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[elinks.git] / src / intl / charsets.c

/* Charsets convertor */

#ifndef _GNU_SOURCE
#define _GNU_SOURCE /* strcasecmp() */
#endif

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#if HAVE_LANGINFO_CODESET
#include <langinfo.h>
#endif

#include <ctype.h>
#include <stdlib.h>
#if HAVE_WCTYPE_H
#include <wctype.h>
#endif

#ifdef HAVE_ICONV
#include <errno.h>
#include <iconv.h>
#endif

#include "elinks.h"

#include "document/options.h"
#include "intl/charsets.h"
#include "util/conv.h"
#include "util/error.h"
#include "util/fastfind.h"
#include "util/hash.h"
#include "util/memory.h"
#include "util/string.h"


/* Fix namespace clash on MacOS. */
#define table table_elinks

struct table_entry {
        unsigned char c;
        /* This should in principle be unicode_val_T, but because all
         * the values currently in codepage.inc fit in 16 bits, we can
         * as well use uint16_t and halve sizeof(struct table_entry)
         * from 8 bytes to 4.  Should other characters ever be needed,
         * unicode_val_T u : 24 might be a possibility, although it
         * seems a little unportable as bitfields are in principle
         * restricted to int, which may be 16-bit.  */
        uint16_t u;
};

struct codepage_desc {
        unsigned char *name;
        unsigned char *const *aliases;

        /* The Unicode mappings of codepage bytes 0x80...0xFF.
         * (0x00...0x7F are assumed to be ASCII in all codepages.)
         * Because all current values fit in 16 bits, we store them as
         * uint16_t rather than unicode_val_T.  If the codepage does
         * not use some byte, then @highhalf maps that byte to 0xFFFF,
         * which C code converts to UCS_REPLACEMENT_CHARACTER where
         * appropriate.  (U+FFFF is reserved and will never be
         * assigned as a character.)  */
        const uint16_t *highhalf;

        /* If some byte in the codepage corresponds to multiple Unicode
         * characters, then the preferred character is in @highhalf
         * above, and the rest are listed here in @table.  This table
         * is not used for translating from the codepage to Unicode.  */
        const struct table_entry *table;

        /* Whether use iconv for translation */
        unsigned int iconv:1;
};

#include "intl/codepage.inc"
#include "intl/uni_7b.inc"
#include "intl/entity.inc"

/* Declare the external-linkage inline functions defined in this file.
 * Avoid the GCC 4.3.1 warning: `foo' declared inline after being
 * called.  The functions are not declared inline in charsets.h
 * because C99 6.7.4p6 says that every external-linkage function
 * declared inline shall be defined in the same translation unit.
 * The non-inline declarations in charsets.h also make sure that the
 * compiler emits global definitions for the symbols so that the
 * functions can be called from other translation units.  */
NONSTATIC_INLINE unsigned char *encode_utf8(unicode_val_T u);
NONSTATIC_INLINE int utf8charlen(const unsigned char *p);
NONSTATIC_INLINE int unicode_to_cell(unicode_val_T c);
NONSTATIC_INLINE unicode_val_T utf8_to_unicode(unsigned char **string,
                                               const unsigned char *end);

static const char strings[256][2] = {
        "\000", "\001", "\002", "\003", "\004", "\005", "\006", "\007",
        "\010", "\011", "\012", "\013", "\014", "\015", "\016", "\017",
        "\020", "\021", "\022", "\023", "\024", "\025", "\026", "\033",
        "\030", "\031", "\032", "\033", "\034", "\035", "\036", "\033",
        "\040", "\041", "\042", "\043", "\044", "\045", "\046", "\047",
        "\050", "\051", "\052", "\053", "\054", "\055", "\056", "\057",
        "\060", "\061", "\062", "\063", "\064", "\065", "\066", "\067",
        "\070", "\071", "\072", "\073", "\074", "\075", "\076", "\077",
        "\100", "\101", "\102", "\103", "\104", "\105", "\106", "\107",
        "\110", "\111", "\112", "\113", "\114", "\115", "\116", "\117",
        "\120", "\121", "\122", "\123", "\124", "\125", "\126", "\127",
        "\130", "\131", "\132", "\133", "\134", "\135", "\136", "\137",
        "\140", "\141", "\142", "\143", "\144", "\145", "\146", "\147",
        "\150", "\151", "\152", "\153", "\154", "\155", "\156", "\157",
        "\160", "\161", "\162", "\163", "\164", "\165", "\166", "\167",
        "\170", "\171", "\172", "\173", "\174", "\175", "\176", "\177",
        "\200", "\201", "\202", "\203", "\204", "\205", "\206", "\207",
        "\210", "\211", "\212", "\213", "\214", "\215", "\216", "\217",
        "\220", "\221", "\222", "\223", "\224", "\225", "\226", "\227",
        "\230", "\231", "\232", "\233", "\234", "\235", "\236", "\237",
        "\240", "\241", "\242", "\243", "\244", "\245", "\246", "\247",
        "\250", "\251", "\252", "\253", "\254", "\255", "\256", "\257",
        "\260", "\261", "\262", "\263", "\264", "\265", "\266", "\267",
        "\270", "\271", "\272", "\273", "\274", "\275", "\276", "\277",
        "\300", "\301", "\302", "\303", "\304", "\305", "\306", "\307",
        "\310", "\311", "\312", "\313", "\314", "\315", "\316", "\317",
        "\320", "\321", "\322", "\323", "\324", "\325", "\326", "\327",
        "\330", "\331", "\332", "\333", "\334", "\335", "\336", "\337",
        "\340", "\341", "\342", "\343", "\344", "\345", "\346", "\347",
        "\350", "\351", "\352", "\353", "\354", "\355", "\356", "\357",
        "\360", "\361", "\362", "\363", "\364", "\365", "\366", "\367",
        "\370", "\371", "\372", "\373", "\374", "\375", "\376", "\377",
};

#ifdef HAVE_ICONV
static iconv_t iconv_cd = (iconv_t)-1;
#endif

static void
free_translation_table(struct conv_table *p)
{
        int i;

        for (i = 0; i < 256; i++)
                if (p[i].t)
                        free_translation_table(p[i].u.tbl);

        mem_free(p);
}

/* A string used in conversion tables when there is no correct
 * conversion.  This is compared by address and therefore should be a
 * named array rather than a pointer so that it won't share storage
 * with any other string literal that happens to have the same
 * characters.  */
static const unsigned char no_str[] = "*";

static void
new_translation_table(struct conv_table *p)
{
        int i;

        for (i = 0; i < 256; i++)
                if (p[i].t)
                        free_translation_table(p[i].u.tbl);
        for (i = 0; i < 128; i++) {
                p[i].t = 0;
                p[i].u.str = strings[i];
        }
        for (; i < 256; i++) {
                p[i].t = 0;
                p[i].u.str = no_str;
        }
        p->iconv_cp = -1;
}

