/*-------------------------------------------------------------------------
 *
 * encode.c
 *	  Various data encoding/decoding things.
 *
 * Copyright (c) 2001 PostgreSQL Global Development Group
 *
 *
 * IDENTIFICATION
 *	  $Header: /cvsroot/pgsql/src/backend/utils/adt/encode.c,v 1.2 2001/09/14 17:46:40 momjian Exp $
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include <ctype.h>
#include "utils/builtins.h"


struct pg_encoding
{
	unsigned		(*encode_len) (const uint8 *data, unsigned dlen);
	unsigned		(*decode_len) (const uint8 *data, unsigned dlen);
	unsigned		(*encode) (const uint8 *data, unsigned dlen, uint8 *res);
	unsigned		(*decode) (const uint8 *data, unsigned dlen, uint8 *res);
};

static struct pg_encoding * pg_find_encoding(const char *name);

/*
 * SQL functions.
 */

Datum
binary_encode(PG_FUNCTION_ARGS)
{
	bytea	   *data = PG_GETARG_BYTEA_P(0);
	Datum		name = PG_GETARG_DATUM(1);
	text	   *result;
	char	   *namebuf;
	int		namelen, datalen, resultlen, res;
	struct pg_encoding *enc;

	datalen = VARSIZE(data) - VARHDRSZ;
	namelen = VARSIZE(name) - VARHDRSZ;

	namebuf = (char *)DirectFunctionCall1(textout, name);

	enc = pg_find_encoding(namebuf);
	if (enc == NULL)
		elog(ERROR, "No such encoding");

	resultlen = enc->encode_len(VARDATA(data), datalen);
	result = palloc(VARHDRSZ + resultlen);

	res = enc->encode(VARDATA(data), datalen, VARDATA(result));
	if (res > resultlen)
		elog(ERROR, "Overflow - encode estimate too small");

	VARATT_SIZEP(result) = VARHDRSZ + res;

	PG_RETURN_TEXT_P(result);
}

Datum
binary_decode(PG_FUNCTION_ARGS)
{
	text	   *data = PG_GETARG_TEXT_P(0);
	Datum		name = PG_GETARG_DATUM(1);
	bytea	   *result;
	char		*namebuf;
	int			namelen, datalen, resultlen, res;
	struct pg_encoding *enc;

	datalen = VARSIZE(data) - VARHDRSZ;
	namelen = VARSIZE(name) - VARHDRSZ;

	namebuf = (char *)DirectFunctionCall1(textout, name);

	enc = pg_find_encoding(namebuf);
	if (enc == NULL)
		elog(ERROR, "No such encoding");

	resultlen = enc->decode_len(VARDATA(data), datalen);
	result = palloc(VARHDRSZ + resultlen);

	res = enc->decode(VARDATA(data), datalen, VARDATA(result));
	if (res > resultlen)
		elog(ERROR, "Overflow - decode estimate too small");

	VARATT_SIZEP(result) = VARHDRSZ + res;

	PG_RETURN_BYTEA_P(result);
}


/*
 * HEX
 */

static const char *hextbl = "0123456789abcdef";

static const int8 hexlookup[128] = {
	-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
	-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
	-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
	0, 1, 2, 3, 4, 5, 6, 7, 8, 9, -1, -1, -1, -1, -1, -1,
	-1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1,
	-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
	-1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1,
	-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
};

static unsigned
hex_encode(const uint8 * src, unsigned len, uint8 * dst)
{
	const uint8	   *end = src + len;

	while (src < end)
	{
		*dst++ = hextbl[(*src >> 4) & 0xF];
		*dst++ = hextbl[*src & 0xF];
		src++;
	}
	return len * 2;
}

static uint8
get_hex(unsigned c)
{
	int		res = -1;

	if (c > 0 && c < 127)
		res = hexlookup[c];

	if (res < 0)
		elog(ERROR, "Bad hex code: '%c'", c);

	return (uint8)res;
}

static unsigned
hex_decode(const uint8 * src, unsigned len, uint8 * dst)
{
	const uint8 *s,
			   *srcend;
	uint8		v1,
				v2,
			   *p = dst;

