEPRECATE_FEATURE("bdl",
                           "Base64Encoder",
                           "use overload with 'options'")
    /// Create a Base64 encoder in the initial state, defaulting the maximum
    /// allowable line-length of the output to 76 (as recommended by the
    /// MIME standard).  Optionally specify an alphabet used to encode
    /// characters.  If `alphabet` is not specified, then the basic
    /// alphabet, "base64", is used.  Note that the `convert` and
    /// `endConvert` methods of this encoder will insert a CRLF to prevent
    /// each line of the output from exceeding 76 characters.
    ///
    /// @deprecated  Create and pass an `options` object instead.
    explicit
    Base64Encoder(Alphabet alphabet);
    /// Create a Base64 encoder in the initial state, defaulting the state
    /// of the maximum allowable line-length, the padding, and the alphabet
    /// according to the values of the specified `options`.
 
    BSLS_DEPRECATE_FEATURE("bdl",
                           "Base64Encoder",
                           "use overload with 'options'")
    /// Create a Base64 encoder in the initial state, setting the maximum
    /// allowable line-length of the output to the specified
    /// `maxLineLength`.  Specifying 0 for `maxLineLength` will result in a
    /// single output line (i.e., one with no CRLF in it).  Optionally
    /// specify an alphabet used to encode characters.  If `alphabet` is not
    /// specified, then the basic alphabet, "base64", is used.The behavior
    /// is undefined unless `0 <= maxLineLength`.  Note that when
    /// `maxLineLength` is positive, the `convert` and `endConvert` methods
    /// of this encoder will insert a CRLF to prevent each line of the
    /// output from exceeding `maxLineLength`.
    ///
    /// @deprecated  Create and pass an `options` object instead.
    explicit
    Base64Encoder(int maxLineLength, Alphabet alphabet = e_BASIC);
 
    /// Destroy this object.
    ~Base64Encoder();
 
    // MANIPULATORS
 
    /// Encode the sequence of input characters starting at the specified
    /// `begin` position up to, but not including, the specified `end`
    /// position, writing any resulting output characters to the specified
    /// `out` buffer.  Optionally specify the `maxNumOut` limit on the
    /// number of bytes to output; if `maxNumOut` is negative, no limit is
    /// imposed.  If the `maxNumOut` limit is reached, no further input will
    /// be consumed.  Load into the (optionally) specified `numOut` and
    /// `numIn` the number of output bytes produced and input bytes
    /// consumed, respectively.  Return a non-negative value on success and
    /// a negative value otherwise.  A positive return status indicates the
    /// number of valid processed output bytes retained by this encoder and
    /// not written to `out` because `maxNumOut` has been reached; these
    /// bytes are available for output if this method is called with
    /// appropriate input.  Note that calling this method after `endConvert`
    /// has been invoked without an intervening `resetState` call will place
    /// this instance in an error state, and return an error status.  Note
    /// also that it is recommended that after all calls to `convert` are
    /// finished, the `endConvert` method be called to complete the encoding
    /// of any unprocessed input characters that do not complete a 3-byte
    /// sequence.
    template <class OUTPUT_ITERATOR, class INPUT_ITERATOR>
    int convert(OUTPUT_ITERATOR out,
                INPUT_ITERATOR  begin,
                INPUT_ITERATOR  end);
    template <class OUTPUT_ITERATOR, class INPUT_ITERATOR>
    int convert(OUTPUT_ITERATOR  out,
                int             *numOut,
                int             *numIn,
                INPUT_ITERATOR   begin,
                INPUT_ITERATOR   end,
                int              maxNumOut = -1);
 
    /// Terminate encoding for this encoder; write any retained output
    /// (e.g., from a previous call to `convert`) to the specified `out`
    /// buffer.  Optionally specify the `maxNumOut` limit on the number of
    /// bytes to output; if `maxNumOut` is negative, no limit is imposed.
    /// Load into the (optionally) specified `numOut` the number of output
    /// bytes produced.  Return 0 if output was successfully completed and a
    /// non-zero value otherwise.  Any retained bytes are available on a
    /// subsequent call to `endConvert`.  Once this method is called, no
    /// additional input may be supplied without an intervening call to
    /// `resetState`; once this method returns a zero status, a subsequent
    /// call will place this encoder in the error state, and return an error
    /// status.
    template <class OUTPUT_ITERATOR>
    int endConvert(OUTPUT_ITERATOR out);
    template <class OUTPUT_ITERATOR>
    int endConvert(OUTPUT_ITERATOR out, int *numOut, int maxNumOut = -1);
 