#define BIN_SEARCH(table, entry, entries, key, result)                                  \
{                                                                                       \
        long _s = 0, _e = (entries) - 1;                                                \
                                                                                        \
        while (_s <= _e || !((result) = -1)) {                                          \
                long _m = (_s + _e) / 2;                                                \
                                                                                        \
                if ((table)[_m].entry == (key)) {                                       \
                        (result) = _m;                                                  \
                        break;                                                          \
                }                                                                       \
                if ((table)[_m].entry > (key)) _e = _m - 1;                             \
                if ((table)[_m].entry < (key)) _s = _m + 1;                             \
        }                                                                               \
}                                                                                       \

static const unicode_val_T strange_chars[32] = {
0x20ac, 0x0000, 0x002a, 0x0000, 0x201e, 0x2026, 0x2020, 0x2021,
0x005e, 0x2030, 0x0160, 0x003c, 0x0152, 0x0000, 0x0000, 0x0000,
0x0000, 0x0060, 0x0027, 0x0022, 0x0022, 0x002a, 0x2013, 0x2014,
0x007e, 0x2122, 0x0161, 0x003e, 0x0153, 0x0000, 0x0000, 0x0000,
};

#define SYSTEM_CHARSET_FLAG 128
#define is_cp_ptr_utf8(cp_ptr) ((cp_ptr)->aliases == aliases_utf8)

const unsigned char *
u2cp_(unicode_val_T u, int to, enum nbsp_mode nbsp_mode)
{
        int j;
        int s;

        if (u < 128) return strings[u];

        if (u < 0xa0) {
                u = strange_chars[u - 0x80];
                if (!u) return NULL;
        }

        to &= ~SYSTEM_CHARSET_FLAG;

        if (is_cp_ptr_utf8(&codepages[to]))
                return encode_utf8(u);

        /* To mark non breaking spaces in non-UTF-8 strings, we use a
         * special char NBSP_CHAR. */
        if (u == UCS_NO_BREAK_SPACE) {
                if (nbsp_mode == NBSP_MODE_HACK) return NBSP_CHAR_STRING;
                else /* NBSP_MODE_ASCII */ return " ";
        }
        if (u == UCS_SOFT_HYPHEN) return "";

        if (u < 0xFFFF)
                for (j = 0; j < 0x80; j++)
                        if (codepages[to].highhalf[j] == u)
                                return strings[0x80 + j];
        for (j = 0; codepages[to].table[j].c; j++)
                if (codepages[to].table[j].u == u)
                        return strings[codepages[to].table[j].c];

        BIN_SEARCH(unicode_7b, x, N_UNICODE_7B, u, s);
        if (s != -1) return unicode_7b[s].s;

        return no_str;
}

static unsigned char utf_buffer[7];

NONSTATIC_INLINE unsigned char *
encode_utf8(unicode_val_T u)
{
        memset(utf_buffer, 0, 7);

        if (u < 0x80)
                utf_buffer[0] = u;
        else if (u < 0x800)
                utf_buffer[0] = 0xc0 | ((u >> 6) & 0x1f),
                utf_buffer[1] = 0x80 | (u & 0x3f);
        else if (u < 0x10000)
                utf_buffer[0] = 0xe0 | ((u >> 12) & 0x0f),
                utf_buffer[1] = 0x80 | ((u >> 6) & 0x3f),
                utf_buffer[2] = 0x80 | (u & 0x3f);
        else if (u < 0x200000)
                utf_buffer[0] = 0xf0 | ((u >> 18) & 0x0f),
                utf_buffer[1] = 0x80 | ((u >> 12) & 0x3f),
                utf_buffer[2] = 0x80 | ((u >> 6) & 0x3f),
                utf_buffer[3] = 0x80 | (u & 0x3f);
        else if (u < 0x4000000)
                utf_buffer[0] = 0xf8 | ((u >> 24) & 0x0f),
                utf_buffer[1] = 0x80 | ((u >> 18) & 0x3f),
                utf_buffer[2] = 0x80 | ((u >> 12) & 0x3f),
                utf_buffer[3] = 0x80 | ((u >> 6) & 0x3f),
                utf_buffer[4] = 0x80 | (u & 0x3f);
        else    utf_buffer[0] = 0xfc | ((u >> 30) & 0x01),
                utf_buffer[1] = 0x80 | ((u >> 24) & 0x3f),
                utf_buffer[2] = 0x80 | ((u >> 18) & 0x3f),
                utf_buffer[3] = 0x80 | ((u >> 12) & 0x3f),
                utf_buffer[4] = 0x80 | ((u >> 6) & 0x3f),
                utf_buffer[5] = 0x80 | (u & 0x3f);

        return utf_buffer;
}

/* Number of bytes utf8 character indexed by first byte. Illegal bytes are
 * equal ones and handled different. */
static const char utf8char_len_tab[256] = {
        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, 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,
        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, 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,
        2,2,2,2,2,2,2,2, 2,2,2,2,2,2,2,2, 2,2,2,2,2,2,2,2, 2,2,2,2,2,2,2,2,
        3,3,3,3,3,3,3,3, 3,3,3,3,3,3,3,3, 4,4,4,4,4,4,4,4, 5,5,5,5,6,6,1,1,
};

#ifdef CONFIG_UTF8
NONSTATIC_INLINE int
utf8charlen(const unsigned char *p)
{
        return p ? utf8char_len_tab[*p] : 0;
}

int
strlen_utf8(unsigned char **str)
{
        unsigned char *s = *str;
        unsigned char *end = strchr((const char *)s, '\0');
        int x;
        int len;

        for (x = 0;; x++, s += len) {
                len = utf8charlen(s);
                if (s + len > end) break;
        }
        *str = s;
        return x;
}

#define utf8_issingle(p) (((p) & 0x80) == 0)
#define utf8_islead(p) (utf8_issingle(p) || ((p) & 0xc0) == 0xc0)

/* Start from @current and move back to @pos char. This pointer return. The
 * most left pointer is @start. */
unsigned char *
utf8_prevchar(unsigned char *current, int pos, unsigned char *start)
{
        if (current == NULL || start == NULL || pos < 0)
                return NULL;
        while (pos > 0 && current != start) {
                current--;
                if (utf8_islead(*current))
                        pos--;
        }
        return current;
}