	srcend = src + len;
	s = src;
	p = dst;
	while (s < srcend)
	{
		if (*s == ' ' || *s == '\n' || *s == '\t' || *s == '\r')
		{
			s++;
			continue;
		}
		v1 = get_hex(*s++) << 4;
		if (s >= srcend)
			elog(ERROR, "hex_decode: invalid data");
		v2 = get_hex(*s++);
		*p++ = v1 | v2;
	}

	return p - dst;
}

static unsigned
hex_enc_len(const uint8 * src, unsigned srclen)
{
	return srclen << 1;
}

static unsigned
hex_dec_len(const uint8 * src, unsigned srclen)
{
	return srclen >> 1;
}

/*
 * BASE64
 */

static const unsigned char _base64[] =
"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

static const int8 b64lookup[128] = {
	-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
	-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
	-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63,
	52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -1, -1, -1,
	-1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14,
	15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1,
	-1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,
	41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1, -1, -1, -1,
};

static unsigned
b64_encode(const uint8 * src, unsigned len, uint8 * dst)
{
	uint8	   *p,
			   *lend = dst + 76;
	const uint8 *s,
			   *end = src + len;
	int			pos = 2;
	uint32		buf = 0;

	s = src;
	p = dst;

	while (s < end)
	{
		buf |= *s << (pos << 3);
		pos--;
		s++;

		/* write it out */
		if (pos < 0)
		{
			*p++ = _base64[(buf >> 18) & 0x3f];
			*p++ = _base64[(buf >> 12) & 0x3f];
			*p++ = _base64[(buf >> 6) & 0x3f];
			*p++ = _base64[buf & 0x3f];

			pos = 2;
			buf = 0;
		}
		if (p >= lend)
		{
			*p++ = '\n';
			lend = p + 76;
		}
	}
	if (pos != 2)
	{
		*p++ = _base64[(buf >> 18) & 0x3f];
		*p++ = _base64[(buf >> 12) & 0x3f];
		*p++ = (pos == 0) ? _base64[(buf >> 6) & 0x3f] : '=';
		*p++ = '=';
	}

	return p - dst;
}

static unsigned
b64_decode(const uint8 * src, unsigned len, uint8 * dst)
{
	const char	   *srcend = src + len,
			   *s = src;
	uint8	   *p = dst;
	unsigned	c;
	int			b = 0;
	uint32		buf = 0;
	int			pos = 0,
				end = 0;

	while (s < srcend)
	{
		c = *s++;

		if (c == ' ' || c == '\t' || c == '\n' || c == '\r')
			continue;

		if (c == '=')
		{
			/* end sequence */
			if (!end)
			{
				if (pos == 2)
					end = 1;
				else if (pos == 3)
					end = 2;
				else
					elog(ERROR, "base64: unexpected '='");
			}
			b = 0;
		}
		else {
			b = -1;
			if (c > 0 && c < 127)
				b = b64lookup[c];
			if (b < 0)
				elog(ERROR, "base64: Invalid symbol");
		}
		/* add it to buffer */
		buf = (buf << 6) + b;
		pos++;
		if (pos == 4)
		{
			*p++ = (buf >> 16) & 255;
			if (end == 0 || end > 1)
				*p++ = (buf >> 8) & 255;
			if (end == 0 || end > 2)
				*p++ = buf & 255;
			buf = 0;
			pos = 0;
		}
	}

	if (pos != 0)
		elog(ERROR, "base64: invalid end sequence");

	return p - dst;
}


static unsigned
b64_enc_len(const uint8 * src, unsigned srclen)
{
	/* 3 bytes will be converted to 4, linefeed after 76 chars */
	return (srclen + 2) * 4 / 3 + srclen / (76 * 3 / 4);
}

static unsigned
b64_dec_len(const uint8 * src, unsigned srclen)
{
	return (srclen * 3) >> 2;
}

/*
 * Escape
 * Minimally escape bytea to text.
 * De-escape text to bytea.
 * 
 * Only two characters are escaped:
 * \0 (null) and \\ (backslash)
 * 
 * De-escapes \\ and any \### octal
 */

