/*
 * encoding.c : implements the encoding conversion functions needed for XML
 *
 * Related specs: 
 * rfc2044        (UTF-8 and UTF-16) F. Yergeau Alis Technologies
 * rfc2781        UTF-16, an encoding of ISO 10646, P. Hoffman, F. Yergeau
 * [ISO-10646]    UTF-8 and UTF-16 in Annexes
 * [ISO-8859-1]   ISO Latin-1 characters codes.
 * [UNICODE]      The Unicode Consortium, "The Unicode Standard --
 *                Worldwide Character Encoding -- Version 1.0", Addison-
 *                Wesley, Volume 1, 1991, Volume 2, 1992.  UTF-8 is
 *                described in Unicode Technical Report #4.
 * [US-ASCII]     Coded Character Set--7-bit American Standard Code for
 *                Information Interchange, ANSI X3.4-1986.
 *
 * See Copyright for the status of this software.
 *
 * daniel@veillard.com
 *
 * Original code for IsoLatin1 and UTF-16 by "Martin J. Duerst" <duerst@w3.org>
 */

#define IN_LIBXML
#include "libxml.h"

#include <string.h>

#ifdef HAVE_CTYPE_H
#include <ctype.h>
#endif
#ifdef HAVE_STDLIB_H
#include <stdlib.h>
#endif
#ifdef LIBXML_ICONV_ENABLED
#ifdef HAVE_ERRNO_H
#include <errno.h>
#endif
#endif
#include <libxml/encoding.h>
#include <libxml/xmlmemory.h>
#ifdef LIBXML_HTML_ENABLED
#include <libxml/HTMLparser.h>
#endif
#include <libxml/globals.h>
#include <libxml/xmlerror.h>

static xmlCharEncodingHandlerPtr xmlUTF16LEHandler = NULL;
static xmlCharEncodingHandlerPtr xmlUTF16BEHandler = NULL;

typedef struct _xmlCharEncodingAlias xmlCharEncodingAlias;
typedef xmlCharEncodingAlias *xmlCharEncodingAliasPtr;
struct _xmlCharEncodingAlias {
    const char *name;
    const char *alias;
};

static xmlCharEncodingAliasPtr xmlCharEncodingAliases = NULL;
static int xmlCharEncodingAliasesNb = 0;
static int xmlCharEncodingAliasesMax = 0;

#ifdef LIBXML_ICONV_ENABLED
#if 0
#define DEBUG_ENCODING  /* Define this to get encoding traces */
#endif
#else
#ifdef LIBXML_ISO8859X_ENABLED
static void xmlRegisterCharEncodingHandlersISO8859x (void);
#endif
#endif

static int xmlLittleEndian = 1;


/************************************************************************
 *									*
 *		Conversions To/From UTF8 encoding			*
 *									*
 ************************************************************************/

/**
 * asciiToUTF8:
 * @out:  a pointer to an array of bytes to store the result
 * @outlen:  the length of @out
 * @in:  a pointer to an array of ASCII chars
 * @inlen:  the length of @in
 *
 * Take a block of ASCII chars in and try to convert it to an UTF-8
 * block of chars out.
 * Returns 0 if success, or -1 otherwise
 * The value of @inlen after return is the number of octets consumed
 *     if the return value is positive, else unpredictable.
 * The value of @outlen after return is the number of octets consumed.
 */
static int
asciiToUTF8(unsigned char* out, int *outlen,
              const unsigned char* in, int *inlen) {
    unsigned char* outstart = out;
    const unsigned char* base = in;
    const unsigned char* processed = in;
    unsigned char* outend = out + *outlen;
    const unsigned char* inend;
    unsigned int c;
    int bits;

    inend = in + (*inlen);
    while ((in < inend) && (out - outstart + 5 < *outlen)) {
	c= *in++;

	/* assertion: c is a single UTF-4 value */
        if (out >= outend)
	    break;
        if      (c <    0x80) {  *out++=  c;                bits= -6; }
        else { 
	    *outlen = out - outstart;
	    *inlen = processed - base;
	    return(-1);
	}
 
        for ( ; bits >= 0; bits-= 6) {
            if (out >= outend)
	        break;
            *out++= ((c >> bits) & 0x3F) | 0x80;
        }
	processed = (const unsigned char*) in;
    }
    *outlen = out - outstart;
    *inlen = processed - base;
    return(*outlen);
}