/* Count number of standard terminal cells needed for displaying UTF-8
 * character. */
int
utf8_char2cells(unsigned char *utf8_char, unsigned char *end)
{
        unicode_val_T u;

        if (end == NULL)
                end = strchr((const char *)utf8_char, '\0');

        if(!utf8_char || !end)
                return -1;

        u = utf8_to_unicode(&utf8_char, end);

        return unicode_to_cell(u);
}

/* Count number of standard terminal cells needed for displaying string
 * with UTF-8 characters. */
int
utf8_ptr2cells(unsigned char *string, unsigned char *end)
{
        int charlen, cell, cells = 0;

        if (end == NULL)
                end = strchr((const char *)string, '\0');

        if(!string || !end)
                return -1;

        do {
                charlen = utf8charlen(string);
                if (string + charlen > end)
                        break;

                cell = utf8_char2cells(string, end);
                if  (cell < 0)
                        return -1;

                cells += cell;
                string += charlen;
        } while (1);

        return cells;
}

/* Count number of characters in string. */
int
utf8_ptr2chars(unsigned char *string, unsigned char *end)
{
        int charlen, chars = 0;

        if (end == NULL)
                end = strchr((const char *)string, '\0');

        if(!string || !end)
                return -1;

        do {
                charlen = utf8charlen(string);
                if (string + charlen > end)
                        break;

                chars++;
                string += charlen;
        } while (1);

        return chars;
}

/*
 * Count number of bytes from begining of the string needed for displaying
 * specified number of cells.
 */
int
utf8_cells2bytes(unsigned char *string, int max_cells, unsigned char *end)
{
        unsigned int bytes = 0, cells = 0;

        assert(max_cells>=0);

        if (end == NULL)
                end = strchr((const char *)string, '\0');

        if(!string || !end)
                return -1;

        do {
                int cell = utf8_char2cells(&string[bytes], end);
                if (cell < 0)
                        return -1;

                cells += cell;
                if (cells > max_cells)
                        break;

                bytes += utf8charlen(&string[bytes]);

                if (string + bytes > end) {
                        bytes = end - string;
                        break;
                }
        } while(1);

        return bytes;
}

/* Take @max steps forward from @string in the specified @way, but
 * not going past @end.  Return the resulting address.  Store the
 * number of steps taken to *@count, unless @count is NULL.
 *
 * This assumes the text is valid UTF-8, and @string and @end point to
 * character boundaries.  If not, it doesn't crash but the results may
 * be inconsistent.
 *
 * This function can do some of the same jobs as utf8charlen(),
 * utf8_cells2bytes(), and strlen_utf8().  */
unsigned char *
utf8_step_forward(unsigned char *string, unsigned char *end,
                  int max, enum utf8_step way, int *count)
{
        int steps = 0;
        unsigned char *current = string;

        assert(string);
        assert(max >= 0);
        if_assert_failed goto invalid_arg;
        if (end == NULL)
                end = strchr((const char *)string, '\0');

        switch (way) {
        case UTF8_STEP_CHARACTERS:
                while (steps < max && current < end) {
                        ++current;
                        if (utf8_islead(*current))
                                ++steps;
                }
                break;

        case UTF8_STEP_CELLS_FEWER:
        case UTF8_STEP_CELLS_MORE:
                while (steps < max && current < end) {
                        unicode_val_T u;
                        unsigned char *prev = current;
                        int width;

                        u = utf8_to_unicode(&current, end);
                        if (u == UCS_NO_CHAR) {
                                /* Assume the incomplete sequence
                                 * costs one cell.  */
                                current = end;
                                ++steps;
                                break;
                        }

                        width = unicode_to_cell(u);
                        if (way == UTF8_STEP_CELLS_FEWER
                            && steps + width > max) {
                                /* Back off.  */
                                current = prev;
                                break;
                        }
                        steps += width;
                }
                break;

        default:
                INTERNAL("impossible enum utf8_step");
        }

invalid_arg:
        if (count)
                *count = steps;
        return current;
}

/* Take @max steps backward from @string in the specified @way, but
 * not going past @start.  Return the resulting address.  Store the
 * number of steps taken to *@count, unless @count is NULL.
 *
 * This assumes the text is valid UTF-8, and @string and @start point
 * to character boundaries.  If not, it doesn't crash but the results
 * may be inconsistent.
 *
 * This function can do some of the same jobs as utf8_prevchar().  */
unsigned char *
utf8_step_backward(unsigned char *string, unsigned char *start,
                   int max, enum utf8_step way, int *count)
{
        int steps = 0;
        unsigned char *current = string;

        assert(string);
        assert(start);
        assert(max >= 0);
        if_assert_failed goto invalid_arg;

        switch (way) {
        case UTF8_STEP_CHARACTERS:
                while (steps < max && current > start) {
                        --current;
                        if (utf8_islead(*current))
                                ++steps;
                }
                break;

        case UTF8_STEP_CELLS_FEWER:
        case UTF8_STEP_CELLS_MORE:
                while (steps < max) {
                        unsigned char *prev = current;
                        unsigned char *look;
                        unicode_val_T u;
                        int width;

                        if (current <= start)
                                break;
                        do {
                                --current;
                        } while (current > start && !utf8_islead(*current));

                        look = current;
                        u = utf8_to_unicode(&look, prev);
                        if (u == UCS_NO_CHAR) {
                                /* Assume the incomplete sequence
                                 * costs one cell.  */
                                width = 1;
                        } else
                                width = unicode_to_cell(u);

                        if (way == UTF8_STEP_CELLS_FEWER
                            && steps + width > max) {
                                /* Back off.  */
                                current = prev;
                                break;
                        }
                        steps += width;
                }
                break;

        default:
                INTERNAL("impossible enum utf8_step");
        }

invalid_arg:
        if (count)
                *count = steps;
        return current;
}