    /// Reset this instance to its initial state (i.e., as if no input had
    /// been consumed).
    void resetState();
 
    // ACCESSORS
 
    /// Return the alphabet supplied at construction of this object.
    Alphabet alphabet() const;
 
    /// Return `true` if the input read so far is considered syntactically
    /// complete and all resulting output has been emitted to `out`, and
    /// `false` otherwise.  Note that `endConvert` must be called if the
    /// total length of all data processed is not divisible by 3.
    bool isAcceptable() const;
 
    /// Return `true` if the current input is acceptable and any additional
    /// input (including `endConvert`) would be an error, and `false`
    /// otherwise.  Note that if this decoder `isDone` then all resulting
    /// output has been emitted to `out`.
    bool isDone() const;
 
    /// Return `true` if there is no possibility of achieving an
    /// "acceptable" result, and `false` otherwise.
    bool isError() const;
 
    /// Return `true` if this instance is in the initial state (i.e., as if
    /// no input had been consumed), and `false` otherwise.
    bool isInitialState() const;
 
    /// Return true if padding by `=` characters was specified at
    /// construction of this object.
    bool isPadded() const;
 
    /// Return the currently installed value for the maximum line length.
    int maxLineLength() const;
 
    /// Return an `options` object reflecting the options this object was
    /// configured with.
    EncoderOptions options() const;
 
    /// Return the total length of the output emitted thus far (including
    /// soft line breaks where appropriate).
    int outputLength() const;
};
 
// ============================================================================
//                            INLINE DEFINITIONS
// ============================================================================
 
                            // -------------------
                            // class Base64Encoder
                            // -------------------
 
// PRIVATE CLASS METHODS
inline
bsl::size_t Base64Encoder::lengthWithoutCrlfs(
                                             const EncoderOptions& options,
                                             bsl::size_t           inputLength)
{
    static const bsl::size_t maxSize_t = bsl::numeric_limits<
                                                           bsl::size_t>::max();
    (void) maxSize_t;
 
    if (0 == inputLength) {
        return 0;                                                     // RETURN
    }
 
    const bsl::size_t numTripletsRoundedDown = (inputLength + 2) / 3 - 1;
    const bsl::size_t numResidual = inputLength - numTripletsRoundedDown * 3;
 
    // 'numResidual' is in the range '[ 1 .. 3 ]'.  If 'numResidual' is '1'
    // byte, that takes 2 bytes to encode, 2 bytes takes 3 bytes to encode, 3
    // bytes takes 4 bytes to encode.
 
    const bsl::size_t pad = options.isPadded() ? 4 : numResidual + 1;
 
    BSLS_ASSERT(numTripletsRoundedDown <= (maxSize_t - pad) / 4);
 
    return numTripletsRoundedDown * 4 + pad;
}
 
// PRIVATE MANIPULATORS
template <class OUTPUT_ITERATOR>
void Base64Encoder::append(OUTPUT_ITERATOR *out,
                           char             value,
                           int              maxLength)
{
    BSLS_ASSERT(out);
 
    if (d_maxLineLength && d_lineLength >= d_maxLineLength) {
        if (d_lineLength == d_maxLineLength) {
            **out = '\r';
            ++*out;
            ++d_outputLength;
            ++d_lineLength;
            if (d_outputLength == maxLength) {
                return;                                               // RETURN
            }
        }
        **out = '\n';
        ++*out;
        ++d_outputLength;
        d_lineLength = 0;
        if (d_outputLength == maxLength) {
            return;                                                   // RETURN
        }
    }
    **out = value;
    ++*out;
    ++d_outputLength;
    ++d_lineLength;
}
 
template <class OUTPUT_ITERATOR>
void Base64Encoder::encode(OUTPUT_ITERATOR *out, int maxLength)
{
    BSLS_ASSERT(out);
 
    if (d_maxLineLength && d_lineLength >= d_maxLineLength) {
        if (d_lineLength == d_maxLineLength) {
            **out = '\r';
            ++*out;
            ++d_outputLength;
            ++d_lineLength;
            if (d_outputLength == maxLength) {
                return;                                               // RETURN
            }
        }
        **out = '\n';
        ++*out;
        ++d_outputLength;
        d_lineLength = 0;
        if (d_outputLength == maxLength) {
            return;                                                   // RETURN
        }
    }
    d_bitsInStack -= 6;
    **out = d_alphabet_p[(d_stack >> d_bitsInStack) & 0x3f];
    ++*out;
    ++d_outputLength;
    ++d_lineLength;
}
 
