/usr/man/cat.3/EVP_DecodeBlock.3



EVP_EncodeInit(3)            OpenSSL            EVP_EncodeInit(3)

NAME

     EVP_EncodeInit, EVP_EncodeUpdate, EVP_EncodeFinal,
     EVP_EncodeBlock, EVP_DecodeInit, EVP_DecodeUpdate,
     EVP_DecodeFinal, EVP_DecodeBlock - EVP base 64 encode/decode
     routines

SYNOPSIS

      #include <openssl/evp.h>

      void EVP_EncodeInit(EVP_ENCODE_CTX *ctx);
      void EVP_EncodeUpdate(EVP_ENCODE_CTX *ctx, unsigned char *out, int *outl,
                            const unsigned char *in, int inl);
      void EVP_EncodeFinal(EVP_ENCODE_CTX *ctx, unsigned char *out, int *outl);
      int EVP_EncodeBlock(unsigned char *t, const unsigned char *f, int n);

      void EVP_DecodeInit(EVP_ENCODE_CTX *ctx);
      int EVP_DecodeUpdate(EVP_ENCODE_CTX *ctx, unsigned char *out, int *outl,
                           const unsigned char *in, int inl);
      int EVP_DecodeFinal(EVP_ENCODE_CTX *ctx, unsigned
                          char *out, int *outl);
      int EVP_DecodeBlock(unsigned char *t, const unsigned char *f, int n);

DESCRIPTION

     The EVP encode routines provide a high level interface to
     base 64 encoding and decoding. Base 64 encoding converts
     binary data into a printable form that uses the characters
     A-Z, a-z, 0-9, "+" and "/" to represent the data. For every
     3 bytes of binary data provided 4 bytes of base 64 encoded
     data will be produced plus some occasional newlines (see
     below). If the input data length is not a multiple of 3 then
     the output data will be padded at the end using the "="
     character.

     Encoding of binary data is performed in blocks of 48 input
     bytes (or less for the final block). For each 48 byte input
     block encoded 64 bytes of base 64 data is output plus an
     additional newline character (i.e. 65 bytes in total). The
     final block (which may be less than 48 bytes) will output 4
     bytes for every 3 bytes of input. If the data length is not
     divisible by 3 then a full 4 bytes is still output for the
     final 1 or 2 bytes of input. Similarly a newline character
     will also be output.

     EVP_EncodeInit() initialises ctx for the start of a new
     encoding operation.

     EVP_EncodeUpdate() encode inl bytes of data found in the
     buffer pointed to by in. The output is stored in the buffer
     out and the number of bytes output is stored in *outl. It is
     the caller's responsibility to ensure that the buffer at out
     is sufficiently large to accommodate the output data. Only
     full blocks of data (48 bytes) will be immediately processed

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EVP_EncodeInit(3)            OpenSSL            EVP_EncodeInit(3)

     and output by this function. Any remainder is held in the
     ctx object and will be processed by a subsequent call to
     EVP_EncodeUpdate() or EVP_EncodeFinal(). To calculate the
     required size of the output buffer add together the value of
     inl with the amount of unprocessed data held in ctx and
     divide the result by 48 (ignore any remainder). This gives
     the number of blocks of data that will be processed.  Ensure
     the output buffer contains 65 bytes of storage for each
     block, plus an additional byte for a NUL terminator.
     EVP_EncodeUpdate() may be called repeatedly to process large
     amounts of input data. In the event of an error
     EVP_EncodeUpdate() will set *outl to 0.

     EVP_EncodeFinal() must be called at the end of an encoding
     operation. It will process any partial block of data
     remaining in the ctx object. The output data will be stored
     in out and the length of the data written will be stored in
     *outl. It is the caller's responsibility to ensure that out
     is sufficiently large to accommodate the output data which
     will never be more than 65 bytes plus an additional NUL
     terminator (i.e. 66 bytes in total).

     EVP_EncodeBlock() encodes a full block of input data in f
     and of length dlen and stores it in t. For every 3 bytes of
     input provided 4 bytes of output data will be produced. If
     dlen is not divisible by 3 then the block is encoded as a
     final block of data and the output is padded such that it is
     always divisible by 4. Additionally a NUL terminator
     character will be added. For example if 16 bytes of input
     data is provided then 24 bytes of encoded data is created
     plus 1 byte for a NUL terminator (i.e. 25 bytes in total).
     The length of the data generated without the NUL terminator
     is returned from the function.

     EVP_DecodeInit() initialises ctx for the start of a new
     decoding operation.

     EVP_DecodeUpdate() decodes inl characters of data found in
     the buffer pointed to by in. The output is stored in the
     buffer out and the number of bytes output is stored in
     *outl. It is the caller's responsibility to ensure that the
     buffer at out is sufficiently large to accommodate the
     output data. This function will attempt to decode as much
     data as possible in 4 byte chunks. Any whitespace, newline
     or carriage return characters are ignored. Any partial chunk
     of unprocessed data (1, 2 or 3 bytes) that remains at the
     end will be held in the ctx object and processed by a
     subsequent call to EVP_DecodeUpdate(). If any illegal base
     64 characters are encountered or if the base 64 padding
     character "=" is encountered in the middle of the data then
     the function returns -1 to indicate an error. A return value
     of 0 or 1 indicates successful processing of the data. A

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EVP_EncodeInit(3)            OpenSSL            EVP_EncodeInit(3)

     return value of 0 additionally indicates that the last input
     data characters processed included the base 64 padding
     character "=" and therefore no more non-padding character
     data is expected to be processed. For every 4 valid base 64
     bytes processed (ignoring whitespace, carriage returns and
     line feeds), 3 bytes of binary output data will be produced
     (or less at the end of the data where the padding character
     "=" has been used).

     EVP_DecodeFinal() must be called at the end of a decoding
     operation. If there is any unprocessed data still in ctx
     then the input data must not have been a multiple of 4 and
     therefore an error has occurred. The function will return -1
     in this case. Otherwise the function returns 1 on success.

     EVP_DecodeBlock() will decode the block of n characters of
     base 64 data contained in f and store the result in t. Any
     leading whitespace will be trimmed as will any trailing
     whitespace, newlines, carriage returns or EOF characters.
     After such trimming the length of the data in f must be
     divisbile by 4. For every 4 input bytes exactly 3 output
     bytes will be produced. The output will be padded with 0
     bits if necessary to ensure that the output is always 3
     bytes for every 4 input bytes. This function will return the
     length of the data decoded or -1 on error.

RETURN VALUES

     EVP_EncodeBlock() returns the number of bytes encoded
     excluding the NUL terminator.

     EVP_DecodeUpdate() returns -1 on error and 0 or 1 on
     success. If 0 is returned then no more non-padding base 64
     characters are expected.

     EVP_DecodeFinal() returns -1 on error or 1 on success.

     EVP_DecodeBlock() returns the length of the data decoded or
     -1 on error.

/usr/man/cat.3/EVP_DecodeBlock.3

NAME

SYNOPSIS

DESCRIPTION

RETURN VALUES

SEE ALSO