/*
 * Find out number of standard terminal collumns needed for displaying symbol
 * (glyph) which represents Unicode character c.
 *
 * TODO: Use wcwidth when it is available. This seems to require:
 * - Make the configure script check whether <wchar.h> and wcwidth exist.
 * - Define _XOPEN_SOURCE and include <wchar.h>.
 * - Test that __STDC_ISO_10646__ is defined.  (This macro means wchar_t
 *   matches ISO 10646 in all locales.)
 * However, these do not suffice, because wcwidth depends on LC_CTYPE
 * in glibc-2.3.6.  For instance, wcwidth(0xff20) is -1 when LC_CTYPE
 * is "fi_FI.ISO-8859-1" or "C", but 2 when LC_CTYPE is "fi_FI.UTF-8".
 * <features.h> defines __STDC_ISO_10646__ as 200009L, so 0xff20 means
 * U+FF20 FULLWIDTH COMMERCIAL AT regardless of LC_CTYPE; but this
 * character is apparently not supported in all locales.  Why is that?
 * - Perhaps there is standardese that requires supported characters
 *   to be convertable to multibyte form.  Then ELinks could just pick
 *   some UTF-8 locale for its wcwidth purposes.
 * - Perhaps wcwidth can even return different nonnegative values for
 *   the same ISO 10646 character in different locales.  Then ELinks
 *   would have to set LC_CTYPE to match at least the terminal's
 *   charset (which may differ from the LC_CTYPE environment variable,
 *   especially when the master process is serving a slave terminal).
 *   But there is no guarantee that the libc supports all the same
 *   charsets as ELinks does.
 * For now, it seems safest to avoid the potentially locale-dependent
 * libc version of wcwidth, and instead use a hardcoded mapping.
 *
 * @return      2 for double-width glyph, 1 for others.
 *              0 for unprintable glyphs (like 0x200e: "LEFT-TO-RIGHT MARK")
 */
NONSTATIC_INLINE int
unicode_to_cell(unicode_val_T c)
{
        if (c == 0x200e || c == 0x200f)
                return 0;
        if (c >= 0x1100
                && (c <= 0x115f                 /* Hangul Jamo */
                || c == 0x2329
                || c == 0x232a
                || (c >= 0x2e80 && c <= 0xa4cf
                        && c != 0x303f)         /* CJK ... Yi */
                || (c >= 0xac00 && c <= 0xd7a3) /* Hangul Syllables */
                || (c >= 0xf900 && c <= 0xfaff) /* CJK Compatibility
                                                                Ideographs */
                || (c >= 0xfe30 && c <= 0xfe6f) /* CJK Compatibility Forms */
                || (c >= 0xff00 && c <= 0xff60) /* Fullwidth Forms */
                || (c >= 0xffe0 && c <= 0xffe6)
                || (c >= 0x20000 && c <= 0x2fffd)
                || (c >= 0x30000 && c <= 0x3fffd)))
                return 2;

        return 1;
}

/* Fold the case of a Unicode character, so that hotkeys in labels can
 * be compared case-insensitively.  It is unspecified whether the
 * result will be in upper or lower case.  */
unicode_val_T
unicode_fold_label_case(unicode_val_T c)
{
#if __STDC_ISO_10646__ && HAVE_WCTYPE_H
        return towlower(c);
#else  /* !(__STDC_ISO_10646__ && HAVE_WCTYPE_H) */
        /* For now, this supports only ASCII.  It would be possible to
         * use code generated from CaseFolding.txt of Unicode if the
         * acknowledgements required by http://www.unicode.org/copyright.html
         * were added to associated documentation of ELinks.  */
        if (c >= 0x41 && c <= 0x5A)
                return c + 0x20;
        else
                return c;
#endif /* !(__STDC_ISO_10646__ && HAVE_WCTYPE_H) */
}
#endif /* CONFIG_UTF8 */

NONSTATIC_INLINE unicode_val_T
utf8_to_unicode(unsigned char **string, const unsigned char *end)
{
        unsigned char *str = *string;
        unicode_val_T u;
        int length;

        length = utf8char_len_tab[str[0]];

        if (str + length > end) {
                return UCS_NO_CHAR;
        }

        switch (length) {
                case 1:         /* U+0000 to U+007F */
                        if (str[0] >= 0x80) {
invalid_utf8:
                                ++*string;
                                return UCS_REPLACEMENT_CHARACTER;
                        }
                        u = str[0];
                        break;
                case 2:         /* U+0080 to U+07FF */
                        if ((str[1] & 0xc0) != 0x80)
                                goto invalid_utf8;
                        u = (str[0] & 0x1f) << 6;
                        u += (str[1] & 0x3f);
                        if (u < 0x80)
                                goto invalid_utf8;
                        break;
                case 3:         /* U+0800 to U+FFFF, except surrogates */
                        if ((str[1] & 0xc0) != 0x80 || (str[2] & 0xc0) != 0x80)
                                goto invalid_utf8;
                        u = (str[0] & 0x0f) << 12;
                        u += ((str[1] & 0x3f) << 6);
                        u += (str[2] & 0x3f);
                        if (u < 0x800 || is_utf16_surrogate(u))
                                goto invalid_utf8;
                        break;
                case 4:         /* U+10000 to U+1FFFFF */
                        if ((str[1] & 0xc0) != 0x80 || (str[2] & 0xc0) != 0x80
                            || (str[3] & 0xc0) != 0x80)
                                goto invalid_utf8;
                        u = (str[0] & 0x0f) << 18;
                        u += ((str[1] & 0x3f) << 12);
                        u += ((str[2] & 0x3f) << 6);
                        u += (str[3] & 0x3f);
                        if (u < 0x10000)
                                goto invalid_utf8;
                        break;
                case 5:         /* U+200000 to U+3FFFFFF */
                        if ((str[1] & 0xc0) != 0x80 || (str[2] & 0xc0) != 0x80
                            || (str[3] & 0xc0) != 0x80 || (str[4] & 0xc0) != 0x80)
                                goto invalid_utf8;
                        u = (str[0] & 0x0f) << 24;
                        u += ((str[1] & 0x3f) << 18);
                        u += ((str[2] & 0x3f) << 12);
                        u += ((str[3] & 0x3f) << 6);
                        u += (str[4] & 0x3f);
                        if (u < 0x200000)
                                goto invalid_utf8;
                        break;
                case 6:         /* U+4000000 to U+7FFFFFFF */
                        if ((str[1] & 0xc0) != 0x80 || (str[2] & 0xc0) != 0x80
                            || (str[3] & 0xc0) != 0x80 || (str[4] & 0xc0) != 0x80
                            || (str[5] & 0xc0) != 0x80)
                                goto invalid_utf8;
                        u = (str[0] & 0x01) << 30;
                        u += ((str[1] & 0x3f) << 24);
                        u += ((str[2] & 0x3f) << 18);
                        u += ((str[3] & 0x3f) << 12);
                        u += ((str[4] & 0x3f) << 6);
                        u += (str[5] & 0x3f);
                        if (u < 0x4000000)
                                goto invalid_utf8;
                        break;
                default:
                        INTERNAL("utf8char_len_tab out of range");
                        goto invalid_utf8;
        }
        *string = str + length;
        return u;
}

/* The common part of cp2u and cp2utf_8.  */
static unicode_val_T
cp2u_shared(const struct codepage_desc *from, unsigned char c)
{
        unicode_val_T u = from->highhalf[c - 0x80];

        if (u == 0xFFFF) u = UCS_REPLACEMENT_CHARACTER;
        return u;
}

/* Used for converting input from the terminal.  */
unicode_val_T
cp2u(int from, unsigned char c)
{
        from &= ~SYSTEM_CHARSET_FLAG;