inline
void Base64Encoder::setState(State newState)
{
    d_state = newState;
}
 
// PRIVATE ACCESSORS
inline
bool Base64Encoder::isResidualOutput(int numBytes) const
{
    BSLS_ASSERT(0 <= numBytes);
    BSLS_ASSERT(d_isPadded);
 
    if (d_maxLineLength) {
        const int lineSize           = d_maxLineLength + 2;
        const int linesSoFar         = numBytes / lineSize;
        const int bytesSinceLastCrlf = numBytes - linesSoFar * lineSize;
        const int partialCrlf        = d_maxLineLength < bytesSinceLastCrlf;
        const int nonCrlfBytes       = linesSoFar * d_maxLineLength +
                                              bytesSinceLastCrlf - partialCrlf;
 
        return 0 != nonCrlfBytes % 4;                                 // RETURN
    }
    else {
        return 0 != numBytes % 4;                                     // RETURN
    }
}
 
inline
Base64Encoder::State Base64Encoder::state() const
{
    return d_state;
}
 
// CLASS METHODS
inline
bsl::size_t Base64Encoder::encodedLength(const EncoderOptions& options,
                                         bsl::size_t           inputLength)
{
    static const bsl::size_t maxSize_t = bsl::numeric_limits<
                                                           bsl::size_t>::max();
    (void) maxSize_t;
 
    if (0 == inputLength) {
        return 0;                                                     // RETURN
    }
 
    const bsl::size_t length   = lengthWithoutCrlfs(options, inputLength);
    const bsl::size_t numCrlfs = 0 == options.maxLineLength()
                               ? 0
                               : (length - 1) / options.maxLineLength();
 
 
    BSLS_ASSERT(numCrlfs <= maxSize_t / 2);
    BSLS_ASSERT(length <= maxSize_t - numCrlfs * 2);
 
    return length + 2 * numCrlfs;
}
 
inline
int Base64Encoder::encodedLength(int inputLength, int maxLineLength)
{
    BSLS_ASSERT(0 <= inputLength);
    BSLS_ASSERT(0 <= maxLineLength);
 
    return static_cast<int>(encodedLength(EncoderOptions::custom(maxLineLength,
                                                                 e_BASIC,
                                                                 true),
                                          inputLength));
}
 
inline
int Base64Encoder::encodedLength(int inputLength)
{
    BSLS_ASSERT(0 <= inputLength);
 
    return static_cast<int>(encodedLength(EncoderOptions::mime(),
                                          inputLength));
}
 
inline
bsl::size_t Base64Encoder::encodedLines(const EncoderOptions& options,
                                        bsl::size_t           inputLength)
{
    return 1 +
        (0 == options.maxLineLength()
         ? 0
         : lengthWithoutCrlfs(options, inputLength) / options.maxLineLength());
}
 
inline
int Base64Encoder::encodedLines(int inputLength, int maxLineLength)
{
    BSLS_ASSERT(0 <= inputLength);
    BSLS_ASSERT(0 <= maxLineLength);
 
    return static_cast<int>(encodedLines(EncoderOptions::custom(maxLineLength,
                                                                e_BASIC,
                                                                true),
                                         inputLength));
}
 
inline
int Base64Encoder::encodedLines(int inputLength)
{
    BSLS_ASSERT(0 <= inputLength);
 
    return static_cast<int>(encodedLines(EncoderOptions::mime(), inputLength));
}
 
// MANIPULATORS
template <class OUTPUT_ITERATOR, class INPUT_ITERATOR>
int Base64Encoder::convert(OUTPUT_ITERATOR out,
                           INPUT_ITERATOR  begin,
                           INPUT_ITERATOR  end)
{
    int dummyNumOut;
    int dummyNumIn;
 
    return convert(out, &dummyNumOut, &dummyNumIn, begin, end, -1);
}
 
template <class OUTPUT_ITERATOR, class INPUT_ITERATOR>
int Base64Encoder::convert(OUTPUT_ITERATOR  out,
                           int             *numOut,
                           int             *numIn,
                           INPUT_ITERATOR   begin,
                           INPUT_ITERATOR   end,
                           int              maxNumOut)
{
    int dummyNumOut;
    if (!numOut) {
        numOut = &dummyNumOut;
    }
    int dummyNumIn;
    if (!numIn) {
        numIn  = &dummyNumIn;
    }
 
    if (e_ERROR_STATE == state() || e_DONE_STATE == state()) {
        setState(e_ERROR_STATE);
        *numOut = 0;
        *numIn  = 0;
        return -1;                                                    // RETURN
    }
 
    const int initialLength = d_outputLength;
    const int maxLength     = d_outputLength + maxNumOut;
 