#ifdef LIBXML_OUTPUT_ENABLED
/**
 * UTF8Toascii:
 * @out:  a pointer to an array of bytes to store the result
 * @outlen:  the length of @out
 * @in:  a pointer to an array of UTF-8 chars
 * @inlen:  the length of @in
 *
 * Take a block of UTF-8 chars in and try to convert it to an ASCII
 * block of chars out.
 *
 * Returns 0 if success, -2 if the transcoding fails, or -1 otherwise
 * The value of @inlen after return is the number of octets consumed
 *     if the return value is positive, else unpredictable.
 * The value of @outlen after return is the number of octets consumed.
 */
static int
UTF8Toascii(unsigned char* out, int *outlen,
              const unsigned char* in, int *inlen) {
    const unsigned char* processed = in;
    const unsigned char* outend;
    const unsigned char* outstart = out;
    const unsigned char* instart = in;
    const unsigned char* inend;
    unsigned int c, d;
    int trailing;

    if ((out == NULL) || (outlen == NULL) || (inlen == NULL)) return(-1);
    if (in == NULL) {
        /*
	 * initialization nothing to do
	 */
	*outlen = 0;
	*inlen = 0;
	return(0);
    }
    inend = in + (*inlen);
    outend = out + (*outlen);
    while (in < inend) {
	d = *in++;
	if      (d < 0x80)  { c= d; trailing= 0; }
	else if (d < 0xC0) {
	    /* trailing byte in leading position */
	    *outlen = out - outstart;
	    *inlen = processed - instart;
	    return(-2);
        } else if (d < 0xE0)  { c= d & 0x1F; trailing= 1; }
        else if (d < 0xF0)  { c= d & 0x0F; trailing= 2; }
        else if (d < 0xF8)  { c= d & 0x07; trailing= 3; }
	else {
	    /* no chance for this in Ascii */
	    *outlen = out - outstart;
	    *inlen = processed - instart;
	    return(-2);
	}

	if (inend - in < trailing) {
	    break;
	} 

	for ( ; trailing; trailing--) {
	    if ((in >= inend) || (((d= *in++) & 0xC0) != 0x80))
		break;
	    c <<= 6;
	    c |= d & 0x3F;
	}

	/* assertion: c is a single UTF-4 value */
	if (c < 0x80) {
	    if (out >= outend)
		break;
	    *out++ = c;
	} else {
	    /* no chance for this in Ascii */
	    *outlen = out - outstart;
	    *inlen = processed - instart;
	    return(-2);
	}
	processed = in;
    }
    *outlen = out - outstart;
    *inlen = processed - instart;
    return(*outlen);
}
#endif /* LIBXML_OUTPUT_ENABLED */

/**
 * isolat1ToUTF8:
 * @out:  a pointer to an array of bytes to store the result
 * @outlen:  the length of @out
 * @in:  a pointer to an array of ISO Latin 1 chars
 * @inlen:  the length of @in
 *
 * Take a block of ISO Latin 1 chars in and try to convert it to an UTF-8
 * block of chars out.
 * Returns the number of bytes written if success, or -1 otherwise
 * The value of @inlen after return is the number of octets consumed
 *     if the return value is positive, else unpredictable.
 * The value of @outlen after return is the number of octets consumed.
 */
int
isolat1ToUTF8(unsigned char* out, int *outlen,
              const unsigned char* in, int *inlen) {
    unsigned char* outstart = out;
    const unsigned char* base = in;
    unsigned char* outend;
    const unsigned char* inend;
    const unsigned char* instop;

    if ((out == NULL) || (in == NULL) || (outlen == NULL) || (inlen == NULL))
	return(-1);

    outend = out + *outlen;
    inend = in + (*inlen);
    instop = inend;
    
    while (in < inend && out < outend - 1) {
    	if (*in >= 0x80) {
	    *out++ = (((*in) >>  6) & 0x1F) | 0xC0;
        *out++ = ((*in) & 0x3F) | 0x80;
	    ++in;
	}
	if (instop - in > outend - out) instop = in + (outend - out); 
	while (in < instop && *in < 0x80) {
	    *out++ = *in++;
	}
    }	
    if (in < inend && out < outend && *in < 0x80) {
        *out++ = *in++;
    }
    *outlen = out - outstart;
    *inlen = in - base;
    return(*outlen);
}

/**
 * UTF8ToUTF8:
 * @out:  a pointer to an array of bytes to store the result
 * @outlen:  the length of @out
 * @inb:  a pointer to an array of UTF-8 chars
 * @inlenb:  the length of @in in UTF-8 chars
 *
 * No op copy operation for UTF8 handling.
 *
 * Returns the number of bytes written, or -1 if lack of space.
 *     The value of *inlen after return is the number of octets consumed
 *     if the return value is positive, else unpredictable.
 */
static int
UTF8ToUTF8(unsigned char* out, int *outlen,
           const unsigned char* inb, int *inlenb)
{
    int len;

    if ((out == NULL) || (inb == NULL) || (outlen == NULL) || (inlenb == NULL))
	return(-1);
    if (*outlen > *inlenb) {
	len = *inlenb;
    } else {
	len = *outlen;
    }
    if (len < 0)
	return(-1);

    memcpy(out, inb, len);