        /* UTF-8 is a multibyte codepage and cannot be handled with
         * this function.  */
        assert(!is_cp_ptr_utf8(&codepages[from]));
        if_assert_failed return UCS_REPLACEMENT_CHARACTER;

        if (c < 0x80) return c;
        else return cp2u_shared(&codepages[from], c);
}

/* This slow and ugly code is used by the terminal utf_8_io */
const unsigned char *
cp2utf8(int from, int c)
{
        from &= ~SYSTEM_CHARSET_FLAG;

        if (is_cp_ptr_utf8(&codepages[from]) || c < 128)
                return strings[c];

        return encode_utf8(cp2u_shared(&codepages[from], c));
}

unicode_val_T
cp_to_unicode(int codepage, unsigned char **string, const unsigned char *end)
{
        unicode_val_T ret;

        if (is_cp_utf8(codepage))
                return utf8_to_unicode(string, end);

        if (*string >= end)
                return UCS_NO_CHAR;

        ret = cp2u(codepage, **string);
        ++*string;
        return ret;
}


#ifdef CONFIG_COMBINE
unicode_val_T last_combined = UCS_BEGIN_COMBINED - 1;
unicode_val_T **combined;
struct hash *combined_hash;

unicode_val_T
get_combined(unicode_val_T *data, int length)
{
        struct hash_item *item;
        unicode_val_T *key;
        int i, indeks;

        assert(length >= 1 && length <= UCS_MAX_LENGTH_COMBINED);
        if_assert_failed return UCS_NO_CHAR;

        if (!combined_hash) combined_hash = init_hash8();
        if (!combined_hash) return UCS_NO_CHAR;
        item = get_hash_item(combined_hash, (unsigned char *)data, length * sizeof(*data));

        if (item) return (unicode_val_T)(long)item->value;
        if (last_combined >= UCS_END_COMBINED) return UCS_NO_CHAR;

        key = mem_alloc((length + 1) * sizeof(*key));
        if (!key) return UCS_NO_CHAR;
        for (i = 0; i < length; i++)
                key[i] = data[i];
        key[i] = UCS_END_COMBINED;

        last_combined++;
        indeks = last_combined - UCS_BEGIN_COMBINED;

        combined = mem_realloc(combined, sizeof(*combined) * (indeks + 1));
        if (!combined) {
                mem_free(key);
                last_combined--;
                return UCS_NO_CHAR;
        }
        combined[indeks] = key;
        item = add_hash_item(combined_hash, (unsigned char *)key,
                             length * sizeof(*data), (void *)(long)(last_combined));
        if (!item) {
                last_combined--;
                mem_free(key);
                return UCS_NO_CHAR;
        }
        return last_combined;
}

void
free_combined()
{
        int i, end = last_combined - UCS_BEGIN_COMBINED + 1; 

        if (combined_hash)
                free_hash(&combined_hash);
        for (i = 0; i < end; i++)
                mem_free(combined[i]);
        mem_free_if(combined);
}
#endif /* CONFIG_COMBINE */


static void
add_utf8(struct conv_table *ct, unicode_val_T u, const unsigned char *str)
{
        unsigned char *p = encode_utf8(u);

        while (p[1]) {
                if (ct[*p].t) ct = ct[*p].u.tbl;
                else {
                        struct conv_table *nct;

                        assertm(ct[*p].u.str == no_str, "bad utf encoding #1");
                        if_assert_failed return;

                        nct = mem_calloc(256, sizeof(*nct));
                        if (!nct) return;
                        new_translation_table(nct);
                        ct[*p].t = 1;
                        ct[*p].u.tbl = nct;
                        ct = nct;
                }
                p++;
        }

        assertm(!ct[*p].t, "bad utf encoding #2");
        if_assert_failed return;

        if (ct[*p].u.str == no_str)
                ct[*p].u.str = str;
}

/* A conversion table from some charset to UTF-8.
 * If it is from UTF-8 to UTF-8, it converts each byte separately.
 * Unlike in other translation tables, the strings in elements 0x80 to
 * 0xFF are allocated dynamically.  */
struct conv_table utf_table[256];
int utf_table_init = 1;

static void
free_utf_table(void)
{
        int i;

        /* Cast away const.  */
        for (i = 128; i < 256; i++)
                mem_free((unsigned char *) utf_table[i].u.str);
}

static struct conv_table *
get_translation_table_to_utf8(int from)
{
        int i;
        static int lfr = -1;

        if (from == -1) return NULL;
        from &= ~SYSTEM_CHARSET_FLAG;
        if (from == lfr) return utf_table;
        lfr = from;
        if (utf_table_init) {
                memset(utf_table, 0, sizeof(utf_table));
                utf_table_init = 0;
        } else
                free_utf_table();

        for (i = 0; i < 128; i++)
                utf_table[i].u.str = strings[i];

        if (is_cp_ptr_utf8(&codepages[from])) {
                for (i = 128; i < 256; i++)
                        utf_table[i].u.str = stracpy(strings[i]);
                return utf_table;
        }

        for (i = 128; i < 256; i++) {
                unicode_val_T u = codepages[from].highhalf[i - 0x80];

                if (u == 0xFFFF)
                        utf_table[i].u.str = NULL;
                else
                        utf_table[i].u.str = stracpy(encode_utf8(u));
        }

        for (i = 0; codepages[from].table[i].c; i++) {
                unicode_val_T u = codepages[from].table[i].u;

                if (!utf_table[codepages[from].table[i].c].u.str)
                        utf_table[codepages[from].table[i].c].u.str =
                                stracpy(encode_utf8(u));
        }

        for (i = 128; i < 256; i++)
                if (!utf_table[i].u.str)
                        utf_table[i].u.str = stracpy(no_str);

        return utf_table;
}

/* A conversion table between two charsets, where the target is not UTF-8.  */
static struct conv_table table[256];
static int first = 1;

void
free_conv_table(void)
{
        if (!utf_table_init) free_utf_table();
        if (first) {
                memset(table, 0, sizeof(table));
                first = 0;
        }
        new_translation_table(table);
#ifdef HAVE_ICONV
        if (iconv_cd != (iconv_t)-1) {
                iconv_close(iconv_cd);
                iconv_cd = (iconv_t)-1;
        }
#endif
}


struct conv_table *
get_translation_table(int from, int to)
{
        static int lfr = -1;
        static int lto = -1;

        from &= ~SYSTEM_CHARSET_FLAG;
        to &= ~SYSTEM_CHARSET_FLAG;
        if (first) {
                memset(table, 0, sizeof(table));
                first = 0;
        }

        if (codepages[from].iconv) {
                struct conv_table *table2 = get_translation_table_to_utf8(34);

                if (table2) table2->iconv_cp = from;
                return table2;
        }

        if (/*from == to ||*/ from == -1 || to == -1)
                return NULL;
        if (is_cp_ptr_utf8(&codepages[to])) {
                struct conv_table *table2 = get_translation_table_to_utf8(from);

                if (table2) table2->iconv_cp = -1;
                return table2;
        }
        if (from == lfr && to == lto)
                return table;
        lfr = from;
        lto = to;
        new_translation_table(table);

        if (is_cp_ptr_utf8(&codepages[from])) {
                int i;