    // Emit as many output bytes as possible.
 
    while (6 <= d_bitsInStack && d_outputLength != maxLength) {
        encode(&out, maxLength);
    }
 
    // Consume as many input bytes as possible.
 
    int tmpNumIn = 0;
 
    while (4 >= d_bitsInStack && begin != end) {
        const unsigned char byte = static_cast<unsigned char>(*begin);
 
        ++begin;
        ++tmpNumIn;
 
        d_stack        = (d_stack << 8) | byte;
        d_bitsInStack += 8;
 
        if (d_outputLength != maxLength) {
            encode(&out, maxLength);
            if (6 <= d_bitsInStack && d_outputLength != maxLength) {
                encode(&out, maxLength);
            }
        }
    }
 
    *numIn  = tmpNumIn;
    *numOut = d_outputLength - initialLength;
 
    return 0;
}
 
template <class OUTPUT_ITERATOR>
int Base64Encoder::endConvert(OUTPUT_ITERATOR out)
{
    int dummyNumOut;
 
    return endConvert(out, &dummyNumOut, -1);
}
 
template <class OUTPUT_ITERATOR>
int Base64Encoder::endConvert(OUTPUT_ITERATOR  out,
                              int             *numOut,
                              int              maxNumOut)
{
    BSLS_ASSERT(numOut);
 
    if (e_ERROR_STATE == state() || isDone()) {
        setState(e_ERROR_STATE);
        *numOut = 0;
        return -1;                                                    // RETURN
    }
 
    const int initialLength = d_outputLength;
    const int maxLength = d_outputLength + maxNumOut;
 
    // Handle trailing bits.
 
    const int residualBits = d_bitsInStack % 6;
    if (residualBits) {
        const int shift = 6 - residualBits;
        d_stack = d_stack << shift;
        d_bitsInStack += shift;
    }
 
    BSLS_ASSERT(0 == d_bitsInStack % 6);
 
    // Emit as many output bytes as possible.
 
    while (6 <= d_bitsInStack && d_outputLength != maxLength) {
        encode(&out, maxLength);
    }
 
    // Append trailing '=' as necessary.
 
    if (0 == d_bitsInStack) {
        while (true) {
            if (!d_isPadded || !isResidualOutput(d_outputLength)) {
                setState(e_DONE_STATE);
 
                break;
            }
 
            if (d_outputLength == maxLength) {
                break;
            }
 
            append(&out, '=', maxLength);
        }
    }
 
    *numOut = d_outputLength - initialLength;
 
    return !isDone();
}
 
inline
void Base64Encoder::resetState()
{
    setState(e_INITIAL_STATE);
    d_outputLength = 0;
    d_lineLength   = 0;
    d_stack        = 0;
    d_bitsInStack  = 0;
}
 
// ACCESSORS
inline
Base64Alphabet::Enum Base64Encoder::alphabet() const
{
    return d_alphabet;
}
 
inline
bool Base64Encoder::isAcceptable() const
{
    return e_ERROR_STATE != state();
}
 
inline
bool Base64Encoder::isDone() const
{
    return e_DONE_STATE == state()
        && !d_bitsInStack
        && (!d_isPadded || !isResidualOutput(d_outputLength));
}
 
inline
bool Base64Encoder::isError() const
{
    return e_ERROR_STATE == state();
}
 
inline
bool Base64Encoder::isInitialState() const
{
    return 0 == d_outputLength && e_INITIAL_STATE == state();
}
 
inline
bool Base64Encoder::isPadded() const
{
    return d_isPadded;
}
 
inline
int Base64Encoder::maxLineLength() const
{
    return d_maxLineLength;
}
 
inline
Base64EncoderOptions Base64Encoder::options() const
{
    return EncoderOptions::custom(
                          d_maxLineLength,
                          alphabet(),
                          d_isPadded);
}
 
inline
int Base64Encoder::outputLength() const
{
    return d_outputLength;
}
}  // close package namespace
 
 
 
#endif
 
// ----------------------------------------------------------------------------
// Copyright 2015 Bloomberg Finance L.P.
//
// 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.
// ----------------------------- END-OF-FILE ----------------------------------
 
/** @} */
/** @} */
/** @} */