#define VAL(CH)			((CH) - '0')
#define DIG(VAL)		((VAL) + '0')

static unsigned
esc_encode(const uint8 *src, unsigned srclen, uint8 *dst)
{
	const uint8	   *end = src + srclen;
	uint8			*rp = dst;
	int				val;
	int				len = 0;

	while (src < end)
	{
		if (*src == '\0')
		{
			val = *src;
			rp[0] = '\\';
			rp[1] = '0';
			rp[2] = '0';
			rp[3] = '0';
			rp += 4;
			len += 4;
		}
		else if (*src == '\\')
		{
			val = *src;
			rp[0] = '\\';
			rp[1] = '\\';
			rp += 2;
			len += 2;
		}
		else
		{
			*rp++ = *src;
			len++;
		}

		src++;
	}
	*rp = '\0';

	return len;
}

static unsigned
esc_decode(const uint8 *src, unsigned srclen, uint8 *dst)
{
	const uint8		*end = src + srclen;
	uint8			*rp = dst;
	int				val;
	int				len = 0;

	while (src < end)
	{
		if (src[0] != '\\')
		{
			*rp++ = *src++;
		}
		else if	( (src[0] == '\\') &&
					(src[1] >= '0' && src[1] <= '3') &&
					(src[2] >= '0' && src[2] <= '7') &&
					(src[3] >= '0' && src[3] <= '7') )
		{
			val = VAL(src[1]);
			val <<= 3;
			val += VAL(src[2]);
			val <<= 3;
			*rp++ = val + VAL(src[3]);
			src += 4;
		}
		else if ( (src[0] == '\\') &&
					(src[1] == '\\') )
		{
			*rp++ = '\\';
			src += 2;
		}
		else
		{
			/*
			 * One backslash, not followed by ### valid octal.
			 * Should never get here, since esc_dec_len does same check.
			 */
			elog(ERROR, "decode: Bad input string for type bytea");
		}

		len++;
	}
	return len;
}

static unsigned
esc_enc_len(const uint8 *src, unsigned srclen)
{
	const uint8		*end = src + srclen;
	int				len = 0;

	while (src < end)
	{
		if (*src == '\0')
			len += 4;
		else if (*src == '\\')
			len += 2;
		else
			len++;

		src++;
	}

	/*
	 * Allow for null terminator
	 */
	len++;

	return len;
}

static unsigned
esc_dec_len(const uint8 *src, unsigned srclen)
{
	const uint8		*end = src + srclen;
	int				len = 0;

	while (src < end)
	{
		if (src[0] != '\\')
		{
			src++;
		}
		else if	( (src[0] == '\\') &&
					(src[1] >= '0' && src[1] <= '3') &&
					(src[2] >= '0' && src[2] <= '7') &&
					(src[3] >= '0' && src[3] <= '7') )
		{
			/*
			 * backslash + valid octal
			 */
			src += 4;
		}
		else if ( (src[0] == '\\') &&
					(src[1] == '\\') )
		{
			/*
			 * two backslashes = backslash
			 */
			src += 2;
		}
		else
		{
			/*
			 * one backslash, not followed by ### valid octal
			 */
			elog(ERROR, "decode: Bad input string for type bytea");
		}

		len++;
	}
	return len;
}

/*
 * Common
 */

static struct {
	const char *name;
	struct pg_encoding enc;
} enclist[] = {
	{"hex", { hex_enc_len, hex_dec_len, hex_encode, hex_decode }},
	{"base64", { b64_enc_len, b64_dec_len, b64_encode, b64_decode }},
	{"escape", { esc_enc_len, esc_dec_len, esc_encode, esc_decode }},
	{NULL, { NULL, NULL, NULL, NULL } }
};

static struct pg_encoding *
pg_find_encoding(const char *name)
{
	int i;

	for (i = 0; enclist[i].name; i++)
		if (!strcasecmp(enclist[i].name, name))
			return &enclist[i].enc;

	return NULL;
}