                /* Map U+00A0 and U+00AD the same way as u2cp() would.  */
                add_utf8(table, UCS_NO_BREAK_SPACE, strings[NBSP_CHAR]);
                add_utf8(table, UCS_SOFT_HYPHEN, "");

                for (i = 0x80; i <= 0xFF; i++)
                        if (codepages[to].highhalf[i - 0x80] != 0xFFFF)
                                add_utf8(table,
                                         codepages[to].highhalf[i - 0x80],
                                         strings[i]);

                for (i = 0; codepages[to].table[i].c; i++)
                        add_utf8(table, codepages[to].table[i].u,
                                 strings[codepages[to].table[i].c]);

                for (i = 0; unicode_7b[i].x != -1; i++)
                        if (unicode_7b[i].x >= 0x80)
                                add_utf8(table, unicode_7b[i].x,
                                         unicode_7b[i].s);

        } else {
                int i;

                for (i = 128; i < 256; i++) {
                        if (codepages[from].highhalf[i - 0x80] != 0xFFFF) {
                                const unsigned char *u;

                                u = u2cp(codepages[from].highhalf[i - 0x80], to);
                                if (u) table[i].u.str = u;
                        }
                }
        }

        return table;
}

static inline int
xxstrcmp(unsigned char *s1, unsigned char *s2, int l2)
{
        while (l2) {
                if (*s1 > *s2) return 1;
                if (*s1 < *s2) return -1;
                s1++;
                s2++;
                l2--;
        }

        return *s2 ? -1 : 0;
}

/* Entity cache debugging purpose. */
#if 0
#define DEBUG_ENTITY_CACHE
#else
#undef DEBUG_ENTITY_CACHE
#endif

struct entity_cache {
        unsigned int hits;
        int strlen;
        int encoding;
        const unsigned char *result;
        unsigned char str[20]; /* Suffice in any case. */
};

/* comparison function for qsort() */
static int
hits_cmp(const void *v1, const void *v2)
{
        const struct entity_cache *a = v1, *b = v2;

        if (a->hits == b->hits) return 0;
        if (a->hits > b->hits) return -1;
        else return 1;
}

static int
compare_entities(const void *key_, const void *element_)
{
        struct string *key = (struct string *) key_;
        struct entity *element = (struct entity *) element_;
        int length = key->length;
        unsigned char *first = key->source;
        unsigned char *second = element->s;

        return xxstrcmp(first, second, length);
}

const unsigned char *
get_entity_string(const unsigned char *str, const int strlen, int encoding)
{
#define ENTITY_CACHE_SIZE 10    /* 10 seems a good value. */
#define ENTITY_CACHE_MAXLEN 9   /* entities with length >= ENTITY_CACHE_MAXLEN or == 1
                                   will go in [0] table */
        static struct entity_cache entity_cache[ENTITY_CACHE_MAXLEN][ENTITY_CACHE_SIZE];
        static unsigned int nb_entity_cache[ENTITY_CACHE_MAXLEN];
        unsigned int slen = 0;
        const unsigned char *result = NULL;

        /* Note that an object of static storage duration is automatically
         * initialised to zero in C.  */

        if (strlen <= 0) return NULL;

#ifdef CONFIG_UTF8
        /* TODO: caching UTF-8 */
        encoding &= ~SYSTEM_CHARSET_FLAG;
        if (is_cp_ptr_utf8(&codepages[encoding]))
                goto skip;
#endif /* CONFIG_UTF8 */

        /* Check if cached. A test on many websites (freshmeat.net + whole ELinks website
         * + google + slashdot + websites that result from a search for test on google,
         * + various ones) show quite impressive improvment:
         * Top ten is:
         * 0: hits=2459 l=4 st='nbsp'
         * 1: hits=2152 l=6 st='eacute'
         * 2: hits=235 l=6 st='egrave'
         * 3: hits=136 l=6 st='agrave'
         * 4: hits=100 l=3 st='amp'
         * 5: hits=40 l=5 st='laquo'
         * 6: hits=8 l=4 st='copy'
         * 7: hits=5 l=2 st='gt'
         * 8: hits=2 l=2 st='lt'
         * 9: hits=1 l=6 st='middot'
         *
         * Most of the time cache hit ratio is near 95%.
         *
         * A long test shows: 15186 hits vs. 24 misses and mean iteration
         * count is kept < 2 (worst case 1.58). Not so bad ;)
         *
         * --Zas */

        /* entities with length >= ENTITY_CACHE_MAXLEN or == 1 will go in [0] table */
        slen = (strlen > 1 && strlen < ENTITY_CACHE_MAXLEN) ? strlen : 0;

        if (strlen < ENTITY_CACHE_MAXLEN && nb_entity_cache[slen] > 0) {
                int i;

                for (i = 0; i < nb_entity_cache[slen]; i++) {
                        if (entity_cache[slen][i].encoding == encoding
                            && !memcmp(str, entity_cache[slen][i].str, strlen)) {
#ifdef DEBUG_ENTITY_CACHE
                                static double total_iter = 0;
                                static unsigned long hit_count = 0;

                                total_iter += i + 1;
                                hit_count++;
                                fprintf(stderr, "hit after %d iter. (mean = %0.2f)\n", i + 1, total_iter / (double) hit_count);
#endif
                                if (entity_cache[slen][i].hits < (unsigned int) ~0)
                                        entity_cache[slen][i].hits++;
                                return entity_cache[slen][i].result;
                        }
                }
#ifdef DEBUG_ENTITY_CACHE
                fprintf(stderr, "miss\n");
#endif
        }
#ifdef CONFIG_UTF8
skip:
#endif /* CONFIG_UTF8 */
        if (*str == '#') { /* Numeric entity. */
                int l = (int) strlen;
                unsigned char *st = (unsigned char *) str;
                unicode_val_T n = 0;

                if (l == 1) goto end; /* &#; ? */
                st++, l--;
                if ((*st | 32) == 'x') { /* Hexadecimal */

                        if (l == 1 || l > 9) goto end; /* xFFFFFFFF max. */
                        st++, l--;
                        do {
                                unsigned char c = (*(st++) | 32);

                                if (isdigit(c))
                                        n = (n << 4) | (c - '0');
                                else if (isxdigit(c))
                                        n = (n << 4) | (c - 'a' + 10);
                                else
                                        goto end; /* Bad char. */
                        } while (--l);
                } else { /* Decimal */
                        if (l > 10) goto end; /* 4294967295 max. */
                        do {
                                unsigned char c = *(st++);

                                if (isdigit(c))
                                        n = n * 10 + c - '0';
                                else
                                        goto end; /* Bad char. */
                                /* Limit to 0xFFFFFFFF. */
                                if (n >= (unicode_val_T) 0xFFFFFFFFu)
                                        goto end;
                        } while (--l);
                }

                result = u2cp(n, encoding);