    *outlen = len;
    *inlenb = len;
    return(*outlen);
}


#ifdef LIBXML_OUTPUT_ENABLED
/**
 * UTF8Toisolat1:
 * @out:  a pointer to an array of bytes to store the result
 * @outlen:  the length of @out
 * @in:  a pointer to an array of UTF-8 chars
 * @inlen:  the length of @in
 *
 * Take a block of UTF-8 chars in and try to convert it to an ISO Latin 1
 * block of chars out.
 *
 * Returns the number of bytes written if success, -2 if the transcoding fails,
           or -1 otherwise
 * The value of @inlen after return is the number of octets consumed
 *     if the return value is positive, else unpredictable.
 * The value of @outlen after return is the number of octets consumed.
 */
int
UTF8Toisolat1(unsigned char* out, int *outlen,
              const unsigned char* in, int *inlen) {
    const unsigned char* processed = in;
    const unsigned char* outend;
    const unsigned char* outstart = out;
    const unsigned char* instart = in;
    const unsigned char* inend;
    unsigned int c, d;
    int trailing;

    if ((out == NULL) || (outlen == NULL) || (inlen == NULL)) return(-1);
    if (in == NULL) {
        /*
	 * initialization nothing to do
	 */
	*outlen = 0;
	*inlen = 0;
	return(0);
    }
    inend = in + (*inlen);
    outend = out + (*outlen);
    while (in < inend) {
	d = *in++;
	if      (d < 0x80)  { c= d; trailing= 0; }
	else if (d < 0xC0) {
	    /* trailing byte in leading position */
	    *outlen = out - outstart;
	    *inlen = processed - instart;
	    return(-2);
        } else if (d < 0xE0)  { c= d & 0x1F; trailing= 1; }
        else if (d < 0xF0)  { c= d & 0x0F; trailing= 2; }
        else if (d < 0xF8)  { c= d & 0x07; trailing= 3; }
	else {
	    /* no chance for this in IsoLat1 */
	    *outlen = out - outstart;
	    *inlen = processed - instart;
	    return(-2);
	}

	if (inend - in < trailing) {
	    break;
	} 

	for ( ; trailing; trailing--) {
	    if (in >= inend)
		break;
	    if (((d= *in++) & 0xC0) != 0x80) {
		*outlen = out - outstart;
		*inlen = processed - instart;
		return(-2);
	    }
	    c <<= 6;
	    c |= d & 0x3F;
	}

	/* assertion: c is a single UTF-4 value */
	if (c <= 0xFF) {
	    if (out >= outend)
		break;
	    *out++ = c;
	} else {
	    /* no chance for this in IsoLat1 */
	    *outlen = out - outstart;
	    *inlen = processed - instart;
	    return(-2);
	}
	processed = in;
    }
    *outlen = out - outstart;
    *inlen = processed - instart;
    return(*outlen);
}
#endif /* LIBXML_OUTPUT_ENABLED */

/**
 * UTF16LEToUTF8:
 * @out:  a pointer to an array of bytes to store the result
 * @outlen:  the length of @out
 * @inb:  a pointer to an array of UTF-16LE passwd as a byte array
 * @inlenb:  the length of @in in UTF-16LE chars
 *
 * Take a block of UTF-16LE ushorts in and try to convert it to an UTF-8
 * block of chars out. This function assumes the endian property
 * is the same between the native type of this machine and the
 * inputed one.
 *
 * Returns the number of bytes written, or -1 if lack of space, or -2
 *     if the transcoding fails (if *in is not a valid utf16 string)
 *     The value of *inlen after return is the number of octets consumed
 *     if the return value is positive, else unpredictable.
 */
static int
UTF16LEToUTF8(unsigned char* out, int *outlen,
            const unsigned char* inb, int *inlenb)
{
    unsigned char* outstart = out;
    const unsigned char* processed = inb;
    unsigned char* outend = out + *outlen;
    unsigned short* in = (unsigned short*) inb;
    unsigned short* inend;
    unsigned int c, d, inlen;
    unsigned char *tmp;
    int bits;

    if ((*inlenb % 2) == 1)
        (*inlenb)--;
    inlen = *inlenb / 2;
    inend = in + inlen;
    while ((in < inend) && (out - outstart + 5 < *outlen)) {
        if (xmlLittleEndian) {
	    c= *in++;
	} else {