encoding.h

著名的加密软件的应用于电子邮件中

/*
 *  Functions to encode and decode using BASE64 or Quoted-Printable
 *  Also a transfer-encoding header line parser
 *
 *  Filename: encoding.h
 *
 *  Last Edited: September 24, 1996
 *
 *  Author: Scott Manjourides
 *
 *  Portions adopted from code originally written by Stever Dorner.
 *  Copyright 1995, 1996 QUALCOMM Inc.
 *
 *  Send comments and questions to <[e-mail]>
 *
 */

#ifndef EMS_ENCODING_H
#define EMS_ENCODING_H

/*
 * state buffer for base64 encoding. Initialize all values to zero.
 */
typedef struct {
	unsigned char partial[4];
	short partialCount;
	short bytesOnLine;
} Enc64, *Enc64Ptr;

/*
 * state buffer for base64 decoding. Initialize all values to zero.
 */
typedef struct {
	short decoderState;		/* which of 4 bytes are we seeing now? */
	long invalCount;		/* how many bad chars found so far? */
	long padCount;			/* how many pad chars found so far? */
	unsigned char partial;	/* partially decoded byte from/for last/next time */
	short wasCR;			/* was the last character a carriage return? */
} Dec64, *Dec64Ptr;

/*
 * used internally to track parsing state
 */
typedef enum {
	qpNormal,
	qpEqual,
	qpEncoded,
	qpTrailingWhitespace,
	qpError
} QPStates;

/*
 * state buffer for QP encoding. Initialize all values to zero.
 */
typedef struct {
	int nCurLineLen; /* Number of characters outputed to current line */
	char cLastChar;  /* Last character read in */
} EncQP, *EncQPPtr;

/*
 * state buffer for QP decoding. Initialize CurState to qpNormal.
 */
typedef struct {
	QPStates CurState;
	char cLastChar;
} DecQP, *DecQPPtr;

/*
 * Valid return values for rfc822_parse_cte which specify the trasnfer
 * encoding found in the parsed header line
 */
typedef enum {
	CTE_Error,
	CTE_Base64,
	CTE_QP,
	CTE_7bit,
	CTE_8bit,
	CTE_Binary,
	CTE_NONE
} TrEncType;

/*****************************************************************************/
/*                                B A S E 6 4                                */
/*****************************************************************************/

/*
 *  Convert binary data to base64
 *
 *  Args:
 *   binPtr     [IN]     the binary data (or NULL to close encoder)
 *   binLen     [IN]     the length of the binary data
 *   sixFourPtr [IN]     pointer to buffer for the base64 data
 *   e64        [IN/OUT] state; caller must preserve
 *
 *  Returns: The length of the base64 data
 */
long Encode64(char *bin, long len, char *sixFour, Enc64Ptr e64);

/*
 *  Convert base64 data to binary
 *
 *  Args:
 *   sixFourPtr [IN]     the base64 data (or nil to close decoder)
 *   sixFourLen [IN]     the length of the base64 data
 *   binPtr     [IN]     pointer to buffer to hold binary data
 *   d64        [IN/OUT] pointer to decoder state; caller must preserve
 *   decErrCnt  [OUT]    the number of decoding errors found
 *
 *  Returns: The length of the binary data
 */
long Decode64(char *sixFour, long sixFourLen, char *bin, Dec64Ptr d64, long *decErrCnt);

/*****************************************************************************/
/*                      Q U O T E D - P R I N T A B L E                      */
/*****************************************************************************/

/* ------------------------------------------------------------------------- */
/* NOTE: To handle BINARY data, you must always quote newline characters,    */
/*   this implementation assumes TEXT data and thus does not encode newlines */
/* ------------------------------------------------------------------------- */

/*
 *  Convert binary data to quoted-printable
 *
 *  Args:
 *   pBin     [IN]     the binary data (or NULL to close the encoder)
 *   nLen     [IN]     the length of the binary data (or 0 to close the encoder)
 *   pQP      [IN]     pointer to buffer for the quoted-printable data
 *   eQPstate [IN/OUT] state; caller must preserve
 *
 *  Returns: The length of the quoted-printable data
 */
long EncodeQP(char *bin, long len, char *qp, EncQPPtr eQP);

/*
 *  Convert quoted printable data to binary
 *
 *  Args:
 *   pQP       [IN]     the quoted printable data (or NULL to close the decoder)
 *   nLen      [IN]     the length of the quoted printable data (or 0 to close the decoder)
 *   pBin      [IN]     pointer to buffer to hold binary data
 *   dQPstate  [IN/OUT] pointer to decoder state; caller must preserve
 *   decErrCnt [OUT]    the number of decoding errors found
 *
 *  Returns: The length of the binary data
 */
long DecodeQP(char *qp, long qpLen, char *bin, DecQPPtr dqp, long *decErrCnt);

/*****************************************************************************/
/*                             CTE   P A R S E R                             */
/*****************************************************************************/

/*
 *  Parse Content-Transer-Encoding header line
 *
 *  Args:
 *   src [IN] Valid Transfer-Encoding header.
 *
 *  Returns: enumerated integer 'TrEncType' type specifying CTE (see above).
 */
TrEncType rfc822_parse_cte(const char *src);

/*
 *  Create Content-Transer-Encoding header line
 *
 *  NOTE: The user of this function is responsible for freeing the
 *        returned string.
 *
 *  Args:
 *   mechanism [IN] Enumerated integer 'TrEncType' type specifying CTE.
 *
 *  Returns: Content tranfer encoding header line string.
 */
char *rfc822_make_cte(TrEncType mechanism);

/*
 *  Finds and extracts the content transfer encoding header line from a full
 *  multi-lined header. All unfolding (removing newlines) is done before
 *  header line is returned.
 *
 *  NOTE: The user of this function is responsible for freeing the
 *        returned string.
 *
 *  Args:
 *   pFullHeader [IN] Pointer to a full RFC822 header, including newlines
 *
 *  Returns: Extracted header line string; dynamically allocated.
 */
char *rfc822_extract_cte(const char *pFullHeader);

#endif /* EMS_ENCODING_H */