#ifdef DEBUG_ENTITY_CACHE
                fprintf(stderr, "%lu %016x %s\n", (unsigned long) n , n, result);
#endif
        } else { /* Text entity. */
                struct string key = INIT_STRING((unsigned char *) str, strlen);
                struct entity *element = bsearch((void *) &key, entities,
                                                 N_ENTITIES,
                                                 sizeof(*element),
                                                 compare_entities);

                if (element) result = u2cp(element->c, encoding);
        }

#ifdef CONFIG_UTF8
        if (is_cp_ptr_utf8(&codepages[encoding])) {
                return result;
        }
#endif /* CONFIG_UTF8 */
end:
        /* Take care of potential buffer overflow. */
        if (strlen < sizeof(entity_cache[slen][0].str)) {
                struct entity_cache *ece;

                /* Sort entries by hit order. */
                if (nb_entity_cache[slen] > 1)
                        qsort(&entity_cache[slen][0], nb_entity_cache[slen],
                              sizeof(entity_cache[slen][0]), hits_cmp);

                /* Increment number of cache entries if possible.
                 * Else, just replace the least used entry.  */
                if (nb_entity_cache[slen] < ENTITY_CACHE_SIZE) nb_entity_cache[slen]++;
                ece = &entity_cache[slen][nb_entity_cache[slen] - 1];

                /* Copy new entry to cache. */
                ece->hits = 1;
                ece->strlen = strlen;
                ece->encoding = encoding;
                ece->result = result;
                memcpy(ece->str, str, strlen);
                ece->str[strlen] = '\0';


#ifdef DEBUG_ENTITY_CACHE
                fprintf(stderr, "Added in [%u]: l=%d st='%s'\n", slen,
                                entity_cache[slen][0].strlen, entity_cache[slen][0].str);

        {
                unsigned int i;

                fprintf(stderr, "- Cache entries [%u] -\n", slen);
                for (i = 0; i < nb_entity_cache[slen] ; i++)
                        fprintf(stderr, "%d: hits=%u l=%d st='%s'\n", i,
                                entity_cache[slen][i].hits, entity_cache[slen][i].strlen,
                                entity_cache[slen][i].str);
                fprintf(stderr, "-----------------\n");
        }
#endif  /* DEBUG_ENTITY_CACHE */
        }
        return result;
}

unsigned char *
convert_string(struct conv_table *convert_table,
               unsigned char *chars2, int charslen2, int cp,
               enum convert_string_mode mode, int *length,
               void (*callback)(void *data, unsigned char *buf, int buflen),
               void *callback_data)
{
        unsigned char *buffer;
        int bufferpos = 0;
        int charspos = 0;
        unsigned char *chars = chars2;
        int charslen = charslen2;

#ifdef HAVE_ICONV
        static char iconv_input[256];
        static char iconv_output[256 * 8];
        static size_t iconv_offset;
        static int iconv_cp;
        static size_t iconv_inleft;
        size_t iconv_outleft = 256 * 8;
        int loop = 0;
        int is_iconv = 0;
        int chars_offset = 0;

        if (!convert_table && !memchr(chars, '&', charslen)) {
                if (callback) {
                        if (charslen) callback(callback_data, chars, charslen);
                        return NULL;
                } else {
                        return memacpy(chars, charslen);
                }
        }

        if (cp >= 0) {
                if (convert_table && convert_table->iconv_cp > 0) {
                        is_iconv = 1;
                        cp = convert_table->iconv_cp;
                } else {
                        is_iconv = codepages[cp & ~SYSTEM_CHARSET_FLAG].iconv;
                }
        }
#endif

        /* Buffer allocation */

        buffer = mem_alloc(ALLOC_GR + 1 /* trailing \0 */);
        if (!buffer) return NULL;

#ifdef HAVE_ICONV
        if (is_iconv) {
                int v;
                size_t before, to_copy;
                char *outp, *inp;

                if (iconv_cd >= 0) {
                        if (cp != iconv_cp) {
                                iconv_close(iconv_cd);
                                iconv_cd = (iconv_t)-1;
                        }
                }
                if (iconv_cd == (iconv_t)-1) {
                        iconv_offset = 0;
                        iconv_cd = iconv_open("utf-8", get_cp_mime_name(cp));
                        if (iconv_cd == (iconv_t)-1) {
                                mem_free(buffer);
                                return NULL;
                        }
                        iconv_cp = cp;
                }
repeat:
                to_copy = charslen2 - chars_offset;
                if (to_copy > 256 - iconv_offset) to_copy = 256 - iconv_offset;
                memcpy(iconv_input + iconv_offset, chars2 + chars_offset, to_copy);
                iconv_outleft = 256 * 8;
                iconv_inleft = iconv_offset + to_copy;
                inp = iconv_input;
                outp = iconv_output;
                before = iconv_inleft;

                v = iconv(iconv_cd, &inp, &iconv_inleft, &outp, &iconv_outleft);
                chars_offset += before - iconv_inleft;
                charslen = 256 * 8 - iconv_outleft;

                chars = (unsigned char *)iconv_output;
                charspos = 0;

                if (v == -1) {
                        switch (errno) {
                        case EINVAL:
                                memcpy(iconv_input, inp, iconv_inleft);
                                iconv_offset = iconv_inleft;
                                break;
                        case EILSEQ:
                                loop = 0;
                                goto out;
                                break;
                        default:
                                iconv_offset = 0;
                        }
                } else {
                        iconv_offset = 0;
                }
                
                loop = chars_offset < charslen2;
        }
#endif
        /* Iterate ;-) */

out:
        while (charspos < charslen) {
                const unsigned char *translit;

#define PUTC do { \
                buffer[bufferpos++] = chars[charspos++]; \
                translit = ""; \
                goto flush; \
        } while (0)

                if (chars[charspos] != '&') {
                        struct conv_table *t;
                        int i;

                        if (chars[charspos] < 128 || !convert_table) PUTC;

                        t = convert_table;
                        i = charspos;

                        while (t[chars[i]].t) {
                                t = t[chars[i++]].u.tbl;
                                if (i >= charslen) PUTC;
                        }

                        translit = t[chars[i]].u.str;
                        charspos = i + 1;

                } else if (mode == CSM_FORM || mode == CSM_NONE) {
                        PUTC;

                } else {
                        int start = charspos + 1;
                        int i = start;

                        while (i < charslen
                               && (isasciialpha(chars[i])
                                   || isdigit(chars[i])
                                   || (chars[i] == '#')))
                                i++;

                        /* This prevents bug 213: we were expanding "entities"
                         * in URL query strings. */
                        /* XXX: But this disables &nbsp&nbsp usage, which
                         * appears to be relatively common! --pasky */
                        if ((mode == CSM_DEFAULT || (chars[i] != '&' && chars[i] != '='))
                            && i > start
                            && !isasciialpha(chars[i]) && !isdigit(chars[i])) {
                                translit = get_entity_string(&chars[start], i - start,
                                                      cp);
                                if (chars[i] != ';') {
                                        /* Eat &nbsp &nbsp<foo> happily, but
                                         * pull back from the character after
                                         * entity string if it is not the valid
                                         * terminator. */
                                        i--;
                                }

                                if (!translit) PUTC;
                                charspos = i + (i < charslen);
                        } else PUTC;
                }

                if (!translit[0]) continue;

                if (!translit[1]) {
                        buffer[bufferpos++] = translit[0];
                        translit = "";
                        goto flush;
                }

                while (*translit) {
                        unsigned char *new_;

                        buffer[bufferpos++] = *(translit++);
flush:
                        if (bufferpos & (ALLOC_GR - 1)) continue;

                        if (callback) {
                                buffer[bufferpos] = 0;
                                callback(callback_data, buffer, bufferpos);
                                bufferpos = 0;
                        } else {
                                new_ = mem_realloc(buffer, bufferpos + ALLOC_GR);
                                if (!new_) {
                                        mem_free(buffer);
                                        return NULL;
                                }
                                buffer = new_;
                        }
                }
#undef PUTC
        }

#ifdef HAVE_ICONV
        if (loop) goto repeat;
#endif
        /* Say bye */

        buffer[bufferpos] = 0;
        if (length) *length = bufferpos;

        if (callback) {
                if (bufferpos) callback(callback_data, buffer, bufferpos);
                mem_free(buffer);
                return NULL;
        } else {
                return buffer;
        }
}


#ifndef USE_FASTFIND
int
get_cp_index(const unsigned char *name)
{
        int i, a;
        int syscp = 0;

        if (!c_strcasecmp(name, "System")) {
#if HAVE_LANGINFO_CODESET
                name = nl_langinfo(CODESET);
                syscp = SYSTEM_CHARSET_FLAG;
#else
                name = "us-ascii";
#endif
        }

        for (i = 0; codepages[i].name; i++) {
                for (a = 0; codepages[i].aliases[a]; a++) {
                        /* In the past, we looked for the longest substring
                         * in all the names; it is way too expensive, though:
                         *
                         *   %   cumulative   self              self     total
                         *  time   seconds   seconds    calls  us/call  us/call  name
                         *  3.00      0.66     0.03     1325    22.64    22.64  get_cp_index
                         *
                         * Anything called from redraw_screen() is in fact
                         * relatively expensive, even if it's called just
                         * once. So we will do a simple strcasecmp() here.
                         */

                        if (!c_strcasecmp(name, codepages[i].aliases[a]))
                                return i | syscp;
                }
        }

        if (syscp) {
                return get_cp_index("us-ascii") | syscp;
        } else {
                return -1;
        }
}

#else

static unsigned int i_name = 0;
static unsigned int i_alias = 0;

/* Reset internal list pointer */
void
charsets_list_reset(void)
{
        i_name = 0;
        i_alias = 0;
}

/* Returns a pointer to a struct that contains current key and data pointers
 * and increment internal pointer.  It returns NULL when key is NULL. */
struct fastfind_key_value *
charsets_list_next(void)
{
        static struct fastfind_key_value kv;

        if (!codepages[i_name].name) return NULL;

        kv.key = codepages[i_name].aliases[i_alias];
        kv.data = (void *) &codepages[i_name]; /* cast away const */

        if (codepages[i_name].aliases[i_alias + 1])
                i_alias++;
        else {
                i_name++;
                i_alias = 0;
        }

        return &kv;
}

static struct fastfind_index ff_charsets_index
        = INIT_FASTFIND_INDEX("charsets_lookup", charsets_list_reset, charsets_list_next);

/* It searchs for a charset named @name or one of its aliases and
 * returns index for it or -1 if not found. */
int
get_cp_index(const unsigned char *name)
{
        const struct codepage_desc *codepage;
        int syscp = 0;

        if (!c_strcasecmp(name, "System")) {
#if HAVE_LANGINFO_CODESET
                name = nl_langinfo(CODESET);
                syscp = SYSTEM_CHARSET_FLAG;
#else
                name = "us-ascii";
#endif
        }

        codepage = fastfind_search(&ff_charsets_index, name, strlen(name));
        if (codepage) {
                assert(codepages <= codepage && codepage < codepages + N_CODEPAGES);
                return (codepage - codepages) | syscp;

        } else if (syscp) {
                return get_cp_index("us-ascii") | syscp;

        } else {
                return -1;
        }
}

#endif /* USE_FASTFIND */

void
init_charsets_lookup(void)
{
#ifdef USE_FASTFIND
        fastfind_index(&ff_charsets_index, FF_COMPRESS);
#endif
}

void
free_charsets_lookup(void)
{
#ifdef USE_FASTFIND
        fastfind_done(&ff_charsets_index);
#endif
}

/* Get the codepage's name for displaying to the user, or NULL if
 * @cp_index is one past the end.  In the future, we might want to
 * localize these with gettext.  So it may be best not to use this
 * function if the name will have to be converted back to an
 * index.  */
unsigned char *
get_cp_name(int cp_index)
{
        if (cp_index < 0) return "none";
        if (cp_index & SYSTEM_CHARSET_FLAG) return "System";

        return codepages[cp_index].name;
}

/* Get the codepage's name for saving to a configuration file.  These
 * names can be converted back to indexes, even in future versions of
 * ELinks.  */
unsigned char *
get_cp_config_name(int cp_index)
{
        if (cp_index < 0) return "none";
        if (cp_index & SYSTEM_CHARSET_FLAG) return "System";
        if (!codepages[cp_index].aliases) return NULL;

        return codepages[cp_index].aliases[0];
}

/* Get the codepage's name for sending to a library or server that
 * understands MIME charset names.  This function irreversibly maps
 * the "System" codepage to the underlying charset.  */
unsigned char *
get_cp_mime_name(int cp_index)
{
        if (cp_index < 0) return "none";
        cp_index &= ~SYSTEM_CHARSET_FLAG;
        if (!codepages[cp_index].aliases) return NULL;

        return codepages[cp_index].aliases[0];
}

int
is_cp_utf8(int cp_index)
{
        cp_index &= ~SYSTEM_CHARSET_FLAG;
        return is_cp_ptr_utf8(&codepages[cp_index]);
}

/* This function will be used by the xhtml parser. */
const uint16_t *
get_cp_highhalf(const unsigned char *name)
{
        int cp = get_cp_index(name);

        if (cp < 0) return NULL;
        cp &= ~SYSTEM_CHARSET_FLAG;
        return codepages[cp].highhalf;
}